high volume fly ash concrete roads mcd200105

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HIGH

VOLUME

FFFFLY LY LY LY AAAASH SH SH SH

CONCRETE

TECHNOLOGY

CONCRETE ROAD PROJECT

FATEHPUR BERI,

NEW DELHI

HIGH VOLUME FLY ASH CONCRETE TECHNOLOGY

FATEHPUR BERI, NEW DELHI

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TABLE OF CONTENTS

Introduction.........................................................................3 HVFAC Project In India.......................................................3 The Project .........................................................................4 The Selection Of Mix Design ..............................................5 � Materials Used .........................................................5 � Aggregates...............................................................6 � Admixture.................................................................6 � Mixture Proportions..................................................6

The Construction ................................................................6 Sampling.............................................................................7 Fresh Properties Of Concrete.............................................8 � Slump.......................................................................8 � Setting Time...........................................................10

Compressive Strength ......................................................11 � Compressive Strength Determined On Cores........12

Flexural Strength ..............................................................13 Modulus Of Elasticity ........................................................14 Abrasion Resistance.........................................................15 Chloride Ion Permeability..................................................17 Economy And Environemental Advantages......................18 Conclusion........................................................................19



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INTRODUCTION

HVFAC – a term coined by CANMET (Canada Centre for Mineral and Energy Technology) in late 1980’s

refers to a concrete having a low water content and in which at least 50% of the Portland cement is replaced by a good quality fly ash satisfying certain

specifications. This concrete usually also incorporates superplasticizers – chemical admixtures which help reduce water while providing the needed workability. Concretes with high

volumes of fly ash have been used in mass concrete applications for more than 75 years, where low heat of hydration instead of strength development was a major criterion. Hoover dam built in 1930 is a fine

standing example of such a concrete. Since 1985, research work carried out at CANMET and elsewhere has shown that HVFAC has the

properties of a high performance structural concrete

Due to its superior performance and engineering properties (in comparison to conventional

concrete), the development of HVFAC has opened new doors to sustainability of modern concrete

construction.

When made with compatible materials and under stringent quality control, HVFAC has excellent

workability, low heat of hydration, adequate early age and high later age strengths, reduced drying shrinkage, reduced micro cracking and hence excellent durability characteristics.

HVFAC PROJECT IN INDIA

CANMET - MTL in partnership with CII and other

partner organizations in India have taken up the HVFAC technology transfer project, funded by the Canada Climate Change Development Fund through CIDA.

The aim is to develop India’s ability to reduce GHG emissions and promote sustainable development of



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the construction industry by increasing use of fly

ash as cement replacement in concrete. As part of this project, several demonstration projects in the form of real life structures are being

taken up all over India and the concrete performance is closely monitored. This is in order to familiarize the local engineers, practitioners and the general public with the in-place performance of

HVFAC made with the locally available materials, in Indian conditions.

THE PROJECT

Construction Research Centre (CRC) is the in-house

R&D cell of a large construction company – Chawla Techno Construct Ltd. The centre has an elaborate material testing facility & is responsible among other things, for providing mix designs for HPC to

the parent company. CRC has been commissioned to collect concrete samples for this demo project and carryout the

required testing at the specified ages in its laboratory situated in Gadaipur, Mehrauli, New Delhi.

The municipal corporation of Delhi (MCD) decided

to do a 300 m stretch of a road pavement - 7m wide at Fatehpur Beri, Mehrauli, New Delhi. The

road stretch carries heavy traffic including overloaded trucks during day as well as night. The

new concrete pavement, designed by a reputed consultant, is 270 mm thick in M30 concrete, laid

on the existing asphalt pavement. With the purpose of comparing the performance of HVFAC

against that of plain concrete (without fly ash), the stretch was divided into 3 parts – each 100 mlong

and executed with 3 different mixes as follows:

1. M 30 Plain concrete

2. M 40 HVFAC

3. M 30 HVFAC



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The concrete was supplied by the RMC facility of

M/s. Associated Cement Company (ACC) from their Faridabad plant. In order to suit the casting schedule, the pavement width was divided in two parts – 3.5 m wide each and the six pours were

completed in six days starting 22nd Feb. and ending on 27th Feb.’2005. On the following pages, each test has been covered

in a separate chapter. A brief on the purpose & procedure is described followed by reporting of the test results.

