THE EFFECT OF RICE HUSK ASH ON STRENGTH AND PERMEABILITY OF

CONCRETE

PERTANDINGAN REKA CIPTA KEJURUTERAAN DAN INOVASI SAINS INTEL 2006

MOHD KHALID BIN KARSIMEN (6217) OF

MALAY COLLEGE KUALA KANGSAR

IntroductionThe production of cement is costly, consumes

high energy, depletes natural resources and emits huge amounts of greenhouse gases (1 ton of cement production emits approximately 1 ton of CO2). Consequently, environmental degradation, pollution and health hazards problems associated with cement industries, have come under scrutiny.

So, now a day’s many people are trying to use industrial and agricultural wastes in concrete. These wastes otherwise pose several environmental problems.

ObjectivesTo investigate compressive strength

properties of concrete containing different percentage of Rice Husk Ash

To investigate the permeability properties of concrete containing different percentage of Rice Husk Ash

To determine the optimal replacement of cement with Rice Husk Ash, by comparing the results of compressive strength and permeability tests.

Methodology (Detail of Tests)

Name of test

Size of specim

en(mm)

No. of mix

No. of specimen for each mix

Total no. of

specimen

Compressive

strength test

150×150×150

4 (0%, 15%, 25%,

35%)

6 (3-7 Days, 3-28

Days)

24

Permeability Test

150x150x150

4 (0%, 15%, 25%,

35%)

6 (3-7 Days, 3-28

Days)24

All the specimen were cast with M25 mix

The specimen were taken out from the mould after 24 hours and cured for 7/28 days.

Specimen of cubes were tested for ‘Compressive Strength’ and ‘Coefficient of Permeability’ and the final results were analysed to find the optimal percentage replacement of cement with Rice Husk Ash (RHA)

Methodology

Material used in the experimental investigation

Cement

Water

Coarse SandRice Husk

AshCoarse

Aggregate

Continue……..

Ordinary Portland Cement of grade – 43 (source J.K Cement)

Rice Husk Ash used in the study has been obtained from NK Enterprises, Singhania House, Jharsuguda, Orissa, India

Water- Tap water was used in concrete masonry

Rice Husk Ash OPC

Fine Aggregates

Coarse Aggregates

Rice Husk Ash Rice husk is one of the main agricultural residues

obtained from the outer covering of rice grains during the milling process. Rice Husk Ash is obtained from burning of Rice Husk, which is the by-product of rice milling. It is estimated that 1,000 kg of rice grain produce 200 kg of Rice Husk after burn.

The rice husk ash had no useful application and had usually been dumped into water streams and caused pollution until it was known to be a useful mineral admixture for concrete.

• Standard Consistency of the cement paste = 29.5

• Initial setting time of cement = 115min

• Final setting time of cement = 220min

• Specific gravity of cement = 3.38

Test on cement

• Fineness modulus of fine aggregates =2.50

• Specific gravity of fine aggregates= 2.65

Test on fine aggregates

• Specific gravity of coarse aggregates= 2.61

• Fineness modulus of coarse aggregates =7.68

Test on coarse aggregates

Mix Design for M25 Grade ConcreteTable of final mix proportion (Wt. in Kg)/m3 concrete

CementFine

Aggregate

Coarse Aggrega

te

Water Cement

ratio

1 1.3 2.9 0.45

Preparation, casting and curing of concrete cubes

Testing MethodsCompressive strength test

Cube failure after compression test

Compression testing machine

Permeability

Permeability of concrete generally refers to the rate at which water or other aggressive substance (sulphates, chlorides ions, etc.) can penetrate concrete.

Low permeability of concrete to moisture and gas is the first line of defence against: frost damage, acid attack, sulphate attack, corrosion of steel embedment and reinforcements, carbonation, alkali-aggregate reaction, and efflorescence.

Methods For Testing Permeability(IS 3085:1965)

Constant flow Method

Darcy’s law has been used to determine the co-efficient of permeability.

The equation used is

Ks=  Where, Ks - Coefficient of saturated permeability

(m/s) Q - Volume of flow rate (m3/s) A -Cross-sectional area (m2) L -Specimen thickness in the direction of flow (m) H - Head of water causing flow (m)

Permeability test

Permeability apparatus Permeability mould

Water reservoir and pressure controler

Air Chamber

Continue……

Permeability test Set-Up (Schematic)Typical Details of Permeability Cell

Sealing of specimen

(1) Filling pieces of jute rope (2) Filling mixture of lac & wax

(3) Filling Epoxy injection grout (4) Applying Sikadur 31 compound(Epoxy Grout)

Leakage testing & Running the test

Fill the water reservoir and apply the desired pressure (10 Kg/cm2) and note the initial gauge reading.

After steady state of flow is reached, put the empty beaker below the mould and note the time and pressure on the gauge

Note the discharge passed in a particular time interval and at an average pressure on gauge.

