Vol.2, No.1, January - March 2015

Company News.............................................................1,7Around the world.............................................................2Concrete Innovations & Trends..................................1,3,4Forum.......................................... .................................5,6Mail Box...........................................................................8

(Continued on page no.7)

Now-a-days, it is not uncommon to construct

foundations and other massive elements for tall

buildings, bridges and other structures requiring single 3concrete pour exceeding say 500 m . A designer always

prefers to have reduction in the number of joints as the

provision of joints involves delay in construction with

consequential increase in cost and also because of the

practical difficulties in forming fully-effective joints. Further,

from long-term durability perspective, less number of joints

(or for that matter no joints at all!) is certainly preferable.

The density of the conventional concrete generally varies 3from 2350 to 2600 kg/m . Concrete having an oven dry

3density in excess of 2600 kg/m is termed as heavy

weight concrete. Such concrete can be advantageously

used in two main applications. Firstly for radiation

shielding as the high density slows down and absorbs

the energy released. Secondly, the high mass to volume

ratio is useful as a ballasting and dead-weight

counterbalancing.

Mix proportioning, production and placement of

heavyweight concrete requires special expertise. RMC

Readymix (I) has developed a special product, named TMas Highdensecrete , catering to the needs of the

customers.

TMHighdensecrete for a hospital in Mumbai

(Continued on page no.3)

Company News

Concrete Innovations & Trends

Recently, this product was supplied to a reputed hospital in TMMumbai. The hospital authorities used Highdensecrete for

the construction of 375-mm thick walls for radiation

shielding.

TMUsing hematite aggregates, Highdensecrete was 3designed to achieve a density of 3500 kg/m and the 28-day

compressive strength of 30 MPa. Initial trials were done in the

laboratory and once the customer was satisfied with the TMproperties of concrete, Highdensecrete was transported in

a transit mix to the hospital and placed into the forms. A

slump of 150mm was achieved at the placement site and

there was no segregation in the mix. Before each delivery, the

density of concrete was measured to the satisfaction of the

customer.

Estimating Peak Temperature in Mass Concrete

PCA Study confirms higher solarreflectance of concrete

Concrete does a very good job of reflecting solar energy, confirms a study by the Portland Cement Association (PCA) which measured the solar reflectance index (SRI) of 45 concrete mixes.

Lighter coloured materials (such as concrete) generally have a higher solar reflectance. They reflect heat from the sun and do not warm the air very much. Darker surfaces such as black roofs and dark pavements generally have a low solar reflectance. They absorb heat from the sun and warm the air through convection, which is generally considered undesirable for its effect on the environment. This may have an immediate, local effect, like heat gain in urban areas, commonly known as 'heat island' effect.

The PCA SRI study measured the solar reflectance of 45 concrete mixes in accordance with ASTM C 1549, Standard Test Method for Determination of Solar Reflectance Near Ambient Temperature Using a Portable Solar Reflectometer. These concretes were selected because they represent the range of concrete and concrete constituents typically used in exterior flat work in the United States.

Solar reflectance (sometimes called albedo) is the ratio of solar energy that falls on a surface to the amount reflected. It is measured with a solar spectrum reflectometer on a scale of 0 (not reflective) to 1: (100 percent reflective). Generally, materials that appear light-coloured have high solar reflectance and those that appear dark-coloured have low solar reflectance. The study revealed that all 45 concretes tested according to ASTM C 1549 have a solar reflectance of at least 0.3 and an SRI of at least 29, and meet or exceed LEED requirements. Regardless of mix constituents, concrete in the United States reduce heat islands and qualify for points in the LEED Green Building Rating System.

Earlier study by the CTL Group, USA, on different concrete mixtures representing exterior concrete flatwork (published in Concrete International) showed that the solar reflectance of the cementitious materials has more effect on the solar reflectance of the concrete than the other constituents. While the solar reflectance of the fine aggregate has a small effect on the solar reflectance of the concrete, that of the coarse aggregate does not have a significant effect. With mixtures including fine aggregate consisting of crushed limestone, average solar reflectances of at least 0.64 (an SRI of at least 78) can be obtained using ordinary Portland cement and light-coloured slag cement or using white cement alone. Solar reflectances ranged from 0.34 to 0.48 for mixtures consisting of ordinary Portland cement and dark gray fly ash.

