2014.09._e-journal

PUBLISHED BY ACC LIMITED

THE INDIAN CONCRETE JOURNAL

September 2014, Vol. 88, No. 9, Rs. 100. 76 pages

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The Indian Concrete Journal September 2014

Founded in 1927

Published by ACC Limited, L.B. Shastri Road, Near

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of indiv idual authors, and ref lect their

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PUBLISHING / EDITORIAL / ADVERTISEMENT & CIRCULATION OFFICEThe Indian Concrete Journal

ACC Limited

L.B. Shastri Road,

Near Teen Haath Naka

Next to Eternity Mall

Thane (West) 400 604,

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Website: www.icjonline.com

E-mail: [email protected]

[email protected]

Editor: Ashish Patil

Editorial Team:

Ulhas Fernandes

S.M. Abbas

Total number of pages including covers are 76

TECHNICAL PAPERS

11Studies on changes in microstructure and thermal conductivity of cement mortar blended with refractory chemical at elevated temperature Uma Suresh, R. Jeyalakshmi and N. Suresh

20

35

46

FEATURES

04 EDITORIAL

06 NEWS & EVENTS

30 POINT OF VIEW: Effect of excessive cement in prestressed concrete girder C.V. Kand, T.P. Thite and S.M. Litake

THE INDIAN CONCRETE JOURNALSeptember 2014, Volume 88, Number 9

Compressive strength development of blended cement concretes containing portland cement, fly ash and metakaolinFolagbade S. Olufemi and Moray Newlands

Comparative studies on mechanical properties in high performance concrete Karthikeyan Jayakumar and K. Shaheer Ali

A proposed revision in national standards for limits on deleterious material (clay lumps) in fine and coarse aggregate R.S.Londhe and Chinmay V. Naik

51 POINT OF VIEW: Earthquake safety of houses in India : Understanding the bottlenecks in implementation Ramancharla Pradeep Kumar and C.V. R. Murty

64 Analytical modeling of damping Muthukumar G and Manoj Kumar

Contents Sep 2014.indd 3 8/23/2014 10:24:55 AM


EDITORIAL

From the Editors Desk...

In the fourth paper, the authors compare the mechanical and

durability related properties on HPC made using metakaolin,

silica fume and FA concrete.

Limits laid down on percentage of various deleterious

materials in aggregate by most of the national standards

are too conservative. The author of this paper suggests

that the limits on percentage of clay lumps in fine and

coarse aggregate can be raised to 3% and by doing so the

compromise on strength will not exceed 15%. This move

will result in economical usage of natural aggregates thus

reducing cost of the project.

In a very interesting paper, the authors look at earthquake

safety of the houses that we live in and state that 47% of

population in India is living in the highest risk! Seismic

hazard, exposure and vulnerability are diagnosed and India

is divided into 4 levels based on the housing risk factors. The

authors also suggest mitigation plans and current bottlenecks

they perceive.

In the last of the seven papers, the paper looks at damping

as a desirable property of a structure from the earthquake

resistant point of view. The authors have reviewed the various

damping models that are currently in practice.

This month, ICJ has stepped into the 88th year and in itself

has created a history! The standing of ICJ is due to the

contributions of our authors, reviewers and readers over these

decades many of whom are with us for so many years! You

are witness to how ICJ has transformed and has stood the

test of time or rather, knowledge? We look forward to your

inclusive participation for bettering the content and value of

ICJ for one and all, for many years to come!

Best Regards,

Ashish Patil

It appears that India is going to push the accelerator and

rev up the engines for a step jump in development! This

is, going by what our leaders are speaking, the general

sentiment has turned positive. If this comes true, our

readers will get much busier as days go by! Touch wood

let it happen!!

Hopefully this time around, the focus on infrastructure

will also bring in easing of clearances by the authorities

thus complimenting project execution within the budgeted

time and cost. This would translate to not only optimising

resources from choice of material, design performance

and age, but would also bring in aspects of sustainability

and credits for greener construction.

In this issue, the first paper studies the change in

microstructure and thermal conductivity of cement

mortar blended with refractory material under elevated

temperatures. The authors bring forth their findings of

how at temperatures above 800oC, blended material

made by replacing cement with FA and zirconium dioxide

can with help retain 70% of the compressive strength.

Studies on binary and ternary concrete blends containing

metakaolin, FA and OPC has revealed improved

compressive strength and is found that the cost for

45 N/mm2 strength is optimised when the level of

metakaolin blending is kept at 5%.

In a case study on a flyover, the effect of excessive cement

used in pre-stressed concrete girder is studied. The authors

examine the codal provisions of maximum cement, the

problems in precast girder and conduct various tests to

draw up their recommendations.


NEWS & EVENTS

NEWS & EVENTS

Deep FounDation technologies For inFrastructure Development in inDia 2014.

Deep Foundations institute (DFi) of india along with indian institute of technology (iit) Delhi, indian geotechnical society (igs) Delhi chapter and construction industry Development council (ciDc) will host a two-day conference on Deep Foundation technologies for infrastructure Development in india at iit Delhi during september 19-20, 2014.

Contact:Deep Foundations Institute of Indiae: [email protected]: www.dfi-india2014.org

aKcs september 2014 programs

the september 2014 programs of ambuja Knowledge centre include the following:

AKC (Andheri)september 18-29, 2014: Workshop on concrete

mix Design

september 19, 2014: managing shrinkage in

large concrete structures (speaker: er. Yogini

Deshpande, renuka consultants)

september 25-26, 2014: Workshop on advance

concrete mix Design

september 26, 2014: non Destructive testing for

concrete structures (speaker: er. hiren Joshi)

AKC (Belapur)september 26, 2014: acceleration & retardation

of cement hydration in concrete (speaker: Dr.

viswanathan mahadevan, technical head south

east asia, basF india)

AKC (Nalasopara)september 24- 25, 2014: Workshop on concrete

mix Design

ContactAmbuja Knowledge Centre, Mumbaie: [email protected]: www.foundationsakc.com

precast concrete technologY

the indian concrete institute is organising a one-day national seminar on precast concrete technology on september 27, 2014 at veer savarkar hall, shivaji park, Dadar, mumbai. the theme is challenges, methods and practices.

the main topics of the workshop are: Design aspects;

production process; transportation and erection; Joints and

connections; admixtures for precast concrete; steel fibre

for precast concrete; precast in infrastructure bridge and

tunnels; Formwork and moulds for precast concrete

Contact:Indian Concrete Institute Mumbai Centree: [email protected] w: www.indianconcreteinstitute.org

FiDic construction WorKshop 2014

ubm india will be organising the FiDic construction workshop 2014 to be held during september 29-30, 2014 at mumbai. this workshop will be addressed by international FiDic expert (Kelvin hughes) along with indian expert giving practical case studies from the indian market. this two day conference will focus on the importance of FiDic in indian infrastructure, epc agreement, FiDic Design


NEWS & EVENTS

NEWS & EVENTS

built, nsc, claims and dispute resolution and strategies to create synergy between employer and contractor.

Contact:FIDIC Construction Workshop 2014e: [email protected]: www.fidicindia.com

pre-cast concrete technologY

the association of consulting civil engineers (acce) india bangalore centre is organising an international seminar and exhibition on recent Developments in Design and construction for pre-cast concrete technology paper to practice to be held during 9th-13th november, 2014 at nimhans convention centre, bengaluru, india.

expert speakers from across the world and india have confirmed and will be sharing their knowledge during this event. Few of the confirmed speakers are: ar. r sundaram, india; Dr. gian carlo giuliani, italy; per oluf h Kjaerbye, Denmark; prof. Fermin blanco, spain; prof. spyros tsoukantas, greece; prof. Xilin lu, china; mr. bruce Fairbanks, spain; prof. roelschipper, netherlands; prof. Jan b. obrebski, poland; Dr. lai hoke sai, singapore; mr. mohan Kumar, singapore; mr. c. Kirubakaran, singapore; prof. ing. camillo nuti, italy; prof. mahesh tandon, india; mr. senou Krishnamoorthy, india; mr. abhishek murthy, singapore; Dr. Denis Konin, russia; prof. behrokh Khoshnevis, usa; Dr. mark son, russia, prof. akira Wada, Japan.

Contact:REDECON 2014e: [email protected]: www.redecon.in

emerging trenDs in sustainable habitat anD integrateD cities

the 12th international conference and exhibition on emerging trends in sustainable habitat and integrated cities

will be held during november 13-15, 2014 at mahatma mandir, gandhinagar, gujarat.

Contact:Sustainable Habitat and integrated citiese: [email protected] w: www.municipalika.com

bc inDia 2014

messe mnchen international, germany is organising the bauma coneXpo shoW bc india 2014 during December 15-18, 2014 at india expo centre, greater noida / Delhi.

the last event in February 2013 in mumbai attracted a total of 710 companies from 33 countries and more than 28,000 trade visitors. Following two successful events in mumbai, bc india is moving to Delhi for its next show.

