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PPR666

The document discusses specifications for low temperature asphalt mixtures like warm mix asphalt, half-warm mix asphalt and cold mix asphalt. It provides the background of reducing carbon footprint in construction. Draft specifications for different types of low temperature asphalt are attached in appendices. The specifications are based on existing standards and specifications for hot mix asphalt. The aim is to encourage greater use of more environmentally friendly low temperature asphalts.

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194 views74 pages

PPR666

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Transport Research Laboratory

Creating the future of transport

PUBLISHED PROJECT REPORT PPR666

Specification for Low Temperature Asphalt Mixtures

J C Nicholls (TRL), H K Bailey (TRL), N Ghazireh (Lafarge

Tarmac) and D H Day (Nynas)

Prepared for:

Lafarge Tarmac

Project Ref:

11112397

Quality approved:
Cliff Nicholls

Michael McHale

(Project Manager)

(Technical Referee)

Low temperature asphalt

Disclaimer
This report has been produced by the Transport Research Laboratory under a contract
with Lafarge Tarmac. Any views expressed in this report are not necessarily those of
Lafarge Tarmac and Business Innovation and Skills.
The information contained herein is the property of TRL Limited and does not necessarily
reflect the views or policies of the customer for whom this report was prepared. Whilst
every effort has been made to ensure that the matter presented in this report is relevant,
accurate and up-to-date, TRL Limited cannot accept any liability for any error or
omission, or reliance on part or all of the content in another context.

Contents amendment record

This report has been amended and issued as follows:
Version

Date

Description

Editor

Technical
Referee

Low temperature asphalt

Contents
Executive summary

iii

Abstract

Introduction

1.1

General

1.2

Background

1.3

Categories of low temperature asphalt

1.4

Carbon savings

Specifications

2.1

Current situation

2.2

Proposed specifications

Conclusions

Acknowledgements

References

Appendix A Standard specification for warm mix asphalt

A.1

Scope

A.2

Normative references

A.3

Terms, definitions, symbols and abbreviations

A.4

Requirements for constituent materials

A.5

Requirements for the warm mix asphalt mixture

A.6

Identification

A.7

Transport, laying and compaction

A.8

Compliance

Appendix B Standard specification for half-warm mix asphalt

B.1

Scope

B.2

Normative references

B.3

Terms, definitions, symbols and abbreviations

B.4

Requirements for constituent materials

B.5

Requirements for the half-warm mix asphalt mixture

B.6

Identification

B.7

Transport, laying and compaction

B.8

Compliance

Appendix C Specification for emulsion-based cold mix asphalt

C.1

Scope

C.2

Normative references

C.3

Terms, definitions, symbols and abbreviations

C.4

Requirements for constituent materials

C.5

Requirements for the cold mix asphalt mixture

C.6

Identification

C.7

Transport, laying and compaction

C.8

Compliance

37
i

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Appendix D Aggregate grading of reclaimed asphalt

D.1

Approach

D.2

Fractions

D.3

Analysis

D.4

Results

D.5

Validity

Appendix E Example standard specification for half-warm asphalt concrete

E.1

General

E.2

Constituent materials

E.3

Mixture specifications

E.4

Transport, laying and compaction

E.5

Compliance

Appendix F Example of standard specification for half-warm hot rolled asphalt

F.1

General

F.2

Constituent materials

F.3

Mixture specifications

F.4

Transport, laying and compaction

F.5

Compliance

Appendix G Example of standard specification for half-warm stone mastic asphalt

G.1

General

G.2

Constituent materials

G.3

Mixture specifications

G.4

Transport, laying and compaction

G.5

Compliance

Appendix H Example specification for emulsion-based cold mix asphalt

H.1

General

H.2

Constituent materials

H.3

Mixture specification

H.4

Transport, laying and compaction

H.5

Compliance

Appendix J Specification requirements for low temperature asphalt mixtures

J.1

96X Warm Mix Asphalt Materials

J.2

96Y Half-Warm Mix Asphalt Materials

J.3

96Z Emulsion-Based Cold Mix Asphalt Materials

Appendix K Notes for Guidance on specification requirements for low temperature

asphalt mixtures

K.1

NG96X Warm Mix Asphalt Materials

K.2

NG96Y Half-Warm Mix Asphalt Materials

K.3

NG96Z Emulsion-Based Cold Mix Asphalt Materials

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Executive summary
The UK government, through the Carbon Trust, have strategically targeted and evaluated
industrial products or processes for ways to reduce their carbon footprint. The energy
used in manufacturing hot mix asphalt in the aggregates sector has been identified as a
major contributor. In an attempt to increase the use of lower carbon asphalt, funding
has been made available to accelerate the introduction of technologies that will
encourage their wider use. As part of this initiative, funding was provided for a project to
look at low temperature asphalt processes, and this was undertaken by Tarmac, Nynas,
Atkins and Mineral Industry Research Organisation.
The second stage of this project has been funded from Business, Innovation and Skills
Regional Growth Funds with TRL replacing Atkins in the consortium. One of the Work
Packages for the project, WP5, was the Development of Specifications for low
temperature and cold mix asphalts, which was allocated to TRL to undertake. This report
is the output for that work package.
Low temperature asphalts, usually classified as warm mix asphalt, half-warm mix asphalt
and cold mix asphalt, are increasingly being used. However, most of the current
specifications are written around hot mix asphalt. There is no reason why specifications
for hot mix asphalt cannot be modified to become applicable to the various categories of
low temperature asphalt. Very little modification is required for warm mix asphalt, with
increasing modification being required as the mix temperature departs from that for hot
mix asphalt.
Examples of documents for use with low temperature asphalt mixtures have been drafted
and are given in a series of appendices. These drafts cover the various levels of standard
currently available for hot mix asphalt, being modelled on the current European
standards, supporting national guidance documents or the Specification for Highway
Works clauses.
It is intended that the availability of these documents will allow warm mix asphalt, halfwarm asphalt and cold-mix asphalt to be procured and that feedback from their use will
help to develop the European and national documents that will replace them in due
course.

iii

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Abstract
Low temperature asphalts, classified as warm mix asphalt, half-warm mix asphalt and
cold mix asphalt, are increasingly being used, but most of the current specifications are
written around hot mix asphalt. The types of specification that are used for hot mix
asphalt are discussed and a series of documents drafted to cover low temperature
asphalt mixtures are attached as appendices. The appendices are modelled on the
current European standards, supporting national guidance documents and the
Specification for Highway Works clauses. It is intended that the availability of these
documents will encourage greater use of low temperature asphalts until the standard
specifications have been updated to explicitly incorporate these environmentally friendly
materials.

1
1.1

Introduction
General

The UK government, through the Carbon Trust, have strategically targeted and evaluated
industrial products or processes for ways to reduce their carbon footprint. The energy
used in manufacturing hot mix asphalt in the aggregates sector has been identified as a
major contributor. In an attempt to increase the use of lower carbon asphalt, funding
has been made available to accelerate the introduction of technologies that will
encourage their wider use. One such technology was low temperature asphalt, for which
they funded a project to look at the process undertaken by Tarmac, Nynas, Atkins and
Mineral Industry Research Organisation.
The second stage of this project has been funded from Business Innovation and Skills
Regional Growth Funds with TRL replacing Atkins in the consortium. One of the Work
Packages for the project, WP5, was the Development of Specifications for low
temperature and cold mix asphalts, which was allocated to TRL to undertake. This report
is the output for that work package.

1.2

Background

The issue of sustainable development and the identification of the need to conserve
resources for use by future generations has been an international focus for decades.
Damage or disruption to ecosystems is generally caused as a result of the destruction or
finite use of natural resources and climate change. The Kyoto protocol, which was
formalised in 1997 as part of The United Nations Framework Convention on Climate
Change, formed an agreement between member states to bring greenhouse gas
emissions down to the levels of 1990. The agreement came into force in February 2005
and several countries have now developed a Climate Change Act, setting targets for the
reduction of greenhouse gas emissions which are categorised as CO 2 or units of CO2 equ

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(equivalent). The UK climate change act of 2008 set a reduction target of 80 %

(compared to a baseline value from 1990) by 2050 whilst the Scottish climate change act
of 2009 goes a step further and has includes an interim target reduction of 42 % by
2020. However, during the last 10 years there seem to have been more abnormal
weather patterns and freak events causing major disruption to sustainable living which
has produced a greater emphasis on climate change and the Kyoto protocol has gained
greater focus.
The main targets for reducing the carbon footprint within highway authority organisations
have focussed on reducing energy consumption, reducing the use of paper and vehicular
emissions. Therefore, the initial focus within the highways sector has tended to be
targeted towards issues such as, for example, reducing electricity consumption of street
lighting. The use of sustainable procurement whereby authorities are encouraged to
purchase goods and services from low carbon sources is only now gaining momentum.
The sustainability argument on asphalt paving systems generally reflects the whole life
value. The development of long-life (perpetual) pavements (defined as An asphalt
pavement designed and built to last longer than 50 years without requiring major
structural rehabilitation or reconstruction, and needing only periodic surface renewal in
response to distresses confined to the top of the pavement) with reduced maintenance
strategies has in recent times been viewed as the way forward in developing sustainable
asphalt paving. Reducing the energy of asphalt manufacture will have a detrimental
effect on the whole life argument if the products become vastly inferior and require
maintenance intervention or replacement more frequently in their life. The use of warm
and half-warm mix asphalts is generally still in its infancy and there is no real evidence
that asphalt manufactured by these technologies is inferior in situ to traditional hot mix
asphalts thus far. However, the use of cold mix asphalts, particularly emulsion-based
cold mix asphalts, has been around internationally for decades but has struggled to gain
market penetration in the UK due to differences in its physical properties compared to
hot mix asphalt. The use of these materials in various applications is much more
common in a number of countries across Europe and in the USA.
A major obstacle to gaining market penetration when developing new products and
processes is the equivalence argument. Products are generally approved based on
design criteria and equivalence to the hot mix asphalt laboratory design protocol; normal
design procedures and specifications. However, these criteria may need to be changed
to reflect the changes in the manufacturing process. This situation was the case in the
UK when developing standards for cold mix using foam bitumen. In the UK, some
evidence exists to support the use of emulsion based cold mix materials that have failed
to meet the specifications set, based on hot mix equivalence. In some instances, these
mixtures have still performed equally as well, and sometimes better than, conventional
hot mix asphalt in situ. The use of emulsion based cold mix to meet the specifications
set to comply with the Highway Authorities and Utilities Committee (HAUC) standard for
permanent cold lay surfacing materials (PCSMs) resulted in materials failing to meet the
specification and, therefore, failed to gain national approval. Some of these failed
materials are still functioning satisfactorily in situ after 15 years in service.

1.3

Categories of low temperature asphalt

Low temperature asphalt mixtures are those that are intentionally manufactured and laid
at temperatures less than the standard temperatures traditionally used for asphalt. They

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are generally categorised into three types depending on the extent of the temperature
reduction (EAPA, 2010) which, with the traditional mixtures, give the following:
a)

Hot mix asphalt

produced and mixed at temperatures roughly between

120 C and 190 C, the production temperatures
depending on the bitumen used.

Warm mix asphalt

produced and mixed at temperatures roughly between

100 C and 140 C.

Half-warm mix asphalt produced with heated aggregate at a mixing temperature

(of the mixture) between approximately 70 C and
roughly 100 C (also known as semi-warm mix asphalt).

Cold mix asphalt

produced with unheated aggregate and bitumen emulsion

or foamed bitumen.

These categories are normally characterised schematically as shown in Figure 1.1.

Figure 1.1 - Schematic of classification for hot, warm, half-warm and cold mix
asphalt mixtures
The technologies behind these systems can vary quite markedly whilst there are also
similarities.
There is no direct correspondence between the classifications and the
technologies, but the most common types of technology for the different classifications are:
Incorporation of chemical additives
o to modify the bitumen viscosity (such as waxes)

Warm

o to modify the frictional resistance of the mixture to compaction

Warm

Foamed bitumen
o by the addition of moisture releasing additives (such as zeolites) within
the mixture
o by foam generation equipment

Warm

Warm or Half-warm

o by the addition of moist aggregates

Half-warm

o other

Half-warm or Cold

Bitumen emulsion

Cold
3

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The chemical additives can either be pre-blended with the bitumen or added at the time
of mixing.

1.4

Carbon savings

The sustainability of low temperature asphalt mixtures can also be assessed by the
carbon dioxide equivalent (CO2 equ) used to produce the asphalt. This estimate is
probably better than just the fuel used as shown in Figure 1.1 for the different types.
However, the reduced temperature is not the only parameter that will affect the CO2 equ
but also the supply of raw materials for, the production of, and the transport of any
additives used in the mixture. As such, the different technologies will produce different
savings and cannot be shown in a similar schematic.
Furthermore, the carbon savings cannot, at this time, be used in requirements when
specifying asphalt and will not be covered in this report.

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Specifications

2.1

Current situation

There are several layers of specifications for materials used in pavement construction as
described figuratively in Figure 2.1.

European
standard

National
Guidance

National
Specification

Job
Specification

which, for (hot mix) asphalt, equates to:

Material:
Application:

BS EN 13108

PD 6691

BS 594987

SHW or
equivalent

Job specific

Figure 2.1 Levels of specification

For asphalt materials, the European standard is the relevant part of BS EN 13108 (CEN,
2006), the national guidance document is PD 6691 (BSI, 2010a) and the national
specification is usually the 900 series in the Specification for Highway Works (HA et al.,
2008) for roads and the standards for airfields (Defence Estates, 2009, 2010). For the
transport, laying and compaction of asphalt, there is no European standard and the
European standard and national guidance levels are combined into BS 594987 (BSI,
2010b); the national specification level documents cover both the materials and their
transport, laying and compaction.
The BS EN 13108 series were originally drafted primarily for hot mix asphalt mixtures,
although this limitation is not explicitly acknowledged in the title or text. However, the
title of the associated test methods, the BS EN 12697 series (CEN, various), does
acknowledge the limitation in its title of Bituminous mixtures Test methods for hot mix
asphalt although most of the test methods (as opposed to the specimen preparation
procedures) are equally applicable to low temperature asphalt mixtures.
The BS EN 13108 series is currently under 5-year review with changes planned, including
extending into warm mix asphalt, although how much will be done in this revision is still
uncertain. It is assumed that it will be extended to explicitly cover warm mix asphalt
(rather than the current situation whereby it is not excluded) whilst cold mix asphalt will
require new parts, for which a part on cold emulsion-based mixtures has already been
started. The position of half-warm mixtures is less clear. Meanwhile, the specimen
preparation procedures in the BS EN 12697 series are being reviewed to make them
applicable to low temperature asphalts, although again some new tests may be required
for cold mix asphalt and the title of the series will need to be changed.
At the national specification level, reference is made to low temperature asphalt, but
most clauses were drafted explicitly for hot mix asphalt and, with the increasing use of
low temperature asphalt (about 20 % of asphalt production in the USA was warm or halfwarm mix asphalt in 2011, Figure 2.2), a more comprehensive set of requirements are
needed if the use of these materials is to be encouraged.

