IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308

HIGH PERFORMANCE CONCRETE FOR HIGH-RISE BUILDINGS:

SOME CRUCIAL ISSUES

Vijay R Kulkarni
Principal Consultant, RMCMA & Past President, Indian Concrete Institute

Abstract
High-rise building construction has been an important driver for the revitalization of urban centers throughout the
world. The paper briefly summarizes the unprecedented growth in tall building construction across the globe during
the past few decades. Review of tall building scenario reveals two interesting trends. Firstly, the centre of gravity of
tall building construction which had already shifted from North America to Asia, is getting strengthened in the latter
region, and secondly, structural concrete has emerged as a dominant material of construction of tall buildings, either
in a stand-alone form or as a part of composites, surpassing structural steel. The use of High-Strength, High-
Performance Concrete (HSC/HPC) has proved to be a boon for high-rise building construction. HSC and HPC are
engineered concretes having vastly improved properties. With such type of concretes, it is possible to achieve high
compressive strengths that are useful in reducing the sections sizes of members and high modulus of elasticity for
controlling deflections. Further, these concretes can be designed to provide immensely improved long-term durability.
Thanks to the availability of a latest generation chemical admixtures, it is now possible to pump HSC/HPC to greater
heights. In India, the scarcity of land in metropolitan centers is driving the land prices sky high and is compelling
developers and builders to build taller buildings. With the rise in the stock of tall buildings in India, the use of
HSC/HPC is also on the rise. The author briefly reviews the broad trends in the use of HSC/HPC in India with
specific reference to the projects he has been associated with recently. Selection of appropriate ingredients of
concrete and mix proportioning methodology are the crucial parameters for achieving the desired properties of
HSC/HPC. Even minor variations in the properties of ingredients and testing regime affect the fresh and hardened
properties of concrete. For HSC/HPC the author makes a strong plea to use manufactured sand having lower
variations in its fines content. Considering that rheology of HSC/HPC is of critical importance, the author emphasizes
that it is essential to resolve the cement-admixture compatibility issue in the initial stage itself. He suggests that use of
cement having low C3A and low C4AF contents would prove to be beneficial. Finally, the author highlights the urgent
need of developing appropriate guideline documents for HSC/HPC in India.

Keywords: High-Strength, High Performance Concrete, Durability, Temperature Control, Fire Resistance
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1. INTRODUCTION Population growth is responsible for migration of people to

urban centers in search of livelihood. Better opportunities in
Twin problems of population growth and rapid urbanization urban centers drive more and more people to migrate to
have assumed serious dimensions in recent times. In 1950, cities. Thus, urbanization is helpful in creating power
30 percent of the world’s population was urban, and 70% houses of economic development, contributing substantially
was rural. This trend is likely to get reversed by 2050. to the national economy. The mid-term appraisal of the
According to the latest report of the United Nations on Eleventh Plan projected the urban share of GDP at 62–63
World Urbanization, continuing population growth and percent in 2009-10. By 2020, this share is likely to increase
urbanization are projected to add 2.5 billion people to the to around 70-75 according to Barclay’s report2. However,
world's urban population by 2050, with nearly 90% of the rapid urbanization also creates a number of social,
economical and cultural problems. Rising slums and scatter
increase concentrated in Asia and Africa1. Just three
population in urban centers are the direct results of rapid
countries — India, China and Nigeria — together are
urbanization. Besides, faster pace of urbanization creates
expected to account for 37 per cent of the projected growth tremendous pressure on the existing urban services – water
of the world’s urban population between 2014 and 2050. In supply, transportation, sanitation, etc.
this projected growth, India’s share will be highest with 404
million urban dwellers, followed by China with 292 million Since land is a scare resource, especially in urban areas, the
and Nigeria with 212 million. Two Indian cities - Delhi tempo of economic development can be sustained if intense
NCR and Mumbai - are amongst the world’s most populous development is allowed by permitting ―vertical‖ growth.
cities having population in excess of 20 million. This means allowing more F S I (Floor Space Index).

