See discussions, stats, and author profiles for this publication at: https://www.researchgate.

net/publication/257389386

Identification of set-accelerator for enhancing the productivity of foam concrete

block manufacture

Article in Construction and Building Materials · December 2012

DOI: 10.1016/j.conbuildmat.2012.07.025

CITATIONS READS
43 1,794

2 authors, including:

Ramamurthy K
Indian Institute of Technology Madras
102 PUBLICATIONS 6,733 CITATIONS

SEE PROFILE

All content following this page was uploaded by Ramamurthy K on 07 January 2018.

The user has requested enhancement of the downloaded file.

Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

Identification of set-accelerator for enhancing the productivity of

foam concrete block manufacture
Sathya Narayanan.J and Dr.K.Ramamurthy
Research Scholar Professor
Building Technology and Construction Management Division
Department of Civil Engineering, Indian Institute of Technology Madras, India

Abstract: Foam concrete is suitable for producing lightweight blocks. This paper deals with

identification of suitable set accelerator for foam concrete made using Sodium Lauryl Sulfate

as foaming agent, i.e. facilitating demoulding within 2 hours and also economical. As

conventional accelerators, viz., Calcium chloride, Calcium nitrate, Triethanol amine were

not-effective in foam concrete, Alum and Class-C Fly ash were tried. Demoulding test was

performed to the mixes having optimum density (1200-1300kg/m3). Class-C Fly ash was

observed as a potential set-accelerator, facilitating demoulding at 90minutes.

Keywords: Set-accelerator; Sodium lauryl sulfate; Foam Concrete; Optimum density;

Demoulding time; Class-C Fly ash.

1 Introduction

There has been renewed research interest in making use of light weight concrete blocks for

wall construction. Attempts are being made to develop light weight solid, hollow and

interlocking blocks. Foam concrete is more suitable for manufacturing of blocks. In foam

concrete, macroscopic air foamed bubbles are produced mechanically and added to the base

mix mortar during mixing. This type of foam concreting technique is called preformed foam

concrete. Foaming agent required for producing aqueous stable foam can be either natural or

synthetic origin.

Foam concrete is highly flowable and self-compacting in nature. Since the foam

concrete contains air bubbles it cannot be rammed and vibrated in a machine to produce the

blocks. Hence the foam concrete needs to be cast in mould. Normal foam concrete when cast

in moulds, can be demoulded only after 24hours. This imposes constraints on the productivity

1
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

of the block manufacture. This also demands a large number of moulds thereby increasing

high cost and will occupy large space. If the process of demoulding could be facilitated by

reducing cycle time, the block production rate can be increased by reusing a reasonable

number of moulds. Hence there is a need to identify suitable accelerator and its dosage which

would reduce the setting time of foam concrete thereby facilitating early demoulding.

Extensive research has been carried out on the use of set-accelerators in normal concrete.

Most of the studies on foam concrete deal with identification of suitable foaming agent,

properties of foam concrete, influence of filler type on fresh and hardened properties of foam

concrete, air void characterization of foam concrete [1-3]. No study has been reported on use

of set-accelerator in foam concrete. In the case of foam concrete, the type of accelerator and

the type of foaming agent influence its performance. This paper first reviews the studies on

use of a few important set-accelerators in concrete, based on which a few accelerators are

identified for the present study.

2 Review of studies on set-accelerators

Accelerators influence the rate of cement hydration, leading to a reduction in setting time

reduces and an increase in early age strength of concrete. The accelerators are used for early

removal of formwork, earlier finishing of surfaces, earlier attainment of strength to carry

construction load. In cold-weather concreting, it accelerates the hydration process because of

low temperature and also prevents damage due to freezing. Acceleration is normally achieved

by i) accelerating the tricalcium aluminate phase (C3A) of Portland cement (Rapid set

accelerators), or ii) accelerating the tricalcium silicate phase in cement (Accelerators for

setting and hardening). Out of the various chemicals reported in literature a brief review of

studies on calcium chloride, calcium nitrate, tri-ethanol amine, lithium salts and calcium

formate as set-accelerator has been presented.