THE SELECTION OF MIX DESIGN

• MATERIALS USED

Cementitious Materials Cement OPC 43 grade and fly ash from Dadri

thermal power station were used in this study. Their physical properties and chemical compositions are presented in Table 1. Table 1 Physical Properties and Chemical Analysis of the Materials Table 1 Physical Properties and Chemical Analysis of the Materials Table 1 Physical Properties and Chemical Analysis of the Materials Table 1 Physical Properties and Chemical Analysis of the Materials usedusedusedused

OPC Cement Grade

43

Dadri fly ash

Physical Tests

Specific gravity 3.15 -

Specific surface, Blaine, m2/kg 315 404

Particle retained on 45 µm sieve, % - 15

COMPRESSIVE STRENGTH OF 51 MM CUBES, MPA

3-day 38 -

7-day 47.5 -

28-day 58.5 -

Lime reactivity, MPa - 4.7

Strength activity index at 28d, % - 85

Chemical Analyses, %

MAGNESIUM OXIDE (MgO) 4.2 0.44

TOTAL ALKALIS as (Na2O) 0.40 0.79

SULPHUR TRIOXIDE (SO3) 1.9 traces

LOSS ON IGNITION 1.6 0.6



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• AGGREGATES

River sand meeting the Indian standard requirements of zone II, and crushed angular aggregates (20mm and 10mm) were used. The gradation of sand and aggregates is presented in

Table 2.

Table 2 Grading of Coarse and fine Table 2 Grading of Coarse and fine Table 2 Grading of Coarse and fine Table 2 Grading of Coarse and fine aggregatesaggregatesaggregatesaggregates

Coarse Aggregate Fine Aggregate Limits Zone

II

Sieve Size, mm

CA 20 mm Passing, %

Limits Passing, %

CA 10 mm Passing, %

Limits Passing, %

Sieve Size, mm

Passing, % Passing, %

25 20

12.5 10

4.75

100 99.5

- 8.1 -

100 85-100

- 0-20 0-5

- -

100 89.4 14.5

- -

100 85-100

0-20

4.75 2.36 1.18 0.60 0.30 0.15

97.0 82.2 66.1 52.4 14.2 2.5

90-100 75-100 55-90 35-59 8-30 0-10

• ADMIXTURE

A naphtalene-based superplasticizer was used.

• MIXTURE PROPORTIONS

Table 3 presents the concrete mixture proportions of the three types of concrete used in this project.

Table 3 Concrete Mixture ProportionsTable 3 Concrete Mixture ProportionsTable 3 Concrete Mixture ProportionsTable 3 Concrete Mixture Proportions

M30 Plain M40 HVFAC M30 HVFAC

Cement, kg/m3 360 220 190

Fly Ash, kg/m3 0 220 190

River Sand, kg/m3 700 681 705

10 mm Coarse agg., kg/m3

570 500 517

20 mm Coarse agg., kg/m3

570 612 633

Water, kg/m3 170 138 136

W/cm 0.47 0.31 0.36

Admixture (% by weight of cement only)

0.7 – 1.0 0.8 – 1.2 0.8 – 1.2

THE CONSTRUCTION

Placing and compaction

The concrete was transported using 6–m3 transit

mixer, and was placed in the forms manually. It



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was then compacted using needle vibrator. The

final finishing was made with wooden trowels. Texturing

Texturing of concrete surface was done through

broom finishing. Curing

After texturing the surface of concrete, it was left

uncovered i.e. air cured for the first 24 hrs. Following that, wet gunny bags and ponding techniques were used for curing for a period of 14 days.

SAMPLING

All sampling for measuring the desired properties was done as per IS 516 – 1959 – ‘Methods of Tests for strength of concrete’.