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IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308

2. WHAT IS A TALL BUILDING?

According to the Criteria for defining and measuring of tall
buildings published by the Council for Tall Buildings and
Urban Habitat (CTBHU)3, there is no ―absolute definition of
what constitutes a tall building‖. It is a building that exhibits
some element of ―tallness‖ in one or more of the following
three categories:

(i) Height relative to context: e.g. A 14-storey building

may not be considered tall in a city like Hong Kong; but
the same may be considered distinctly taller in a rural
area
(ii) Proportion: e.g. A building may not be particularly tall,
but it could be slender enough to give the appearance of
a tall building.
(iii) Tall building technologies: e.g. buildings having Fig 1. Evolution of New York city Skyline 1879-2013
(Source: http://theyard.nyc/blog/the-evolution-of-the-new-
specific vertical transport technologies, structural wind
york-city-skyline)
bracing system may be classified as tall building.
The construction of tall buildings gathered momentum in the
CTBHU has developed specific criteria on measuring the second half of the 20th century. According to the latest data
height of buildings. Generally speaking, height is measured published by the CTBHU, the total number of tall building
from the level of the lowest, significant, open-air, pedestrian having heights exceeding 200-m reached the 1,000 mark in
entrance to the architectural top of building including spires, 20155. It is evident from Fig 2 that although it took 95 years
but not including antennae, signage, flagpoles or other to achieve the 1000-mark in the 200-m plus tall buildings
functional equipment. register, the spurt in activities in this field commenced only
from the year 2000 onwards. During the past 15 years, the
The draft Indian Standard on Criteria for Structural Safety of number of 200-m tall buildings increased from 265 (2000)
Tall Buildings states that it is applicable to building heights to 1040 (2015) – an increase of nearly 392%! The addition
greater than 45m, but less than 250m4. It may be inferred of 106 numbers to the 200-m plus tall buildings count
from this that in India buildings with heights greater than during the year 2015 was itself a world record. This trend is
45m can be considered as tall buildings. expected to gather further momentum.

Incidentally, CTBHU has made two more categories in the

tall building sphere. It defines ―Supertall‖ as a building over
300m in height and a ―Megatall‖ as a building over 600m in
height.

It is reported that as of June 2015, there were 91 Supertall

and 2 Megatall buildings fully completed and occupied
globally5.

3. TALL BUILDINGS SCENARIO

3.1 Brief History
Home Insurance Building located in Chicago is considered
the first skyscraper. This building constructed in 1885 in
Fig 2 Number of 200-m plus tall buildings in the world
cast iron had a height of 55 m ( 12 storeys) 6 . Another
landmark skyscraper, Empire State Building completed in exceeded the 1000 mark in 2015 (source: CTBHU)
1931 had a height of 382m.
3.2 Perceptible Shifts in Locations of Tall Buildings
In the sphere of concrete, Ingalls Building in Cincinnati, the It is interesting to note that North America no longer
15-storey building built in 1903 by A O Elzner is reported to dominates the tall building sphere. By the turn of last
be the first concrete skyscraper7. century, the centre of gravity of construction of tall
buildings had shifted from North America to Asia. In the
The trend of high-rise building construction began with year 1930, all the 100 tallest buildings in the world were
major cities like New York and Chicago in the USA since located in North America. This number has come down to
the first half of the 20th century. The change in city skyline just 17 in 2015, Fig 3. The place earlier occupied by North
of New York over the past nearly one-and-a-half century America in the 100 tallest buildings category is now
(1879 to 2013) depicted in Fig 1 is a clear testimony of this occupied by Asia (48), followed by Middle East (28),
trend. Fig 35.
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IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308

It is interesting to note that 2015 saw a spike in the number

of buildings completed with concrete structures – 52 out of
106 (49%)5. This is a dramatic increase over 2014, when
only 39 out of 99 were completed in concrete (39% of total).
All-steel towers were very scanty in 2015, with only three
200-m-plus completions around the globe.