2
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

2.1 Calcium Chloride: It acts as a catalyst and promotes the hydration of C3S and C2S or

reduction in alkalinity of the pore solution promotes the hydration of silicates [4]. Usual

dosage is 2% by the weight of cement [5]. Ramachandran [6] studied the hydration

characteristics of C3S in the presence of CaCl2, and observed that CaCl2 alters the rate of

hydration and also chemical composition of C-S-H. In the mix containing 2% CaCl2 the

setting time is reported to occur at 105 minutes, while it was 790 minutes for the mix without

CaCl2. The presence of CaCl2 leads to corrosion of reinforcement bars [4]. For reactive

aggregates the addition of CaCl2 increases the reactivity of alkali-silica reaction there by

deteriorating the concrete [6].

2.2 Calcium Nitrate (CN): Justnes and Nygaard [7] studied the efficiency of CN as a

set-accelerator for different cements at low temperature and observed that the set-accelerator

efficiency of CN increases with an increase in belite content of cement. The optimum dosage

of CN with ASTM type I cement is 3.86% the weight of cement. CN was observed to

accelerate the C3A phase. Hydration mechanisms were modified which resulted in altered

products. Aggoun et al. [8] studied the set-accelerator efficiency of CN and concluded that it

depends on chemical composition cement.

2.3 Triethanolamine (TEA): Depending upon the cement type and addition rate TEA

can produce either set-acceleration or retardation, i.e., it is a dosage sensitive admixture [9].

In the presence of TEA, the reaction between C3A and gypsum gets accelerated and ettringite

is converted into monosulfoaluminate. Ramachandran [10] reported that the initial setting

characteristics were drastically reduced at a dosage of 0.1%, and 0.5% weight of cement.

Aiad et al. [11] studied on alkanoamines on the rheological and setting properties of cement

paste and reported that TEA accelerate the setting time at a dosage of 0.1% only.

2.4 Lithium salts: Novinson and Crahan [12] studied the use of lithium salts as a set

accelerator for refractory concretes. The reaction rates are related to the pH of the lithium

3
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

salts in mixing water. The lithium cation has more effect than other cation (like Na, K)

because of its smaller size, higher hydration energy and simple electronic structure (Lithium

has smaller crystal radii of 0.6 Å, it has higher hydration energy of 123kcal/mol when

compared to sodium or potassium whose crystal radii is 0.95, 1.33 Å having hydration energy

of 97 and 77 kcal/mol receptively). The class of anion is also very important as it controls the

rate of lithium hydration (Lithium acts as a catalyst. Lithium cation is smaller in size when

compared to sodium and magnesium as a result lithium has higher hydration energy and it

coordinate with many water molecule per atom to hydrate faster). Lithium salts is reported to

acts as quick set accelerator with the anion like carbonate, nitrate, fluoride and tetraborate.

2.5 Calcium formate: The solubility of calcium formate at room temperature is 15%.

Singh and Abha [13] concluded that calcium formate accelerates the C3S hydration with the

dosage of 0.5 to 6%. The effect of calcium formate depends up on composition of cement.

For cements with C3A/SO3 ratio higher than 4, calcium formate is reported to process good

potential for acceleration in strength.

The above review has helped in identifying most widely used / studied accelerators,

their behavior, hydration mechanism and dosage ranges to be tried. This paper deals with the

experimental investigation conducted to ascertain the setting of foam concrete (evaluated

through shape retention while demoulding of cubes) using identified set accelerators. The

objective is to identify accelerators which have the capacity to retain its shape after

demoulding within two hours. As a first stage, the cost effectiveness of the reviewed

accelerators (Calcium chloride (CaCl2), Calcium nitrate (CN), and Triethanolamine (TEA))

based on the dosage recommended in literature have been tried initially. As a next stage, viz.,

Alum (hydrated potassium aluminium sulfate), and Class-C fly ash have also been tried to

explore their potential to serve as an accelerator and to establish their relative performance in

foam concrete with sodium lauryl sulfate (SLS) as foaming agent.

4
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

3 Materials used and methodology

As the water-solid ratio, surfactant concentration and foam volume are normally varied in

foam concrete, to obtain foam concrete with desired density and workability, the performance

of accelerators under varying conditions of these parameters has also been investigated. The

demoulding time of desired mix whose density ratio (ratio of measured/actual fresh density to

the design density) is approximately one were reported in the following sections.