ContactbC Expo India Pvt. Ltd.e: [email protected] w: www.bcindia.com

concrete shoW inDia 2015

concrete show india 2015 will be held during 7 9 may, 2015 at the bombay convention & exhibition centre, mumbai.

Contact:Concrete Show India 2015e: [email protected]: www.concreteshowindia.com

protect2015

the Fifth international Workshop on performance, protection & strengthening of structures under extreme loading - protect2015 will be held during June 28-30,


NEWS & EVENTS

10

NEWS & EVENTS

2015 at michigan state university in east lansing, mi, usa

the main topics of the workshop are:

performance of structures

strengthening of structures under extreme loading

performance of materials

structural management and protection

ContactPROTECT2015e: [email protected]: www.egr.msu.edu/protect2015

report construction inDustrY Database

the first task Force meeting for ciDc - construction industry database was held on 25th July 2014 at the india international centre, new Delhi. the meeting drew participation from both the private and public sector and representatives from leading construction organizations like ircon, nbcc, epil, eil, l&t, etc. Keeping in view, the focus of the government on providing impetus to infrastructure development, a tremendous opportunity exists in the development process by supplying goods & services to the major project owners & their contractors & service providers. construction of river bridges, highway bridges and structures, tracks for railways, sports stadia, industrial buildings, residential and commercial complexes, integrated projects for power generation and distribution systems, air conditioning systems, finishing/ interiors works, piling located at various locations across india and other south asian nations present opportunities that demand a whole array of products and services to deliver on time and within costs. the task is very large in volume and scope with corresponding increase in procurement of goods & services, increasing from the present annual level of usD 70 billion to over usD 200 billion per annum in the 12th plan. a reliable and robust construction industry Database is the need of the hour that may be browsed by the project owners and implementers alike for finding the right set of organizations that can deliver.

construction industry Development council (ciDc), understands the importance of this exercise and with an intent to create one seamless database for use by all stakeholders, calls upon your expertise to fix the framework, categories, and the registration process for prequalification of construction companies, material handling organizations

and service providers for the ciDc construction industry Database.

Benefitsthe database will be representative of the demands of the construction sector in india and south east asia and encourage project owners and implementers to log in to the same for finding the right match for their requirements. some envisaged benefits are listed below:

better and more efficient procurement of ser-vices and goods

better authenticity and capability assessment of the supplier and listed organizations

regular updation regarding costs and product range

Processin order to save on the time being spent on prequalification of vendors in various categories, ciDc proposes to undertake the first round of site inspections of all the applicants participating in this process. the final listing of any entity in the database shall only be based upon the report submitted by the ciDc evaluation team post site inspection.

the process would include:

call for registration to be published every quarter

submission of application in pre-prescribed for-mats along with relevant annexure

site inspections

presentation of the report to the Jury

Fixing of category listing based on Jury recom-mendation

the task Force members endorsed this initiative and suggested scalability, robustness, timely inspections as some of the key features that need to be inbuilt in the process for making this effort a truly representative one for the indian construction industry. members expressed their willingness to participate in Jury meetings and volunteered to nominate the concerned officers from their respective organizations.

Contact:Construction Industry Development Council e: [email protected]: www.cidc.in

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PB 11The Indian Concrete Journal September 2014 The Indian Concrete Journal September 2014

TECHNICAL PAPERTECHNICAL PAPER

Studies on changes in microstructure and thermal conductivity of cement mortar blended with refractory

chemical at elevated temperature

Uma Suresh, R. Jeyalakshmi and N. Suresh

The Indian Concrete Journal, September 2014, Vol. 88, Issue 9, pp. 11-19

The present study explores the influence of zirconium dioxide as refractory material in blended cements. Zirconium

dioxide has been replaced by 2% and 4% by mass in fly ash blended cements. Mortar cube specimens were prepared

and exposed to different level of temperature up to 800oC for 2 hours and 4 hours, after 28 days curing. The specimens

were tested for compressive strength after air cooling and were found to retain compressive strength. Microstructural

studies were carried out through X-ray diffraction and SEM analysis. It was found that Gismondine and Afwillite formed

at higher temperatures had influence on cement mortar.

Keywords : Cement; elevated temperatures; fly ash; zirconium dioxide; X-ray diffraction; SEM; thermal conductivity.

INTRODUCTION

There has been significant increase in the production

of blended cement since the mid- nineties due to the increasing demand of sustainability in the construction sector. A number of researches have been carried out using blended cement because of the advantages of mechanical properties and durability provided over normal Portland cement. Replacement of cement by various percentages of silica fume, fly ash, metakoalin and G.G.B.F.S. has

yielded improved mechanical properties, decreasing the rate of hydration, decreasing the permeability of concrete [1 - 8]. Most of the researches are towards the effect of mineral addition in terms of the strength of mixes and durability benefit. Few reports on the study of hydration

kinetics oxides of chromium, titanium on tricalcium

silicate paste are reported and observed to have higher

rate of hydration at the replacement level of 2% [9] [10]. The addition of PbO, ZrO2 and Cr2O3 as admixtures accelerated the hardening of the cement mortars when added to cement in percentages of 0.7, 1.0 and 4%.This effect is shown by the accelerated strength development of related mortars [11]. The addition of transition metal oxides to raw mixes does not affect the formation of Ca(OH)2 during hydration of the cement. The transition metal (Zr,Ti,Cr) ions preferably substitute Si4+ in the matrix [12].

Most concretes are subjected to temperatures no more severe than that caused by weather but in certain important cases the concrete is subjected to sustained elevated temperatures. Such instances being accidental fires in building, furnaces, chemical metallurgical

industrial applications, jet aircraft runways, nuclear reactors, oil and gas industries [13, 14]. Such fires and

12 13The Indian Concrete Journal September 2014 The Indian Concrete Journal September 2014




elevated temperatures result in considerable physical deterioration included spalling, cracking etc. and damage

to structures. In general, at nearly 100oC the physisorbed moisture (free water) begins to evaporate. Though elasticity is reduced by about 10%-20%, the compressive strength remains unchanged. As the temperature exceeds 300oC, the hydration water of silicate is released and causes the paste to contract. However, in concrete, the aggregate depending on their type it may expand. The temperature range of 400o-500oC, considerable loss in the compressive strength occurs. Most of the compressive strength before heating may be lost from 600o-800oC. It is because the calcium hydroxide and other cement hydration products begin to dehydrate, which contributes to the deterioration of concrete structure. Above 900oC, calcium carbonate decompose by the loss of carbon-di-oxide along with loss of free or bound water. Under exposure to high temperature, a change in pore structure like increase

in concrete permeability and incompatibility between the aggregate and cement paste worsen the durability characteristics [15, 16, 17]. Compared with compressive strength, tensile splitting strength suffers a more severe loss under identical temperature, as the latter is more sensitive to thermally induced cracking [18].

Fly ash blended Portland cement pastes have performed

better at these temperatures than Portland cement alone since the fly ash reduced the amount of Ca(OH)2 in the binder following hydration . Inert materials like quartz,

calcite, TiO2, alumina, ZrO2 enhance the cement hydration and thus improve the thermal resistance [19. 20, 21, 11]. When the amount of fly ash in cement clinker is increase

from 15% to 35% the compressive strength of the mortar decreased. When the replacement was 25% the mortar

gave the highest compressive strength [22]. Zro2 is used in ceramic industry due to it hardness and high melting point. When nano fly ash and Zro2are added to polyimide composites, its mechanical properties increases [23]. The use of TiO2 and Zro2 together with fly ash in applications where these components are subjected to elevated temperatures is based on the fact that TiO2 and Zro2 have mineral phases with certain properties analogues to those of silica contained in the fly ash. Under certain conditions

of temperature and composition, the silica or calcium silicate crystals may become distorted as a result of the replacement of Si4+ ions by Ti4+ ions,/Zr+4 producing different types of titanates in the CaOSiO2TiO2 system [9, 10]. Therefore, the mixture of FA and residues with

TiO2 mineral phases may generate different thermally stable titanates at high temperatures [24].

Ali Nazari et al have reported that the replacement of

cement by 0.5%-2.0% nano ZrO2, nano TiO2 and nano Al2O3 improves the tensile strength and flexural strength [25, 26, 27, 28]. They have also reported that the split tensile strength of self compacting cement with 4% replacement of ZrO2. The pore structure of the SCC also improved with the increase in content of mesopores and macropores. The compressive and flexural strength of

cement with nano silica and nano Fe2O3 were higher than that of plain cement. The nano materials in such instances not only act as fillers but also as an activator to promote

hydration and thus improve the microstructure [29, 30].