4. WHY CONCRETE?
During the initial phase of tall building construction,
structural steel was the preferred material, especially in
North America. This was because the material was available
in the required shapes and sizes and the mechanized tools
were available for transporting and placing the same in
position at site. As the advances in concrete technology
became available to the industry, the shift from steel to
concrete commenced.

Fig 3 Perceptible shift from North America to to Asia Technological advances in the following four main areas
(Source: CTBHU) were mainly responsible for establishing the dominance of
concrete over steel in the tall building sphere.
Asia has been the major driver for the growth in this sector
since the year 2000. Asia has been outperforming the other  Advances in high-strength concrete, high-
regions. Out of the 106 tall buildings completed during the performance concrete, self-compacting concrete
year 2015, 81 were from Asia, representing 76% of the total
stock. Advances in chemical admixtures
advances in transport and delivery of concrete
For the past few years, China has been the leader in tall Advances in formwork system
building construction. According to the CTBHU report, the
number of 200-m-plus tall building completed in China 4.1 High-strength, High-performance Concrete
during 2015 was 62. Out of the 29 Chinese cities with 200-
m-plus tall building completions, Nanjing, Nanning and The development and use of high-strength concrete (HSC)
Shenzhen had the most with five each. has proved to be a boon for high-rise building construction.
It has been established that the use of HSC in columns,
shear walls, transfer beams, etc. helps in reducing the
3.3 Concrete Scores over Other Materials section sizes and the percentage of reinforcement. The twin
There is a clear shift in the use of materials of construction reduction in the quantity of concrete and steel not only
for tall buildings. From the beginning of tall building results in bringing down the materials costs but the useable
construction, structural steel was the preferred choice. floor space is also increased, thereby yielding higher
However, since 1980, there is a perceptible shift from steel revenues.
to concrete and composites! The trend has become more
As the use of HSC gathered momentum, properties other
pronounced in recent years, Fig 4.
than compressive strength also became important. This gave
rise to the evolution and use of what is today known as high
performance concrete (HPC).

High-strength, high-performance concrete invariably uses

one or more supplementary cementitious materials such as
fly ash, ground-granulated blast-furnace slag, silica fume,
rice husk ash. In addition, the water-to-binder ratio of
HSC/HPC is also low. Both these characteristics of
HSC/HPC are responsible in improving the long-term
durability of HSC/HPC. This has been proved from a
plethora of research conducted globally. The improvement
in long-term durability of concrete will indirectly improve
the sustainability of construction.

ACI 363R:2010 reports that in many areas and for many

uses, the benefits of HSC more than compensate for the
increased costs of raw materials and quality control8.