(Source: PCA News and Concrete International)

Haulage weight of transport vehicles

increased in Austria

Recently, Austrian Parliament has unanimously voted in favour of an increase of total weight of 4-axle vehicles circulating on the Austrian road network, from 32 to 36 tons.

This decision of the Austrian National Assembly will go a long way in reducing CO emissions on Austrian roads and will 2

also help in reducing traffic.

The Stone and Ceramics Industry Association and the Ready-Mixed Concrete Association of Austria welcomed the unanimous decision of the National Assembly.

The Austrian ready-mixed concrete producers are a deeply regionally-anchored and mostly owner-managed industry. These are primarily small and medium-sized companies and create jobs in often structurally weak regions.

"By strengthening these companies, it also strengthens the regions in a sustainable way and secures jobs", says Peter Neuhofer, President of the Austrian Ready-Mixed Concrete Association. "Moreover, this new regulation will lead to a reduction of up to 200,000 trips per year and a significant decrease of traffic."

Source: Fachverband der Stein- und keramischen Industrie

Regulatory issues in Quarrying in Australia

Cement Concrete & Aggregates Australia (CCAA) is the industry body for the heavy construction materials industry in Australia. CCAA recently commissioned a study by the Centre for International Minerals and Energy Law (CIMEL) at the University of Queensland Law School (internationally renowned as a leading centre of knowledge in resource law) into the legal and policy frameworks for the extractive industry in Australia. The study report concludes,

“the current regulatory framework for access to and the supply of aggregates in Australia is not optimal and that the regulatory system for the extractive industry is likely to struggle significantly in the future to meet increased demand for aggregate due to increases in population significant infrastructure projects.”

These conclusions are also similar to the 2014 Productivity Commission report on Public Infrastructure in Australia which noted the raft of social and environmental regulation affecting quarries, some of which may impose undue costs and restrict supply. It noted that a failure to allow new quarry developments or expansions, particularly close to cities,“could lead to future scarcity of some key inputs into many infrastructure projects”.

Sounds familiar? Are the Regulatory authorities in India listening?

Source: Policy Priorities for Australia's Extractive Industry, CCAA

Around the World

While these advantages of large volume concrete pours

are obvious, their successful execution demands

attention to specific technical requirements. The most

important technical requirement is to control the risk of

early-age thermal cracking. The risk mitigation exercise

generally includes a variety of provisions such as

appropriate selection of concrete mix ingredients and

their proportions, control on temperature profiles in fresh

and hardening states of concrete, insulation or cooling

of cast elements, etc.

Incidentally, it is observed that the risk of early-age

thermal cracking also exists in deep lift construction, for

example, in walls, deep beams and large-sized

columns. Neville reports that

mass concrete temperature

prof i les are observed in

concrete elements that are only 10.5-m thick ! Many of the deep

lift constructions that are being

done today are more than 0.5-m

thick. Thus, it is highly essential

to take proper precautions while

designing and constructing

concrete elements using large

concrete pours and deep lift

constructions.

With a view to control the risk of

thermal cracking, codes and

standards do not specify the

exact value of the lowest

p o s s i b l e p l a c e m e n t

temperature for mass concrete.

Some guidance on initial

c o n c r e t e p l a c e m e n t

temperature is available in the

standards on hot-weather

concrete. For example, ACI's guide on hot-weather

concrete (ACI 305R-10) recommends the initial concrete

placement temperature should be limited to 24-38°C,

depending on the placement conditions. The Indian

Standard on Extreme Weather Concreting, IS 7861,

suggests to maintain the placement temperature below 040 C.