In the present study, an attempt have been made to determine the thermal resistance of ternary mixture of refractory material with fly ash blended cement under

sustained elevated temperature condition

Materials and Mixes

Fly ash was introduced as 20 % replacement by mass

of cement. Portland cement graded as 43 confirming to

IS 8112, was used for this study. The fly ash was siliceous,

with chemical composition conforming to Part 1 of IS: 3812 as shown in Table 2. The properties of plain cement and that blended with fly and fly ash with zirconium dioxide

is given in Table 1. The refractory chemical zirconium

dioxide were added as replacement at 2% and 4% by mass of cement, along with reference mix having portland cement as sole binder. All mixes were proportioned and

Table 1. Properties of mixesSl. No.

Material Properties CM CM20FA CM20FAZrO2

2% 4%

1. Specific Gravity 3.4 3.20 3.12 3.08

2. Consistency (%) 33 28 30 30.5

3. Initial Setting time (min) 88 80 87 76

4. Final Setting time (min) 190 165 165 170

5. Compressive strength at 28 D 47.65 48.05 53.02 51.2





Table 2. Chemical properties of fly ash used

Sl. No.

Test conducted Obtained results

Requirements as per

IS 3812 :2003 [22] Part 1

1. Specific Gravity 2.0 ----

2.

Fineness, specific surface area determined by Blaines Air Permeability apparatus, (minimum)

298 320

3.Soundness, by autoclave expansion of contraction in %, (maximum)

0.035 0.8

4.Particle retained on 45 micron IS sieve (wet sieving) in % maximum.

38.5 34

prepared as per IS 10262 to achieve a 28 day strength .The water to binder ratio was maintained at 0.3. A total of 276 cement mortar cubes of side 70.6 mm were cast. Sixteen specimens of each mix were cast. The cubes were cured for 28 days at the end of which, they were air dried to remove the surface moisture. Three cube samples from each mix were exposed to specific temperature 100C, 200C, 400C, 600C and 800C for a duration of 2 hours and 4 hours. An electric oven measuring 1.1 m x 1.0 m x 2.1 m was used to attain the elevated temperatures. The temperature was increased to predetermined value and then sustained at that level by an automatic digital control unit. The heated specimens were the removed from the

oven and left to cool to room temperature. Samples for XRD and SEM analysis were obtained from the cubes used for compressive test.

RESUlTS AND DISCUSSION

A) Effect of temperature and exposure time on

strength with and without addition of ZrO2 to CM and CM20%FA

The compressive strength of the mixes which was replaced by 20% of fly ash showed an increase in compressive of

about 15% as compared to normal Portland cement, Figure 1. At 100oC, the increase in strength could be due to the secondary hydration of cement caused by evaporation of free water. The mortars which were blended with fly

ash & zirconium dioxide (CM20FA and CM20FA2%ZrO2, CM20FA4%ZrO2) also showed an increase in strength at all elevated temperatures. The mixes which were blended with both fly ash and zirconium dioxide showed a

strength gain of nearly 20-25% at room temperature. Figure 2 shows the %residual strength for the mixes CM,

CM0FA2%ZrO2, CM0FA4%ZrO2, CM20FA, CM20FA2%ZrO2, CM20FA4%ZrO2 exposed to elevated temperatures of 100

o, 200o, 400o, 600o, 800oC for a duration of 2 hours and also at room temperature. It can be observed that the mixes CM0FA2%ZrO2 and CM0FA4%ZrO2 is able to retain a better

Figure 1. Compressive strength (CM, CM20FA and CM20FA 2ZrO2

CM20FA ) at different temperatures after 2 hr exposure.4ZrO2

compressive strength for 2 hr exposure

CM

CM20FA

CM20FA 2% zro 2

CM20FA 4% zro 2

Temperature, C

room 100 200 400 600 800temp

Co

mp

ressiv

e s

tren

gth

80

70

60

50

40

30

20

10

0

Figure 2. Residual compressive strength (CM, CM20FA and

CM20FA CM20FA ) at different temperatures after 2 hr 2ZrO2, 4ZrO2

exposure.

% R

esid

ual

str

en

gth

160

140

120

100

80

60

40

20

0

RT 100 200 400 600 800

% Residual compressive strength 2hr

CM

CM0FA2%ZrO2

CM0FA4%ZrO2

CM20FA

CM20FA2%ZrO2

CM20FA4%ZrO2

Temperature, C





strength than the mix CM at all the temperatures. Though the residual strengths of all the mixes are decreasing with increasing temperature, the mixes CM0FA2%ZrO2, CM0FA4%ZrO2, CM20FA2%ZrO2, CM20FA4%ZrO2 have a better residual strength than the mix CM. The ternary blends perform better than the binary and plain cement when exposed to higher temperature.

There is a decrease in strength of all mixes for four hour duration of exposure. But CM20FA and CM20FA2%ZrO2, CM20FA4%ZrO2 had a 30 -33% better compressive strength, as compared to the plain cement mortar, Figure 3. Figure 4

shows % residual strength of the mixes CM, CM0FA2%ZrO2, CM0FA4%ZrO2, CM20FA, CM20FA2%ZrO2, CM20FA4%ZrO2

exposed to elevated temperatures of 100o, 200o, 400o, 600o, 800o for a duration of 4 hours. The mixes CM0FA2%ZrO2, CM0FA4%ZrO2, CM20FA2%ZrO2, CM20FA4%ZrO2 have retained the compressive strength till 400oC for 4hour duration of exposure. Even though the residual compressive strength decreased by 60% for the mix CM20FA4%ZrO2 at 600

o, 800o, it has retained better strength than the mixes CM20FA,

CM20FA2%ZrO2.

Figures 5 and 6 represent the XRD diagrams of cement

mortar at room temperature and 800oC respectively. The decrease in strength can be explained by the decomposition of calcium silicate hydrates (2-theta =32o

-34o, 50o) at 800oC. These phases are absent in the mortar

Figure 3. Compressive strength (CM, CM20FA and CM20FA2ZrO2,

CM20FA ) at different temperatures after 4 hr exposure4ZrO2

co

mp

ressiv

e s

tren

gth 60

50

40

30

20

10

0

Temperature

100 200 400 600 800room

temp

compressive strength for 4 hr exposure

CM

CM20FA

CM20FA 2% zro 2

CM20FA 4% zro 2

Figure 4. Residual compressive strength (CM, CM20FA and

CM20FA CM20FA ) at different temperatures after 4 hr 2ZrO2, 4ZrO2

exposure.

% R

esid

ual

str

en

gth 120

100

0

Temperature

RT 100 200 400 600 800

% Residual compressive strength 4hr

CM CM0FA2%ZrO2

Figure 5. CM Unheated

1000

30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 110.00 120.00 130.00

950900850800750700650600550500450400

350300250200

150

100

50

Cu-Ka1 ( 1.540598A) 2theta

I rel

Experimental pattern

Calculated pattern ( exp. peaks ) (Rp=15.2 %)

[96-901-2601] 02 Si Quartz

[96-901-2725] Si Silicon

1000

25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00

950

900

850

800

750

700

650

600

550

500

450

400

350

300

250

200

150

100

50

Cu-Ka1 ( 1.540598A) 2theta

I rel

Figure 6. CM 800 C

[96-100-8703] Cu0.375 Nd1.625 06.625 Ru2 Neodymium

copper ruthenium oxide (1.63/37/2/6.63)

Experimental pattern

Calculated pattern ( exp. peaks ) (Rp=20.9%)





(CM) after exposure to elevated temperature. The amount of Portlandite (2-theta =18o, 34o, 42o) has increased in the mixes (CM0FAZrO2) and hydrated calcium silicate phases (2-theta = 32o -34o, 50o) has also increased. This can be attributed to enhanced hydration of cement due to the presence of Zirconium dioxide. The Zirconium dioxide also has the ability to form ZrO3

2- and the amorphous ZrO2 which is capable of binding Ca(OH)2 and increases the amount of hydrated phases. This leads to development of compressive strength and stability [11]. The strength loss below 600oC is generally caused by the coarsening of pore structure. There could be an additional loss in strength due to decomposition of calcium hydroxide (portlandite) and calcium carbonate (calcite) [31]. In the mixes CM0FA2%ZRO2 XRD shows the presence of portlandite and calcite both at room temperature and at elevated temperature. The presence of zirconium dioxide has helped these phases

to remain intact and thus the mixes have a better residual strength at elevated temperature.