From the Darcy's law find the coefficient of permeability.

Result and DiscussionType of

Mix RHA (Kg) OPC (Kg)Compressi

ve Strength

(MPa)

Average Compress

ive Strength

(MPa)

Percentage Improvement w.r.t. M0 Mix

M0

(0%)

19.8421.2420.56

20.55 ----

M1

(15%)

24.4024.9125.46

24.92 17.54

M2

(25%)

24.7621.0521.50

22.44 8.42

M3

(35%)

19.0018.1017.16

18.08 -13.66

Values of Compressive Strength (7-days curing)

Continue……

Type of Mix RHA (%)

Compression Strength

(MPa)

Average Strength

(MPa)

Ratio of RHAC/OPC

Percentage Improvement

w.r.t. OPC

M0 0%33.4131.2330.30

31.64 ---- ----

M1 15%34.2634.5635.00

34.61 1.09 8.58

M2 25%33.3533.2031.80

32.78 1.03 3.47

M3 35%30.2029.7828.98

29.65 0.93 -6.71

Values of Compressive Strength (28-days curing)

Compressive Strength of different mixes (7 & 28 days)

M0 M1 M2 M30

5

10

15

20

25

30

35

40

20.55

24.92

22.44

18.08

31.64

34.61

32.78

29.65

7 days28 days

Concrete Mix

Com

pres

sive

Str

engt

h (M

Pa)

Permeability test results

Mix Sampl

e

Discharge Q (ml)

TimeT (Hrs)

Head of waterH (m)

Co-efficient of permeability,

K(m/sec) X 10-12

Avg. K(m/sec) X

10-12

M0 1618

18 68.6771.12

23.9726.04

25.01

M1 1214

18 73.5876.03

16.7818.94

17.86

M2 710

18 66.2278.48

10.8813.11

12.00

M3 1516

18 68.6773.58

22.4722.37

22.42

Values of coefficient of permeability for 7-days water curing

Coefficient of permeability of RHAC at 7-days water curing

M0 M1 M2 M30

5

10

15

20

25

30

25.01

17.86

12

22.42

Concrete Mix

Coe

ffici

ent o

f Per

mea

bilit

y (1

0-12

m/s)

Continue……

Mix Sampl

e

Discharge Q (ml)

TimeT (Hrs)

Head of waterH (m)

Co-efficient of permeability,

K(m/sec) X 10-12

Avg. K(m/sec) X

10-12

M0 810

18 63.7763.77

12.9116.13

14.52

M1 67

18 68.6771.12

8.9910.13

9.56

M2 44

18 73.5871.12

5.65.77

5.69

M3 98

18 66.2268.67

13.9812.0

13.00

Values of coefficient of permeability for 28-days water curing

Coefficient of permeability of RHAC at 28-days water curing

M0 M1 M2 M30

2

4

6

8

10

12

14

1614.52

9.56

5.69

13

Concrete Mix

Coe

ffici

ent o

f Per

mea

bilit

y (1

0-12

m/s)

Coefficient of Permeability of all mixes at both 7 and 28-days water curing

M0 M1 M2 M30

5

10

15

20

25

30

25.01

17.86

12

22.42

14.52

9.56

5.69

137 days

28 days

Concrete Mixes

Coe

ffici

ent o

f Per

mea

bilit

y (1

0-12

m/s)

Permeability of concrete is influenced primarily by following factors:

The nature of the hardened cement paste Porosity and interconnectivity of pores in the

cement paste and micro-cracks in the concrete.

w/c ratioDegree of hydrationThe degree of compactionThe type and quantity of constituent

materials. (fine cement tends to reduce permeability, well graded aggregate tends to decrease permeability)

Conclusions The coefficient of permeability of RHAC is significantly

lower than that of OPC for all percent changes. The coefficient of permeability of RHAC decreases for

15 % & 25 % replacement but it starts increasing at 35% replacement for cement.

The permeability of OPC and RHAC decreases with increase in curing period of samples.

The addition of RHA had a significant effect on the compressive strength of concrete. Compressive strength of concrete increases with the addition of RHA upto a certain level, after which it decreases.

Optimal cement replacement level (by RHA) is 25%, for which the compressive strength is maximum.

Continue……. The compressive strength is maximum at 15%

replacement and then it starts decreasing for both 7 and 28 days cured specimens.

With 25% replacement the compressive strength of cubes is nearly equal but slightly above then the OPC mix concrete specimens, but at 35% replacement the strength is less then the OPC mix for both 7 and 28 days cubes.

The compressive strength of OPC & RHAC increases with increase in curing period of samples.

The permeability of all mixes decreases with increase in compressive strength as compared to control concrete mix accept at 25% replacement.

Continue…….The results obtained from this study

indicates that up to 25% of RHA could be advantageously blended with cement without adversely affecting the strength and permeability properties of concrete.