For mass concreting some consultants and concrete

technologists specify much lower limits. Although there 0are cases in India where around 20 C placement

temperature was specified and achieved in actual

practice, a number of practical difficulties exist in

achieving lower temperatures. It is well known that

replacing ordinary Portland cement with supplementary

cementitious materials (SCMs) like fly ash, blast-furnace

slag, metakaolin, etc. reduces the heat of hydration.

However, there are code-specified restrictions on the level of

percentage replacement of ordinary Portland cement by

SCM and the mix designer also needs to take into account

the early-age strength requirements. The use of cold water

and ice flakes are effective in reducing the placement

temperature. In particular, use of ice flakes as a part

replacement of mixing water is quite effective in bringing

down the placement temperature.

However, storing and dispensing of ice involves certain

operational difficulties. RMC Readymix (India) is able to

overcome all such problems

and has been producing a

special product, named as TMThermocrete , catering to the

specific placement temperature

requirement of its client.

Here, it must be stated that

engineers and contractors need

to understand that there is cost

involved in reducing every

single degree of the placement

temperature. Restricting the use

of supplementary cementitious

materials or specifying the limit

on the percentage replacement

of OPC may not lead to cost-

effective and technically-sound

solution. Further, wherever

possible the minimum 28-day

compressive strength criteria

need to be replaced with say 56-

day or even 90-day criteria

(especially for foundations).

In addition to placement temperature requirement, two other

temperature-related parameters are equally important in

mass concrete and deep-lift applications. The first relates to

the maximum allowable temperature gradient and the

second to the permissible peak temperature within the

concrete mass. As regards the former parameter, there

seems to be a broad agreement amongst concrete

technologists that maximum temperature difference

between the hottest portion and the surface of the concrete 0should be limited to 20 C to avoid possible internal cracking.

Strict enforcement of this requirement becomes the

responsibility of the contractor who needs to devise a

suitable insulation regime. Further, the removal of insulation

(Continued on page no.4)

Concrete Innovations & Trends

(Continued from page no.1)

ThermocreteMix with the Best

Beat the Heat

(Continued from page no.3)

and formwork need to be based on temperature

monitoring with the help of thermo-couples inserted in

the concrete mass at suitable levels and locations. It is

heartening to note that a few leading contractors in India

have started adopting such practice.

The second important factor is to estimate the peak

temperature within the body of the concrete mass. ACI

310 on structural concrete limits the maximum 0temperature in concrete to 70 C to minimize concerns

due to a phenomenon known as Delayed Ettringite

Formation (DEF). It is observed that high temperatures

during hardening of concrete may inhibit the normal

formation of ettringite, resulting in both sulfate and

alumina being encapsulated in the rapidly forming inner

calcium-silicate-hydrate (C-S-H). Later, in the long run,

the sulphate and aluminate absorbed by the C-S-H are

released into the pore solution of the hardened cement

paste and form ettringite. This ettringite tends to grow in

small, confined spaces, and as it expands, it leads to

very significant pressures that cause the concrete to

expand and crack. Therefore it is essential to control the 0peak temperature of concrete below 70 C.

For arriving at the temperature profiles at different

intervals including the peak temperature, experts can

conduct a complicated thermal analysis with the help of

finite element analysis in combination with cement

hydration model. However, from practical perspective,

ready-mixed concrete producers need to have a rough

idea of the possible peak temperature when designing

their concrete mixes. With this in view, a researcher from

Europe has recently developed an innovative

Nomogram (Fig 1) which enables quick and reliable 2estimation of peak temperature in concrete .

The procedure of obtaining the estimate of peak

temperature from the nomograph is simple. The inputs

required for this purpose are: cement type, unit mass of

total binder content, effective percentage of SCM,

element thickness, initial concrete temperature, and

average ambient temperature. Amongst these inputs,

finding out the effective percentage of SCM requires the

use of equation which is included in the paper.

The nomogram is validated with field data and it was

observed that the prediction error was of the order of only 04 C. The nomogram was evolved for European cement

CEM I 42.5. The author has however developed graphs

to find out corrected values for CEM I 32.5 and CEM I

52.5 cements. Thus, the nomogram is indeed a good

tool for the ready-mixed concrete producers for quickly

Concrete Innovations & Trends

2Fig 1 Nomogram for estimating peak temperature in concrete

arriving at the desired peak temperature by making suitable

adjustments in the mix proportions.