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Figure 2.2 - Development in the production of warm and half-warm mix asphalt
in USA

2.2
2.2.1

Proposed specifications
Overview

Whilst there are plans to update various documents to incorporate the various categories
of low temperature asphalt, there is a need for documents that can be used in the
interim. Therefore, a series of documents have been drafted to cover the European
standard, national guidance and national specification levels for warm mix, half-warm
mix and emulsion-based cold mix asphalt. Only a slight modification has been made to
warm mix because the existing hot mix documents can effectively be used. These
documents have been prepared by TRL in collaboration with Lafarge Tarmac and Nynas
UK AB for the Carbon Trust and the Region Growth Fund.
2.2.2

Warm mix standard

For warm mix asphalt, the only requirement that will not be complied with is the
minimum temperature of the mixture, as given in clause 5.2.10 of BS EN 13108-1 (CEN,
2006) for asphalt concrete. The European standard temperature ranges are given for
each paving grade of bitumen, but there is a statement that The minimum temperature
of the asphalt mix(ture) at delivery shall be declared by the manufacturer which makes
the lower bound informative rather than normative. These minimum temperatures are
due to be removed in the next edition expected to be published in 2015. Until then, the
current standards could be used for softer grades (when the minimum is below 140 C)
or with the exception being clearly identified. Nevertheless, Appendix A is provided as a
draft specification for warm mix asphalt should one be felt necessary.
2.2.3

Half-warm mix standard

The exception is greater for half-warm mix asphalts, so Appendix B is provided as a draft
specification that provides one approach of specifying half-warm mix asphalt. This
approach specifies half-warm mix asphalt in terms of component materials and
proportions with additional requirements based on performance-related tests. The main
text follows the technical approach used in the various parts of BS EN 13108 (CEN, 2006)
6

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and is based on the draft revisions following 5-year review of the harmonised European
standards for hot mix asphalt. The specification includes reference to BS 594987 (BSI,
2010b) for transporting, laying and compaction together with compliance requirements
to verify compliance.
2.2.4

Emulsion-based cold mix standard

Appendix C is a draft specification that provides one approach of specifying emulsionbased cold mix asphalt. This approach specifies emulsion-based cold mix asphalt in
terms of component materials and proportions with additional requirements based on
performance-related tests. The main text is based on the early drafts for a harmonised
European standard that has the same technical approach as used in the various existing
parts of BS EN 13108 (CEN, 2006) whilst the specification includes reference to
BS 594987 (BSI, 2010b) for transporting, laying and compaction with compliance
requirements to verify compliance.
2.2.5

Foamed-bitumen cold mix standard

Foamed-bitumen cold mix asphalt has not been covered because that family of materials
is already well-established with a specification in TRL Report TRL611 (Merrill et al., 2004)
that is supported by clause 947 and 948 of the Specification for Highway Works (HA et
al, 2008).
2.2.6

Supporting appendices

The Appendix A and Appendix B specifications are supported by Appendix D defining how
to treat the grading of reclaimed asphalt and, for Appendix B, there are three informative
appendices equivalent to the example specifications given as figures in the Annexes of
PD 6691 (BSI, 2010a) that are generally used in the UK. These draft national guidance
documents are Appendix E for asphalt concrete, Appendix F for hot rolled asphalt and
Appendix G for stone mastic asphalt.
As with Appendix B, the Appendix C specification is supported by Appendix D on how to
treat the grading of reclaimed asphalt and an informative appendix, Appendix H,
equivalent to the example specifications given as figures in the Annexes of PD 6691 (BSI,
2010a) that are general used in the UK.
2.2.7

Specification clause

Appendix J gives a series of specification requirements based on the 900 series in the
Specification for Highway Works (HA et al., 2008). There are separate sections for warm
mix asphalt, half-warm asphalt and emulsion-based cold-mix asphalt. Appendix K gives
the associated notes for guidance, again in three sections. As such, there is a certain
amount of repetition in the sections of both Appendix J and Appendix K.
2.2.8

Cross-references

In these appendices, cross references are used to the hot mix asphalt documents where
that information is equally appropriate in order to avoid potential conflicts. However, the
references have been kept to the document rather than a specific clause or table (whose
number may change in a future version) so that the document date does not have to be
included in the reference. A referenced document without a date implies the current
version of that standard whilst a dated reference implies that specific version and needs
7

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to be updated when the reference has been revised or superseded. The lack of dated
references is particularly important because the various parts of BS EN 13108 (CEN,
2006) together with PD 6691 (BSI, 2010a) and BS 594987 (BSI, 2010b) are all expected
to be updated in the next few years. The one exception is that the specific Annexes in
PD 6691 have been referenced without giving the date. This approach is technically
incorrect but was considered pragmatic in order to avoid leaving it unclear which material
annex was applicable without giving dated references that would have needed updating
whenever PD 6691 is revised.

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Conclusions

Low temperature asphalts (warm mix asphalt, half-warm mix asphalt and cold mix
asphalt) are increasingly being used, but most of the current specifications are written
around hot mix asphalt. However, there is no reason why these specifications for hot
mix asphalt cannot be modified to become applicable to the various categories of low
temperature asphalt. Very little modification is required for warm mix asphalt, with
increasing modification being required as the mix temperature departs from that for hot
mix asphalt.
Examples of documents for use with low temperature asphalt mixtures have been drafted
and are given in a series of appendices. These drafts cover the various levels of standard
currently available for hot mix asphalt, being modelled on the current European
standards, supporting national guidance documents or the Specification for Highway
Works clauses.
It is intended that the availability of these documents will allow warm mix asphalt, halfwarm asphalt and emulsion-based cold-mix asphalt to be procured and that feedback
from their use will help to develop the European and national documents that will replace
them in due course.

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Acknowledgements
The work described in this report was carried out in the Infrastructure Division of the
Transport Research Laboratory and funded by Lafarge Tarmac as part of a contract with
Business Innovation and Skills. The authors are grateful to Michael McHale for carrying
out the technical review and auditing of this report.
The authors wish to thank the Carbon Trust and the Department for Business, Innovation
and Skills for providing the funding for this project.
The authors are grateful for the guidance, assistance and contribution of the Project
Advisory Group (PAG) formed from industry specifically for this project at inception stage
whose members include:
Andy Bailey

Department for Transport

Donna James

Highways Agency

Dougie Millar

Transport Scotland

Peter Barclay

Leicestershire County Council for Midlands Highway Alliance

Nick Twaite

Worcestershire County Council for West Midlands Highway Alliance

Andrew Warrington

Nottinghamshire County Council

Iain Waddell

Tayside Contracts

Malcolm Simms

Mineral Products Association

John Barritt

Waste and Resources Action Programme

Al-Karim Govindji

Carbon Trust

Nizar Ghazireh

Lafarge Tarmac

Dennis Day

Nynas

Steve Harris

Nynas

Steve Biczysko

Formerly Atkins

Mike Gibb

Formerly Atkins

Alan Gibbon

Mineral Industry Research Organisation

Cliff Nicholls

Transport Research Laboratory

Particular thanks are due to Steve Biczysko for his work as part of the project team for
the earlier stage of this project and to Rod Hook from Leicestershire County Council for
his invaluable support. David Hardy from Lafarge Tarmac is acknowledged for his
contribution to this document and Brian Kent from Lafarge Tarmac for his overall support
and encouragement to this project.

References
British Standards Organisation (2010a). Guidance on the use of BS EN 13108
Bituminous mixtures Material specifications. PD 6691:2010. London: BSI.
British Standards Organisation (2010b). Asphalt for roads and other paved areas
Specification for transport, laying, compaction and type testing protocols.
BS 594987:2010. London: BSI.

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Comit Europen de Normalisation (2006).

Bituminous mixtures Material
specifications. BS EN 13108-1:2006 to BS EN 13108-7:2006. London: British Standards
Organisation.
Comit Europen de Normalisation (various). Bituminous mixtures Test methods
for hot mix asphalt. BS EN 12697-1 to BS EN 12697-47. London: British Standards
Organisation.
Defence Estates (20009, 2010). Asphalt for airfields. SPEC 12, SPEC 13, SPEC 40
and SPEC 49.
Sutton Coldfield: Defence Infrastructure Organisation.
[On line
www.gov.uk/government/publications/specifications, last accessed April 2013].
European Asphalt Pavement Association (2010). The use of warm mix asphalt.
EAPA position paper. Brussels: EAPA. [On line http://eapa.org/usr_img/position_paper/
the_use_of_warm_mix_asphalt_january_2010.pdf, last accessed May 2013].
Highways Agency, Transport Scotland, Welsh Assembly Government and The
Department for Regional Development Northern Ireland (2008). Road pavements
Bituminous bound materials. Manual of Contract Documents for Highway Works,
Volume 1: Specification for Highway Works, Series 900. London: The Stationery Office,
London. [On line www.dft.gov.uk/ha/standards/mchw/vol1/pdfs/ series_0900.pdf, last
accessed April 2013].
Merrill, D, M E Nunn and I Carswell (2004). A guide to the use and specification of
cold recycled materials for the maintenance of road pavements. TRL Report TRL611.
Crowthorne: Transport Research Laboratory.

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Appendix A Standard specification for warm mix asphalt

A.1 Scope
This Specification sets out requirements for mixtures of warm mix asphalt for use on
roads, airfields and other trafficked areas. It includes requirements for the selection of
the constituent materials. Warm mix asphalt can be used for surface courses, binder
courses, regulating courses and bases.

A.2 Normative references

This Specification incorporates, by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text
and the publications are listed hereafter. For dated references, subsequent amendments
to or revisions of any of these publications apply to this Specification only when
incorporated in it by amendment or revision. For undated references, the latest edition
of the publication referred to applies (including amendments).
BS 594987, Asphalt for roads and other paved areas. Specification for transport, laying,
compaction and type testing protocols
BS EN 12697-13, Bituminous mixtures Test methods for hot mix asphalt Part 13:
Temperature measurement
BS EN 13108-1, Bituminous mixtures Material specifications Part 1: Asphalt concrete
BS EN 13108-2, Bituminous mixtures Material specifications Part 2: Very thin layer
asphalt concrete
BS EN 13108-4, Bituminous mixtures Material specifications Part 4: Hot rolled asphalt
BS EN 13108-5, Bituminous mixtures Material specifications Part 5: Stone mastic
asphalt
BS EN 13108-7, Bituminous mixtures Material specifications Part 7: Porous asphalt
BS EN 13108-20, Bituminous mixtures Material specifications Part 20: Type testing of
asphalt mixes
BS EN 13108-21, Bituminous mixtures Material specifications Part 21: Factory
production control

A.3 Terms, definitions, symbols and abbreviations

A.3.1

Terms and definitions

For the purposes of this Appendix, the terms and definitions given in BS EN 13108-1
together with the following apply.
A.3.1.1
asphalt
homogenous mixture of coarse and fine aggregates, filler aggregate and bituminous
binder which is used in the construction of flexible pavement layers
NOTE:

The asphalt may include one or more additives to enhance the laying characteristics,
performance or appearance of the mixture. Natural asphalt is defined in BS EN 13108-4.

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A.3.1.2
warm mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at temperatures at least 20 C below
conventional hot mix asphalt mixtures but still above 100 C
A.3.1.3
half-warm mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at temperatures in the range 70 C to
100 C
NOTE:

Also known as semi-warm mix asphalt

A.3.1.4
cold mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at ambient temperature
A.3.1.5
emulsion-based cold mix asphalt
cold mix asphalt in which the binder is a bituminous emulsion with a viscosity such that
the mix is workable at ambient temperature
A.3.1.6
foamed asphalt
asphalt in which, during mixing, the binder is caused to foam by the presence of steam,
reducing the surface tension and easing coating of the aggregate particles
A.3.1.7
moisture content in the mix
water content expressed in per cent of the dry aggregate mass
A.3.2

Symbols and abbreviations

WMA

General designation for a warm mix asphalt.

XX D WMA

Designation of mixture type followed by an indication of D, the upper sieve

size of the aggregate in the mixture, in millimetres (mm), and the general
designation for warm mix asphalt.

EXAMPLE:

AC 14 WMA is a warm mix asphalt concrete with an upper sieve size of the
aggregate of 14 mm.

A.4 Requirements for constituent materials

A.4.1

General

As in BS EN 13108-1 for warm mix asphalt concrete; BS EN 13108-2 for warm mix very
thin layer asphalt concrete; BS EN 13108-4 for warm mix hot rolled asphalt;
BS EN 13108-5 for warm mix stone mastic asphalt; or BS EN 13108-7 for warm mix
porous asphalt.

PPR666

Low temperature asphalt

A.4.2
A.4.2.1

Binder
General

Selection of binder

A.4.2.3

The ageing of binder during the mixing and placement of hot mix asphalt, particularly
when using batch mixers, in terms of the binder penetration is generally a reduction of
the order of 33 %, or one binder grade, which does not occur to the same extent for
warm mix asphalt. Consideration should be given to reducing the required binder
penetration where equivalence is intended with hot mix asphalt.

Surface courses with reclaimed asphalt

Regulating courses, binder courses and bases with reclaimed asphalt

As in BS EN 13108-1 for warm mix asphalt concrete; BS EN 13108-4 for warm mix hot
rolled asphalt; or BS EN 13108-5 for warm mix stone mastic asphalt.
NOTE:

Not applicable for warm mix very thin layer asphalt concrete or warm mix porous asphalt.

A.4.3

Aggregates

Reclaimed asphalt
As with hot mix asphalt, reclaimed asphalt containing tar shall not be used.

A.4.4.2
As in BS EN 13108-1 for warm mix asphalt concrete; BS EN 13108-2 for
warm mix very thin layer asphalt concrete; BS EN 13108-4 for warm mix hot rolled
asphalt; BS EN 13108-5 for warm mix stone mastic asphalt; or BS EN 13108-7 for warm
mix porous asphalt.
A.4.4.3
If reclaimed asphalt is controlled using analysis of particles without removing
the binder, the aggregate grading in the reclaimed asphalt for calculation of the
aggregate grading in the mixture shall be determined in accordance with Appendix D.
A.4.5

Additives

As in BS EN 13108-1 for warm mix asphalt concrete; BS EN 13108-2 for warm mix very
thin layer asphalt concrete; BS EN 13108-4 for warm mix hot rolled asphalt;
15

PPR666

Low temperature asphalt

BS EN 13108-5 for warm mix stone mastic asphalt; or BS EN 13108-7 for warm mix
porous asphalt.

A.5 Requirements for the warm mix asphalt mixture

A.5.1

General

A.5.1.1
The target composition of the mixture in terms of its constituent materials,
the proportions (in per cent) passing the specified sieves, the target binder content and
where relevant the binder from natural asphalt and the proportion(s) of additive(s) shall
be declared and documented. The target grading curve shall be declared for the sieve
1.4 D and the sieves as called up in A.5.2.
A.5.1.2
At the target composition, the mixture shall conform to the specified
requirements in accordance with this specification.
A.5.1.3
A.5.2

The test results shall be made available.

Composition and grading

Coated chippings to BS EN 13108-4 are not included because they are not suitable for
rolling into hot rolled asphalt at warm mix asphalt temperatures.

A.5.3

Binder content

Additives

Properties
Specimens

A.5.5.1.1
For application of this Specification, specimens shall be manufactured in
accordance with clause 6.2 of BS EN 13108-20:2014 except for the temperature at which
they are mixed and compacted.
A.5.5.1.2
The temperature at which samples shall be mixed and compacted shall be
at the standard temperature for each operation less the difference between the
temperature at which the warm asphalt will be prepared on site and the temperature at
which hot asphalt will be prepared on site.

PPR666

Low temperature asphalt

A.5.5.1.3
When testing a sample of warm asphalt for refusal density, the sample
shall be heated to the same temperature as an equivalent hot mix asphalt before
compaction.
A.5.5.1.4
The relevant technology that allows the asphalt to be mixed and laid at a
reduced temperature shall be employed in the manufacture of samples used to
demonstrate the properties of the asphalt mixture.
If the technology cannot be
replicated in the laboratory, plant-produced samples shall be used for type testing and
factory production control.
A.5.5.2

Standard properties

The ageing of binder during the mixing and placement of hot mix asphalt, particular when
using batch mixers, in terms of the binder penetration is generally a reduction of the
order of 33 %, or one binder grade, which does not occur to the same extent. Where
equivalence is intended with hot mix asphalt and the binder grade selected has been
adjusted, the selected categories of the standard mechanical properties may need to be
adjusted when laboratory prepared mixtures are used to assess the performance.

A.5.6

Temperature of the mixture

A.5.6.1
The maximum temperature requirements apply at any place in the plant and
shall be declared.
A.5.6.2

The minimum temperature of the mixture at delivery shall be declared.

A.5.6.3
Depending on local conditions and for specific application the minimum
temperature, measured according to EN 12697-13, may be specified.
A.5.6.4
When using paving grade binder, the maximum temperature of a warm mix
asphalt, measured according to BS EN 12697-13, shall target 140 C (grades 20/30 to
70/100), 130 C (grades 100/150 and 160/220) or 120 C (grades 250/330 and
330/430).
A.5.6.5
When using modified bitumen or hard grade bitumen, additives or premix
bitumen, different temperatures may be applicable. These shall then be documented and
declared.
A.5.7

Dangerous substances

Conflicting specifications

PPR666

Low temperature asphalt

A.6 Identification
The delivery ticket shall contain at least the following information relating to
identification:
the manufacturer and mixing plant;
designation of the mixture:
AC/BBTM/HRA/SMA/PA
where:

NOTE:

AC
BBTM
HRA
SMA
PA
D
surf
base
bin
binder
WMA

is
is
is
is
is
is
is
is
is
is
is

surf/base/bin

Binder

WMA

Asphalt Concrete;
asphalt concrete for very thin layers;
Hot Rolled Asphalt;
Stone Mastic Asphalt;
Porous Asphalt;
the upper sieve size;
the surface course;
the base course;
the binder course;
the designation of binder used;
warm mix asphalt.