For the MCD project, the samples were collected from the three pours adjoining the central kerb on three separate days. They were designated as follows:

Date of Casting Type of Mix Designation

22nd Feb.’05 M 30 Plain C – (Control) 23rd Feb.’05 M 40 HVFAC F – (Fly Ash)

25th Feb.’05 M 30 HVFAC G – (Fly Ash)

Moulds in sufficient number were oiled & brought

to site on each day, neatly arranged in an open pick-up truck, to facilitate filling without removal

from the truck. The truck was parked within 5m of the pour location.

The concrete for filling the moulds was taken from

the freshly unloaded pile with shovels in Tasla’s (steel pans), which were manually carried to the

pick-up. The cube moulds were filled in 3 layers

with 35 strokes of the compacting rod to each layer. Moulds for flexure, Abrasion, Chloride-ion



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permeability & Elastic Modulus were also filled with

due manual compaction. The filled up moulds were covered with a poly sheet and transported immediately to the testing lab (4

km from the site) for proper storage. The total time elapsed between the filling of the mould and its final resting position in the lab was less than half an hour.

On reaching the lab, the moulds were placed in a shaded space at ambient conditions, covered with steel plates to prevent evaporation. After

approximately 24 hours (to ensure full set) the moulds were demoulded & the samples transferred into a curing tank after proper marking. The water

in the tank is potable water, which is changed once every week. The level of the water is maintained so

as to remain at least 6” above the tallest sample.

The samples were placed in 3 separate groups in the common curing tank with their identification

marked in 3 different colours Just before the test at the relevant age, the test samples were taken out of the curing tank, wiped

clean & tested immediately. Cylinder specimens for measuring Modulus of Elasticity as well as Cores from the in-place

concrete were thinly capped with a special epoxy to

ensure level & parallel surfaces, one day before the test. All samples were tested in wet condition.

FRESH PROPERTIES OF CONCRETE

• SLUMP The slump cone continues to be the most

commonly used method to assess the workability & consistency of fresh concrete, due to its

simplicity.

In the present context, the aim was to ensure a

minimum slump to facilitate proper placement



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with minimum voids, as well as a consistent

quality of concrete at all locations of the pavement stretch. Concrete samples were picked in tasla’s (steel

pans) with a shovel, immediately after the transit mixer poured out the fresh concrete. The slump was measured as per prescribed standard practice, close to the poured pavement. The

measurements were taken on the first 3 days for every truck load and are as follows: Table 4 Slump of Plain concrete and HVFACTable 4 Slump of Plain concrete and HVFACTable 4 Slump of Plain concrete and HVFACTable 4 Slump of Plain concrete and HVFAC

Date Mix Time T.M. No. Slump Temp.

22.02.2005

M 30 PLAIN

01.55 pm 02.10 pm 03.00 pm 04.00 pm 05.40 pm 06.14 pm

1 2 2 3 3 4

100 50 50 50 50 35

27ºC 27ºC 26ºC 25ºC

21.5ºC 20ºC

23.02.2005

M 40 HVFAC

- -

5.40 pm 6.14 pm

1 2 3 4

85* 50* 50 35

22ºC 22ºC

21.5ºC 20ºC

25.02.2005

M 30 HVFAC

11.15 am 11.35 am 12.00 pm 12.30 pm 12.45 pm 01.49 pm

1 1 2 3 3 4

50 65 60 65 60 60

22.5ºC 22.5ºC 23ºC 23ºC 23ºC 23ºC

* As reported by site engineers.

The above table shows that the slump of plain

concrete ranged from 35 to 100 mm;that of HVFAC M40 and M30 grade ranged from 35 to 85 mm, and from 50 to 65 mm, respectively.

The above Table also shows that in general the slump of the three concretes investigated was similar, ranging from 50 to 65 mm. It should be noted that for similar slump, HVFAC required

lower content of water and lower dosage of admixture compared to plain concrete (Table 3).

This is generally attributed to the spherical shape and smooth surface of fly ash particles as

opposed to angular cement particles.