There has been an increase in compressive strength in mixes (CM20FA, CM20FA4%ZrO2, CM20FA4%ZrO2 ) containing both fly ash and Zirconium dioxide at room temperature

and elevated temperatures for both 2 hr and 4 hr exposure, The increase in strength even at elevated temperature is due to the formation of Gismondine. (2-theta 22o, 28o, 36o) and Afwillite (2-theta 27o, 38o) by the pozzolanic

reaction between fly ash and ordinary portland cement.

The formation of gismondine at elevated temperature above 500oC, is because of accelerated hydration due to the presence of quick lime obtained by the decomposition

of calcium hydroxide and these crystals fills up the pores

and account for better strength of these mixes at 600 and 800 [32, 33].

Marine algae such as U. fasciata deteriorates the concrete structures by the consumption of gismondine formed in the concrete. This indicates the importance of gismondine for the maintaining the strength of concrete [34]. Ettringite and gismondine are the main products found in stabilized

clay with the blend of calcium carbide residue and bio

Figure 7. CM20FA2%ZrO unheated2

room temp Zr 2%

Co

un

ts

80

60

40

20

Position, 2 theata

20 30 40 50 60 70

Ett

rin

git

e, h

ille

bran

dit

e

Po

rtl

an

dit

e, S

yn

, C

usp

idin

e,

Calc

ite, E

ttrin

git

e,

ro

sen

hah

nit

e, h

ille

bran

dit

e

Po

rtl

an

dit

e, sy

n, ett

rin

git

e, h

ille

bran

dit

e

Po

rtl

an

dit

e, sy

n, ett

rin

git

e

Calc

ite, ett

rin

git

e

Po

rtl

an

dit

e, sy

n, calc

ite

Figure 8. CM20 FA Unheated

1000

30.00

950900850800750

700650

600550500

450400

350300

250

200

150

100

50

Cu-Ka1 ( 1.540598A)

I rel

40.00 50.00 60.00 70.00 80.00 90.00

2theta


Experimental pattern : FLY ASH ( normal)

[96-230-0371] 02 Si

1000

25.00

900

800

700

600

500

400

300

200

100

Cu-Ka1 ( 1.540598A)

I rel

30.00 35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00

2theta

Figure 9. CM20FA 800 C

Experimental pattern : FA+OPC-800 c-4hrs


[96-901-5085] AL2 Ca6 H64 050 S3 Ettringite

[96-901-6707] C Ca O3 Calcite

[96-900-6838] Ca H2 O2 Portiandite

[96-901-3985] Ca3 H6 O10 Si2 Afwillite

[96-901-0147 ] O2 Si Quartz

[96-900-1690] Ca3 H2 O7.5 Si1.5 Hillebrandite

[96-901-5085]Ai2 Ca6 H64 O50 S3 Ettringite





Position, 2Theata

Ett

ein

git

e

20 30 40 50 60 70

Co

un

ts

2000

1500

1000

500

0

Figure 10. CM20FA 100 C 4%zro2

4Z14

Calc

ite, sy

n

Calc

ite, sy

n

Figure 11. CM20FA 800C 4%zro2

Position, 2Theata

Gis

mo

nd

ine

Calc

ite, (C

alc

ite, M

ag

en

siu

m, S

yn

)

Gis

mo

nd

ine C

alc

ite,

(Ca

lcit

e,

Ma

gen

siu

m,

Sy

n)

Ca

lciu

m s

ilic

ate

ox

ide

Gis

mo

nd

ine

Gis

mo

nd

ine

Gis

mo

nd

ine

20 30 40 50 60 70

Co

un

ts

400

300

200

100

0

4Z84

Figure 12a. CM R00MTEMP [2]

Figure 12d. CM0FA4%ZR02ROOMTEMP

Figure 12b. CM 30 C

Figure 12e. 0

CM0FA2%ZR0 300 C2

Figure 12c. CM0FA2%ZR02ROOMTEMP

Figure 12f. CM 0FA at 4002%ZRO

Figure 12g. CM20FA

ROOMTEMP

Figure 12h. CM20FA4%ZRO 2

ROOMTEMP

Figure 12i. 0

CM20FA 200 C2%ZRO2 Figure 12j.

0

CM20FA 800 C4%ZRO2





mass ash at room temperature [35]. Gismondine is

responsible for the long term strength gain a these phases are known to be refractory in nature. These phases are

present even after exposure to elevated temperature for both the durations. The thermal endurance of zirconium

dioxide, Gismondine and an Afwillite allow these mixes

to have a better residual strength at normal temperature and at higher temperatures. The addition of zirconium

dioxide aids in the formation of gismondine.

Micro structural analysis of Mixes at different

temperature

Figure 12 (a, b, c, d) represents the SEM micrographs of

CM, CM0FA2%ZR02, CM0FA4%ZRO2 at room temperature. Figure (12 g, h) represents the Sem micrographs of

CM20FA, CM20FA4%ZRO2 respectively, Figure 12 (e, f, i, j)

represents the SEM micrographs CM0FA2%ZR02 at 300o,

CM0FA2%ZRO at 400, CM20FA2%ZRO2 at 200oC CM20FA4%ZRO2

800oC respectively. From the micrographs it is clear that the mixes containing Zro2 have a dense well structured C-S-H and sheets of Ca(OH)2 at room temperature. This is due to enhanced hydration of cement in the presence of zirconium dioxide [11]. The dense structure of cement gel

is destroyed which has lead to the reduction in strength at higher temperature. The hydrated phases and these the products of hydration C-S-H are not completely destroyed even after exposure upto 800oC. The microstucture of blended cement mortars containing 2% and 4% of zirconium

dioxide indicated compact cement phase with very low porosity. This indicates that the hydrated phases are not

decomposed completely in the presence of refractory chemical Zirconium dioxide and pore coarsening is not observed. The non decomposition of crystalline hydrated phases and the formation of Gismondine supported by

XRD explains the better residual compressive strength of the mortars blended with fly ash and Zirconium dioxide

at elevated temperatures.

Thermal conductivity

Thermal conductivity for mixes CM2OFA2%ZRO2, CM2OFA4%ZRO2 for 2 and 4 hours durations of exposure. Figures 14 and 15 shows the variation of thermal

conductivity with temperature for the mixes . The thermal conductivity study was carried out using KD2 PRO.

Thermal conductivity is an important property of concrete since it controls the propagation of heat in a concrete element. The thermal conductivity of concrete is reduced with the loss of moisture during heating. Concrete with lower cement paste content as in the case of high-strength concrete can be expected to have a lower thermal conductivity than for lean concrete mixtures. [36]

At room temperature the thermal conductivity of the mortar samples decreased with the replacement with 20% fly ash and 2% and 4% Zirconium dioxide. But the

mortar CM20FA2%ZrO2 and CM2OFA4%ZrO2 had greater thermal conductivity than the plain cement mortar CM. For mortars CMOFA2%ZRO2, CMOFA4%ZRO2 ,the thermal conductivity decreased by nearly 23% after being subjected

Figure 13. Thermal conductivity of different mixes for 2 hr duration

of exposure with ZrO2

Temperature

RT 100 200 400 600 800Th

erm

al

co

nd

ucti

vit

y

0.8

0.6

0.4

0.2

0

Thermal conductivity for 2 hr duration of exposure

CM

CM20FA

CM0FA 2% zro 2

CM0FA 4% zro 2

CM20FA 2% zro 2

CM20FA 4% zro 2

Figure 14. Thermal conductivity of different mixes for 4 hr duration

of exposure with ZrO2

Temperature

RT 100 200 400 600 800Th

erm

al

co

nd

ucti

vit

y

0.8

0.6

0.4

0.2

0

Thermal conductivity for 4 hr duration of exposure

CM

CM20FA

CM0FA 2% zro 2

CM0FA 4% zro 2

CM20FA 2% zro 2





to 100oC for 2 hours. The decrease in thermal conductivity could be due to loss of water at this temperature. For

mortars CM2OFA2%ZRO2 and CM2OFA4%ZRO2 the thermal conductivity decreased at 100oC but their values were higher than that of the mix CM. This could be due to lesser loss of pore water, at this temperature in these mixes. Thus between 100oC and 200o C, there is decrease in thermal conductivity for all the mixes. Between 200oC and 400oC the thermal conductivity increases slightly due to the removal of water from the hydrated compounds. The thermal conductivity of cement mortar is expected to decrease at temperature between 600o C and 800o C. This is due to decrease in crystallinity with increase in temperature. The thermal conductivity decreases when the heating temperature increases. This is due to the deterioration of the micro structure. The voids limit the heat transfer. [37]. This also could be due to filled action of

ZrO2. [38] The decrease thermal conductivity of the mixes CM20FA2%ZRO2 and CM2OFA4%ZRO2 is lower than the mix CM. This means that the thermal endurance of zirconium

dioxide and the presence of thermally stable gismondine in the cement mortar has prevented the disintegration of C-S-H gel formed. This accounts for the better residual strength of these mortars at the temperature 600oC.