The raw materials used for foam concrete are cement, sand, water, preformed foam

and a set-accelerator. 53 Grade Ordinary Portland cement conforming to IS 12269-1987 was

used throughout this study. The chemical composition of Ordinary Portland Cement and

Class-C Fly ash used are presented in Table-1.

River sand passing through 2.36mm sieve was used. Based on the earlier study of Ranjani

and Ramamurthy [14] commercially available Sodium lauryl sulfate (SLS), has been used as

foaming agent. Two concentrations of Sodium lauryl sulfate, viz., 2% and 8% were adopted.

(Ex: For 2% surfactant concentration, 1000 gram of water, 20 gram of Sodium lauryl sulfate

is added and mixed thoroughly till a homogeneous solution is achieved). Then the solution is

kept undisturbed for 5minutes and then the required quantity of foaming premix solution is

added to the foam generator to produce the foam. The foam was generated using

indigenously developed laboratory scale foam generator by adopting a foam generation

pressure 117 kPa.

The foam volume required to be added to the mix depends on design density of foam

concrete and the density of foam itself. The fresh density of foam concrete was fixed as

1250 kg/m3, allowing a variation of ± 50 kg/m3. The density of foam achieved with SLS is

between 20 to 23 kg/m3 depending on the surfactant concentration. A modified guideline

given in ASTM C796-04 has been adopted for arriving volume of air (Va) and the foam

volume required to be added to achieve a density of 1250 kg/m3.

5
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

1250 kg/m3 = (WTW + WC + WS/FA) / [(WTW/1000) + (WC/(3.15 X 1000)) + (WS/FA/((2.6 or

2.4) X 1000)) + Va] --------------1
3
Va = (0.61WC + 0.52WS – 0.25WTW) / 1250m (only sand) --------------2
3
Va = (0.61WC + 0.48WFA – 0.25WTW) / 1250m (only fly ash) --------------3

Vf = 1000Va / (1000 – Df)/m3 --------------4

Where, Va - Volume of air, (m3), Vf - Volume of foam, (m3), WC - Weight of cement, (kg),

WS/FA - Weight of sand/fly-ash, (kg), WTW - Weight of total water including weight of foam,

(kg), Df – Density of foam, (kg/m3).

4 Fresh properties of accelerated foam concrete

Having arrived at the foam volume required to produce foam concrete of 1250 kg/m3, as a

next step, the water-solid ratio required to achieve this density needs to be determined

through stability test. At lower water-solid ratio, the mix will be dry and bubbles will escape

resulting in increased density, while at higher water-solid ratio there is again increase in

density as higher water content make the slurry too thin to hold the bubbles resulting in

segregation of the mix. Hence for a stable mix there is a small range of water-solid ratio in

which the mix will be closer to the design density.

4.1 Stability test: To assess the stability of fresh concrete, the water required was

gradually increased and the fresh density of foam concrete was measured in container of

known volume (0.0012m3) and its density was compared with the design density.

Based on the mix proportion (cement-sand), surfactant concentration (2 and 8%) and

type of accelerator (alum, Fly ash), the specific gravity of the material (when sand is replaced

with fly ash) and the fines in the mix vary, due to which the water demand varies to achieve

the design density of 1250 kg/m3. After determination of the optimal water-solid ratio which

produces a density ratio of closer to one, such mixes are taken up for studying the influence

of accelerators in reducing the setting time of foam concrete.

4.2 Demoulding test: As the objective of this study is to facilitate faster demoulding of
6
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

the interlocking blocks, instead of conventional setting tests it was decided to adopt

demouldability of 50mm cube specimens, i.e., the ability of the cube to retain its shape after

demoulding as a basis for arriving at the relative performance of the accelerator. Totally

12 numbers of 50 mm cubes were cast for each mix (with 3 cubes for each time of

demoulding). The demoulding was started after the top surface of the concrete in the mould

becomes dry and non-sticky. Demoulding of cubes was carried out at 15 minutes interval till

cube was able to retain its shape.