Example: SMA 14 base 40/60 WMA (in which 40/60 is the binder used and not the
equivalent properties for hot mix asphalt).

A.7 Transport, laying and compaction

A.7.1
This clause gives general requirements for the transport, placing and compaction
of bituminous mixtures, which are complementary and additional to the requirements of
BS 594987. These requirements and the requirements of BS 594987 shall apply to all
warm mix asphalt mixtures, unless otherwise specified in A.7.2 of this Appendix.
NOTE:

BS 594987 states that it does not cover the supply, laying and compaction of lowtemperature warm mix and other reduced temperature asphalts. Nevertheless, its main
requirements, other than those on the temperature of the mixture, are generally
applicable to warm mix asphalt.

A.7.2 Minimum delivery and rolling temperatures for warm mix asphalt mixtures shall
be declared by the supplier with evidence to support their suitability.

A.8 Compliance
A.8.1 Compliance with the requirements for mixture composition and properties
(A.4 and A.5) shall be by type testing and factory production control. The factory
production control shall be in accordance with the principles and frequencies of
BS EN 13108-21. A certificate defining compliance supported by test reports shall be
made available for inspection.
A.8.2 Audit checking to confirm that the mixture composition and properties claimed
are those of the mixture delivered to site may be undertaken.
A.8.3 Compliance with the requirements for transporting, laying and compacting the
asphalt (A.7) shall be monitored against the requirements of BS 594987 and test reports
demonstrating compliance shall be made available for inspection.

PPR666

Low temperature asphalt

Appendix B Standard specification for half-warm mix

asphalt
B.1 Scope
This Specification sets out requirements for mixtures of half-warm mix asphalt for use on
roads, airfields and other trafficked areas. It includes requirements for the selection of
the constituent materials. Half-warm mix asphalt can be used for surface courses, binder
courses, regulating courses and bases.

B.2 Normative references

properties

aggregates

BS EN 12697-13, Bituminous mixtures Test methods for hot mix asphalt Part 13:
Temperature measurement
BS EN 12697-14, Bituminous mixtures Test methods for hot mix asphalt Part 14:
Water content
BS EN 13108-1, Bituminous mixtures Material specifications Part 1: Asphalt concrete
BS EN 13108-2, Bituminous mixtures Material specifications Part 2: Very thin layer
asphalt concrete
BS EN 13108-4, Bituminous mixtures Material specifications Part 4: Hot rolled asphalt
BS EN 13108-5, Bituminous mixtures Material specifications Part 5: Stone mastic
asphalt
BS EN 13108-7, Bituminous mixtures Material specifications Part 7: Porous asphalt
BS EN 13108-20, Bituminous mixtures Material specifications Part 20: Type testing of
asphalt mixes
BS EN 13108-21, Bituminous mixtures Material specifications Part 21: Factory
production control

B.3 Terms, definitions, symbols and abbreviations

B.3.1

Terms and definitions

For the purposes of this Appendix, the terms and definitions given in BS EN 13108-1
together with the following apply.

PPR666

Low temperature asphalt

B.3.1.1
asphalt
homogenous mixture of coarse and fine aggregates, filler aggregate and bituminous
binder which is used in the construction of flexible pavement layers
NOTE:

The asphalt may include one or more additives to enhance the laying characteristics,
performance or appearance of the mixture. Natural asphalt is defined in BS EN 13108-4.

B.3.1.2
warm mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at temperatures at least 20 C below
conventional hot mix asphalt mixtures but still above 100 C
B.3.1.3
half-warm mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at temperatures in the range 70 C to
100 C
NOTE:

Also known as semi-warm mix asphalt

B.3.1.4
cold mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at ambient temperature
B.3.1.5
emulsion-based cold mix asphalt
cold mix asphalt in which the binder is a bituminous emulsion with a viscosity such that
the mix is workable at ambient temperature
B.3.1.6
foamed asphalt
asphalt in which, during mixing, the binder is caused to foam by the presence of steam,
reducing the surface tension and easing coating of the aggregate particles
B.3.1.7
moisture content in the mix
water content expressed in per cent of the dry aggregate mass
B.3.2

Symbols and abbreviations

HWMA

General designation for a half-warm mix asphalt.

XX D HWMA

Designation of mixture type followed by an indication of D, the upper sieve

size of the aggregate in the mixture, in millimetres (mm), and the general
designation for half-warm mix asphalt.

EXAMPLE:

BBTM 10 HWMA is a half-warm mix very thin asphalt concrete with an upper sieve
size of the aggregate of 10 mm.

B.4 Requirements for constituent materials

B.4.1

General

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

mix very thin layer asphalt concrete; BS EN 13108-4 for half-warm mix hot rolled asphalt;

PPR666

Low temperature asphalt

BS EN 13108-5 for half-warm mix stone mastic asphalt; or BS EN 13108-7 for half-warm
mix porous asphalt.
B.4.2
B.4.2.1

Binder
General

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

mix very thin layer asphalt concrete; BS EN 13108-4 for half-warm mix hot rolled asphalt;
BS EN 13108-5 for half-warm mix stone mastic asphalt; or BS EN 13108-7 for half-warm
mix porous asphalt.
B.4.2.2

Selection of binder

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

B.4.2.3

The ageing of binder during the mixing and placement of hot mix asphalt, particularly
when using batch mixers, in terms of the binder penetration is generally a reduction of
the order of 33 %, or one binder grade, which does not occur to the same extent for halfwarm mix asphalt. Consideration should be given to reducing the required binder
penetration where equivalence is intended with hot mix asphalt.

Surface courses with reclaimed asphalt

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

Regulating courses, binder courses and bases with reclaimed asphalt

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-4 for half-warm

mix hot rolled asphalt; or BS EN 13108-5 for half-warm mix stone mastic asphalt.
NOTE:

Not applicable for half-warm mix very thin layer asphalt concrete or half-warm mix
porous asphalt.

B.4.3

Aggregates

B.4.3.1

General

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

Water content of aggregates

The water content of the aggregate prior to mixing shall be determined in accordance
with BS EN 1097-5. The minimum and maximum water contents of the aggregate or a
specified aggregate fraction shall comply with the selected category from Table B.1.

PPR666

Low temperature asphalt

Table B.1 Minimum and maximum water content of aggregate,

WAmin and WAmax
Water content (%)

Minimum
category

Maximum
category

3.0

WAmin 3.0

WAmax 3.0

4.0

WAmin 4.0

WAmax 4.0

5.0

WAmin 5.0

WAmax 5.0

6.0

WAmin 6.0

WAmax 6.0

8.0

WAmax 8.0

10.0

WAmax 10.0

No requirement

WAmin NR

WAmax NR

NOTE:

The range between the upper and lower limits selected should be at least 1 %.

B.4.4

Reclaimed asphalt

B.4.4.1

As with hot mix asphalt, reclaimed asphalt containing tar shall not be used.

B.4.4.2
As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for
half-warm mix very thin layer asphalt concrete; BS EN 13108-4 for half-warm mix hot
rolled asphalt; BS EN 13108-5 for half-warm mix stone mastic asphalt; or BS EN 13108-7
for half-warm mix porous asphalt.
B.4.4.3
If reclaimed asphalt is controlled using analysis of particles without removing
the binder, the aggregate grading in the reclaimed asphalt for calculation of the
aggregate grading in the mixture shall be determined in accordance with Appendix D.
B.4.5

Additives

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

mix very thin layer asphalt concrete; BS EN 13108-4 for half-warm mix hot rolled asphalt;
BS EN 13108-5 for half-warm mix stone mastic asphalt; or BS EN 13108-7 for half-warm
mix porous asphalt.

B.5 Requirements for the half-warm mix asphalt mixture

B.5.1

General

B.5.1.1
The target composition of the mixture in terms of its constituent materials,
the proportions (in per cent) passing the specified sieves, the target binder content and
where relevant the binder from natural asphalt and the proportion(s) of additive(s) shall
be declared and documented. The target grading curve shall be declared for the sieve
1.4 D and the sieves as called up in B.5.2.
B.5.1.2
At the target composition, the mixture shall conform to the specified
requirements in accordance with this specification.
B.5.1.3
B.5.2

The test results shall be made available.

Composition and grading

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

mix very thin layer asphalt concrete; BS EN 13108-4 for half-warm mix hot rolled asphalt;

PPR666

Low temperature asphalt

BS EN 13108-5 for half-warm mix stone mastic asphalt; or BS EN 13108-7 for half-warm
mix porous asphalt.
NOTE:

Coated chippings to BS EN 13108-4 are not included because they are not suitable for
rolling into hot rolled asphalt at half-warm mix asphalt temperatures.

B.5.3

Binder content

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

Additives

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

Properties
Specimens

B.5.5.1.1
For application of this Specification, specimens shall be manufactured in
accordance with clause 6.2 of BS EN 13108-20:2014 except for the temperature at which
they are mixed and compacted and the time between the two operations.
B.5.5.1.2
The temperature at which samples shall be mixed and compacted shall be
at the standard temperature for each operation less the difference between the
temperature at which the half-warm asphalt will be prepared on site and the temperature
at which hot asphalt will be prepared on site.
B.5.5.1.3
The time between the completion of mixing and the start of compaction of
samples shall be (120 10) min, during which time the specimens shall be stored in
their moulds at 95 C.
NOTE 1: Reheating of specimens should be avoided.
NOTE:

Half-warm mixtures will slowly eliminate water after manufacture during the delivery and
application process. Therefore, it is important not to compact laboratory prepared
mixtures immediately because the excess water present may have a negative impact on
some comparative tests. This phenomenon has been studied and conditioning at 95 C
for 2 h prior to compaction at 95 C has produced samples with superior water sensitivity
performance to ones compacted immediately.

B.5.5.1.4
When testing a sample of half-warm asphalt for refusal density, the sample
shall be heated to the same temperature as an equivalent hot mix asphalt before
compaction.
B.5.5.1.5
The relevant technology that allows the asphalt to be mixed and laid at a
reduced temperature shall be employed in the manufacture of samples used to
demonstrate the properties of the asphalt mixture.
If the technology cannot be
replicated in the laboratory, plant-produced samples shall be used for type testing and
factory production control.

PPR666

Low temperature asphalt

B.5.5.2

Standard properties

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

B.5.5.3

Water content of asphalt

The water content of freshly mixed half-warm mix asphalt shall be determined in
accordance with BS EN 12697-14. The maximum water content shall comply with the
selected category from Table B.2.
Table B.2 Maximum water content of asphalt, WCmax

B.5.6

Maximum water content

(%)

Category

1.0

WCmax 1.0

2.0

WCmax 2.0

3.0

WCmax 3.0

4.0

WCmax 4.0

5.0

WCmax 5.0

6.0

WCmax 6.0

No requirement

WCmax NR

Temperature of the mixture

B.5.6.1
The maximum temperature requirements apply at any place in the plant and
shall be declared.
B.5.6.2

The minimum temperature of the mixture at delivery shall be declared.

B.5.6.3
Depending on local conditions and for specific application the minimum
temperature, measured according to EN 12697-13, may be specified.
B.5.6.4
When using paving grade binder, the maximum temperature of a half-warm
mix asphalt, measured according to BS EN 12697-13, shall target 100 C but shall not
exceed 110 C.
B.5.6.5
When using modified bitumen or hard grade bitumen, additives or premix
bitumen, different temperatures may be applicable. These shall then be documented and
declared.
B.5.7

Dangerous substances

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

mix very thin layer asphalt concrete; BS EN 13108-4 for half-warm mix hot rolled asphalt;
BS EN 13108-5 for half-warm mix stone mastic asphalt; or BS EN 13108-7 for half-warm
mix porous asphalt.

PPR666

Low temperature asphalt

B.5.8

Conflicting specifications

As in BS EN 13108-1 for half-warm mix asphalt concrete; BS EN 13108-2 for half-warm

mix very thin layer asphalt concrete; BS EN 13108-4 for half-warm mix hot rolled asphalt;
BS EN 13108-5 for half-warm mix stone mastic asphalt; or BS EN 13108-7 for half-warm
mix porous asphalt.

B.6 Identification
The delivery ticket shall contain at least the following information relating to
identification:
the manufacturer and mixing plant;
designation of the mixture:
AC/BBTM/HRA/SMA/PA
where:

NOTE:

AC
BBTM
HRA
SMA
PA
D
surf
base
bin
binder
HWMA

is
is
is
is
is
is
is
is
is
is
is

surf/base/bin

Binder

HWMA

Example: SMA 14 base 40/60 HWMA (in which 40/60 is the binder used and not the
equivalent properties for hot mix asphalt).

B.7 Transport, laying and compaction

B.7.1
This clause gives general requirements for the transport, placing and compaction
of bituminous mixtures, which are complementary and additional to the requirements of
BS 594987. These requirements and the requirements of BS 594987 shall apply to all
half-warm mix asphalt mixtures, unless otherwise specified in B.7.2 of this Appendix.
NOTE:

B.7.2 Minimum delivery and rolling temperatures for half-warm mix asphalt mixtures
shall be declared by the supplier with evidence to support their suitability.

B.8 Compliance
B.8.1 Compliance with the requirements for mixture composition and properties
(B.4 and B.5) shall be by type testing and factory production control. The factory
production control shall be in accordance with the principles and frequencies of
BS EN 13108-21. A certificate defining compliance supported by test reports shall be
made available for inspection.
B.8.2 Audit checking to confirm that the mixture composition and properties claimed
are those of the mixture delivered to site may be undertaken.

PPR666

Low temperature asphalt

B.8.3 Compliance with the requirements for transporting, laying and compacting the
asphalt (B.7) shall be monitored against the requirements of BS 594987 and test reports
demonstrating compliance shall be made available for inspection.

PPR666

Low temperature asphalt

Appendix C Specification for emulsion-based cold mix

asphalt
C.1 Scope
This Specification sets out requirements for mixtures of emulsion-based cold mix asphalt
for use on roads, airfields and other trafficked areas, such as gravel emulsion, dense and
open graded mixtures. It includes requirements for the selection of the constituent
materials. Emulsion-based cold mix asphalt can be used for surface courses, binder
courses, regulating courses and bases. This Specification does not cover in-situ recycling
or bagged cold ready-use mixtures.

C.2 Normative references

properties

aggregates

BS EN 12591, Bitumen and bituminous binders Specifications for paving grade

bitumens
BS EN 12697-1, Bituminous mixtures Test methods for hot mix asphalt Part 1:
Soluble binder content
BS EN 12697-2, Bituminous mixtures Test methods for hot mix asphalt Part 2:
Determination of particle size distribution
BS EN 12697-6, Bituminous mixtures Test methods for hot mix asphalt Part 6:
Determination of bulk density of bituminous specimens
BS EN 12697-8, Bituminous mixtures Test methods for hot mix asphalt Part 8:
Determination of voids characteristics of bituminous specimen
BS EN 12697-10, Bituminous mixtures Test methods for hot mix asphalt Part 10:
Compactibility
BS EN 12697-12, Bituminous mixtures Test methods for hot mix asphalt Part 12:
Determination of the water sensitivity of bituminous specimens
BS EN 12697-22, Bituminous mixtures Test methods for hot mix asphalt Part 22:
Wheel tracking
BS EN 12697-25, Bituminous mixtures Test methods for hot mix asphalt Part 25:
Cyclic compression

PPR666

Low temperature asphalt

BS EN 12697-26, Bituminous mixtures Test methods for hot mix asphalt Part 26:
Stiffness
BS EN 12697-27, Bituminous mixtures Test methods for hot mix asphalt Part 27:
Sampling
BS EN 12697-30, Bituminous mixtures Test methods for hot mix asphalt Part 30:
Specimen preparation by impact compactor
BS EN 12697-31, Bituminous mixtures Test methods for hot mix asphalt Part 31:
Specimen preparation by gyratory compactor
BS EN 12697-33, Bituminous mixtures Test methods for hot mix asphalt Part 33:
Specimen prepared by roller compactor
BS EN 12697-34, Bituminous mixtures Test methods for hot mix asphalt Part 34:
Marshall test
BS EN 13043, Aggregates for bituminous mixtures and surface treatments for roads,
airfields and other trafficked areas
BS EN 13108-1, Bituminous mixtures Material specifications Part 1: Asphalt concrete
BS EN 13108-4, Bituminous mixtures Material specifications Part 4: Hot rolled asphalt
BS EN 13108-5, Bituminous mixtures Material specifications Part 5: Stone mastic
asphalt
BS EN 13108-21, Bituminous mixtures Material specifications Part 21: Factory
production control
BS EN 13501-1, Fire classification of construction products and building elements
Classification using test data from reaction to fire tests
BS EN 13808, Bitumen and bituminous binders Framework for specifying cationic
bituminous emulsions
BS EN 13924, Bitumen and bituminous binders Specifications for hard paving grade
bitumens
BS EN 14023, Bitumen and bituminous binders Framework specification for polymer
modified bitumens
BS EN 15322, Framework for specifying cut-back and fluxed bituminous binders

C.3 Terms, definitions, symbols and abbreviations

C.3.1

Terms and definitions

For the purposes of this Appendix, the terms and definitions given in BS EN 13108-1
together with the following apply.
C.3.1.1
asphalt
homogenous mixture of coarse and fine aggregates, filler aggregate and bituminous
binder which is used in the construction of flexible pavement layers
NOTE:

The asphalt may include one or more additives to enhance the laying characteristics,
performance or appearance of the mixture. Natural asphalt is defined in BS EN 13108-4.