CONClUSIONS

The replacement of portland cement by 20% fly

ash improves the compressive strength of mortars at elevated temperatures of 100oC, 200oC, 400oC, 600oC, 800oC by about 15%.

The addition of 2% and 4% zirconium dioxide

along with 20% fly ash helps in retaining the

compressive strength upto 70% at all elevated temperatures and durations of exposure.

The addition of 2% and 4% zirconium dioxide

facilitates the formation of gismodine in the fly

ash blended cement mortar

The increase in thermal endurance could be because of formation of Gismondine and

Afwillite which is refractory in nature and are not decompose by elevated temperatures aids in retaining the compressive strength.

1.

2.

3.

4.

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Luis F. Vilches, Constantino Fernndez-Pereira, Joaqun Olivares del Valle, Jos Vale, Recycling potential of coal fly ash and titanium waste as new fireproof products, Chemical Engineering Journal, 2003, Vol. 95, pp. 155161. Ali Nazari, Shadi RiahiTiO2 Nanoparticles effects on physical, thermal and mechanical properties of self compacting concrete with ground granulated blast furnace slag as binder Energy and Buildings, 2011, Vol. 43, pp. 9951002.Ali Nazari, Shadi Riahi, Shirin Riahi, Seyedeh Fatemeh Shamekhi and A. Khademno, An investigation on the Strength and workability of cement based concrete performance by using ZrO2 Nanoparticles, Journal of American Science, 2010, Vol. 6, No. 4, pp. 29-32.Ali Nazari, Shadi Riahi, Shirin Riahi, Seyedeh Fatemeh Shamekhi and A. Khademno, Improvement the mechanical properties of the cementitious composite by using TiO2 nanoparticles, Journal of American Science, 2010, Vol. 6, No. 4, pp 98-101.Ali Nazari, Shadi Riahi, Shirin Riahi, Seyedeh Fatemeh Shamekhi and A. Khademno, Mechanical properties of cement mortar with Al2O3 nanoparticles, Journal of American Science, 2010, Vol. 6(4), pp 94-97.Ali Nazari et al; ZrO2 nanoparticles effect on split tensile strength of self compacting cement, Materials Research, 2010, Vol. 13, No. 4, pp. 485-495. Hui. Li, Hui gand Xiao, Jie Yuan, Microstructure of cement mortar with nano particles, Composites Part B., 2004, Vol. 35, pp. 185-189.Peng, G.F. Huang Z.S., Change in microstructure of hardened cement paste subjected to elevated temperatures, Construction and Building Materials, 2008, Vol. 22, pp. 593599.

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38.

Uma Suresh is research scholar at SRM university, Chennai. She is presently working as Head of Department, Chemistry at V.V.S.G.J.PU College. Mysore. Her field of interest is cement chemistry at elevated temperature.

Dr. R. Jeyalakshmi is a Professor in the Department of Chemistry, Faculty of E&T, SRM University. Her fields of interest include material technology, reaction engineering, environmental chemistry, nanotechnology and corrosion engineering.

Dr. N. Suresh is Professor & Director, Building Fire Research Centre, The National Institute of Engineering, Mysore. His fields of interest are studies on the behaviour of concrete at elevated temperatures. He is member of BIS CED2 & CED22.

20 The Indian Concrete Journal September 2014

TECHNICAL PAPER TECHNICAL PAPER

Compressive strength development of blended cement concretes containing portland cement,

fly ash and metakaolin

Folagbade S. Olufemi and Moray Newlands

INtrOductION

Metakaolin is a highly reactive non-crystalline pozzolanic material. Calcination of Kaolinite produces it in two colours; off-white and white. Its particles are coarser than those of silica fume but finer than those of Portland

cement [1]. The specific gravity and specific surface of

metakaolin are 2.6 and 15000 m2/kg respectively [1]. Due to its fineness, metakaolin forms more nucleation sites

to accelerate cement hydration and enhance strength development [2-5]. However, being an expensive product,

it is used in small quantities of (about 5-15%) as a cement replacement material [1]. In addition, its high specific

surface and chemical reactivity result in workability challenges characterized by a high water demand [6,7].

On the other hand, concretes incorporating fly ash

are characterized by a low water demand, reduced

water/cement ratio at equal consistency and improved workability [8,9]. Its spherical particles and electronic

dispersion when enough of it is adsorbed on the surface of Portland cement particles to cover and deflocculate

them help impart these properties [10-12]. Hence, fly

ash concretes show reduced bleeding and ensure good placing and finish. Incorporating fly ash in concrete

does not contribute to early-age strength development,

so the strength development at early ages is relatively low in such concretes [13,14]. However, the pozzolanic

reactivity of fly ash with curing age does result in

improved compressive strength development at later age strengths [15]. Hence, due to its availability and low

cost, fly ash constitutes the primary pozzolana in blended

cements [16]. The use of gas-fired and co-combustion fly The Indian Concrete Journal, September 2014, Vol. 88, Issue 9, pp. 20-29.

this paper investigates the compressive strength development of binary and ternary cement concretes containing

Portland cement, fly ash and metakaolin at various ages and water/cement ratios. the material costs and embodied

carbon dioxide (e-cO2) levels of these concretes at the strength of 45 N/mm2 are also presented. the results suggest

that metakaolin improves compressive strength at both early and later ages, while fly ash contributes to strength

development at later ages. the concretes made with blended cements have lower e-cO2 levels than those made with

Portland cement. the cost data suggest that at 45 N/mm2 strength, economic blended cement concretes are possible

when the level of metakaolin blending is kept at 5%.

Keywords: Cement combination; cement combination concrete; compressive strength; concrete construction.

21The Indian Concrete Journal September 2014

TECHNICAL PAPER

Table 1. Physical and chemical properties of cementsProperty Cements

PC FA MK

Blaine fineness, m2/kg 395 388 2588

Loss on ignition, % a) 1.9 6.1 b) 0.9

Particle density, g/cm3 3.17 2.26 2.51

% retained by 45 m sieve b)- 11.0 -

Bulk oxide composition, % c)

CaO 64.5 3.2 0.0

SiO2 20.0 52.0 57.6

Al2O3 4.6 26.0 38.9Fe2O3 3.7 10.1 0.6MgO 2.5 1.5 0.3MnO 0.1 0.1 0.0

TiO2 0.3 1.5 0.0

K2O 0.7 2.8 2.4

Na2O 0.3 1.2 0.1

P2O5 0.1 0.5 0.1

Cl 0.1 0.0 0.0

SO3 3.1 1.1 0.0

a) In accordance with BS EN 196-2b) In accordance with EN 450- 1 c) Obtained by x-ray fluorescence (XRF)

ash would also ensure the availability of quality fly ash

for future use in concrete [17].

From these descriptions it would appear that a ternary blend of Portland cement, fly ash and metakaolin would

offer significant advantage over a binary blend of

Portland cement with fly ash or metakaolin. When these

two pozzolanas are blended with Portland cement, their

combination would complement each other to improve the performance of concrete [9]. While metakaolin would

support early age strength development, fly ash would

contribute to later age strength development [18]. The ternary combination would also result in reducing the dosage of water or water reducing admixtures [19]. Hence,

metakaolin could serve as an alternative to silica fume in some mixes. Cement and concrete standards such as BS

EN 197- 1, BS EN 206- 1 and BS 8500 support the use of

ternary blended cements. Also, the construction industry

now uses several types of blended cements [20].

Ternary blended cements, by virtue of their strength

development characteristics at early ages, suit mass

concreting and hot weather concreting requirements. Their improved pozzolanic reaction with curing age, is

useful for under-water applications. BS EN 197- 1 permits

the use of fly ash up to 55% and metakaolin up to 15%.

However, the data from the European Ready Mixed

Concrete Organisation show that addition levels do not exceed 20% of the total cement [21]. Ternary blends are

not only structurally important but also economically and environmentally desirable.

Although the literature shows that the use of cement additions such as these results in high strength and environmentally compatible concrete, there is little or

no information on the economic implication of using such materials. Hence, working within the limits of up

to 55% fly ash and 15% metakaolin in BS EN 197- 1, this

paper describes the compressive strength development in concretes containing binary and ternary blended concretes. In addition, the material cost and environmental

impact (embodied carbon dioxide content) of using these

blended concretes are presented.

ExPErIMENtal MatErIalS aNd MEthOdS

Portland cement (PC, 42.5 type) conforming to BS EN 197-

1, Fly ash (FA, Siliceous or Class F type) conforming to BS

EN 450- 1, Metakaolin (MK) treated as calcined natural

pozzolana conforming to BS EN 197- 1. Table 1 gives the

properties of PC, FA and MK. The cements were stored

in plastic containers to prevent their degradation from environmental exposure.