5 Performance of accelerators

5.1 Calcium Chloride: Calcium chloride of commercial grade was used as

set-accelerator. As a first stage, a mix with 1:1 cement-sand ratio, 2% surfactant

concentration and 2% CaCl2 by weight of cement was tried. Soon after the foam was added to

the base mix, bursting of foam bubbles was observed resulting in reduction in the volume of

foam concrete. It was also observed that, for the mixes whose density ratio closer to one,

there was settlement of sand in the bottom of the container. Fig. 1 shows the behavior of

CaCl2 for various mix ratios.

A dosage of 4% CaCl2 was tried with foam concrete mixes of 1:1, 1:2 and 1:3 cement-sand

ratios. The fresh density of foam concrete decreased with an increase in water-solids ratio.

Water demand required to achieve the design density was reduced with increase in sand

content. But at higher water-solid ratio, the settlement of sand and foam bursting occurred at

all the mixes. Such a behavior can be explained through the observations made by Miles and

Ross [15]. They studied the behavior of mixed calcium salts of soaps and anionic detergents,

and reported that for a mix containing solution of sodium lauryl sulfate and calcium chloride

the critical pH value for stable foam is 5.0 to 5.5, while a pH of about 7.0 the foam becomes

unstable and falls to zero. Irrespective of the mix and dosage of CaCl2 the cubes could not be

demoulded up to 4hour 30minutes. Skalny and Maycock [16] reported that pH value of

7
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

concrete containing portland cement and 2% CaCl2 was approximately 12. Hence at this high

pH value foam concrete with SLS as foaming agent, foam become unstable and start bursting

and there was reduction in level of concrete.

5.2 Triethanol amine and Calcium nitrate: Based on literature 0.1% to 1% of

triethanol amine by weight of cement was tried. For these dosages the demoulding time of

foam concrete exceeded 6hour 30minutes. Heren and Olmez [17] studied the effect of

ethanolamines; Monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine

(TEA) on hydration and mechanical properties of white Portland cement. It has been

concluded that ethanolamines showed the retarding effect on setting time of white Portland

cement at various dosage in the order of TEA > DEA > MEA. Similar phenomenon was

observed with foam concrete. A dosage of 3.5% calcium nitrate by weight of cement was

used. The cube could not retain its shape even beyond 4hours. As the conventionally reported

accelerator did not result in reducing the setting time of foam concrete made with SLS as a

next step, Alum and Class-C fly ash were tried.

5.3 Alum: Alum is hydrated potassium aluminium sulfate. Alum instantaneously reacts

with slaked lime discharged by a hydration reaction of cement to form ettringite and thereby

accelerate the setting and curing [18]. Commercial grade alum was tried as set-accelerator.

Initial studies with an alum dosage of 5% by weight of cement, did not result in accelerating

the setting time. Hence dosage of 10% alum was tried on foam concrete with 1:1, 1:2, 1:3

cement sand mixes and two surfactant concentrations of 2% and 8%. For making the alum in

solution form, small quantity of water from the calculated quantity of water was taken. The

influence of water-solid ratios in the fresh densities for different foam concrete mixes with

two surfactant concentrations are presented in Figs. 2 to 4. In these figures the solid lines

represents the fresh density, while long dash line indicates the density ratio. Dotted line

represents the optimum mix.

8
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

It can be inferred from Fig. 2, that for foam concrete with 1:1 cement-sand mix, the water

required to achieve the desired design density is lower for 2% surfactant concentration as

compared to that of 8% surfactant concentration. For 1:2 and 1:3 cement-sand mix

(Figs. 3 & 4) i.e., (with an increase in sand content in the mix) the water required to achieve

the design density of 1250 kg/m3 was same irrespective of surfactant concentration even

though there is variation in profile. For each mix, the range of water-solids ratio which

produces density ratio closer to 1 was noted and demoulding test was carried out within this

range of water-solid ratio and the results are presented in Table-2.

For a given foam concrete mix (say 1:1) the surfactant concentration did not influence the

setting time. As expected, the demoulding time reduced with an increase in cement content in

the foam concrete mix i.e., from 185minutes to 140minutes. Alum exhibited potential to

reduce demoulding time of various mixes of foam concrete.

5.4 Class-C Fly ash: Fly ash is an industrial waste available in large quantities.

Conventionally, studies have been made to utilise fly ash as replacement for cement (as a

pozzolanic material), fine aggregate (as filler) in concrete, manufacture of PPC Cement, fly

ash bricks and fly ash aggregate.