PPR666

Low temperature asphalt

C.3.1.2
warm mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at temperatures at least 20 C below
conventional hot mix asphalt mixtures but still above 100 C
C.3.1.3
half-warm mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at temperatures in the range 70 C to
100 C
NOTE:

Also known as semi-warm mix asphalt.

C.3.1.4
cold mix asphalt
asphalt in which the aggregate particles are continuously graded or gap-graded to form
an interlocking structure that is mixed and laid at ambient temperature
C.3.1.5
emulsion-based cold mix asphalt
cold mix asphalt in which the binder is a bituminous emulsion with a viscosity such that
the mix is workable at ambient temperature
C.3.1.6
foamed asphalt
asphalt in which, during mixing, the binder is caused to foam by the presence of steam,
reducing the surface tension and easing coating of the aggregate particles
C.3.1.7
emulsion content
proportion of bituminous emulsion by mass versus dry aggregate mass in per cent
C.3.1.8
residual anhydrous binder
binder in which water is evaporated
C.3.1.9
residual anhydrous binder content in the mix
residual anhydrous binder content expressed in per cent of the dry aggregate mass
C.3.1.10
moisture content in the mix
water content expressed in per cent of the dry aggregate mass
C.3.2

Symbols and abbreviations

CME

General designation for an emulsion-based cold mix asphalt.

XX D CME

Designation of asphalt mixture type followed by an indication of D, the

upper sieve size of the aggregate in the mixture, in millimetres (mm), and
the general designation for emulsion-based cold mix asphalt.

EXAMPLE:

SMA 6 CME is an emulsion-based cold mix stone mastic asphalt having an upper
sieve size of the aggregate of 6 mm.

PPR666

Low temperature asphalt

C.4 Requirements for constituent materials

C.4.1

General

As in BS EN 13108-1 for emulsion-based cold mix asphalt concrete; or BS EN 13108-5

for emulsion-based cold mix stone mastic asphalt.
C.4.2

Binder

C.4.2.1

General

C.4.2.1.1
The emulsion shall conform to BS EN 13808. The binder shall be emulsion
from paving grade bitumen, modified bitumen, fluxed bitumen or hard grade bitumen
conforming to BS EN 12591, BS EN 14023, BS EN 15322 or BS EN 13924, respectively.
C.4.2.1.2
C.4.2.2

Natural asphalt may be added and shall conform to BS EN 13108-4.

Category of bituminous emulsion

The cationic bituminous emulsion category (B, P, F and breaking value) shall be selected
from BS EN 13808. Depending on the conditions of use, the grade of the bitumen, the
type and grade of modified bitumen and the amount and category of natural asphalt may
be specified.
C.4.3

Aggregates

As in BS EN 13108-1 for emulsion-based cold mix asphalt concrete; or BS EN 13108-5

for emulsion-based cold mix stone mastic asphalt.
C.4.4

Reclaimed asphalt

C.4.4.1
As in BS EN 13108-1 for emulsion-based cold mix asphalt concrete; or
BS EN 13108-5 for emulsion-based cold mix stone mastic asphalt.
C.4.4.2
The use of reclaimed asphalt containing tar is permitted unless otherwise
specified.
NOTE:

All reclaimed asphalt containing coal tar has to be treated in accordance with the latest
Regulatory Position Statement as published by the Environment Agency and also in line
with the advice given in the latest ADEPT document.

C.4.4.3
If reclaimed asphalt is controlled using analysis of particles without removing
the binder, the aggregate grading in the reclaimed asphalt for calculation of the
aggregate grading in the mixture shall be determined in accordance with Appendix D.
C.4.5

Additives

As in BS EN 13108-1 for emulsion-based cold mix asphalt concrete; or BS EN 13108-5

for emulsion-based cold mix stone mastic asphalt.

C.5 Requirements for the cold mix asphalt mixture

C.5.1

General

C.5.1.1
The target composition of the mixture in terms of its constituent materials,
the proportions (in per cent) passing the specified sieves, the target binder content and
where relevant the binder from natural asphalt and the proportion(s) of additive(s) shall

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be declared and documented. The target grading curve shall be declared for the sieve
1.4 D and the sieves as called up in C.5.2.
C.5.1.2
At the target composition the mixture shall conform to the specified
requirements in accordance with this specification.
C.5.1.3
C.5.2

The test results shall be made available.

Composition and grading

As in BS EN 13108-1 for emulsion-based cold mix asphalt concrete; or BS EN 13108-5

for emulsion-based cold mix stone mastic asphalt.
C.5.3

Residual anhydrous content

C.5.3.1
The minimum residual anhydrous binder content shall be specified, either by
requirement from Table C.1 or by requirement from the coating test in C.5.5.
C.5.3.2
The minimum residual anhydrous binder content of the target composition
shall comply with the selected category from Table C.1. The binder content requirements
shall be corrected by multiplying by the factor:
2,650

where:
a

is the apparent particle density, in megagrams per cubic metre (Mg/m 3), determined
on the weighted mean of the total mineral fraction according to BS EN 1097-5.

NOTE:

The binder content includes binder in reclaimed asphalt and natural asphalt when used.

Table C.1 Minimum residual anhydrous binder content, Bmin

Minimum residual
anhydrous binder content
(% to change)

Category

Minimum residual
anhydrous binder content
(% to change)

Category

3.0

Bmin 3.0

5.8

Bmin 5.8

3.5

Bmin 3.5

6.2

Bmin 6.2

4.0

Bmin 4.0

6.6

Bmin 6.6

4.5

Bmin 4.5

7.0

Bmin 7.0

5.0

Bmin 5.0

7.4

Bmin 7.4

5.4

Bmin 5.4

No requirement

Bmin NR

C.5.4

Air voids content

Specimens at the target composition shall be compacted in accordance with

BS EN 12697-31 for 100 gyrations. The bulk density and maximum density shall be
determined in accordance with BS EN 12697-6 (Procedure C, sealed specimen using wax)
and BS EN 12697-6 (Procedure A, volumetric in water), respectively. The air voids content
of the specimens, measured in accordance with BS EN 12697-8, shall lie between
maximum and minimum values selected from the categories in Table C.2 and C.3.

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Table C.2 Maximum air voids

content, Vmax

Table C.3 Minimum air voids

content, Vmin

Maximum air
voids content (%)

Category

Minimum air voids

content (%)

Category

8.0

Vmax 8.0

4.0

Vmin 4.0

10.0

Vmax 10.0

4.5

Vmin 4.5

12.0

Vmax 12.0

5.0

Vmin 5.0

14.0

Vmax 14.0

5.5

Vmin 5.5

16.0

6.0

Vmax 16.0

Vmin 6.0

No requirement

Vmin NR

18.0

Vmax 18.0

20.0

Vmax 20.0

No requirement

Vma NR

C.5.5

Coating and homogeneity

The coating of specimens at the target composition compacted in accordance with

BS EN 12697-31 for 100 gyrations and tested in accordance with ASTM D6998-11 shall
comply with the selected category from Table C.4.
C.5.6

Water sensitivity

Four 150 mm diameter x 75 mm to 100 mm high, cylinder test specimens at the target
composition shall be compacted to refusal by vibratory compaction in a cylindrical metal
mould, using the compaction mould assembly and vibratory hammer described in
BS EN 12697-32. The specimens shall be cured for a period of 72 h at a nominal
temperature of 60 C and then conditioned in air for a minimum period of 12 h at 20 C.
The specimens shall be tested in accordance with BS EN 12697-26 to determine the
IT-CY stiffness (dry), then immersed in water at 20 C for a minimum period of 24 h and
the IT-CY stiffness tests (wet) repeated on each specimen. The water sensitivity shall be
the wet IT-CY stiffness as a proportion of the dry IT-CY stiffness and shall comply with
the selected category for the indirect tensile strength ratio or compressive strength ratio
from Table C.5.
Table C.4 Minimum coating, Cmin
Minimum coating
(%)

Category

75
70
No requirement

Table C.5 Minimum water

sensitivity, IT-CYwet/dry

Cmin75

Minimum ratio
(%)

Category

Cmin 70

IT-CY wet/dry 80

IT-CY wet/dry 70

IT-CY wet/dry 60

IT-CY wet/dry 50

No requirement

IT-CY wet/dry NR

min NR

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C.5.7

Resistance to permanent deformation (Rut depth and rut rate in wheeltracking)

The resistance to permanent deformation of specimens at the target composition

compacted in accordance with BS EN 12697-33 to the air voids content determined for
0 1.0 % and tested (28 1) days later (when stored at ambient temperature) or
(7 days 4 h) later (when stored at (40 5) C) in accordance with BS EN 12697-22
shall comply with the selected category from Tables C.6 or C.7.
Table C.6 Resistance to
permanent deformation, small size
device, Procedure B, conditioning in
air, maximum wheel tracking slope,
WTSAIR

Table C.7 Resistance to

permanent deformation, small size
device, Procedure B, conditioning in
air, maximum proportional rut
depth, PRD

Maximum wheel tracking

slope
(mm per 103 load cycles)

Category

Maximum
proportional rut
depth (%)

Category

0.03

WTSAIR 0.03

1.0

PRD AIR 1.0

0.05

WTSAIR 0.05

1.5

PRD AIR 1.5

0.07

WTSAIR 0.07

2.0

PRD AIR 2.0

0.10

WTSAIR 0.10

3.0

PRD AIR 3.0

0.15

WTSAIR 0.15

5.0

PRD AIR 5.0

0.20

WTSAIR 0.20

7.0

PRD AIR 7.0

0.30

WTSAIR 0.30

9.0

PRD AIR 9.0

0.40

WTSAIR 0.40

No requirement

PRD AIR NR

0.50

WTSAIR 0.50

0.60

WTSAIR 0.60

0.80

WTSAIR 0.80

1.00

WTSAIR 1.00

No requirement

WTSAIR NR

C.5.8

Reaction to fire

Cold mix asphalt is class Cfl reaction to fire according to BS EN 13501-1 without testing.
C.5.9

Resistance to fuel for application on airfields

The resistance to fuel of specimens at the target composition measure in accordance

with BS EN 12697-43 shall comply with the selected category from good, moderate, poor
or no requirement.
NOTE:

The classifications will have to be defined here after the current revision of
BS EN 12697-43, which will remove the definition of the categories good, moderate and
poor in that document, is published.

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C.5.10 Marshall values for application on airfields

The Marshall stability, the Marshall flow and the Marshall quotient, of specimens at the
target composition compacted in accordance with BS EN 12697-30 and tested
(28 1) days later (when stored at ambient temperature) or (7 days 4 h) later (when
stored at (40 5) C) in accordance with BS EN 12697-34 shall comply with the
selected categories in Tables C.8, C.9 and C.10, respectively. When both a minimum
and maximum value for Marshall flow are selected, the range shall be at least 2.
Table C.8 Minimum and minimum Marshall stability, Smin and Smax
Marshall stability (kN)

Minimum
category

Maximum
category

15.0

Smax 15.0

12.5

Smin 12.5

Smax 12.5

10.0

Smin 10.0

Smax 10.0

7.5

Smin 7.5

Smax 7.5

5.0

Smin 5.0

2.5

Smin 2.5

No requirement

Smin NR

Smax NR

Table C.9 Marshall flow, F

Marshall flow
(mm)

Minimum
category

Maximum
category

Fmin 1

1.5

Fmin 1.5

Fmin 2

Table C.10 Minimum Marshall

quotient, Qmin
Minimum Marshall quotient
(kN/mm)

Category

4.0

Qmin 4.0

Fmax 2

3.5

Qmin 3.5

Fmin 3

Fmax 3

3.0

Qmin 3.0

Fmin 4

Fmax 4

2.5

Qmin 2.5

Fmax 5

2.0

Qmin 2.0

Fmax 8

1.5

Qmin 1.5

No requirement

Fmin NR

Fmax NR

1.0

Qmin 1.0

No requirement

Qmin NR

C.5.11 Compactibility
The minimum air voids content of samples at the target composition, determined in
accordance with BS EN 12697-10, after compaction by 10 gyrations shall comply with
the selected category from Table C.11.

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Table C.11 Maximum void content at 10 gyrations, V10Gmin

Maximum void content at
10 gyrations (%)

Category

25.0

V10Gmin 25

20.0

V10Gmin 20

18.0

V10Gmin 18

14.0

V10Gmin 14

11.0

V10Gmin 11

9.0

V10Gmin 9

No requirement

V10Gmin NR

C.5.12 Stiffness
The stiffness of specimens at the target composition cored in accordance with
BS EN 12697-27 from a slab compacted in accordance with BS EN 12697-33 to the air
voids content determined for C.5.4 1.0 % and tested (28 1) days (when stored at
ambient temperature) or (7 days 4 h) (when stored at (40 5) C) after compaction
in accordance with BS EN 12697-26 shall comply with the selected category from
Table C.12.
Table C.12 Minimum stiffness, Smin
Minimum stiffness
(MPa)

Category

Minimum stiffness
(MPa)

Category

9 000

Smin 9 000

1 800

Smin 1 800

7 000

Smin 7 000

1 500

Smin 1 500

5 500

Smin 5 500

1 200

Smin 1 200

4 500

Smin 4 500

1 000

Smin 1 000

3 600

Smin 3 600

800

Smin 800

2 800

Smin 2 800

600

Smin 600

2 200

Smin 2 200

No requirement

Smin NR

C.5.13 Resistance to permanent deformation in tri-axial compression test

The creep rate of specimens at the target composition cored in accordance with
BS EN 12697-27 from a slab compacted in accordance with BS EN 12697-33 to the air
voids content determined for C.5.4 1.0 % and tested (28 1) days (when stored at
ambient temperature) or (7 days 4 h) (when stored at (40 5) C) after compaction
in accordance with BS EN 12697-25 shall comply with the selected category from
Table C.13.

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Table C.13 Maximum creep rate, fcmax

Creep rate fc
(m/m/N)

Category

Creep rate fc
(m/m/N)

Category

0.2

fcmax 0.2

fcmax 2

0.4

fcmax 0.4

fcmax 4

0.6

fcmax 0.6

fcmax 6

0.8

fcmax 0.8

fcmax 8

1.0

fcmax 1.0

fcmax 10

1.2

fcmax 1.2

fcmax 12

1.4

fcmax 1.4

fcmax 14

1.6

fcmax 1.6

fcmax 16

No requirement

fcmax NR

C.5.14 Dangerous substances

As in BS EN 13108-1 for emulsion-based cold mix asphalt concrete; or BS EN 13108-5
for emulsion-based cold mix stone mastic asphalt.
C.5.15 Conflicting specifications
As in BS EN 13108-1 for emulsion-based cold mix asphalt concrete; or BS EN 13108-5
for emulsion-based cold mix stone mastic asphalt.