Can we use this nomogram in India? The answer to this

question is – not in the present form! This is mainly because

the hydration kinetics of Indian cements may be different

from those of the European varieties. Secondly, we observe 0

that in India the ambient temperature Ta goes above 40 C 0reaching around 45 C or even more at some locations and

the specified initial concrete temperature Ti also exceeds 0 030 C, going up to 35 C. Therefore, the boundary conditions

in the current nomogram need to be accordingly extended.

We suggest that attempts should be made to develop a

nomogram suitable for Indian cements and the higher

ambient temperature prevailing in India. Possibly, the

academics in India can a take a lead in this direction and

develop nomogram suitable for indigenous materials and

conditions. RMC Readymix (India) would be pleased help

this process by participating in the authentication of the

developed nomogram.

References

1. Neville A. M., Properties of Concrete, fourth edition, John Wiley &

Sons Inc., London, UK, 1996.

2. Wilson Ricardo Leal da Silva and Vít Šmilauer, Nomogram for

Maximum Temperature of Mass Concrete, Concrete

International, May 2015, pp. 30-36.

Aggregates used in concrete are generally inert in

nature, in that they will neither react chemically with

cement in a harmful manner nor be affected chemically

by normal external influences. However, sometimes

certain naturally occurring aggregates contain some

active mineral component which can react with alkalis in

concrete, mainly derived from cement. The chemical

reaction between alkali hydroxides in concrete and

reactive component of aggregate is termed as Alkali-

Silica Reaction (ASR), resulting in the formation of an

alkali-silica gel which has a tendency to absorb moisture

and swell. This may result in abnormal expansion and

cracking.

The draft revision to IS 383 on aggregates from natural

sources, which was recently available for wide

circulation, includes separate clauses of ASR and also

specifies the accelerated mortar bar test. It would be

appropriate here to provide broad background

information on the subject and also acquaint readers

with the new IS draft provisions.

Worldwide, ASR is one of the major phenomena of

deterioration affecting concrete structures. Fortunately, it is

not as widespread as other deterioration phenomena, like for

example, corrosion of reinforcement in concrete. However,

when ASR occurs, the adverse effects of disruptive

deterioration of plain and reinforced concrete are quite

serious.

Generally ASR is caused by siliceous minerals like chert,

chalcedony, opal, etc. which could occur in quartzose,

opaline cherts or siliceous limestone and volcanic rock.

Presence of strained and microcrystalline quartz in some

aggregates may also be reactive leading to ASR.

With the rapid depletion of known “safe” clusters of

aggregate sources the concrete industry is now constrained

to exploit unknown sources of aggregates. Simultaneously,

in view of the constraints of energy savings in the production

of cement, it is quite likely that the total alkali content in

cement may sometimes cross the threshold limit. Thus, the

risk of ASR cannot be underestimated.

Forum

Assessment of Aggregates for Potential Alkali-Silica Reaction

(Continued on page no.6)

TM TM TM TMAquaresistcrete •Coastcrete • Dyecrete • FoundationcreteTM TM TM TMEasycrete • Enviroprotectcrete • Elitecrete • Portacrete

TM TM TM TM FRCcrete • Highdensecrete • Megacrete • XpresscreteTM ® TMPerviouscrete • Readyplast • Thermocrete

RMC Specials

Besides ASR, there is another kind of harmful reaction

known as alkali-carbonate reaction (ACR) which occurs

between alkalis and argillaceous dolomitic limestone.

ASR is more widespread than ACR. Both ASR and ACR

are classified under the broad category of alkali-

aggregate reaction (AAR).