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• SETTING TIME

Fresh concrete was sieved at the pour location & three - 15 cm cubes were filled with the concrete fraction finer than 4.75mm.

These were transported to the lab along with the other samples. The penetrometer as per the relevant standard was used every ½ hr & the

penetrating resistance noted in kg. The penetrating heads were appropriately changed to get a resistance range between 0 to 290 kg/cm2. A plot was made with the readings obtained &

the time corresponding to a penetrating resistance of 35 kg/cm2 for initial set & 275 kg/cm2 for final set was read off from the plot

directly. The setting times for the 3 mixes under study are as follows:

Table 5 Setting times of Plain concrete and HVFACTable 5 Setting times of Plain concrete and HVFACTable 5 Setting times of Plain concrete and HVFACTable 5 Setting times of Plain concrete and HVFAC

Initial Setting Final Setting

M 30 Plain 08.00 hrs. 10.30 hrs.

M 40 HVFAC 05.30 hrs. 09.45 hrs.

M 30 HVFAC 09.30 hrs. 12.15 hrs.

Table 5 shows that M30 HVFAC had 1:30 to 1:45

longer setting times than those of M30 plain concrete. This is in line with published data that shows that HVFAC generally has longer setting times than normal Portland cement concrete

with similar 28-d compressive strength. This is

because HVFAC has lower cement content and the pozzolanic reaction of fly ash is slow.

However, the above table shows that M40 HVFAC had shorter setting times than those of

M30 plain concrete, which is not in line with published data on HVFAC.



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COMPRESSIVE STRENGTH

The compressive strength of concrete has been considered its most valuable property to structural

engineers, though recently other engineering properties such as permeability & durability have also come into focus.

The strength gives a general picture of the concrete

quality and is directly related to the hydrated cement paste chemistry & structure.

It is measured by making concrete cubes of 150

mm side or concrete cylinders 150 mm diameter x 300 mm long. Due to greater end restraining effect of test platens on a cube, compared to cylinders, researchers have a tendency to use cylinders for

studying compressive strength. However the Indian Standard Code practice being the use of cubes, the same was followed for this project site.

Just before the test, the cubes were taken out of

the curing tank, wiped and weighed. The cube samples were then placed in the compression-

testing machine one by one & tested to failure. The rate of loading was kept in the vicinity of 140

kg/cm2/min. as prescribed by the standard. The maximum load value was noted and the strength

calculated.

To check the variation in different batches, 3 more samples were taken from 3 subsequent batches

(transit mixer trucks) and compressive strength was measured at 28 days. The compressive

strengths up to 91 days are presented in Table 6.

Table 6 Compressive strengths of plain concrete and HVFACTable 6 Compressive strengths of plain concrete and HVFACTable 6 Compressive strengths of plain concrete and HVFACTable 6 Compressive strengths of plain concrete and HVFAC

Compressive strength, MPa

3-d 7-d 14-d 28-d 91-d

M 30 Plain

17.9 24.7 29.9 33.3 30.6 30.9 32.2 37.1

M 40 HVFAC

8.9 14.2 20.0 30.0 40.0 40.1 36.2 45.5

M 30 HVFAC

12.3 16.0 23.1 32.7 30.4 32.0 28.0 46.0



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As expected, the early strengths at 3, 7 & 14 days of the plain concrete were higher than the HVFAC

concrete. The three-day strength of plain concrete was nearly 1½ to 2 times that of HVFAC. This

difference however diminishes with age and at 28 days was reduced to less than 2–10%. At 91 days,

due of the pozzolanic reaction of fly ash, HVFAC developed almost 25% higher strength than that of

plain concrete.

The batch-to-batch strength variations measured on four consecutive batches for each mix are acceptable for the plain concrete and the M 30

HVFAC, but too high for the M40 HVFAC. For the latter concrete, the 28-d compressive strength ranged from 30.0 to 40.1 MPa. This underlines the importance of the quality control at RMC plant,

especially for HVFAC. It should be noted that all three mixes seem to fall short of their desired 28 days strengths.