C.6 Identification
The delivery ticket shall contain at least the following information relating to
identification:
the manufacturer and mixing plant;
designation of the mixture:
AC/SMA
where:

NOTE:

AC
SMA
D
Surf
base
bin
binder
CME

surf/base/bin
is
is
is
is
is
is
is
is

Binder

CME

Asphalt Concrete;
Stone Mastic Asphalt;
the upper sieve size;
the surface course;
the base course;
the binder course;
the designation of binder used;
emulsion-based Cold Mix Asphalt.

Example: AC 14 surf C60 B5 CME.

C.7 Transport, laying and compaction

C.7.1
This clause gives general requirements for the transport, placing and
compaction of bituminous mixtures, which are complementary and additional to the
requirements of BS 594987. These requirements and the requirements of BS 594987
shall apply to all emulsion-based cold mix asphalt mixtures, unless otherwise specified in
C.7.2 to C.7.4 of this Appendix.

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NOTE:

C.7.2 The substrate onto which emulsion-based cold mix asphalt is to be laid shall
have a stiffness determined by in situ testing using a dynamic plate from the selected
category in Table C.14.
Table C.14 Minimum stiffness of substrate, Sf min

NOTE:

Minimum stiffness (MPa)

Category

500

Sf min 500

400

Sf min 400

300

Sf min 300

250

Sf min 250

200

Sf min 200

150

Sf min 150

100

Sf min 100

Sf min 50

No requirement

Sf min NR

Emulsion-based cold mix asphalt mixtures are hybrid granular materials and, therefore,
need a slightly different approach to traditional hot mix asphalt.

C.7.3 Where the existing substrate fails to comply with C.7.2, the substrate shall be
stabilised or replaced so that the stabilised or replaced substrate does comply.
C.7.4 No minimum delivery or rolling temperatures for cold mix asphalt mixture shall
be enforced.
C.7.5 Compaction of emulsion-based cold mix asphalt shall include not less than four
passes with a pneumatic tyre roller (PTR). For layers other than the surface course, this
requirement can be omitted with prior approval by the Overseeing Organisation.

C.8 Compliance
C.8.1

General

C.8.1.1
Compliance with the requirements for mixture composition and properties
(C.4 and 0) shall be by type testing to C.8.2 and factory production control to C.8.3. A
certificate defining compliance supported by test reports shall be made available for
inspection.
C.8.1.2
Audit checking to confirm that the mixture composition and properties
claimed are those of the mixture delivered to site may be undertaken.
C.8.1.3
Compliance with the requirements for transporting, laying and compacting
the asphalt (C.7) shall be monitored against the requirements of BS 594987 and test
reports demonstrating compliance shall be made available for inspection.

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C.8.2

Type testing

C.8.2.1
For each mix formulation, type testing shall be carried out to provide proof
that the formulation meets the relevant requirements. A complete set of tests or other
procedures shall be undertaken to determine the performance of samples of bituminous
mixtures representative of the product type against all the required properties.
C.8.2.2
Where raw materials are used whose characteristics have already been
determined by the material supplier on the basis of conformity with other technical
specifications, these characteristics need not be reassessed provided that the raw
materials performance remain the same.
C.8.2.3
All testing shall be carried out strictly in accordance with the appropriate test
method on samples taken strictly in accordance with the appropriate sampling method to
be representative of the normal constituents and mixed materials.
C.8.2.4
Type testing shall be carried out before the mixture is used and then at a
frequency of at least once every five years.
C.8.3

Factory production control

C.8.3.1
The manufacturer shall establish, document and maintain a Factory
Production Control (FPC) system to ensure that the products placed on site comply with
the declared performance of the required properties. The FPC system shall consist of
procedures, regular inspections and tests and/or assessments and the use of the results
to control raw and other incoming materials or components, equipment, the production
process and the product.
C.8.3.2
The manufacturer shall establish and maintain his policy and procedures for
Factory Production Control in a quality plan. The quality plan shall particularly include a
means for identifying and detailing the specific processes, which directly affect product
quality and conformity. The quality plan shall particularly include:
manufacturers organisational structure relating to conformity and quality;
document control;
control procedures for constituent materials and purchaser supplied product;
process control;
requirements for the handling and storage of the product;
plant calibration and maintenance;
requirements for inspection and testing of processes and products;
procedures for handling non-conformity
frequencies of inspection and testing.
C.8.3.3
The quality plan shall identify those items of measuring equipment which
require calibration. The frequency of such calibration shall comply with the requirements
of Table C.15.

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Table C.15 Minimum plant calibration requirements

Item of plant

Weighing equipment

Inspection/test

Purpose

Minimum frequency

Visual inspection as
described in
procedures

To ascertain that
weighing equipment is
functioning correctly

Daily

Testing of weighing
accuracy
(recalibration)

To ensure accuracy
within quality plan
requirements

To ascertain that
Organoleptic inspection dispenser is functioning
correctly
Admixture dispensers

a) On installation *,
b) Every year, and
c) In case of doubt
First batch of the day
containing admixture

Test for accuracy as

described in
procedures.

To ensure accuracy
within quality plan
requirements

a) On installation *,

Comparison of the
actual amount with the
metered amount by
reconciliation

To ensure accuracy
within quality plan
requirements

a) On installation *,

Batching system
(on batch plants)

Comparison of actual
mass of constituents in
the batch with the
intended mass using
the method
prescribed in the
quality plan

To ascertain the
batching accuracy in
accordance with the
quality plan

a) On installation *,

Proportioning system
(on continuous plants)

Comparison of actual
mass in a measured
period of time with the
intended mass using
the method prescribed
in the quality plan

Flow meters

Temperature,
monitoring equipment

b) Every year, and

c) In case of doubt

b) Every year, and

c) In case of doubt

b) Every year, and

c) In case of doubt

a) On installation *,
To ascertain the
accuracy in accordance b) Every year, and
with the quality plan c) In case of doubt

Visual as described in
procedures

To ascertain the
equipment is
functioning correctly

Test of accuracy as
described in
procedures.

To ensure correct
temperatures are
recorded

Daily
a) On installation *,
b) Every year, and
c) In case of doubt

NOTE:

In case of doubt refers to the reasonable judgement of an experienced plant operator

Or after comprehensive repair

C.8.3.4
Incoming constituent materials shall be inspected and tested using
procedures detailed in the quality plan and to a schedule complying with Table C.16 for
aggregates, Table C.17 for filler, Table C.18 for binders, Table C.19 for additives and
Table C.20 for reclaimed asphalt.
NOTE:

These tables may include the results of tests and inspections by the supplier as part of
his Factory Production Control.

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Table C.16 Minimum inspection and test frequencies for aggregates

Inspection/Test

Purpose

Frequency

Tests for intrinsic properties of

aggregate (strength etc.)

To check suitability for intended use

Source approval before initial

use in accordance with
BS EN 13043

Inspection of delivery ticket *

To check consignment is as ordered

and from correct source

Each delivery

Organoleptic check of stockpile *

For comparison with normal

appearance with respect to source,
grading, shape and impurities

Daily
a) First delivery from new
source,

By sieve analysis

To assess compliance with standard

b) In case of doubt following
or other agreed grading
organoleptic check, and
c) 1 per 2 000 t / product / size

Shape, crushed particle index,

etc.

a) First delivery from new

source,
To assess compliance with standard
or other agreed specification
b) In case of doubt, and
c) As indicated in quality plan

Moisture content
*

Process control

As indicated in the quality plan

These requirements will not apply in the case of direct supplies from an aggregate production
unit to an asphalt plant on the same site.

Table C.17 Minimum inspection and test frequencies for filler

Inspection/test

Purpose

Frequency

Tests for intrinsic properties of

filler (bulk density, stiffening
properties etc.)

To check suitability for

intended use

Supplier approval before initial use in

accordance with BS EN 13043

Inspection of delivery ticket

To check consignment is as
ordered and from the correct
source

Each delivery

Sieve analysis

To check compliance with

standard or other agreed
grading

a) First delivery from new source, and

b) As indicated in the quality plan

Table C.18 Minimum inspection and test frequencies for binders

Inspection/test

Purpose

Frequency

Intrinsic properties of binder

To confirm characteristics of
product and compliance with
appropriate specification

Source approval before initial

use in accordance with the
relevant binder standards

Inspection of delivery ticket

To check consignment is as
ordered and from the correct
source

Each delivery

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Table C.19 Minimum inspection and test frequencies for additives

Inspection/test

Purpose

Frequency

Appropriate tests to determine intrinsic

properties

To confirm characteristics of
product or check compliance
with specification

Inspection of delivery ticket

To check that consignment is

as ordered and from the
correct source

Each delivery

Organoleptic check of consignment

For comparison with normal

appearance

Each delivery, if practicable;

otherwise in accordance with
quality plan

a) Source approval prior to

initial use and
b) As stated in the quality plan

Table C.20 Minimum inspection and test frequencies for reclaimed asphalt
Inspection/test

Purpose

Frequency

Organoleptic check of feedstock

For comparison with normal

appearance with respect to
source, grading, shape and
impurities

Daily

Moisture content

Process control

As indicated by the quality plan

C.8.3.5
The finished bituminous mixture shall be inspected and tested using
procedures detailed in the quality plan and to a schedule complying with the
requirements of this clause, Table C.21 and Table C.22. Appropriate statistical records
shall be maintained in order to monitor and verify process capability and product
characteristics.
Table C.21 Minimum inspection/test frequencies for delivered product
Inspection/test

Purpose

Frequency

Organoleptic check on mixed asphalt

For comparison with normal

appearance with respect to
grading, evenness of mixing
and adequacy of coating

Every load

Grading and binder content

To ensure material conforms to

specification

Weekly

Other characteristics included in

technical specifications

To assess conformity

As detailed in quality plan

Cleanliness of delivery vehicles by

visual assessment

To avoid contamination

Every load prior to loading

C.8.3.6
The construction tolerances of individual measurements from the target
grading and binder contents shall be as given Table C.22.

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Table C.22 Construction tolerances from the target in absolute proportion

individual samples
Sieve size / binder content

Tolerance about target composition (%)

Small aggregates

Large aggregates

8 +5

9 +5

Characteristic coarse sieve

2 mm

Characteristic fine sieve

0,063 mm

Soluble binder content

0.5

0.6

NOTE 1: Small aggregate mixtures have D < 16 mm; large aggregate mixtures have D 16 mm.
NOTE 2: A tolerance of 2 % shall apply to the requirement of 100 % passing 1.4 D.

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Appendix D Aggregate grading of reclaimed asphalt

(Normative)
D.1 Approach
D.1.1 The grading of the reclaimed asphalt can be used as the grading of the
aggregate in the reclaimed asphalt if:
the reclaimed asphalt is sufficiently aged so that the conglomerated particles on it will
not be broken down during the mixing process; and/or
the reclaimed asphalt is to be added at a small enough proportion that the difference
in the grading of the reclaimed asphalt and that of the aggregate particles in the
reclaimed asphalt will not significantly affect the overall grading of the new mixture.
NOTE 1: The first option is when the reclaimed asphalt is regarded as black rock.
NOTE 2: The second option is generally when the reclaimed asphalt at proportions up to about
10 %.

D.1.2

If D.1.1 is not applicable, carry out a comparison in accordance with D.2 to D.5.

D.2 Fractions
A sample shall be taken of each fraction that the reclaimed asphalt will be separated into
for production in accordance with BS EN 12697-27.
NOTE:

The use of more fractions, whilst requiring more analysis, will allow the required
aggregate and binder contents to be met more easily, particularly at high proportions of
reclaimed asphalt.

D.3 Analysis
D.3.1 Take a sample of the reclaimed asphalt particles from each stockpile containing
a fraction in accordance with BS EN 12697-27.
D.3.2 If required, determine the grading of each sample in accordance with
BS EN 12697-2.
D.3.3 Analyse the sample in accordance with BS EN 12697-1 for binder content and
the grading of the aggregate particles in the fraction in accordance with BS EN 12697-2.

D.4 Results
D.4.1 If required, the grading analysis from D.3.2 can be plotted against the analysis
from D.3.3 to determine the extent of the difference.
D.4.2 The contribution to the binder content of the new mixture from the reclaimed
asphalt shall be determined as:
(
where: bRA

is the binder content of the new mixture from the reclaimed asphalt

bf, i

is the binder contents of fraction i determined in D.3.3

pf, i

is the proportion of fraction i of the reclaimed asphalt added to the new

mixture.

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D.4.3 The contribution to the aggregate in the new mixture passing each sieve size
from the reclaimed asphalt shall be determined as:
(

where: aRA, j is the proportion of aggregate in the new mixture that passes sieve size j
and comes from the reclaimed asphalt
bf, i

is the proportion of aggregate passing sieve size j from fraction i

determined in D.3.3

pf, i

is the proportion of fraction i of the reclaimed asphalt added to the new

mixture.

D.5 Validity
D.5.1 The grading of the reclaimed asphalt particles in the fraction shall be determined
not less than once per 500 tonnes of production of that fraction or whenever the
source(s) of reclaimed asphalt change.
NOTE:

Where the reclaimed asphalt is sourced from multiple sources, a change would be
considered to have occurred if the proportion from any one of the sources changes by
more than 20 %.

D.5.2 The conversion of the grading of the reclaimed asphalt particles into the grading
of the aggregate particles and associated binder content shall only be valid providing the
grading of the reclaimed asphalt particles in the fraction does not differ from that
determined in D.4.3 by more than 5 % for each sieve size other than 0.06 mm and by
more than 1 % for the 0.06 mm sieve.

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Appendix E Example standard specification for halfwarm asphalt concrete

(informative)
E.1 General
Half-warm mix asphalt concrete mixtures shall conform to the specification for half-warm
mix asphalt in Appendix B.

E.2 Constituent materials

E.2.1

Binder

The binder shall be paving grade bitumen conforming to BS EN 12591 or polymermodified bitumen conforming to BS EN 14023.
E.2.2
E.2.2.1

Bitumen
Paving grades

E.2.2.1.1
The preferred paving grades for half-warm mix asphalt concrete are
30/45, 40/60, 70/100, 100/150, 160/220 and 250/330.
NOTE:

70/100 and 100/150 pen paving grade bitumen may be produced by blending in the
mixer at the asphalt plant.

E.2.2.1.2
Paving grades can be blended. The grades used for blending shall be not
harder than 30/45 pen or softer than 160/220 pen, and shall conform to BS EN 12591.
The producer shall be able to demonstrate that the plant is capable of adequately
blending the bitumens. Measures for ensuring consistency of proportioning of the blend
shall be included in plant quality management systems. These shall include evidence of
type tests carried out on a laboratory blend of the bitumens to demonstrate conformity
to BS EN 12591. The quality assurance/management systems shall also include the
steps to be taken to demonstrate the continuing adequacy of the process following
significant changes being made to those parts of the plant involved in the process of
bitumen blending. No grades of bitumen harder than 70/100 pen shall be blended in the
mixer.
NOTE 1: Other grades may be in-plant blended provided that the resulting bitumen can be
sampled and tested before it is added to the aggregate to ensure it conforms to
BS EN 12591.
NOTE 2: The grades of binders recommended here are suitable for machine-laid materials. For
hand-laid mixtures and for deferred set and depot stock mixtures, petroleum bitumen
conforming to BS EN 12591:2000, Table 1, Grade 160/220 or 250/330 pen, to which a
flux oil conforming to the requirements shown in E.2.3 has been added, should be used.

E.2.2.2

Polymer modified bitumen

NOTE:

Because polymer-modified bitumens in the UK are proprietary materials, selection of an

appropriate polymer modified bitumen should be agreed between supplier and user.

E.2.3

Fluxing of hand-laid materials

As in Appendix B of PD 6691.

PPR666

Low temperature asphalt

E.2.4
E.2.4.1

Aggregates
General

As in Appendix B of PD 6691.
E.2.4.2

Water content of aggregates

If the system has been pre-selected, the minimum and/or maximum water contents of
the aggregate or a specified aggregate fraction can be limited, otherwise the aggregate
shall be classed as WAmin NR and WAmax NR.
E.2.5

Additives

As in Appendix B of PD 6691.