The technical and economic benefits of HSC/HPC were

Fig 4 Perceptible shift in the material of construction – from conducive to their use in tall buildings.
steel to concrete composites (source: CTBHU)
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4.2 Chemical Admixtures modern concrete pumps have enormous power, high
capacity and a reliable hydraulic system for pumping. They
Till the first half of 20th century, lignosuphonate-based can pump concrete vertically more than 500m and deliver it
chemical admixture was the main source of reducing water horizontally up to 500m or so. Their outputs range from
demand in concrete. With this type of admixture, it was between 30 to 150 m3 per hour. The pumping records are
possible to reduce the water demand in concrete to the getting broken quite often. The latest was the pumping
extent of around 5% or so. It was in the 1960s that the concrete at a height of 606m for the Burj Dubai tower 9.
naphthalene and melamine sulphonate-based admixtures
emerged on the scene. These admixtures were able to reduce
4.5 Advances in Formwork Systems
the water demand in concrete substantially - by around 20%
or so. This improvement in the chemical admixture Traditionally, forms and supporting system were made up of
technology gave a boost to the development of high-strength wood. As the technology advanced, new materials were
and high-performance concretes. With such admixtures, it introduced. Forms became a combination of wood,
was also possible to pump the concrete at greater heights. plywood, steel, aluminium. plastic, fibreglass, etc. The
supporting structure and bracings which were earlier made
Recently, polycarboxyl -based (PCE-based) admixture, up of wood were replaced with steel trusses, H-frames, etc.
which is considered to be the fourth-generation type Job-built forms which are built by assembling individual
chemical admixture is available. With this admixture, it is component, piece by piece are now available. Prefabricated
possible to reduce water demand in concrete by as much as job-built forms are used for mass production where several
40%. The use of such admixture was conducive to the reuses are possible.
development of HSC/HPC on the one hand and pumping of
concrete on the other. Formwork affects the quality of concrete. Poor quality
formwork may lead to excessive deflection and bulging of
4.3 Self-compacting Concrete concrete. Misalignment can destroy integrity of structure.
Quality of surface finish gets directly affected by the form
Self-compacting concrete (SCC) is a highly workable and material. Poor workmanship may lead to leakages and
flowable mix, which flows around obstructions, honeycombs. It is therefore essential to have a properly
encapsulates congested reinforcement, and fills up the forms designed formwork system, which is erected with due
completely under its self weight without segregation or consideration to quality and safety.
excessive bleeding. The use of SCC increases speed of
construction, reduces construction joints, provides better Fortunately, a number of proprietary modular formwork
surface finish, reduces noise, and results in reduction in site systems are now available. Broadly speaking the available
manpower. systems can be grouped into following five categories:
These benefits of SCC have been found to be useful in tall  Table formwork or flying formwork
building construction, especially for elements having
 Slip formwork
congested reinforcement. Further, with SCC it is possible to
 Travelling formwork
place concrete in elements having greater lift heights. This
helps in speeding up construction.  Tunnel formwork
 Jump formwork
4.4 Advances in Concrete Delivery System 
Advances in the formwork systems have been of great value
Until the early 20th century, concrete was mixed on the job in the construction of high-rise buildings. The use of
site and transported from the mixer to the formwork, either advanced systems has helped in achieving higher speed of
in wheelbarrows or in buckets. In developing countries like construction and better quality of concrete. Of course, for
India it was transported on headload by a long chain of this purpose the construction team needs to take proper care
labourers. in the selection of appropriate formwork system, its design,
erection and dismantling.
In the initial phase concrete used to be placed with the use
of buckets and crane. However, as the heights increased, this
5. TALL BUILDINGS IN INDIA
system was found to be cumbersome and time-consuming.
No authentic data is available on the number of tall building
First concrete pump was patented in Holland in 1932 by constructed in India. Some unauthenticated data are
Jacob Cornelius Kweimn. The popularity of pumps grew in available on the Internet. It is reported that 84 tall building
the 1930s and 1940s. After World War II, many European with heights greater than 140m have been completed and
countries had to rebuild their bombed cities, increasing the 157 buildings with heights greater than 130m or floors more
need for concrete pumps.
than 40 are under construction10. It is also reported that 20
The introduction of hydraulics during the 1950s buildings with heights greater than 150m are on the hold and
revolutionized the concrete pumping industry. Since then some 74 buildings with heights greater than 150m have been
there have been many developments in this field. Today, proposed.

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Although authentic data on tall buildings are not available, High-strength concrete is widely available throughout the
one is able to notice the changing skylines in major world in including India, and its use continues to spread.
metropolitan cities of India. Fig 4 shows the changed Most of the tall buildings constructed in recent past have
skyline of central Mumbai where some of the tall buildings some structural contribution from HSC in vertical column
have been constructed or under construction. and wall elements.

6.2 High-performance Concrete

While using HSC, the emphasis gradually shifted from
compressive strength to other properties of concrete such as
high modulus of elasticity, high density, low permeability,
higher resistance to aggressive chemicals, etc. It was
considered more logical and prudent to describe such
concrete by a more widely embracing term – high-
performance concrete (HPC).