The size of the fine aggregates was 0 - 4 mm and the coarse

aggregates were in two sizes; 4 - 10 mm and 10 - 20 mm.

The coarse aggregates were uncrushed and they come in varied shapes. The 4 - 10 mm aggregates had rough

texture while the 10 - 20 mm aggregates were smooth.

Table 2 presents the physical properties of the aggregates. Potable water, conforming to BS EN 1008 was used for

mixing and curing the concrete specimens. To achieve

good cohesion and finishability, a workability level

defined by a nominal slump of 50-100 mm (consistence

level of S2, BS EN 206- 1) was kept, a polymer carboxylic



ether based superplasticiser conforming to EN 934-2 was

used.

The mix proportion was carried out in accordance with

the BRE Design Guide [22]. The yield corrected mix

proportions, to the nearest 5 kg/m3, using a free water

content of 165 kg/m3 to avoid an excessively sticky mix for the saturated surface dry (SSD) aggregates used are

presented in Table 3 for the cement combinations. The cement combinations consist of the binary blends of fly

ash and metakaolin with Portland cement and ternary

blends prepared by introducing metakaolin to part-replace the fly ash in the binary blends of fly ash and

Portland cement.

Concrete preparation followed BS EN 12390- 2. The

specimens, after casting, were cured in the mould under

a damp hessian cloth covered with a polythene sheet for about 24 hours. Subsequently, they were demoulded

and cured in water tank maintained at about 20oC until testing. The compressive strength test was carried out in accordance with BS EN 12390- 3. Two 100 mm cubes,

at the test ages, were loaded to failure using the Avery

Denison cube crushing machine (Figure 1) with a base load of 10kN and a loading rate of 7.0 kN/m2.

aNalySIS aNd dIScuSSION OF rESultS

Compressive strength of concrete at equal water/cement ratio

Table 4 presents the cube compressive strengths obtained

for the cubes at 3, 7, 28, 90 and 180 days. The mixes were

tested at three water to cementitious ratios; 0.35, 0.50 and

0.65. The strength factors, presented in the Table, are

strength ratios obtained with respect to the strength of concretes containing Portland cement only.

As expected, the strengths of concretes made with fly

ash blended binary cements are lower than those of the Portland cement concrete. With increasing fly ash content

the strength reduces at all ages. The lower strengths are due to the slow pozzolanic reaction of fly ash at early

ages. However, by allowing a longer curing period, the

continuing pozzolanic reaction of fly ash improves the

strength factors. On the other hand, the strengths of the

concretes containing metakaolin binary cements were nearly the same as that of concrete containing Portland

cement. These results show metakaolins contribution to the development of early age strength.

Table 5 shows the cube compressive strengths of ternary blends concretes and their strength factors with respect to the fly ash based binary blends. Generally, these ternary

blends gave better strengths than the binary ones. Table 5 shows that strength increases as the metakaolin content

Table 2. Physical properties of fine and coarse aggregates

Property Fine aggregates #

0 - 4 mm Coarse aggregates #

4 - 10 mm

10 - 20 mm

Shape, visual - Varied Varied

Surface texture, visual - Rough Smooth

Particle density * 2.6 2.6 2.6

Water absorption, % ** 1.0 1.7 1.2

% passing 600 m sieve55.0 - -

# Aggregates were obtained from Wormit Quarry. * In accordance with BS EN 1097- 6 ** In accordance with BS EN 1097- 6, Laboratory-dry condition


TECHNICAL PAPER

Table 3. Mix proportions of concrete at a free water content of 165 kg/m3

Mix combination w/c Mix proportion, kg/m3

Cements Aggregates SP #,

% CEM I FA MK 0 - 4 mm 4 - 10

mm10 - 20

mm

100%PC

0.35 475 - - 650 375 755 0.41

0.50 330 - - 740 385 770 0.33

0.65 255 - - 820 380 765 0.25

80%PC+20%FA

0.35 375 95 - 640 370 745 0.37

0.50 260 65 - 735 385 765 0.30

0.65 200 50 - 815 375 760 0.23

80%PC+15%FA+5%MK

0.35 375 70 25 640 370 745 0.43

0.50 265 50 15 735 385 765 0.35

0.65 200 40 15 820 375 760 0.26

65%PC+35%FA

0.35 305 165 - 635 365 740 0.33

0.50 210 115 - 730 380 760 0.27

0.65 165 90 - 815 375 755 0.20

65%PC+30%FA+5%MK

0.35 305 140 25 635 365 740 0.40

0.50 210 100 15 730 380 760 0.35

0.65 165 75 15 815 375 755 0.27

65%PC+25%FA+10%MK

0.35 305 115 45 635 365 740 0.45

0.50 210 80 35 730 380 760 0.39

0.65 165 65 25 815 375 755 0.31

45%PC+55%FA

0.35 205 255 - 625 360 730 0.31

0.50 145 180 - 725 375 755 0.26

0.65 110 135 - 810 370 750 0.19

45%PC+45%FA+10%MK

0.35 210 210 45 630 365 730 0.38

0.50 145 145 30 725 380 755 0.34

0.65 115 115 25 810 375 750 0.27

45%PC+40%FA+15%MK

0.35 210 185 70 630 365 730 0.410.50 145 130 50 725 380 755 0.37

0.65 115 100 40 810 375 750 0.28

95%PC+5%MK

0.35 450 - 25 645 375 750 0.430.50 315 - 15 740 385 770 0.350.65 240 - 15 820 380 760 0.26

90%PC+10%MK

0.35 425 - 45 645 375 750 0.470.50 295 - 35 740 385 770 0.39

0.65 230 - 25 820 380 760 0.29

85%PC+15%MK

0.35 400 - 70 645 370 750 0.51

0.50 280 - 50 740 385 770 0.43

0.65 215 - 40 820 380 760 0.33

# % Superplasticiser (SP) required for consistence class 2 (BS EN 206-1) is related to the total cement content.



Table 4. Cube compressive strengths of cement combination concretes and their strength factors with respect to Portland cement at different ages

Mix combination w/c Compressive cube strength, N/mm2 Strength factors, % #

3d 7d 28d 90d 180d 3d 7d 28d 90d 180d

100%PC

0.35 54.0 68.0 80.0 90.0 96.0 100 100 100 100 100

0.50 32.0 43.5 54.0 61.0 64.0 100 100 100 100 100

0.65 21.0 28.0 38.5 43.0 45.0 100 100 100 100 100

80%PC+20%FA

0.35 46.0 58.0 72.0 83.0 92.0 85 85 90 92 96

0.50 25.5 35.0 46.5 55.0 59.0 79 80 86 90 92

0.65 12.0 19.0 30.0 37.0 41.0 57 68 78 86 91

80%PC+15%FA+5%MK

0.35 48.0 62.0 82.0 91.0 95.0 89 91 102 101 99

0.50 27.0 39.0 53.0 60.0 63.0 84 89 98 98 98

0.65 13.5 22.0 34.0 39.0 42.0 64 78 88 90 93

65%PC+35%FA

0.35 34.0 42.0 60.0 72.0 80.0 63 61 75 80 83

0.50 18.0 25.0 35.0 45.0 50.0 56 57 65 74 78

0.65 8.0 11.0 20.0 28.0 34.0 38 39 52 65 75

65%PC+30%FA+5%MK

0.35 37.0 50.0 64.0 73.0 80.0 68 73 80 81 83

0.50 19.0 28.0 42.0 49.0 52.0 59 64 78 80 81

0.65 10.0 15.0 24.0 30.0 34.0 47 53 62 70 75

65%PC+25%FA+10%MK

0.35 38.0 52.0 68.0 80.0 87.0 70 76 85 89 90

0.50 20.0 30.0 43.0 50.0 54.0 62 69 79 82 84

0.65 10.5 16.0 25.0 31.0 36.0 50 57 65 72 80

45%PC+55%FA

0.35 20.0 26.0 42.0 55.0 62.0 37 38 52 61 64

0.50 11.0 15.5 24.0 34.0 40.0 34 35 44 55 62

0.65 5.0 6.0 12.0 20.0 26.0 24 21 31 46 58

45%PC+45%FA+10%MK

0.35 20.0 29.0 47.0 58.0 64.0 37 42 59 64 66

0.50 12.0 19.0 32.5 43.0 48.0 37 43 60 70 75

0.65 6.0 8.5 18.5 28.0 32.0 28 30 48 65 71

45%PC+40%FA+15%MK

0.35 20.0 30.0 50.0 59.0 65.5 37 44 62 65 68

0.50 12.0 19.5 33.0 44.0 49.5 37 45 61 72 77

0.65 6.0 9.0 20.0 31.0 36.0 28 32 52 72 80

95%PC+5%MK

0.35 54.0 68.0 80.0 86.0 90.0 100 100 100 95 94

0.50 32.0 44.0 56.0 63.0 66.0 100 101 103 103 103

0.65 19.0 26.0 37.0 41.0 42.0 90 93 96 95 93

90%PC+10%MK

0.35 54.0 68.0 78.0 84.0 87.0 100 100 97 93 90

0.50 30.0 43.0 54.5 63.0 66.0 93 99 101 103 103

0.65 17.0 27.0 38.0 42.0 43.0 81 96 98 97 95

85%PC+15%MK

0.35 46.0 64.0 76.0 84.0 87.0 85 94 95 93 90

0.50 28.0 42.0 54.0 63.0 66.0 87 96 100 103 103

0.65 17.0 26.0 41.0 44.0 46.0 81 93 106 102 102

# Strength ratios determined with respect to Portland Cement (PC) values


TECHNICAL PAPER

increases. The strength factors of the ternary blends increase up to 28 days and thereafter the rate of increase decreases. In the initial stages, the higher fineness and