It is widely recognised that damage due to AAR can

occur and be sustained only if three basic conditions are

satisfied - first, sufficient alkalis are present in concrete;

second, aggregates contain an alkali-reactive

component; and third, sufficient moisture level is

present within the concrete. The source of alkalis in

concrete could be either from the cement, from alkali-

bearing aggregates used in the concrete, or from

external sources. The moisture level required for the

reaction to occur needs to be of the order of over 80-85

percent of relative humidity. Under dry conditions, there

will be no scope for the reaction to get initiated. There are

examples where ASR-affected aggregates used in

outdoor exposure conditions have shown early signs of

deterioration, but the same aggregates when used in

indoor exposure conditions proved innocuous for a long

time. High ambient temperature is also one more

causative factor. Some aggregates which are relatively

not-so-reactive may show deleterious expansion at 0temperature above 40 C.

Testing for ASR

Past reliable field performance of the aggregates in

existing structures is considered a reliable yardstick in

selecting the source of aggregate for any new

construction. However, if such information is not readily

available laboratory testing of aggregate becomes

essential. IS 4926 on ready-mixed concrete specifies

that testing for potential alkali-aggregate reactivity

including petrography should be conducted at a 5-yearly

interval or when there is a change in the source. A

number of test methods including the conventional

mortar-bar test method are available to verify the

potential reactive aggregates. However, what is

important is to select test methods that are rapid,

reliable, simple and reproducible.

In this context, the revised draft IS 383 provides a good

guidance. The best initial practice would be to carry out

the petrography analysis of aggregates to identify

presence of reactive materials. The IS 2386 (Part 7)

specifies two more tests, namely the chemical method

and the mortar bar method. The chemical method is

quicker; however it is not found suitable for slowly reactive

aggregates or for aggregates containing carbonates or

magnesium silicates. The mortar bar method takes

excessively longer time to get results. The code suggests

that the length change measurements should be taken

periodically at the ages of 1, 2, 3, 6, 9 and 12 months, and if

necessary, at an interval of 6 months thereafter.

The revised draft of IS 383 therefore specifies an accelerated

mortar bar method which requires 16 days and which is

specially found suitable for slowly reacting aggregates. A

comprehensive criteria for qualifying the aggregates as

innocuous has been developed for this test.

One business vertical of RMC Readymix (I) is involved in the

aggregate mining, processing and supply of aggregates.

The Company has been taking care to ensure that the

aggregates supplied by it meet the specifications of various

tests (including the test on evaluating potential alkali-

aggregate reaction) specified by the Bureau of Indian

Standards. A typical third-party test report included in Fig 1

shows that aggregates samples from of the aggregate-

processing plants belonging to the Company was found to

be innocuous. In addition, the Company will be pleased to

share data on the new ASR test viz. accelerated. Mortar bar

test specified in draft IS 383, whenever demanded by the

customers.

6

(Continued from page no.5)

Fig 1 A typical test report showing that aggregates samples from one of the plants belonging to RMC

Readymix (I) was found to be innocuous

Forum

TMEasycrete at Raipur

A developer in Raipur wanted to construct the compound

wall of his housing project without any horizontal joint.

RMC Readymix (I) approached the developer with a TM

proposal to construct the wall with Easycrete and the

same was accepted.

(Continued from page no.1)

mpo aC ny NewsCompany News

does not get affected adversely. Also, the need of carrying

out prolonged curing was impressed upon the contractor .

Further, as against the 28-day compressive strength of 34

MPa specified by the designer, the actual value of strength

obtained was 42 MPa. Further the concrete has developed

and attained a compressive strength of 58 MPa at 56 days.

7

TMThe work involved designing M25 grade Easycrete . This

was done to the satisfaction of the customer. The

standard tests on the fresh concrete such as slump flow,

U box, L box etc. were conducted as a part of the initial

laboratory work.

The thickness of the wall is 230mm and height 2.4m.

Besides achieving a good jointless external finish, the use TM

of Easycrete also helped in completing work speedily.

TMFoundationcrete for a Residential Tower

in Chennai

It was pointed out in the TechBeat issue (Vol. 2, No 4) that

site engineers are required to face two major challenges

in the construction of massive rafts. Firstly, it is essential

to ensure that concrete fully encapsulates the congested

reinforcement and flows easily to all corners of the raft.