HPC is aptly described in the following ACI definition:

―HPC is the concrete meeting special combinations of
performance and uniformity requirements that cannot
always be achieved routinely using conventional
constituents and normal mixing, placing and curing
Fig 4. Changing skyline of central Mumbai practices.‖

Incidentally, a Special Issue of the Indian Concrete Journal HPC has a number of advantageous properties compared to
devoted to Tall Buildings in Mumbai described in detail the the conventional normal strength concrete (NSC). HPC mix
design and construction aspects of three tall buildings in the can be engineered based on the specific performance
city completed in late 1990s. requirements, such as strength, low heat of hydration,
shrinkage and creep; high impermeability; high workability;
Looking at the constrains in the availability of land in major resistance to high abrasion, high toughness; etc.
metropolitan centers and business districts in the country, it
is obvious that the demand for tall buildings is bound to The ingredients of NSC and HPC are essentially the same
grow in the near future. However, no reliable estimates of cement, aggregates, water and chemical and mineral
projected growth are available. admixtures. According to Neville and Aitcin, the difference
lies in the knowhow – i.e. the knowledge of properties of
6. HIGH-STRENGTH, HIGH-PERFORMANCE ingredients and their interaction11.

CONCRETE FOR TALL BUILDINGS In India, HPC has been adopted recently in the construction
6.1 High-strength Concrete of a few major projects, like the Inner Containment Dome of
the Reactor Building, Kaiga Project Unit-2 (Kaiga-2),
The use and definition of high-strength concrete has Rajasthan Atomic Power Project Unit-3 (RAPP-3), J.J
witnessed continuous upward revisions. In the USA, 35 flyover, Mumbai , and Worli-Bandra sea link.
MPa concrete was considered HSC in the 1950s. In the
1960s, HSC threshold raised to M50 and in 1970s it was For tall buildings too, HPC is an appropriate material and
M60. According to ACI 363:2010 compressive strengths the same is being used at certain locations in India.
approaching 20,000 psi (138 MPa) have presently been used
in cast-in-place buildings. 7. HSC/HPC: SOME CRUCIAL ISSUES