reactivity of metakaolin helps gain strength at a faster rate. However, at later ages, this effect wanes. The minor gains

at 90 and 180 days are due to the pozzolanic reactivity

of fly ash. These differences in the behaviour of binary

and ternary blends are consistent with the understanding that metakaolin helps both early and later age strength development and fly ash contributes to the later age

strength development.

The strength factors of the ternary blend with 80%PC+15%FA+5%MK and 80%PC+20%FA concrete

again confirm that metakaolin supports the early age

strength development. After 28 days, however, the ternary

blended cements show no significant improvement over

the binary blended cements. The strength factors of the ternary blends with 65% and 45%PC contents show

the effect of higher Portland cement dilution. When

the amount of Portland cement in the mix is low, the

Ca(OH)2 released to support pozzolanic reaction is also low. Accordingly, the strength factor shows a gradual

improvement up to 180 days. The fact that the strength factors for the 65% and 45%PC ternary cement concretes

Table 5. Cube compressive strengths of cement combination concretes and their strength factors (with respect to their respective fly ash binary cement) at different ages

Mix combination w/c Compressive cube strength, N/mm2 Strength factors, % #

3d 7d 28d 90d 180d 3d 7d 28d 90d 180d

80%PC+20%FA

0.35 46.0 58.0 72.0 83.0 92.0 100 100 100 100 100

0.50 25.5 35.0 46.5 55.0 59.0 100 100 100 100 100

0.65 12.0 19.0 30.0 37.0 41.0 100 100 100 100 100

80%PC+15%FA+5%MK

0.35 48.0 62.0 82.0 91.0 95.0 104 107 114 109 103

0.50 27.0 39.0 53.0 60.0 63.0 106 111 114 109 107

0.65 13.5 22.0 34.0 39.0 42.0 112 116 113 105 102

65%PC+35%FA

0.35 34.0 42.0 60.0 72.0 80.0 100 100 100 100 100

0.50 18.0 25.0 35.0 45.0 50.0 100 100 100 100 100

0.65 8.0 11.0 20.0 28.0 34.0 100 100 100 100 100

65%PC+30%FA+5%MK

0.35 37.0 50.0 64.0 73.0 80.0 109 119 106 101 100

0.50 19.0 28.0 42.0 49.0 52.0 105 112 120 109 104

0.65 10.0 15.0 24.0 30.0 34.0 125 136 120 107 100

65%PC+25%FA+10%MK

0.35 38.0 52.0 68.0 80.0 87.0 112 124 113 111 109

0.50 20.0 30.0 43.0 50.0 54.0 111 120 123 111 108

0.65 10.5 16.0 25.0 31.0 36.0 131 145 125 110 106

45%PC+55%FA

0.35 20.0 26.0 42.0 55.0 62.0 100 100 100 100 100

0.50 11.0 15.5 24.0 34.0 40.0 100 100 100 100 100

0.65 5.0 6.0 12.0 20.0 26.0 100 100 100 100 100

45%PC+45%FA+10%MK

0.35 20.0 29.0 47.0 58.0 64.0 100 111 112 105 103

0.50 12.0 19.0 32.5 43.0 48.0 109 122 135 126 120

0.65 6.0 8.5 18.5 28.0 32.0 120 141 154 140 123

45%PC+40%FA+15%MK

0.35 20.0 30.0 50.0 59.0 65.5 100 115 119 107 105

0.50 12.0 19.5 33.0 44.0 49.5 109 126 137 129 124

0.65 6.0 9.0 20.0 31.0 36.0 120 150 166 155 138

# Strength ratios determined with respect to their respective fly ash binary cement concrete values at different ages



with higher dilution effect (i.e. lower content of Portland

cement and hence lower content of Ca(OH)2 released to support pozzolanic reaction) improved progressively up to 180 days shows that the non-improvement in the strength factors of the 80%PC ternary cement concretes

would be due to the fact that the cement addition content at 20% is not high enough to fully react with the Ca(OH)2 released from the hydration reaction of Portland cement

to support the pozzolanic reactions required to produce a significant difference in their strengths beyond the age

of 28 days. These observations suggest that pozzolanic reaction is a function of the availability of Ca(OH)2 and the quantum of available cementitious materials in the blend. Conversely, the strength factors of the 65% and 45% PC

concretes (Table 4) which continued to increase up to 180

days, suggests that the amount of cement additions were

high enough to support long-term pozzolanic reaction.

Compressive strength of concrete at equal strength

The following section uses the 28-day strength to assess the cost and environmental implications of using blended cements in concrete. Tables 4 and 5 show that equal

strengths of the cement combination concretes at equal water/cement ratios would be achieved at different ages. In other words, equal strengths of the cement

combination concretes at equal age would be achieved at different water/cement ratio and therefore at different material contents, material costs and embodied carbon

dioxide (e-CO2) contents. Concrete in practice is specified

on the basis of strength. The hydration reaction is a long-term process but since at 28 days a substantial quantity of hydration would have taken place in concrete, design

strengths are based on the strength of concrete at 28 days (BS 8110, BS EN 206- 1 and BS 8500). Hence, this

section used the cost and environmental implications of the cement combination concretes, at equal strength, to

investigate the effect of cement combinations on concrete construction.

The cost implication of using cement combinations in concrete was examined with the help of material cost.

Profit, overhead and the costs of other resources such as

equipment, manpower, money and management were

excluded from the cost data. The environmental impact

was examined with the help of the embodied carbon

dioxide (e-CO2) contents of the cement combination concretes. The e-CO2 is a measure of the carbon dioxide emitted owing to the energy used in heating the kiln and the chemical reaction that takes place in the kiln when cement is manufactured.

As expected, the material cost of concrete decreased

with increasing water/cement ratio. This is because the quantity of the expensive materials namely cements

and superplasticiser decreased with increasing water/cement ratio. The addition of fly ash as a binary cement

component reduced the material costs of concrete with increasing content. While the addition of metakaolin as a

binary cement component increased the material costs of concrete with increasing content, the material costs of the

ternary cement concretes (though higher than that of their respective fly ash binary cement concretes) are lower than

that of Portland cement concrete at all the water/cement

ratios tested.

The e-CO2 values of the concretes decreased with increasing water/cement ratio. The addition of fly ash as

a binary cement component reduced substantially the e-CO2 values of the binary cement concretes with increasing

Table 6. Cost (from cradle to gate) and embodied CO2 content of concrete constituent materials

Concrete constituent material

Cost of material a), /tonne

(Rs./tonne)*

e-CO2 content of material b),kg/tonne

Portland cement (PC) 60.00 (6000) 930

Fly ash 20.00 (2000) 4

Metakaolin 100.00 (10000) 300

0 - 4 mm aggregates 10.00 (1000) 4

4 - 10 mm aggregates 10.00 (1000) 4

10 - 20 mm aggregates 10.00 (1000) 4

Water 10.00 (1000) 0.3

Admixture (superplasticiser) 1300.00 (130000) 0.72

* 1 (British Pound) = Rs. 100 (Indian Rupee) in August 2014 Sources: a) Supplier b) Mineral Products Association (MPA) figures


TECHNICAL PAPER

cONcluSION

Metakaolin as a binary cement component contributed to both early and later age strength development of concrete. The compressive strengths of fly ash binary

cement concretes which were considerably lower than that of Portland cement concrete at early ages improved

progressively with age to reduce the disparity between their strengths and that of Portland cement at later ages.