High calcium fly ash (Class-C) is characterised by its hydraulic activity. The main

constituents of high calcium fly ash are free lime, anhydrite CaSO4, reactive silica and

alumina [19]. Higher the ratio of SO3 to f-CaO is beneficial for self cementing characteristics.

After addition of water to the fly ash, it exhibit setting and hydration characteristics. The

main hydrated product, as a result of reaction between fly ash and water are C-S-H and

ettringite. C-S-H is formed by the reaction between f-CaO and active silica in the ash where

as ettringite is formed by the reaction between f-CaO, active alumina and CaSO4 [20]. In

view of the above observations, an attempt has been made in this study to explore the
9
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

performance of Class-C fly ash by replacing sand with fly ash as an accelerator. The range of

replacement by weight considered are i) Complete replacement of sand by fly ash having

cement-fly ash ratio of 1:1, 1:2 and 1:3. ii) Combination mix by partially replacing the sand

by fly ash for the ratios of 1:2 and 1:3. As the volume of fly ash in the mix increases (i.e., at

higher replacement of sand with fly ash), due to increase in fines, the foam volume was

appropriately enhanced to achieve the design density. Because of its self cementing property

and addition of cement in the mix, the hydration mechanisms gets accelerated which in turn

helps in quicker demoulding.

i) Complete replacement of sand by Fly ash

Figs. 5 to 8 show the influence of water-solids ratio in the fresh density of three foam

concrete mixes with Class-C fly ash. With an increase in fines content in the mix due to the

addition of fly ash instead of sand, the water-solids ratio required to achieve design density

was higher than those of cement-sand mix. For 1:1 cement-class-C fly ash mix, the

water-solid ratio required to achieve the design density increased with foam concentration

(Fig. 5). Figs. 6 to 8 indicates that, for 1:2 and 1:3 cement-fly ash mix, as the fines in the mix

was high, the desired density could not be achieved with the calculated quantity of foam. The

desired density in these mixes could be achieved with 150% of foam volume (Figs. 7 and 8).

It is interesting to observe from the Figs. 7 and 8, that a surfactant concentration of 8%

demanded lower water-solid ratio to achieve the desired density.

The range of water-solid ratio which produces density ratio closer to one for various cement-

fly ash mizes are presented in Table-3 along with the corresponding demoulding time.

Though the achieved fresh density was marginally higher 2.3 to 4.5% the demoulding time

almost same for 1:2 cement-fly ash mix with 1.5 times the foam volume. For given cement

fly ash mix, variation in surfactant concentration did not exhibit significant variation in

demoulding time. Keeping the cement content constant, an increase in fly ash content in the

10
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

mix i) demands higher water-solid ratio to achieve the design density, and ii) increases

demoulding ti8me marginally.

ii) Combination mix

Fig. 9 shows the behavior of foam concrete with cement, sand and fly ash mixes. For the

combination mixes, the study was limited to 2% surfactant concentration. For 1:2 mix, 50%

sand was replaced with Class-C fly ash by weight resulting Cement: Sand: Class-C fly ash in

the ratio 1:1:1. For 1:3 mix, the sand was replaced with Class-C fly ash in two levels. One at

33.3% and other at 66.7% resulting Cement: Sand. i.e., Class-C fly ash in the ratios of 1:2:1

and 1:1:2.

The details regarding demoulding time and optimum mix for combination mixes are

presented in Table-4. It is inferred from Table 2, 3 and 4 that for 1:2 mixes of foam concrete,

the mix containing sand requires lower water-solid ratio and foam volume as compared to

those with fly ash to achieve the desired density. In combination mix (1:1:1), it took longer

time to demould when compared to mixes with 100% fly ash or alum. When compared with

1:3 cement-fly ash mix and combination mix (1:1:2, 1:2:1) the water demand required to

achieve the desired density was lower in combination mix because of higher coarser sand

content. Mix containing higher fly ash content demands higher foam volume because of its

higher fineness. Combination mix containing higher fly ash content was able to be

demoulded quicker when compared with other mixes (90 minutes). It was observed that for

all the mix ratios class-C fly ash could accelerate the demoulding time, even though it

demanded higher water-solid ratio and foam volume.