Even in India, the Bureau of Indian Standard’s code, IS 456, In case of HSC/HPC, attempts are made to extract the
has changed its definition of HSC from time to time as maximum possible potential from the properties of different
shown below: ingredients of concrete. In this exercise, the properties of the
ingredients getting utilized are usually pushed to their
IS Revisions HSC grade designation extremes. It is therefore essential to have - what Aitin and
Neville describes - the full "knowhow" of individual
IS 456: 1978: M40, M45, M50, M55, M60 properties of ingredients, their integration with each other
IS 456: 2000 M60, M65, M70, M75, M80 and the effect of variations of these properties on the final
properties of HSC/HPC. As the compressive strength is
IS 456: 2000 M65, M70, M75, M80, M90, M100
increased, such issues become more crucial. This is more so
th
(4 amendment) for grades higher than M60. The following discussion on
the crucial issues is based on the authors' recent laboratory
and field experience in the production of concretes of grades
M60, M70, M80 to M95.
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45.00
7.1 Effect of Variation in Properties of Ingredients
Cement 35.00
All types and brands of OPC may not be suitable for
HSC/HPC. While from the strength perspective, high C3S 25.00
and C3A cement may be desirable, from the rheological
angle, low C3A and C4FA cements may prove to be better. It
15.00
is reported that besides Blaines's fineness of cement, its
alkali, suphate and C3A contents as well as the crystal 600 micron passing
symetry of the latter also affect cement-SCM-admixture 5.00 300 micron passing
150 micron passing
compatibility at low water-binder ratio12. Problems of
cement-SCM-chemical admixture compatibility are -5.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00
reflected in the sudden loss of slump and/or slump retention
over longer duration. As recent experience has indicated Fig 5 Variation in % passing 150, 300 and 600 micron
this may result in serious problems in pumping of concrete sieves
such as choking of pump pipelines, difficulties in
compaction and finishing, etc. 7.3 Supplementary Cementitious Materials
Therefore the compatibility issue of cement and chemical Use of one or more supplementary cementitious materials
admixture on the one hand and cement, SCM and chemical (SCM) become essential to achieve the strength, durability
admixture on the other hand needs to be resolved and other properties of HSC/HPC. Two major categories of
satisfactorily at the initial stage only during lab trials. For SCMs used today include: fly ash and ground granulated
the selection cement, SCM and chemical admixture for a blast-furnace slag. The pozzolanic and/or hydraulic
particular project it is essential to evaluate different properties of SCMs help a great deal in improving the fresh
available brands in lab trials. Based on the lab trials, final and hardened properties of HSC/HPC. These mainly include
decision should taken on procuring the raw materials of improved workability and pumpability, reduction in water
concrete. demand and in the permeability of concrete. Moreover, use
of SCMs has proved to be cost-effectiveness, owing to the
Considering the crucial role of cement in determining the reduction in cement content.
strength and rheology of concrete, Aitcin and Mindess in a
recent article suggest that the cement industry should In addition to these two SCMs, HSC/HPC needs addition of
consider producing two types of ordinary Portland cement, a finer variety of SCMs - either condensed silica fume,
one for water-binder ratio lower than 0.5 and the other ultrafine GGBS, high-reactive metakaolin, rice husk ash or a
higher than 0.513. The parameters suggested by the two combination of thereof. The finer varieties of SCMs are
experts are given in Table 1. highly reactive and their incorporation in the concrete mix
helps in achieving the desired properties of strength and
durability at different ages for HSC/HPC.
Table 1 : Suggested parameters for two types of OPC by
Aitcin and Mindess13
7.4 Chemical Admixture
For concretes with C3A 6% max
w/c < 0.5 HSC/HPC necessarily include one or more chemical
Fineness 350-400 m2/kg admixture. The introduction of 4th generation admixture, i.e.
For concretes with C3A 8% max polycarboxylate-based (PCE-based), which has a capability
w/c > 0.5 Fineness 400-450 m2/kg of reducing the water demand by around 35-40% has been
instrumental in producing concretes having very low water-
binder ratio that are pumpable too.
7.2 Fine Aggregates
In view of the scarcity of river sand in metropolitan areas 7.5 Mix Proportioning of HSC/HPC
and other big cities in India, the use of manufactured sand as High-strength concrete mixture proportioning is a more
an alternative to the river sand has emerged and its use has critical process than proportioning normal-strength concrete
been growing. The mix proportioning of HSC/HPC can mixtures. The use of SCMs and chemical admixtures, and
certainly be done with manufactured sand; however, care the attainment of a low water-binder ratio are considered
should be taken to avoid the use of crushed rock fines (CRF) essential in high-strength concrete mix proportioning. ACI
- a waste product known as quarry dust. As the fractions 363R:2010 provides detailed guidelines8. Aitcin has also
passing 300, 150 and 75 micron sieves play a crucial role in proposed a methodology on mix proportioning of HPC.
determining the water demand in concrete, care shall be