At early ages, all the ternary cement concretes have

lower strength than Portland cement concrete and these

strengths increased progressively such that at 180 days some of the mixes have slightly higher strengths than

Portland cement concrete. Also, the propensity for strength

development reduced with increasing fly ash content of

the ternary cement concrete. The reduction in the strength factors of the ternary cement concretes, with respect to the

fly ash binary concrete, between 7 and 28 days onwards

shows that while metakaolin would support early age strength development, fly ash would only contribute to

later age strength development. The comparison of the strength factors of the ternary cement concretes with that of Portland cement concrete shows that a total cement

Table 7. Material cost and embodied carbon dioxide (CO2) content of concrete

Mix combination Material cost and embodied CO2 content of concrete #

w/c = 0.35 w/c = 0.50 w/c = 0.65

Cost/m3, (Rs)*

e-CO2, kg/m3

Cost/m3, (Rs)*

e-CO2, kg/m3

Cost/m3, (Rs)*

e-CO2, kg/m3

100%PC 50.48 (5048) 449 41.82 (4182) 315 37.43 (3743) 245

80%PC+20%FA 45.86 (4586) 356 38.67 (3867) 250 34.90 (3490) 194

80%PC+15%FA+5%MK 48.23 (4823) 364 40.40 (4040) 259 36.36 (3636) 199

65%PC+35%FA 42.67 (4267) 291 36.39 (3639) 203 33.46 (3346) 162

65%PC+30%FA+5%MK 45.09 (4509) 299 37.93 (3793) 208 34.90 (3490) 166

65%PC+25%FA+10%MK 46.87 (4687) 305 39.70 (3970) 214 35.83 (3583) 169

45%PC+55%FA 38.10 (3810) 199 33.55 (3355) 143 30.81 (3081) 111

45%PC+45%FA+10%MK 42.45 (4245) 217 36.21 (3621) 152 33.55 (3355) 123

45%PC+40%FA+15%MK 44.63 (4463) 224 38.06 (3806) 158 34.78 (3478) 127

95%PC+5%MK 51.51 (5151) 433 42.50 (4250) 305 38.01 (3801) 236

90%PC+10%MK 52.52 (5252) 416 43.47 (4347) 292 38.51 (3851) 229

85%PC+15%MK 53.42 (5342) 400 44.25 (4425) 283 39.24 (3924) 220

# cost and e-CO2 content calculated based on material content (Table 3) and rates (Table 6)* 1 (British Pound) = Rs. 100 (Indian Rupee) in August 2014

content. Metakaolin as binary cement component also reduced the e-CO2 values of concrete with increasing content but not as much as fly ash. Hence, while metakaolin

ternary cement concretes have slightly higher e-CO2 values than fly ash binary cement concretes, their e-CO2 values were lower than that of Portland cement concrete

at equal water/cement ratio. The material costs and e-CO2 contents of the cement combination concretes at the cube compressive strength of 45 N/mm2 at 28 days (Table 8) obtained by interpolating the values in Tables 4, 5 and

7 confirm that this strength of the cement combination

concretes would be achieved at different costs and e-CO2 contents. The ranking of the concretes in terms of cost and e-CO2 contents is also given in Table 8. The Table also shows that while all the cement combination concretes are more environmentally compatible than Portland cement

concrete, six out of the 11 cement combination concretes

are more economical than Portland cement concrete.

These are the fly ash binary cement concretes and the

5%MK binary and ternary cement concretes. Hence, with

proper selection, cement combination concretes could be

made more environmentally compatible and economic than Portland cement concrete.



Table 8. Material cost and embodied CO2 content of concrete at the strength of 45 N/mm2

Mix combination Material cost and embodied CO2 content of concrete at the strength of 45 N/mm2

w/c Cost/m3, (Rs)*

Rank e-CO2, kg/m3

Rank

100%PC 0.57 39.66 (3966) 7 274 12

80%PC+20%FA 0.51 38.31 (3831) 1245 9

80%PC+15%FA+5%MK 0.55 38.63 (3863) 2 234 6

65%PC+35%FA 0.43 38.91 (3891) 5239 7

65%PC+30%FA+5%MK 0.48 38.65 (3865) 3 217 4

65%PC+25%FA+10%MK 0.49 40.08 (4008) 8 219 5

45%PC+55%FA 0.33 38.85 (3885) 4 208 3

45%PC+45%FA+10%MK 0.37 41.41 (4141) 11 206 2

45%PC+40%FA+15%MK 0.39 42.56 (4256) 12 203 1

95%PC+5%MK 0.58 39.54 (3954) 6 261 11

90%PC+10%MK 0.58 40.31 (4031) 9 252 10

85%PC+15%MK 0.59 40.74 (4074) 10 239 7

* 1 (British Pound) = Rs. 100 (Indian Rupee) in August 2014

addition content of more than 20% would be required to effectively support long-term strength development.

Equal strengths of cement combination concretes, at

equal ages, were achieved at different water/cement

ratios, material contents, material costs and embodied

carbon dioxide contents. At equal water/cement ratio

and strength, the cement combination concretes, because

of their lower embodied carbon dioxide contents, are

more environmentally compatible than Portland cement

concrete. The fly ash binary cement concretes are more

economical than Portland cement concrete at equal

water/cement ratio and strength. While, at equal water/

cement ratio, the metakaolin binary cement concretes are

more expensive and the ternary cement concretes are

more economical than Portland cement concrete, only

the metakaolin binary and ternary cement concretes at a metakaolin content of not more than 5%MK are cheaper than Portland cement concrete at the strength of 45 N/

mm2. Since concrete is specified on the basis of strength in practice, cement combination concretes would be more

environmentally compatible and economic than Portland

cement concrete if properly proportioned.

Acknowledgement

The authors are thankful to the Department of Civil Engineering, University of Dundee, Dundee, United

Kingdom for the facilities and guidance provided for this research.

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Bai J., Wild S., Sabir B. B. and Kinuthia J. M., Workability of concrete incorporating pulverized fuel ash and metakaolin, Magazine of Concrete Research, 1999, Vol. 51, No. 3, pp. 207-216.

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TECHNICAL PAPER

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Dr. Folagbade S. Olufemi holds a BSc (Hons.) in Building from University of Ife, Nigeria; an MSc in Construction Technology, University of Lagos, Nigeria; an MSc in Structural Engineering from University of Glasgow, United Kingdom (UK); PhD in Civil Engineering from University of Dundee, UK. He is a Lecturer in the Department of Building, Obafemi Awolowo University, Ile-Ife, Nigeria. His areas of interest are construction technology and materials (especially concrete) and structural mechanics and design.

Moray Newlands PhD holds a BEng Honours degree in Civil Engineering; an MSc in Concrete Technology, Construction and Management, University of Dundee, UK; PhD from Concrete Technology Unit (CTU), University of Dundee, UK. His PhD project developed a simulated natural carbonation performance test which is now a CEN Technical Specification (CEN TS 12390-10). He is a lecturer within the Division since 2005. Previously, he was a Research Fellow and CPD/Consultancy Manager for the CTU. He is also currently Secretary for CEN TC51/WG12/TG5 which is developing test methods for concrete performance.

The Indian Concrete Journal September 201430 31

POINT OF VIEWPOINT OF VIEW

30 31

POINT OF VIEWPOINT OF VIEW

Effect of excessive cement in prestressed concrete girder

C.V. Kand, T.P. Thite and S.M. Litake

DETAILS OF FLYOVER AND METHOD OF CONSTRUCTION

This flyover was on an important road with heavy traffic,

had 46 spans and length of 1230 m viaduct. The width

of flyover was 10.5 m and 8 m. In 10.5 m there were 10

precast prestressed girder and in 8 m width 6 girders. The

L-section and cross section is shown in Figure 1.

Construction method

Precast pre-stressed multiple girders were cast at the

ground at available places and towed to the site and lifted.

The form work for deck slab fixed to precast girders and

slab cast in situ.

Foundations, piers/abutments were cast in situ along

with bearings and precast girders were launched. The

girders were 3 spans continuous; after launching girders

on individual spans, the continuity was given in the

girders through a cross girder and continuous slab.

CODAL REQUIREMENT FOR MAXIMUM CEMENT CONTENT

Section of IRC-21 2000 gives minimum cement

content for PSC members as 400 kg/m3 for up to

M40 concrete vide table no. 5.

MORT&H specifications for road and bridge works

Fourth Revision of 2001 specify maximum cement

content as 540 kg/m3 as per clause 1703.2; however,

the revised MORT&H specification for road and

bridge works, Fifth Revision of 2013 has given the

limit of 450 kg/m3 as per clause 1703.3.

Maximum cement content has been reduced from

540 to 450 kg/m3

The main reason for reducing the cement content is,

if there is more cement per cubic metre in concrete, it

will cause shrinkage cracks. High grade cement (Grade

53) is generally used in rich concrete (mainly used for

pre-stressed concrete). This cement consumption i.e. 450 kg/m3 is used for a 80 s

2014.09._e-journal

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