Secondly, effective measures are needed to mitigate the

adverse effects of high heat of hydration generated

within the large concrete mass. With a view to meet the

above challenges in a satisfactory manner, RMC

Readymix (India) has developed an innovative special TMproduct – Foundationcrete .

Recently, one of the leading builders in the country TMutilized Foundationcrete for the construction of a large

raft foundation in the central core area of his multi-3storeyed residential tower in Chennai. A total of 2,900 m

TMof Foundationcrete was supplied. While supplying this

concrete it was ensured that the fresh concrete

properties like slump-flow, density, temperature

matched with those specified. Proper precautions were

taken to ensure that the final setting time of concrete

Fig 1 Congested reinforcement in the raft foundation

TMFig 2 Foundationcrete after pouring in raft foundations

Students Visit Lab and RMC Plant

During the month of April a large section of students from

engineering colleges and polytechnic visited the NABL-

accredited laboratory of RMC Readymix (I) as well as the

Ghatkopar plant. Students from following colleges

participated in the industrial visit:

• K. J. Somaiya Polytechnic, Vidyavihar on April 6, 2015

• Sardar Patel College of Engineering, Andheri, Mumbai, on

April 10, 2015

• Saraswati College of Enigineering Kharaghar on April 14,

2015

Students were briefed by Mr. Uttam Bhandare and Ms. Aarati

Prabhu. A large number of students informed the company

officials that they were immensely benefited from the visit to

the plant and laboratory.

Q. : We are a Mumbai-based organization and have obtained concrete from your Company

in the past. We recently learnt that your Company's Laboratory at Ghatkopar received NABL

accreditation. While we congratulate you for this achievement, what are the advantages of

this accreditation for a customer like ours?

A.

accreditation recently under ISO/IEC 17025:2005 in the field of mechanical testing of aggregate, cement and concrete. In

fact, RMC Readymix (India) has the distinction of being the first ready-mixed concrete manufacturer in Mumbai region to

have acquired the NABL accreditation for its laboratory. The Company's incessant quest for technical superiority has

helped us in achieving this milestone. National Accreditation Board for Testing and Calibration Laboratories (NABL) is an autonomous body under the aegis of

Department of Science and Technology, Government of India, and is registered under the Societies Act 1860. NABL

accreditation provides formal recognition of competent laboratories, thus providing a ready means for customers to get

reliable testing and calibration services in order to meet their demands. The certification also means that systematic

procedures given in relevant standards are followed in the working of our laboratory and records are maintained properly.

The laboratory functioning and record keeping are subject to regular audit by the NABL authorities.

For a customer like you, buying concrete from a plant having NABL-accredited lab certainly means a higher level of quality

assurance. With NABL accreditation to our lab, we are of the opinion that there is no need to test samples of our concrete

either in your lab or in a third-party lab. While the slump testing and cube filling operations can be done by our

representative in the presence of your authorized site personnel, you are most welcome to send your representative to our

lab on the day of compressive strength testing to witness the test. Your representative can also witness the procedures of

different tests followed by our lab personnel and the efforts we pursue in maintaining the NABL accreditation.

We may also mention that our Ghatkopar plant is also certified by the Quality Council of India (QCI) under its Production

Control Scheme. Under this scheme we are required to conduct selected tests on concrete and its ingredients at regular

intervals as specified under various BIS Standards.

In addition, we are also required to get the

ingredient testing verified from a third-party lab

once in six months. Thus, stringent testing regimes

under the QCI and NABL certification provide you

double assurance about the quality of our

products.

Incidentally, a variety of testing services of our

NABL accreditated laboratory would be available

to you commercially, even when you are not

obtaining concrete from our Company.

It may be mentioned that the laboratory attached to our Whitefield Plant in Bangalore received NABL accreditation last year.

We have plans to undertake NABL accreditation for some more labs attached with our plants in near future – all this with the

objective of enhancing customer confidence.

We thank you for your compliments. Yes, our Company's central laboratory in Ghatkopar received the prestigious NABL

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Inside view of NABL accreditated lab at Ghatkopar

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