taken to exercise limits on these fractions. Fig 5 shows Many trial batches are often required to generate the data
typical variations of fines passing through the three sieves that helps in identifying the optimum mix proportions of
from a project in Mumbai during monsoon period when HSC/HPC to be used.
severe shortage of sand was experienced..
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7.6 Durability of Concrete used for Tall buildings to the evolution of high heat of hydration. Concrete mixes
used for such elements usually contain high cementitious
Ensuring long-term durability of concrete will be of materials content, low water-binder ratio and sometimes
paramount importance in case of tall buildings. This is lower maximum size of aggregate (the latter in view of
because the maintenance, repair and restoration of tall heavy congestion of steel). The design of such concretes
buildings will be comparatively difficult, time consuming shall be done in such a manner that the peak temperature in
and costly. It is therefore appropriate to introduce stringent concrete shall not exceed 700C and that the thermal gradient
durability criteria for concrete used for Tall Buildings. The within the concrete mass does not exceed 200C.
author would like to suggest the following threshold values
of the most commonly used durability test methods:
While appropriately designed mock trials shall be conducted
prior to actual concreting to demonstrate that these
 Rapid chloride ion permeability test (ASTM 1202) parameters are satisfied, temperature monitoring shall be
 Foundations: Not more than 1000 done in massive elements by installing adequate number of
Coulombs temperature sensors to record temperature data on a
 Superstructure: Not more than 1500 continuous basis to demonstrate that the temperature rise
Coulombs and thermal gradients are within the specified limits.
 Water penetration test (DIN 1048)
 Foundations: 15 mm max
 Superstructure: 20 mm max. 7.9 Fire Resistance of Concrete in Tall Buildings
Fire may be a serious hazard in case of tall buildings. In
7.7 Quality Control and Testing HSC/HPC view of concrete's low thermal conductivity and high heat
Since there are likely to be variations in the properties of capacity, it generally provides better fire protection when
different ingredients of concrete, strict quality control and compared with other construction materials such as steel,
quality assurance procedures needs to be followed aluminum, wood, etc. However, the behavior of HSC in fire
meticulously during the production, transport and placement is slightly different than that of normal-strength concrete. In
of concrete. Otherwise these variations will get reflected in case of fire, HSC has a tendency to exhibit explosive
the final product. In case of HSC/HPC more stricter QA & spalling.
QC procedures need to be followed since this type of
concrete is very sensitive to variations in properties of While densification of concrete microstructure owing to the
ingredients. combined use of low water-binder ratio and large percentage
of SCMs helps in achieving high strength and durability,
For ensuring quality of concrete produced from ready-mixed this very densification of microstructure makes concrete
concrete plants, the Quality Council of India (QCI) has vulnerable to explosive spalling during fire.
already developed a comprehensive framework of audit of
the plant and equipment as well as the production control It is observed that polypropylene fibres if incorporated in
process15. It will be appropriate to have the plant facility concrete melt at about 140-1600C, creating ―channels‖ for
certified under the QCI Scheme. However, this may not steam pressure in concrete to escape, thereby releasing pore
suffice. The QCI audit happens only once in 6 months. For pressure which help in preventing spalling. Further, results
plants producing HSC/HPC, this is too long a period. It is from fire resistance studies clearly show that the layout of
therefore essential to conduct comprehensive production ties and confinement of columns have an influence on the
control audit every month for plants producing HSC/HPC. fire performance of HSC columns. Studies done at NRC
Canada and by Prof Kodur suggest that provision of bent
It is now well established that measured strength of ties at 1350 back into concrete core and closer tie spacing are
HSC/HPC is more sensitive to testing variables. ACI 363 helpful in protecting concrete in during fire14.
reports that measured strengths between laboratories were as
high as 10%. ACI 363.2R provides a detailed guidance on CONCLUSION
testing and quality control of HSC. India is poised to witness considerable growth in tall
building construction and the use of HSC/HPC is bound to
The cost of QA & QC in producing HSC/HPC will be increase. Considering the intricacies involved in the design,
comparatively high. However, considering the resulting production and quality control of HSC/HPC, it is suggested
benefits of improved ability to produce good quality that a comprehensive document should be prepared and
concrete with reduced variations, this will prove to be more published for the guidance of all stakeholders involved in
rewarding. tall buildings.

7.8 Temperature Control in Massive Concrete

Elements
Thick raft foundations are needed to support tall buildings.
Shear walls, columns and transfer beams have massive
sections. Concrete used in such massive elements may lead
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IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308

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