• COMPRESSIVE STRENGTH DETERMINED ON CORES

The concrete cores were drilled at 14, 28 and 91

days with a HILTI core-cutting machine. After extraction from the site, the cores were packed in a

wooden crate for safe transportation to the test laboratory.

The core openings created in the pavement were

examined for any notable features and then filled with a special non-shrink concrete.

At the laboratory, the cores were examined for

various features like surface texture, size & frequency of voids etc. They were then cut to the required length and capped with a special epoxy mortar. After the epoxy set, the cores were

immersed back into water to achieve full saturation.

Twenty-four hours later the core specimens were taken out, measured and weighed before testing in

the compression testing machine.



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Two cores for each age and each mix were

taken. All cores exhibit the following:

• A greyish concrete • Well-distributed aggregates of

different sizes starting from 20mm, down to 1 – 2 mm.

• Carbonation depth – NIL • No honeycombing but air pockets up

to 8mm in some places • Air blow holes from 1mm – 3mm

moderately distributed • Smooth surface texture

The failure compressive load was converted into an equivalent cube compressive strength by using

appropriate factors for H/D ratio as well as cylinder to cube strength factor. The results on compressive

strength are presented in Table 7.

Table 7 Compressive strength of concrete determiTable 7 Compressive strength of concrete determiTable 7 Compressive strength of concrete determiTable 7 Compressive strength of concrete determined on coresned on coresned on coresned on cores


14-d 28-d 91-d

M 30 Plain 17.9 22.0 24.3

M 40 HVFAC 22.9 33.5 42.0

M 30 HVFAC 22.8 30.3 42.6

The results show unexpected low values for the plain concrete. The HVFAC cores show good

strengths close to the cast cube strengths.

FLEXURAL STRENGTH

Flexural strength of concrete is an important property for concrete pavements. These rigid pavements are assumed to rest on a flexible soil sub-grade & undergo mainly flexural stresses

during service. In order to determine this property, un-reinforced concrete beams of size 10cm x 10cm x 50cm (as

per IS 516) were cast and subjected to flexure

using a symmetrical 2-point loading, until failure occurred.



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On the stipulated age, the beams were taken out of the curing tank, wiped clean and mounted in the test machine. They were tested with the top surface (of the as-cast position) towards the side.

In all the beams the failure occurred in the middle one third and hence the flexural strength was calculated based on the elastic theory. The results

are presented in Table 8.

Table 8: Flexural strength of plain concrete and HVFACTable 8: Flexural strength of plain concrete and HVFACTable 8: Flexural strength of plain concrete and HVFACTable 8: Flexural strength of plain concrete and HVFAC


40-d* 91-d

M 30 Plain 3.3 4.3

M 40 HVFAC 3.2 6.2

M 30 HVFAC 3.3 6.1

* the 28-d results appeared strange, the test was redone at 40 days.

The flexural strength development trend was similar to that of the compressive strength. At 40 days, all concretes developed similar flexural strength, and at 91 days both HVFAC developed higher flexural

strength compared to that of plain concrete. This shows the advantage that HVFAC roads have over plain concrete roads by gaining significant flexural strength with time.

MODULUS OF ELASTICITY

Concrete is to a certain degree, an elastic material.

The knowledge of stress vs. strain behaviour of concrete is of keen interest to a structural engineer.

When concrete is subjected to a compressive load, the stress-strain curve follows a linear path up to

some point & then gets gradually convex. The modulus of elasticity is the slope of the linear

portion of this curve.

For the purpose of determination of this parameter, 150 mm dia. X 300 mm long cylinders were cast at

the time of concreting from the same batch of concrete and kept in the curing tank until the test.



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Two days before the test, the specimen cylinders were capped on the top face of ‘as–cast’ cylinders. After 24 hours, when the epoxy cap had completely set, the cylinders were placed back in the curing

tank for 1 day to ensure complete saturation. The results are presented in Table 9.