E.3 Mixture specifications

E.3.1

Binder content

As in Appendix B of PD 6691.
E.3.2
E.3.2.1

Designed base mixtures

Aggregate grading and binder content

As in Appendix B of PD 6691 except that the binder shall conform to BS EN 12591 grade
100/150, 70/100, 35/50 or 20/30.
E.3.2.2

Air voids content

As in Appendix B of PD 6691.
E.3.2.3

Resistance to permanent deformation

As in Appendix B of PD 6691.
E.3.3
E.3.3.1

Designed binder course mixtures

Aggregate grading and binder content

As in Appendix B of PD 6691 except that the binder shall conform to BS EN 12591 grade
100/150, 70/100, 35/50 or 20/30.
E.3.3.2

Air voids content

As in Appendix B of PD 6691.
E.3.3.3

Resistance to permanent deformation

As in Appendix B of PD 6691.
E.3.4
E.3.4.1

EME2 mixtures
Aggregate grading and binder content

As in Appendix B of PD 6691.

PPR666

Low temperature asphalt

E.3.4.2

Air voids content

As in Appendix B of PD 6691.
E.3.4.3

Water sensitivity

As in Appendix B of PD 6691.
E.3.4.4

Deformation resistance

As in Appendix B of PD 6691.
E.3.4.5

Stiffness modulus

As in Appendix B of PD 6691.
E.3.4.6

Fatigue properties

As in Appendix B of PD 6691.
E.3.5
E.3.5.1

Recipe dense base and binder course

Aggregate grading and binder content

As in Appendix B of PD 6691 except that the binder shall conform to BS EN 12591 grade
100/150, 70/100, 35/50 or 20/30.
E.3.6

Other base and binder course

As in Appendix B of PD 6691 except that the binder shall conform to BS EN 12591 grade
160/220, 100/150 or 70/100.
E.3.7
E.3.7.1

Recipe surface courses

Paving graded surface course

As in Appendix B of PD 6691 except that the binder shall conform to BS EN 12591 grade
160/220 or 100/150.
E.3.7.2

Close graded surface course

As in Appendix B of PD 6691 except that the binder shall conform to BS EN 12591 grade
160/220, 100/150, 70/100 (preferred grade) or 50/70.
E.3.7.3

Dense, medium graded and fine graded surface course

As in Appendix B of PD 6691 except that advice on the selection of binder grade is given
in Table E.1.

PPR666

Low temperature asphalt

Table E.1 Guidance on selection of binder grades

Paving grade

AC 6 dense surf

AC 6 med surf

AC 4 fine surf

50/70

100/150

160/220

70/100

* Preferred grade.

E.3.8

Water content of asphalt

The water content of freshly mixed half-warm mix asphalt shall be determined in
accordance with BS EN 12697-14. The maximum water content shall comply with
category WCmax 2.0.
E.3.9

Temperature of the mixture

The maximum temperature of a half-warm mix asphalt concrete, measured according to

BS EN 12697-13, shall target 100 C but shall not exceed 110 C.
NOTE:

BS 594987 does not give guidance on suitable minimum temperatures at delivery and for
compaction of half-warm mixtures; the supplier of the mixture should provide details.

E.4 Transport, laying and compaction

E.4.1
This clause gives general requirements for the transport, placing and
compaction of bituminous mixtures, which are complementary and additional to the
requirements of BS 594987. These requirements and the requirements of BS 594987
shall apply to all half-warm mix asphalt mixtures, unless otherwise specified in E.4.2 of
this Appendix.
NOTE:

E.4.2 Minimum delivery and rolling temperatures for half-warm mix asphalt mixtures
shall be declared by the supplier with evidence to support their suitability.

E.5 Compliance
E.5.1 Compliance with the requirements for mixture composition and properties (E.1
to E.3) shall be by type testing and factory production control. The factory production
control shall be in accordance with the principles and frequencies of BS EN 13108-21. A
certificate defining compliance supported by test reports shall be made available for
inspection.
E.5.2 Audit checking to confirm that the mixture composition and properties claimed
are those of the mixture delivered to site may be undertaken.
E.5.3 Compliance with the requirements for transporting, laying and compacting the
asphalt (E.4) shall be monitored against the requirements of BS 594987 and test reports
demonstrating compliance shall be made available for inspection.

PPR666

Low temperature asphalt

Appendix F Example of standard specification for halfwarm hot rolled asphalt

(Informative)
F.1 General
Half-warm mix hot rolled asphalt mixtures shall conform to the specification for halfwarm mix asphalt in Appendix B.

F.2 Constituent materials

F.2.1

Binder

As in Appendix C of PD 6691.
F.2.2

Paving grades

As in Appendix B of PD 6691 except for the notes 1 and 3.

NOTE 1: The preferred paving grade for HRA is 35/50. The following grades are also suitable:
30/45, 40/60, and 70/100.
NOTE 3: 35/50, 70/100 and 100/150 pen paving grade bitumen may be produced by blending in
the mixer at the asphalt plant.

F.2.3
F.2.3.1

Aggregates
General

As in Appendix C of PD 6691.
F.2.3.2

Water content of aggregates

Additives

As in Appendix C of PD 6691.
F.2.5

Coated chippings for application to the surface course

Chippings shall not be used in half-warm mix hot rolled asphalt surface courses.

F.3 Mixture specifications

F.3.1

Target binder content

As in Appendix C of PD 6691.
F.3.2

Base and binder course mixtures

As in Appendix C of PD 6691.

PPR666

Low temperature asphalt

F.3.3

Surface course mixtures

As in Appendix C of PD 6691.
F.3.4

Water content of asphalt

The water content of freshly mixed half-warm mix asphalt shall be determined in
accordance with BS EN 12697-14. The maximum water content shall comply with
category WCmax 2.0.
F.3.5

Temperature of the mixture

The maximum temperature of a half-warm mix hot rolled asphalt, measured according to
BS EN 12697-13, shall target 100 C but shall not exceed 110 C.
NOTE:

BS 594987 does not give guidance on suitable minimum temperatures at delivery and for
compaction of half-warm mixtures; the supplier of the mixture should provide details.

F.4 Transport, laying and compaction

F.4.1 This clause gives general requirements for the transport, placing and
compaction of bituminous mixtures, which are complementary and additional to the
requirements of BS 594987. These requirements and the requirements of BS 594987
shall apply to all half-warm mix asphalt mixtures, unless otherwise specified in F.4.2 of
this Appendix.
NOTE:

F.4.2 Minimum delivery and rolling temperatures for half-warm mix asphalt mixtures
shall be declared by the supplier with evidence to support their suitability.

F.5 Compliance
F.5.1 Compliance with the requirements for mixture composition and properties (F.1
to F.3) shall be by type testing and factory production control. The factory production
control shall be in accordance with the principles and frequencies of BS EN 13108-21. A
certificate defining compliance supported by test reports shall be made available for
inspection.
F.5.2 Audit checking to confirm that the mixture composition and properties claimed
are those of the mixture delivered to site may be undertaken.
F.5.3 Compliance with the requirements for transporting, laying and compacting the
asphalt (F.4) shall be monitored against the requirements of BS 594987 and test reports
demonstrating compliance shall be made available for inspection.

PPR666

Low temperature asphalt

Appendix G Example of standard specification for halfwarm stone mastic asphalt

(Informative)
G.1 General
Half-warm mix stone mastic asphalt mixtures shall conform to the specification for halfwarm mix asphalt in Appendix B.

G.2 Constituent materials

G.2.1
G.2.1.1

Binder
General

As in Appendix D of PD 6691.
G.2.1.2

Paving grades

As in Appendix D of PD 6691 except that the preferred paving grade for SMA is 35/50;
the following grades are also suitable: 40/60 and 70/100; and 35/50 paving grade may
also be produced by blending in the mixer at the asphalt plant.
G.2.2
G.2.2.1

Aggregates
General

As in Appendix D of PD 6691.
G.2.2.2

Water content of aggregates

Additives

As in Appendix D of PD 6691.

G.3 Mixture specifications

G.3.1

Composition

As in Appendix D of PD 6691.
G.3.2

Grading and binder content

As in Appendix D of PD 6691.
G.3.3

Target binder content

As in Appendix D of PD 6691.

PPR666

Low temperature asphalt

G.3.4

Air voids content

As in Appendix D of PD 6691.
G.3.5

Binder drainage

As in Appendix D of PD 6691.
G.3.6

Water sensitivity

For half-warm mix SMA mixtures with foamed bitumen, the water sensitivity category
shall be ITSR80. For other half-warm mix SMA mixtures, the water sensitivity category
shall be ITSRNR.
G.3.7

Resistance to permanent deformation

As in Appendix D of PD 6691.
G.3.8

Water content of asphalt

The water content of freshly mixed half-warm mix asphalt shall be determined in
accordance with BS EN 12697-14. The maximum water content shall comply with
category WCmax 2.0.
G.3.9

Temperature of the mixture

The maximum temperature of a half-warm mix stone mastic asphalt, measured

according to BS EN 12697-13, shall target 100 C but shall not exceed 110 C.
NOTE:

BS 594987 does not give guidance on suitable minimum temperatures at delivery and for
compaction of half-warm mixtures; the supplier of the mixture should provide details.

G.4 Transport, laying and compaction

The transport, placing and compaction of half-warm mix asphalt mixtures shall be in
compliance with BS 594987.

G.5 Compliance
G.5.1 Compliance with the requirements for mixture composition and properties (G.1
to G.3) shall be by type testing and factory production control. The factory production
control shall be in accordance with the principles and frequencies of BS EN 13108-21. A
certificate defining compliance supported by test reports shall be made available for
inspection.
G.5.2 Audit checking to confirm that the mixture composition and properties claimed
are those of the mixture delivered to site may be undertaken.
G.5.3 Compliance with the requirements for transporting, laying and compacting the
asphalt (G.4) shall be monitored against the requirements of BS 594987 and test reports
demonstrating compliance shall be made available for inspection.

PPR666

Low temperature asphalt

Appendix H Example specification for emulsion-based

cold mix asphalt
(Informative)
H.1 General
Emulsion-based cold mix asphalt mixtures shall conform to the specification for
emulsion-based cold mix asphalt in Appendix C.

H.2 Constituent materials

H.2.1

Binder

The cationic emulsion category shall comply with BS EN 13808 and the breaking value
may be Class 0 (no performance declared, NPD).
H.2.2

Coarse aggregates

As in Appendix B of PD 6691.
H.2.3

Fine aggregate

As in Appendix B of PD 6691.
H.2.4

Added filler

As in Appendix B of PD 6691.
H.2.5

Reclaimed asphalt

Where reclaimed asphalt is to be used in asphalt concrete mixtures the following

requirements shall apply.
a)

All reclaimed asphalt shall be classified in accordance with BS EN 13108-8.

The reclaimed asphalt shall conform to foreign matter category F5.

H.2.6

Additives

As in Appendix B of PD 6691.

H.3 Mixture specification

H.3.1

Composition

As in Appendix B of PD 6691 for emulsion based cold mix asphalt concrete or as in

Appendix D of PD 6691 for emulsion based cold mix stone mastic asphalt.
H.3.2

Properties

H.3.2.1
The mixture at the target composition shall have the selected categories of the
physical properties as given in Tables H.1 and H.2 for roads and Tables H.1 and H.3 for
airfields. For mechanical properties, these shall be as measured (28 1) days (when stored
at ambient temperature) or (7 days 4 h) (when stored at (40 5) C) after compaction.

PPR666

Low temperature asphalt

Table H.1 Minimum property requirements for cold mix asphalt mixtures
Property

Base

Binder course

Surface course

Residual anhydrous content

Bmin 4.0

Bmin 4.5

Bmin 5.0

Low stress sites

Vmax 18.0

Vmax 16.0

Vmax 14.0

Medium stress sites

Vmax 16.0

Vmax 14.0

Vmax 12.0

High stress sites

Vmax 14.0

Vmax 12.0

Vmin 6.0

Vmin 5.0

Vmin 4.0

Maximum air voids

content

Minimum air voids content

Coating

min NR

Low stress sites

IT-CY wet/dry 50

IT-CY wet/dry 60

Medium stress sites

IT-CY wet/dry 60

IT-CY wet/dry 70

High stress sites

IT-CY wet/dry 70

IT-CY wet/dry 80

Compactibility

V10Gmin NR

Resistance to permanent deformation in

tri-axial compression test

fcmax NR

Water sensitivity

Table H.2 Minimum property requirements for cold mix asphalt mixtures
to be used on roads
Property

Base

Binder course

Surface course

WTSAIR NR

WTSAIR 0.40

WTSAIR 0.30

PRDAIR NR

PRDAIR 7.0

PRDAIR 5.0

WTSAIR NR

WTSAIR 0.30

WTSAIR 0.20

PRDAIR NR

PRDAIR 5.0

PRDAIR 3.0

WTSAIR NR

WTSAIR 0.20

WTSAIR 0.15

PRDAIR NR

PRDAIR 3.0

PRDAIR 2.0

Resistance to fuel

No requirement

Resistance to de-icing fuels

Minimum Marshall stability

Smin NR

Maximum Marshall stability

Smax NR

Minimum Marshall flow

Fmin NR

Maximum Marshall flow

Fmax NR

Marshall quotient

Qmin NR

Low stress sites

Smin 800

Smin NR

Medium stress sites

Smin 1 000

Smin NR

High stress sites

Smin 2 000

Smin 1 400

Smin NR

Low stress sites

Resistance to
permanent
deformation

Medium stress sites

High stress sites

Stiffness

PPR666

Low temperature asphalt

Table H.3 Minimum property requirements for cold mix asphalt mixtures
to be used on airfields
Property

Base

Binder course

Surface course

WTSAIR NR

PRDAIR NR

Resistance to fuel

No requirement

Moderate

Resistance to de-icing fuels

Low stress sites

Smin NR

Smin 5.0

Smin 7.5

Medium stress sites

Smin 5.0

Smin 7.5

Smin 10.0

High stress sites

Smin 7.5

Smin 10.0

Smin 12.5

Maximum Marshall stability

Smax NR

Minimum Marshall flow

Fmin NR

Maximum Marshall flow

Fmax NR

Marshall quotient

Qmin NR

Low stress sites

Smin 1 800

Smin NR

Medium stress sites

Smin 2 200

Smin 1 500

Smin NR

High stress sites

Smin 2 800

Smin 1 800

Smin NR

Resistance to permanent deformation

Minimum Marshall
stability

Stiffness

H.4 Transport, laying and compaction

H.4.1
Emulsion-based cold mix asphalt shall be transported, placed and compacted to
the requirements of BS 594987 unless otherwise specified in H.4.2 to H.4.4 of this
appendix.
H.4.2 The substrate onto which emulsion-based cold mix asphalt is to be laid shall
have a stiffness determined by in situ testing using a dynamic plate of Sf min 100.
H.4.3 Where the existing substrate fails to comply with H.4.2, the substrate shall be
stabilised or replaced so that the stabilised or replaced substrate does comply.
H.4.4 Compaction of emulsion-based cold mix asphalt shall include not less than four
passes with a pneumatic tyre roller (PTR). For layers other than the surface course, this
requirement can be omitted with prior approval by the Overseeing Organisation.

H.5 Compliance
H.5.1 Compliance with the requirements for mixture composition and properties (H.1
to H.3) shall be by type testing to C.8.2 of Appendix C and factory production control to
C.8.3 of Appendix C. A certificate defining compliance supported by test reports shall be
made available for inspection.
H.5.2 Audit checking to confirm that the mixture composition and properties claimed
are those of the mixture delivered to site may be undertaken.
H.5.3 Compliance with the requirements for transporting, laying and compacting the
asphalt (H.4) shall monitored against the requirements of BS 594987 and test reports
demonstrating compliance shall be made available for inspection.

PPR666

Low temperature asphalt

PPR666

Low temperature asphalt

Appendix J Specification requirements for low

temperature asphalt mixtures
ROAD PAVEMENTS BITUMINOUS BOUND MATERIALS
J.1 96X Warm Mix Asphalt Materials
J.1.1

SHW 943 for warm mix hot rolled asphalt

surface course and binder course
(performance-related design mixtures)

General

3.
The requirements of SHW 901 for
bituminous pavement materials, SHW 902 for
reclaimed bituminous materials, SHW 903 for
placing and compaction of bituminous
mixtures, SHW 907 for regulating course and
SHW 920 for bond coats, tack coats and other
bituminous sprays shall apply to warm mix
asphalt mixtures.