6 Conclusion

The conclusions drawn below are applicable to the materials used and the range of
parameters investigated.

1. Among the conventional accelerators tried, use of i) CaCl2 resulted in instability of foam
concrete mix and mix did not set up to 4hours 30minutes. ii) Triethanol amine and
11
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

Calcium nitrate though produce stable mixes of foam concrete, the setting did not occur
even after 6 hours and 4 hours respectively.

2. Though Alum exhibited its potential to serve as an accelerator for foam concrete with
SLS by facilitating demouldability within 140 minutes to 185 minutes, the dosages
required to such range of setting time makes it uneconomical.

3. Class-C fly ash has been identified as the most appropriate accelerator for foam concrete
mix with SLS. Use of class-C fly ash as (i) complete replacement of sand and (ii)
combination mixes provide flexibility in its adoption as an accelerator.

References

[1] Kearsley EP, Weinwright PJ. Porosity and permeability of foam concrete.
Cem Concr Res 2001;31:805-12.

[2] Nambiar EKK. Influence of composition and pore parameters on properties of

preformed foam concrete, Ph.D. thesis, IIT Madras, India, 2006.

[3] Ranjani GIS. Investigations on the behavior of preformed foam concrete using two
synthetic surfactants as foaming agent, Ph.D. thesis, IIT Madras, India, 2011.

[4] Neville AM. Properties of concrete. Pearson education Inc., India, 2011.

[5] ACI Committee 212. Chemical admixtures for concrete (ACI 212.3R-91). Detroit:
American Concrete Institute; 1999:10-14.

[6] Ramachandran VS. Chemical admixtures handbook properties, science and technology.
Noyes publications, New Jersey, 2002.

[7] Justness H, Nygaard EC. Technical calcium nitrate as set accelerator for cement at low
temperatures. Cem Concr Res 1995;25:1766-774.

[8] Aggoun S, Cheikh-Zouaoui M, Chikh N, Duval R. Effect of some admixtures on setting

time and strength evolution of cement paste at early ages. Constr Building Mater
2008;22:106-10.

[9] Dodson V. Chemical admixtures. Van Nostrand Reinhold, New York, 1990.

[10] Ramachandran VS. Hydration of cement – role of triethanolamine. Cem Concr

Res 1976;6:623-32.

12
Accepted-un-edited manuscript of the paper titled "Identification of set-accelerator for enhancing the productivity of foam concrete block manufacture",
published in "Construction and Building Materials", Construction and Building Materials 37 (2012) 144–152
http://dx.doi.org/10.1016/j.conbuildmat.2012.07.025

[11] Aiad I, Mohammed AA, Abo-EL-Enin SA. Rheological properties of cement paste
admixed with some alkanolamines. Cem Concr Res 2003;33:9-13.

[12] Novinson T, Crahan J. Lithium salt as set accelerator for refractory concretes:
correlations of chemical properties with setting time. ACI Mater J 1988;85:12-16.

[13] Singh NB, Abha K. Effect of calcium formate on the hydration of tricalcium silicate.
Cem Concr Res 1983;13:619-25.

[14] Ranjani GIS, Ramamurthy K. Relative assessment of density and stability of foam
produced with four synthetic surfactants. Materials and Structures 2010;43:1317-325.

[15] Miles GD, Ross J. Mixed calcium salts of soaps and anionic detergents. Industrial and
engineering chemistry 1943;35:1298-301.

[16] Skalny J, Maycock JN. Mechanisms of acceleration by calcium chloride: a review.

ASTM Journal of testing and evaluation 1975;3:303-11.

[17] Heren Z, Olmez H. The influence of ethanolamines on the hydration and mechanical
properties of Portland cement. Cem Concr Res 1996;26:701-05.

[18] Watanabe Y, et al. Process for producing a concrete product. U.S. Patent 6126875,
2000.

[19] Giergiczny Z. The hydraulic activity of high calcium fly ash. Journal of thermal
analysis and calorimetry 2006;83:227-32.

[20] Sheng G, Li Q, Zhai J, Li F. Self-cementitious properties of fly ashes from CFBC

boilers co-firing coal and high sulphur petroleum coke. Cem Concr Res
2007;37:871-76.

13

View publication stats