Table 9 Modulus of Elasticity of plain concrete and HVFACTable 9 Modulus of Elasticity of plain concrete and HVFACTable 9 Modulus of Elasticity of plain concrete and HVFACTable 9 Modulus of Elasticity of plain concrete and HVFAC

Modulus of Elasticity, GPa

28-d 91-d

M 30 Plain 30.1 32.8

M 40 HVFAC 32.2 33.6

M 30 HVFAC 34.3 38.9

The results show similar modulus of Elasticity for the three concretes at 28 days, at 91 days the M30 HVFAC showed higher value. The 28-d results are

in line with the predicted values given by the empirical formula i.e. 5000 times the square root of the compressive strength. The 91 day results that show high modulus of elasticity for HVFAC is in line

with CANMET published data. In fact, unreacted fly ash particles in HVFAC can act as fine aggregates

and result in higher modulus of elasticity. However, the 91-d results showing the modulus of elasticity of M40 HVFAC lower than that of M30 HVFAC was

unexpected.

ABRASION RESISTANCE

Abrasion resistance is another important property of concrete used in pavements. None of the various

procedures used to determine this parameter give a direct quantitative measurement of the service life of a concrete pavement. Only a relative abrasion resistance can be obtained with respect to a control

sample. In the present case, the rotating ball bearing method was used. The apparatus consists of a ring

of ball bearings rapidly rotated by a motor driven vertical shaft. Ten 14mm dia. steel balls are equally



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spaced in a retainer ring. The vertical shaft rotates

at 1000 rpm & has a flanged bearing at its lower end, grooved to match the ball circle. The total load on the ball bearing including the drive shaft assembly is 15 kgs. The bearing ring is allowed to

run over the wet concrete surface for 1minute or 1000 revolutions of the shaft. (A digital counter is used to control that). Water is used to flush out loose particles from the test path, bringing the ball

bearings in contact with the concrete, providing impact as well as sliding friction - conditions that an actual pavement in service is subjected to.

For the MCD project - 10cm cube samples were cast at the time of concreting, & transferred to the curing tank after demoulding.

Two faces of each cube sample were subjected to

the rotating ball bearing test after clamping in the machine. Depth of indentation was measured to an

accuracy of 0.01mm on 8 equally spaced points on the freshly abraded ball circle on the concrete

surface. The average of the 8 points gave the depth of wear. The wear depth of the two faces gives a mean wear depth in mm. The abrasion resistance was determined at 14, 28, and 91 days. The results

are presented in Table 10.

Table 10 Abrasion resistance of plain concrete and HVFACTable 10 Abrasion resistance of plain concrete and HVFACTable 10 Abrasion resistance of plain concrete and HVFACTable 10 Abrasion resistance of plain concrete and HVFAC

Depth of abrasion, mm

14-d 28-d 91-d

M 30 Plain 1.22 0.84 0.82

M 40 HVFAC 1.34 1.30 0.98

M 30 HVFAC 1.44 1.30 1.05

Published data show that abrasion resistance is

closely related to the compressive strength of concrete. The type of aggregate and surface finish

or treatment used also has a strong influence on abrasion resistance. Fly ash generally does not

affect this property beyond its influence on strength and finishing. Since Table 6 has shown higher

compressive strengths for plain concrete at early ages and lower strength at 91 days compared to



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those of HVFAC, it was expected to have the same

trend for abrasion resistance. However the above results show that plain concrete had higher abrasion resistance than HVFAC at all ages. The depth of abrasion was generally low for all concrete.

The visual evaluation of the road after four months of service has shown fairly good and similar abrasion resistance of plain concrete and M 30

HVFAC, but lower abrasion resistance for M 40 HVFAC in specific slabs. This might have been due to the finishing of these particular slabs, or the compressive strength of these slabs was lower than

expected.