1.
The warm mix asphalt mixtures shall
conform to the specification for warm mix
asphalt in Appendix A of this Report; the
relevant example specification in PD 6691;
and requirements specified in Appendix 7/1.
2.
The requirements in the Specification
for Highway Works (SHW) for specific hot mix
asphalt mixtures shall also apply to warm mix
asphalt of the same material type.
In
particular:
SHW 904 for
asphalt base

warm

mix

hot

J.1.2

Variations

4.
The temperature at which samples for
assessing the properties of the mixture are
mixed and compacted shall be at the
standard temperature for each operation less
the difference between the temperature at
which the warm asphalt will be prepared on
site and the temperature at which hot asphalt
will be prepared on site.

rolled

SHW 905 for warm mix hot rolled

asphalt binder course (recipe mixtures)
SHW 906 for warm mix dense base and
binder course asphalt concrete with
paving grade bitumen (recipe mixtures)

5.
The relevant technology that allows the
asphalt to be mixed and laid at a reduced
temperature shall be employed in the
manufacture of laboratory samples used to
demonstrate the properties of the asphalt
mixture.
If the technology cannot be
replicated in the laboratory, plant-produced
samples shall be used for type testing and
factory production control.

SHW 909 for warm mix 6 mm dense

asphalt concrete surface course
SHW 910 for warm mix hot rolled
asphalt surface course (recipe mixtures)
SHW 911 for warm mix hot rolled asphalt
surface course (design mixtures)
SHW 912 for warm mix close graded
asphalt concrete surface course

6.
However, when testing samples of
warm mix asphalt for refusal density, the
sample shall be heated to the same
temperature as an equivalent hot mix asphalt
before compaction.

SHW 914 for warm mix fine graded

asphalt concrete surface course
SHW 916 for warm mix open graded
asphalt concrete surface course
SHW 929 for warm mix dense base and
binder course asphalt concrete (design
mixtures)

J.1.3

Additives

7.
Evidence shall be provided on the
suitability of any additive incorporated into
the mixture to the Overseeing Organisation
before work commences. This evidence may
be based on research combined with evidence
from practice.

SHW 937 for warm mix stone mastic

asphalt (SMA) binder course and
regulating course
SHW 938 for warm mix porous asphalt
surface course
SHW 942 for warm mix thin surface
course systems

PPR666

Low temperature asphalt

J.1.4

Coated chippings

8.
Coated chippings shall not be applied to
HRA surf WMA mixtures.
J.1.5

Health and Safety

9.
Health and Safety information and safe
handling guidance shall be provided, including
any COSHH data sheets for any component
materials.

J.2 96Y Half-Warm Mix Asphalt

Materials
J.2.1

General

2.
If not a thin surfacing system, the
mixture designation shall be one of the
following:

(iii)
(iv)
(v)
(vi)
(vii)
(viii)
(ix)

HRA 60/32 base 35/50 HWMA.

HRA 60/20 base 35/50 HWMA.
HRA 60/32 bin 35/50 HWMA.
HRA 60/20 bin 33/50 HWMA.
AC 32 dense base 35/50 rec HWMA.
AC 32 dense base 70/100 rec HWMA.
AC 32 dense base 100/150 rec HWMA.
AC 32 dense bin 35/50 rec HWMA.
AC 32 dense bin 70/100 rec HWMA.

(x)
(xi)

AC 6 dense surf 70/100 HWMA.

AC 6 dense surf 50/70 HWMA.

(xii)
(xiii)

HRA 0/2 F surf 35/50 HWMA.

HRA 15/10 F surf 35/50 HWMA.

(xiv)
(xv)
(xvi)
(xvii)
(xviii)
(xix)

HRA
HRA
HRA
HRA
HRA
HRA

(xx)
(xxi)
(xxii)
(xxiii)

AC
AC
AC
AC

(xxiv)
(xxv)

AC 4 fine surf 100/150 HWMA.

AC 4 fine surf 160/220 HWMA.

close
close
close
close

surf
surf
surf
surf

(xxxii)
(xxxiii)
(xxxiv)

AC 32 HDM base 35/50 des HWMA.

AC 32 dense base 35/50 des HWMA.
AC 32 HMB base 20/30 des HWMA.
AC
AC
AC
AC
AC
AC

10
10
10
14
14
14

20
32
20
32
20
32

open
open
open
open
open
open

surf
surf
surf
surf
surf
surf

100/150 HWMA.
70/100 HWMA.
50/70 HWMA.
100/150 HWMA.
70/100 HWMA.
70/100 HWMA.

HDM bin 35/50 des HWMA.

HDM bin 35/50 des HWMA.
dense bin 35/50 des HWMA.
dense bin 35/50 des HWMA.
HMB bin 20/30 des HWMA.
HMB bin 20/30 des HWMA.

(xli)
(xlii)
(xliii)
(xliv)

SMA
SMA
SMA
SMA

6
6
6
6

(xlv)
(xlvi)
(xlvii)
(xlviii)

SMA
SMA
SMA
SMA

10
10
10
10

bin
bin
bin
bin

35/50 HWMA.
50/70 HWMA.
70/100 HWMA.
PMB HWMA.

(xlix)
(l)
(li)
(lii)

SMA
SMA
SMA
SMA

14
14
14
14

bin
bin
bin
bin

35/50 HWMA.
50/70 HWMA.
70/100 HWMA.
PMB HWMA.

(liii)
(liv)
(lv)
(lvi)

SMA
SMA
SMA
SMA

20
20
20
20

bin
bin
bin
bin

35/50 HWMA.
50/70 HWMA.
70/100 HWMA.
PMB HWMA.

(lvii)
(lviii)
(lix)

bin
bin
bin
bin

35/50 HWMA.
50/70 HWMA.
70/100 HWMA.
PMB HWMA.

PA 20 surf HWMA.
PA 14 surf HWMA.
PA 10 surf HWMA.

3.
Unless
otherwise
specified
in
Appendix 7/1, the grade of bitumen for HRA
surf xx/yy des HWMA mixtures shall be
35/50.
4.
When the mixture designation is not
specified in Appendix 7/1, the mixture
selected by the Contractor shall be notified to
the Overseeing Organisation prior to its use in
the Works.

0/2 F surf xx/yy des HWMA.

55/10 F surf xx/yy des HWMA.
55/14 F surf xx/yy des HWMA.
0/2 C surf xx/yy des HWMA.
55/10 C surf xx/yy des HWMA.
55/14 C surf xx/yy des HWMA.

10
10
14
14

AC
AC
AC
AC
AC
AC

(xxxv)
(xxxvi)
(xxxvii)
(xxxviii)
(xxxix)
(xl)

1.
Half-warm mix asphalt mixtures shall
conform to the specification for half-warm
mix asphalt in Appendix B of this Report; the
relevant example specification in Appendix E,
Appendix F or Appendix G of this Report; and
requirements specified in Appendix 7/1.

(i)
(ii)

(xxvi)
(xxvii)
(xxviii)
(xxix)
(xxx)
(xxxi)

J.2.2

70/100 HWMA.
50/70 HWMA.
70/100 HWMA.
50/70 HWMA.

Coarse aggregate

5.
To ensure adequate resistance to
polishing and abrasion, the coarse aggregate
of surface course mixtures shall have a
minimum declared PSV and a maximum AAV,
as specified in Appendix 7/1.

PPR666

Low temperature asphalt

J.2.3

J.3 96Z Emulsion-Based Cold Mix

Asphalt Materials

Additives

6.
Evidence shall be provided on the
suitability of any additive incorporated into
the mixture to the Overseeing Organisation
before work commences. This evidence may
be based on research combined with evidence
from practice.
J.2.4

J.3.1

1.
Emulsion-based
cold
mix
asphalt
mixtures shall conform to the specification for
emulsion-based cold mix asphalt in Appendix C
of this Report; the relevant example
specification in Appendix H of this Report;
and requirements specified in Appendix 7/1.

Health and Safety

7.
Health and Safety information and safe
handling guidance shall be provided, including
any COSHH data sheets for any component
materials.
J.2.5

2.
The mixture designation shall be one of
the following:

Coated chippings

8.
Coated chippings shall not be applied to
HRA surf HWMA mixtures.
J.2.6

Dense base and binder course

asphalt course (design mixtures)

9.
Half-warm mix asphalt dense base and
binder
course
asphalt
course
(design
mixtures) mixtures shall comply with SHW
Clause
929
for
volumetric
properties,
deformation
resistance,
stiffness
and
compaction control for the permanent works.
J.2.7

AC
AC
AC
AC
AC
AC

6 dense surf CME.

10 close surf CME.
14 close surf CME.
4 fine surf CME.
10 open surf CME.
14 open surf CME.

(vii)
(viii)
(ix)
(x)
(xi)
(xii)

AC
AC
AC
AC
AC
AC

20
32
20
32
20
32

(xiii)
(xiv)
(xv)

AC 32 HDM base CME.

AC 32 dense base CME.
AC 32 HMB base CME.
SMA
SMA
SMA
SMA

HDM bin CME.

HDM bin CME.
dense bin CME.
dense bin CME.
HMB bin CME.
HMB bin CME.

6 bin CME.
10 bin CME.
14 bin CME.
20 bin CME.

3.
The mixtures shall be design and not
recipe mixtures.
4.
When the mixture designation is not
specified in Appendix 7/1, the mixture
selected by the Contractor shall be notified to
the Overseeing Organisation prior to its use in
the Works.

Thin surface course systems

11. Half-warm mix asphalt thin surface

course systems shall comply with SHW
Clause 942.
J.2.9

(i)
(ii)
(iii)
(iv)
(v)
(vi)

(xvi)
(xvii)
(xviii)
(xix)

Stone mastic asphalt binder

course and regulating course

10. Half-warm mix asphalt stone mastic

asphalt binder course and regulating course
mixtures shall comply with SHW Clause 937
for
binder
modification,
deformation
resistance and compaction control for the
permanent works.
J.2.8

General

J.3.2

Coarse aggregate

5.
To ensure adequate resistance to
polishing and abrasion, the coarse aggregate
of surface course mixtures shall have a
minimum declared PSV and a maximum AAV,
as specified in Appendix 7/1.

Percentage refusal density

12.
When testing samples of half-warm
mix asphalt for refusal density, the sample
shall be heated to the same temperature as
an equivalent hot mix asphalt before
compaction.

J.3.3

Additives

6.
Evidence shall be provided on the
suitability of any additive incorporated into
the mixture to the Overseeing Organisation
before work commences. This evidence may
59

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be based on research combined with evidence

from practice.
J.3.4

Binder

7.
Binder shall be bitumen
complying with BS EN 13808.
J.3.5

10.
The performance properties of the
conditioned specimens shall be declared. The
results shall be considered as indicative only,
because the compliance criterion applies only
to specimens prepared during the execution
of the works.

emulsion

J.3.8

Binder modification

8.
The Contractor shall provide data sheets
giving details of the properties of the modified
binders or additives (including natural or
man-made fibres) proposed, including those
specified in Appendix 7/1. The information
covered shall include rheological data for preblended
polymer
modified
binders
in
accordance with SHW Clause 956.
J.3.6

11.
Production of the emulsion-based cold
mix asphalt mixture shall be subject to
process control detailed in the quality plan
and meeting the following requirements:
(i)

There shall be a description of the plant

and the production process, preferably
including a flow diagram, detailing how
material is to be produced in accordance
with this specification.

(ii)

Calibration schedules for all parts of the

plant involved in determining mixture
consistency shall be provided. These shall
be accompanied by calibration records.

(iii)

Measures to avoid problems caused by

extreme
weather.
In
particular,
production shall not proceed if the
feedstock is frozen or excessively wet.

Design proposal

9.
The Contractor shall submit a Design
Proposal which shall state the aggregate
characteristics and sources, the binder to be
used and provide an example of the target
grading curve and binder content together
with details of the proposed filler and fibre if
used. In the works, the grading and binder
content shall not differ from the proposed
target values by more than the tolerances
detailed in the Design Proposal.
J.3.7

Process Control

J.3.9

Mixture Design Validation

Inspection and Test

13. There shall be a schedule of inspection

and test frequencies to be made during
production of emulsion-based cold mix
asphalt.
This schedule shall cover the
aggregate
stockpiles,
the
binder,
the
combined grading of the mixture and the
moisture content of the mixture.

10.
When a mix design validation is
required it shall be carried out on aggregates
and binders representative of those to be
used on the works. The validation may be
carried out on emulsion-based cold mix
asphalt at the target composition mixed
either in the laboratory or on a pilot basis on
a full scale plant.

J.3.10 Laying

11.
Representative samples of the mixture
shall be taken from which 150 mm diameter
cylindrical specimens shall be produced.
These specimens shall be between 70 mm
and 75 mm high.

12.
A written procedure for the laying of the
emulsion-based cold mix asphalt shall be provided.
13.
The plant used for placing the material
shall be capable of laying the material without
significant segregation, evenly and to the required
thickness across at least one lane width.

12.
The density of each specimen shall be
measured by dimensions to BS EN 12697-6
and, using the respective moisture content
values, the dry density values shall be
determined. The cylindrical specimens shall
be conditioned and tested. The conditioning
and testing regime shall be agreed with the
Overseeing Organisation.

14.
A
method
for
the
making
of
longitudinal and transverse joints, appropriate
to the type of emulsion-based cold mix
asphalt being laid shall be provided.

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J.3.11 Compaction

Table J.1: End Product Criteria

15.
The compaction of each layer shall be
carried out as described in the laying
procedure. Open edges shall be protected
from traffic.
16.
After trimming and final compaction of
the layer, the material strength shall be
assessed using a lightweight deflectometer.
The stiffness determined shall be not less than
50 MPa before the layer can be overlaid
or trafficked.

Material
property or
characteristic

Individual
results

Mean from test

set of six
specimens

Particle size
distribution

Zone

Moisture
content

2 %

Minimum
relative in situ
density

93 %

95 %

Layer thickness

25 mm of
specified

15 mm of
specified

J.3.12 Sealing grit

17.
Sealing grit may be applied to the
surface when required to prevent pick-up
from trafficking in the early life.

J.3.14 Percentage refusal density

22.
When testing samples of emulsionbased cold mix asphalt for refusal density, the
sample shall be heated to the same
temperature as an equivalent hot mix asphalt
before compaction provided there is no water
present in the mixture.

J.3.13 End Product Testing

18.
The end product testing of the
emulsion-based cold mix asphalt shall be
assessed on the basis of representative
specimens made up in accordance with the
schedule in Appendix 7/1.

NOTE:

19.
Representative samples shall be taken
either at the mixing plant or from site.
150 mm diameter cylindrical test specimens
shall be manufactured in sets of six by
compacting to refusal in accordance with
BS EN 1269732. The test specimens shall
have a nominal height of 75 mm and
diameter of 150 mm.

The presence of water can present a

safety issues from the generation of
steam when heated. In such instances,
the sample needs to be dried prior to
raising to the relevant temperature.

J.3.15 Health and Safety

23.
Health and Safety information and safe
handling guidance shall be provided, including
any COSHH data sheets for any component
materials.

20.
Prior to testing, specimens shall be
conditioned in a controlled environment. The
purpose of this conditioning is to simulate the
likely curing over the first year in the road.

J.3.16 Layer thickness

24.
When required, the minimum and/or
maximum thickness of emulsion-based cold
mix asphalt shall be as specified in
Appendix 7/1.

21.
The minimum specification compliance
criteria for the process control tests shall be
as described in Table J.1.

J.3.17 Dense base and binder course

asphalt course
25.
Emulsion-based cold mix asphalt
dense base and binder course asphalt course
mixtures shall comply with SHW Clause 929
for
volumetric
properties,
deformation
resistance and compaction control for the
permanent works.

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J.3.18 Stone mastic asphalt binder

course and regulating course
26.
Emulsion-based cold mix asphalt stone
mastic asphalt binder course and regulating
course mixtures shall comply with SHW
Clause 937 for binder modification, deformation resistance and compaction control for the
permanent works.

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Appendix K Notes for Guidance on specification

requirements for low temperature asphalt
mixtures
ROAD PAVEMENTS BITUMINOUS BOUND MATERIALS
K.1 NG96X Warm Mix Asphalt
Materials
K.1.1

6.
When testing
asphalt for refusal
need to be heated
as an equivalent
compaction.

General

1.
Warm mix asphalt is asphalt in which
the aggregate particles are continuously
graded or gap-graded to form an interlocking
structure that is mixed and laid at
temperatures
at
least
20 C
below
conventional hot mix asphalt mixtures but
still above 100 C.

K.1.3

Use of organic waxes

(ii)

Use of chemical additives

(iii)

Use of a bitumen foaming process

3.
The properties of warm mix asphalt
should be judged against the same criteria as
hot mix asphalt.
The difference is the
reduced temperature at which the material is
mixed, transported, laid and compacted.
K.1.2

Grading of reclaimed asphalt

7.
Reclaimed asphalt is an accepted
component material in asphalt mixtures that
is encouraged in warm mix asphalt.
However, the grading of the reclaimed
asphalt particles will not be the same as the
grading of the aggregate particles within the
reclaimed asphalt.
The reclaimed asphalt
particles will include finer particles adhering
to
larger
particles
and
occasional
conglomerates of coarse particle stuck
together. Therefore, if the grading of the
reclaimed asphalt particles is to be used for
control of the final grading, the relationship
between the gradings for each reclaimed
asphalt source will be needed.
This
conversion in gradings becomes more critical
in achieving the required aggregate grading
of the output mixture as the proportion of
reclaimed asphalt is increased.

2.
There are several technologies intended
to improve the workability of the mixture and,
hence, allow the asphalt temperatures to be
reduced in order to produce a warm mix
asphalt. These methods are generally based
on one of, or a combination of, the following:
(i)

a sample of warm mix

density, the sample will
to the same temperature
hot mix asphalt before

K.1.4

Mixture temperatures

Tar

8.
Tar was used as a binder in highway
construction, but was subsequently identified
as a carcinogen and is no longer used.
However, tar can be found in reclaimed
asphalt if the material being planed up is of
sufficient age. Because that tar can be a
health hazard if heated, reclaimed asphalt
containing tar should not be used for hot mix
asphalt, warm mix asphalt or half-warm mix
asphalt; it can, however, be incorporated into
cold mix asphalt.

4.
In order to assess warm mix asphalt
fairly against hot mix asphalt, the samples
used to determine the properties need to
have been mixed and transported at the
appropriate reduced temperature compared
to standard hot mix asphalt temperatures.
5.
There are a number of methods to
reduce the temperature at which an asphalt
mixture needs to be mixed, transported, laid
and compacted, not all of which can be
replicated easily in the laboratory. The same
technology needs to be used in preparing
specimens as will be used on site. If that
technology cannot be replicated in the
laboratory,
samples
will
have to be
manufactured from plant-mixed material.

K.1.5

Energy consumption and carbon

dioxide production

9.
When assessing the sustainability of
warm mix asphalt as an alternative
technology, the reduced temperature is not

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the only change in the input to produce and

lay the material. The energy consumption
and carbon dioxide equivalent production
from:
the supply of raw materials for,
the production of, and
the transport of
any additives used in the mixture needs to be
included in any calculation.

K.2.2

5.
In order to assess half-warm mix
asphalt fairly against hot mix asphalt, the
samples used to determine the properties
need to have been mixed and transported at
the
appropriate
reduced
temperature
compared to standard hot mix asphalt
temperatures.
6.
There are a number of methods to
reduce the temperature at which an asphalt
mixture needs to be mixed, transported, laid
and compacted, not all of which can be
replicated easily in the laboratory. The same
technology needs to be used in preparing
specimens as will be used on site. If that
technology cannot be replicated in the
laboratory,
samples
will
have to be
manufactured from plant-mixed material.

K.2 NG96Y Half-Warm Mix Asphalt

Materials
K.2.1

General

1.
Half-warm (or semi-warm) asphalt is
asphalt in which the aggregate particles are
continuously graded or gap-graded to form an
interlocking structure that is mixed and laid at
temperatures in the range 70 C to 100 C.

7.
When testing a sample of half-warm
mix asphalt for refusal density, the sample
will need to be heated to the same
temperature as an equivalent hot mix asphalt
before compaction.

2.
There are several technologies intended
to improve the workability of the mixture and,
hence, allow the asphalt temperatures to be
reduced in order to produce a half-warm mix
asphalt. These methods are generally based
on one of, or a combination of, the following:
(i)

Use of organic waxes

(ii)

Use of chemical additives

(iii)

Use of a bitumen foaming process

Mixture temperatures

K.2.3

Composition

8.
The asphalt types, gradings and binder
contents for half-warm mix asphalts should
essentially be the same as for hot mix
asphalts. The main difference will be the
additives and/or the mixing sequence in order
to be capable of being mixed and compacted
at the lower temperatures.

However, option (iii) is the most common for

half-warm mixtures.
3.
Some foam technology processes rely
on the foaming of the bitumen from the use
of specialist foaming equipment whilst others
use the principle of foaming on contact with
the mineral water.
With the process of
adding hot bitumen to damp aggregate, a
portion of the water in the aggregate should
vaporise and foam the bitumen whilst another
portion should escape as steam, leaving a
final portion to remain as water in the
aggregate. The size of these portions will
depend on the moisture content and the
mixing temperature,

9.
The binder grades may need to have
similar properties in the compacted mixture
as that for hot mix asphalts in order for the
asphalt to have similar properties, such as
deformation
resistance
and
stiffness.
However, the binder may need different
binder properties in the mixing and laying
process. The binder grade can be stated in
Appendix 7/1, but it could limit the half-warm
asphalt mixtures that comply.
10. The ageing of binder during the mixing
and placement of hot mix asphalt, particularly
when using batch mixers, in terms of the
binder penetration is generally a reduction of
the order of 33 %, or one binder grade, which
does not occur to the same extent with halfwarm mixtures.
Where equivalence is
intended with hot mix asphalt, the binder
grade may need to be adjusted down in order
to get the same properties, such as
deformation resistance.

4.
The mixture type(s) required for each
layer should be stated in Appendix 7/1. The
mixture designation for the selected mixture
type should be chosen to suit the thickness of
the layer as indicated in the relevant table of
BS 594987:2010 (Table 1A for AC, Table 1B
for HRA or Table 1C for SMA) as with hot mix
asphalt mixtures.

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K.2.4

Grading of reclaimed asphalt

produced samples with superior water

sensitivity performance to ones compacted
immediately.

10. Reclaimed asphalt is an accepted

component material in asphalt mixtures that
is encouraged in half-warm mix asphalt.
However, the grading of the reclaimed
asphalt particles will not be the same as the
grading of the aggregate particles within the
reclaimed asphalt.
The reclaimed asphalt
particles will include finer particles adhering
to
larger
particles
and
occasional
conglomerates of coarse particle stuck
together. Therefore, if the grading of the
reclaimed asphalt particles is to be used for
control of the final grading, the relationship
between the gradings for each reclaimed
asphalt source will be needed.
This
conversion in gradings becomes more critical
in achieving the required aggregate grading
of the output mixture as the proportion of
reclaimed asphalt is increased.
K.2.5

K.2.7

14. In order to assess half-warm mix

asphalt fairly against hot mix asphalt, the
samples used to determine the properties
need to have been mixed and transport at the
appropriate reduced temperature compared
to standard hot mix asphalt temperatures.
15. There are a number of methods to
reduce the temperature at which an asphalt
mixture needs to be mixed, transported, laid
and compacted, not all of which can be
replicated easily in the laboratory. The same
technology needs to be used in preparing
specimens as will be used on site. If that
technology cannot be replicate in the
laboratory,
samples
will
have to be
manufactured from plant-mixed material.

Tar

16. The temperature ranges for mixing,

laying and compacting a half-warm mixture
need to be known for implementing and
controlling those processes efficiently.
In
particular,
the
minimum
compaction
temperature at which the required air voids
content on site can be achieved needs to be
determined. The ranges should be identified
by those developing the mixture and then
used to assess the required properties; if the
properties are not appropriate at those
temperature ranges, in particular the binder
coating, then either the ranges or some other
aspect will need to be adjust until they do.

11. Tar was used as a binder in highway

construction, but was subsequently identified
as a carcinogen and is no longer used.
However, tar can be found in reclaimed
asphalt if the material being planed up is of
sufficient age. Because that tar can be a
health hazard if heated, reclaimed asphalt
containing tar should not be used for hot mix
asphalt, warm mix asphalt or half-warm mix
asphalt; it can, however, be incorporated into
cold mix asphalt.
K.2.6

Mixture temperatures

Sample preparation

12. Due to the nature of the standard

foaming equipment/process, it is difficult to
make small batches of consistent binder
content and sample size may need to be as
much as 40 kg. Moisture levels need to be
controlled and a standard procedure may be
required for controlling aggregate moisture
prior to laboratory mixing. Substantially
inconsistent mixing times will result in
variability in resultant mix moisture content;
this in turn could affect compactibility.

17. The validated range should be given to

everyone involved in the production, laying,
compaction and supervision of the material
for use in their part for the works.
K.2.8

Water contents

18. Some half-warm asphalt technologies

require the aggregates to contain some water
in order for that water to be used to foam the
binder.
Other technologies inject water
directly into the bitumen so that enters the
mixture as foamed bitumen. In either case,
the water entering the mixture needs to be
controlled to the appropriate contents
required for the particular half-warm asphalt
technology being used.
The required
moisture content of aggregate and the
quantity of any additional water to be added
need to be declared in the declaration for the
mixture.

13. Half-warm mixtures will slowly eliminate

water after manufacture during the delivery
and application process.
Therefore, it is
important not to compact laboratory prepared
mixtures immediately because the excess
water present may have a negative impact on
some comparative tests. This phenomenon
has been studied and conditioning at 95 C
for 2 h prior to compaction at 95 C has
65

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19. With water being added to the asphalt

in different ways for many of the half-warm
technologies, there is a concern about
whether that moisture can impair the longerterm performance of the material. Therefore,
the water sensitivity of the mixture and its
components becomes more critical.
K.2.9

K.3.2

15. The emulsion binder should comply with

BS EN 13808. The binder shall be emulsion
from
paving
grade
bitumen,
modified
bitumen, fluxed bitumen or hard grade
bitumen conforming to the relevant European
Standard.
16. The emulsions which are manufactured
for mixing techniques need to cope with some
or all of the following depending on end
requirement:

Compaction

20. The compaction techniques required for

hot mix asphalt may need to be reviewed for
use with half-warm mix asphalt. However,
the potential change from current practices
associated with hot-mix asphalt will depend
on the technology used to achieve the lower
temperature and will need to be identified for
each system.

The high surface area of the asphalt

aggregate structure.
Be suitably stable to the shearing forces
exerted by the mixing and pumping
processes adopted.
Be able to coat the mineral materials
used.

21. The relationship between the field

compaction and the final moisture content of
the mixture needs to be established for each
design. The compaction applied can then be
controlled so that the compacted water
content of the mixture is not going to impair
the durability that can be achieved on site.

Be able to give satisfactory adhesion of

binder to aggregate once broken
Remain in the
excessively drain.

mixture

and

not

The resultant mixtures will need to be well

coated,
workable,
easily
compactable,
cohesive and capable of withstanding running
traffic soon after laying.

K.2.10 Energy consumption and carbon

dioxide production
22. When assessing the sustainability of
half-warm mix asphalt as an alternative
technology, the reduced temperature is not
the only change in the input to produce and
lay the material. The energy consumption
and carbon dioxide equivalent production
from:
the supply of raw materials for,
the production of, and
the transport of
any additives used in the mixture needs to be
included in any calculation.

K.3.3

Pre-treatment of aggregate
particles

17. The double coating or pre-treatment of

the aggregate particles can be used to
overcome the variability in the chemistry of
the mineral surface and the emulsions as well
as the high volume liquid content in the final
mixture. The processes include:
Pre-coating of sand either with bitumen
or emulsion.
Pre-treatment of sand with a chemical
agent.

K.3 NG96Z Emulsion-Based Cold Mix

Asphalt Materials
K.3.1

Binder

Pre-coating the coarse aggregate.

Phase coating.
18. The use of reclaimed asphalt in mixtures
reduces or eliminates the need to pre-coat
the aggregate particles because binder
already exists on the reclaimed asphalt
planings.

General

14. Emulsion-based cold mix asphalt is

asphalt in which the aggregate particles are
continuously graded or gap-graded to form an
interlocking structure and the binder is a
bituminous emulsion with a viscosity such
that the mix is workable at ambient
temperature.

K.3.4

Grading of reclaimed asphalt

11. Reclaimed asphalt is an accepted

component material in asphalt mixtures that
is encouraged in emulsion-based cold mix
66

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asphalt.
However, the grading of the
reclaimed asphalt particles will not be the
same as the grading of the aggregate
particles within the reclaimed asphalt. The
reclaimed asphalt particles will include finer
particles adhering to larger particles and
occasional conglomerates of coarse particle
stuck together. Therefore, if the grading of
the reclaimed asphalt particles is to be used
for control of the final grading, the
relationship between the gradings for each
reclaimed asphalt source will be needed. This
conversion in gradings becomes more critical
in achieving the required aggregate grading
of the output mixture as the proportion of
reclaimed asphalt is increased.

K.3.7

K.3.5

24. Hot mix asphalt binder ages during

manufacture and continues to age until it has
cooled. The rate of ageing in cold mix asphalt
is substantially reduced compared to hot mix
asphalt because of the lower temperature.
This reduced ageing could explain the slower
rate of stiffness development within the
pavement and also the resistance to cracking
and healing properties that have been
observed.

23. Cold mix asphalt made with emulsions

can be manufactured using an array of plant.
These include mobile, stationary, continuous
or batch units, which can be further broken
down into:
Static hot mix asphalt plants which have
been modified for cold feeding the
aggregates and adapted to feed
emulsion into the batch mixer.
Static concrete plants.
Mobile concrete plants.
Mobile mix plants.
K.3.8

Tar

19. Tar was used as a binder in highway

construction, but was subsequently identified
as a carcinogen and is no longer used.
However, tar can be found in reclaimed
asphalt if the material being planned up is of
sufficient age. Because that tar can be a
health hazard if heated, reclaimed asphalt
containing tar should not be used for hot mix
asphalt, warm mix asphalt or half-warm mix
asphalt; it can, however, be incorporated into
cold mix asphalt.
K.3.6

Mixing plant

K.3.9

Ageing during manufacture

Substrate

25. The substrate onto which emulsionbased cold mix asphalt is to be laid needs to
have an acceptable stiffness in order to allow
the longer-term gain of strength after
construction.
If the asphalt is disturbed
excessively in its early life, it will not reach its
potential strength.

Sample preparation

20. The use of emulsions means that the

physical properties of samples will change as
the water in the emulsion is removed from
the mixture. Hence, the age of specimens
when samples are tested for mechanical
properties can be an important parameter.

K.3.10 Water content

21. The standard for emulsion-based cold

mix asphalt in Appendix C of this Report uses
28 days as the standard age when the
samples are stored at ambient temperature
but also gives an accelerated age of 7 days
when the samples at stored at elevated
temperature of 40 C.

26. The water content in an emulsion-based

cold mix asphalt mixture after compaction
needs to be limited in order to attain both the
required gain in early-age physical properties
and
the
maintenance
of
longer-term
durability.
However, the current limit of
5.0 % by mass of the dry aggregate 24 h
after compaction is an arbitrary value that
may need to be refined when further data is
available.

22. Greater acceleration could be achieved

at
higher
temperatures,
but
if
the
temperature is excessive, it could age the
binder. Any regime for greater acceleration
would need to be validated against the
standard conditions before it could be used
for certifying the properties of a mixture.

K.3.11 Compaction
27. Compaction of emulsion-based cold mix
asphalt is preferable with a pneumatic tyre
roller (PTR). However, other types of rollers
can be used with the recommended types of

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compaction
Table K.1.

equipment

being

given

cold mix asphalt as an alternative technology,

the reduced temperature is not the only
change in the input to produce and lay the
material.
The energy consumption and
K.3.12 Energy consumption and carbon
carbon dioxide equivalent production from:
dioxide production
the supply of raw materials for,
28. Emulsion-based cold mix asphalt is one
the production of, and
of the key processes for maximising savings
the transport of
in energy and greenhouse gas emissions. any additives used in the mixture needs to be
However, when assessing the sustainability of included in any calculation.
Table K.1: Recommended type of compaction
Location

Pneumatic
Tyre

Tandem

Mixed

Vibrating
Plate*

dense or semi-dense mixture

+++

open graded cold mixture

+++

Surface course

Binder course and base

dense or semi-dense cold mixture

open graded cold mixture

for local repairs only

+++

Highly suited

Possible

+ Possible with caution

Not suited

PPR666

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