CHLORIDE ION PERMEABILITY

This test method, the electrical conductivity of concrete is measured to give an indication of

permeability of concrete. A 100 mm diameter., 50mm thick cylindrical sample is mounted such that

one face of the sample is exposed to a specified concentration of chloride solution (NaCl) whereas

the other face is exposed to a NaOH solution. The permeability of concrete (the connected capillaries) determines the amount of ingress of chloride ions

into the concrete. This in turn affects the electrical conductivity. Hence the measure of electrical conductivity indirectly assesses the resistance of concrete to the deleterious atmospheric elements,

which affect the durability of concrete in the long run. The ASTM standard C 1202 – 94 has been followed

in which a fixed DC voltage of 60V is maintained across the two faces of the sample and current readings in mA taken every ½ hr. The total charge passed in Coulombs is calculated from these

readings. The chloride ion permeability is expressed

in relative terms such as High, Moderate, Low etc. corresponding to the charge passed in Coulombs

(as per table given in the code).



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For measuring this parameter, two samples for

each mix and age were cast in moulds at the time of concreting & transferred to the curing tank immediately after demoulding. Two more samples were extracted by coring from the in-place concrete

pavement at the specified age. The samples were first subjected to vacuum saturation in a special desiccator (pic.) as per the

codal specification. They were then mounted in the acrylic test cell and sealed with the help of an RTV silicon sealant. The two MMA (Methyl Meta Acrylate) chambers of the test cell were then filled with 3%

NaCl solution & 0.3N NaOH solutions respectively. The current passing through the specimens was recorded every ½ hour.

The results are presented in Table 11.

Table 11: Chloride ion permeability of Plain concrete and HVFACTable 11: Chloride ion permeability of Plain concrete and HVFACTable 11: Chloride ion permeability of Plain concrete and HVFACTable 11: Chloride ion permeability of Plain concrete and HVFAC

28-d chloride ion permeability, Coulombs

Cast moulds Cores

M 30 Plain High High

M 40 HVFAC Low Low

M 30 HVFAC Low Moderate

The results confirmed the published data that HVFAC have lower permeability than plain concrete. The results on cores concurred with those determined on cast moulds, except for M30 HVFAC

for which the permeability was moderate on cores

and low on cast moulds. This could be due to the difference between batches that was noticed on the

compressive strength results as well.

ECONOMY AND ENVIRONEMENTAL ADVANTAGES

Both HVFAC required less cement contents and less

dosage of admixture to achieve similar 28-d compressive strength as that of plain concrete. For example, M 30 HVFAC required 190 kg/m3 of cement and an average of 2 kg/m3 of admixture,

whereas, plain concrete required 360 kg/m3 of

cement and an average of 3 kg/m3 of admixture.



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This shows the economical advantages of HVFAC

over plain concrete. In terms of environmental advantages, it is known that the production of 1 tone of cement releases

approximately 1 tone of CO2 into the atmosphere. Therefore, since both HVFAC required 140 to 170 kg/m3 less of cement, respectively, this results in a CO2 reduction of the same quantities for each m3 of

concrete used.

CONCLUSION

This project has shown that HVFAC outperformed plain concrete in all aspects. In terms of

workability, HVFAC required less dosage of admixture to achieve similar workability as that of

plain concrete. In terms of mechanical properties and chloride-ion permeability, HVFAC developed

higher compressive and flexural strength at later ages, and low to moderate permeability compared

to plain concrete. HVFAC was also more economical and had less impact on the environment in terms of

GHG emissions compared to plain concrete.

When comparing the performance of both HVFACs, it appeared that they both performed similarly,

which might lead to the conclusion that the use of M 40 HVFAC was economically not advantageous, since M30 HVFAC with lower cement content

generally performed at the same level. However, it should be noted that the batch of M40 HVFAC, from which most of the samples were taken generally performed below the other batches from which only

cubes for 28-d compressive strength were cast. In general, M40 HVFAC should test higher and perform

better than M30 HVFAC. On the other hand, these results raise an important issue regarding the

implementation of HVFAC technology in India, that is the quality control of concrete production at the

RMC plants. The batch-tobatch variation for HVFAC should be pf the same order as that of plain OPC

concrete.

high volume fly ash concrete roads mcd200105

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