EFFECTIVE UTILIZATION OF RICE HUSK ASH BY · PDF fileeffective utilization of rice husk ash by partial replacement of cement g m institute of technology, davanagere - 577006 page 1

EFFECTIVE UTILIZATION OF RICE HUSK ASH BY PARTIAL REPLACEMENT OF CEMENT

G M INSTITUTE OF TECHNOLOGY, DAVANAGERE - 577006 Page 1

CHAPTER 1

INTRODUCTON

1.1 GENERAL

Concrete is by far the most widely used construction material today. Concrete

has attained the status of a major building material in all branches of modern construction

because of following reasons.

It is possible to control the properties of cement concrete with in a wide range by using

appropriate ingredients and by applying special processing techniques- mechanical, chemical

and physical. It is possible to mechanize completely its preparation and placing process. It

possess adequate plasticity for mechanical working.

It is difficult to point out another material of constructions which is as versatile as concrete.

Concrete is by far the best material of choice where strength, durability, permanence,

impermeability, fire resistance and abrasion resistance are required.

In present world, inflation is one of the main problems faced by every country. It has become

essential to lower the construction cost without much compromise as far as strength and

durability of the structure is concerned. The lowering of cost can be brought about in number

of ways. Among all the methods available the most optimum at our disposal is the use of

waste material as substitute.

The basic requirement of all mankind is shelter. Hence the shelter is based on the building

construction in which the cement concrete is an essential requirement. The cement concrete

is a well-known building material and has occupied an indispensable place in construction

work.

From the materials of varying properties, to make concrete of stipulated qualities and

intimate knowledge of the interaction of various ingredients, that go into the making of

concrete is required to be known, both in plastic condition and in the harden condition.

The strength of concrete depends upon the components such as aggregate, quality of

cement, water-cement ratio, workability, normal consistency of mix, proportion and age of



concrete .New building materials are used to accelerate the construction work, in which the

mixture plays an important role in characteristics of concrete .

The growth in various types of industries together with population growth has

resulted in the enormous increase in the production of various types of industrial waste

materials such as rice husk ash, foundry sand, blast furnace slag, fly ash, steel slag, scrap

tires, waste plastic, broken glass, etc.

1.2 STATEMENT OF PROBLEM

A comparative evaluation of strength characteristics of control concrete of grade M20

and RHA concrete produced by replacing cement by raw RHA in different percentage (

0,5,10, 15, and 20 % ).

1.3 OBJECTIVESOF THE STUDY

The primary aim of experimental work is to study the properties of rice husk ash.

Preparation of mix design Replacement of cement with RHA as different proportions with

cement.

Effect of rice husk ash on workability

Effect on compressive strength of concrete

Effect on split tensile strength of concrete

Todetermine the optimum dosage of the rice husk to be added to the concrete mix.

Comparison of result of different tests with varying proportion of RHA.

1.4 SCOPE OF THE STUDY

The increasing demand for producing durable materials is the outcome of fast

polluting environment. Supplementary cementations materials prove to be effective to meet

most of the requirements of the durable concrete. Rice husk ash is found to be greater to

other supplementary materials like silica fume and fly ash.



1.5 RICE HUSK ASH (RHA)

1.5.1 HISTORICAL BACKGROUND

Rice plant is one of the plants that absorbs silica from the soil and assimilates it into

its structure during the growth. Rice husk is the outer covering of the grain of rice plant with

a high concentration of silica, generally more than 80-85%. It is responsible for

approximately 30% of the gross weight of a rice kernel and normally contains 80% of

organic and 20% of inorganic substances. Rice husk is produced in millions of tons per year

as a waste material in agricultural and industrial processes. It can contribute about 20% of its

weight to Rice Husk Ash (RHA) after incineration. RHA is a highly pozzolanic material. The

non-crystalline silica and high specific surface area of the RHA are responsible for its high

pozzolanic reactivity. RHA has been used in lime pozzolanic mixes and could be a suitable

partly replacement for Portland cement. RHA concrete is like fly ash/slag concrete with

regard to its strength development but with a higher pozzolanic activity it helps the

pozzolanic reactions occur at early ages rather than later as is the case with other replacement

cementing materials.

Rice husk ash (RHA) is a by-product from the burning of rice husk. Rice husk is

extremely prevalent in East and South-East Asia because of the rice production in this area.

The rich land and tropical climate make for perfect conditions to cultivate rice and is taken

advantage by these Asian countries. The husk of the rice is removed in the farming process

before it is sold and consumed. It has been found beneficial to burn this rice husk in kilns to

make various things. The rice husk ash is then used as a substitute or admixture in cement.

Therefore the entire rice product is used in an efficient and environmentally friendly

approach.



Raw Rice Husk Burnt RHA After sieving

Fig 1.1 RICE HUSK ASH

1.5.2 BURNING PROCESS

The rice husk ash is a highly siliceous material that can be used as an admixture in

concrete if the rice husk is burnt in a specific manner. The characteristics of the ash are

dependent on the components, temperature and time of burning. During the burning process,

the carbon content is burnt off and all that remains is the silica content. The silica must be

kept at a non-crystalline state in order to produce an ash with high pozzalanic activity. The

high pozzalanic behaviour is a necessity if you intend to use it as a substitute or admixture in

concrete. It has been tested and found that the ideal temperature for producing such results is

between 600 °C and 700 °C. If the rice husk is burnt at too high temperature or for too long

the silica content will become a crystalline structure. If the rice husk is burnt at too low

temperature or for too short period of time the rice husk ash will contain too large an amount

of un-burnt carbon.



1.6 PROPERTIES:

1.6.1 SPECIFICATION OF RICE HUSK ASH:

Table1.1SpecificationsofRiceHuskAsh

SL No. Parameter Values

1 SiO2-Silica 85% minimum

2 Humidity 2% maximum

3 Mean Particle Size 25µ

4 Colour Grey

5 Loss on Ignition at 800

0

C 4% maximum

1.6.2 PHYSICAL PROPERTIES OF RICE HUSK ASH:

Table 1.2 Physical Properties of Rice HuskAsh

Sl No. Parameter Value

1 Physical State Solid-NonHazardous

2 Appearance Very fine powder

3 Particle Size 25 microns-mean

4 Colour Grey

5 Odour Odourless

6 Specific Gravity 2.3



1.6.3 CHEMICAL PROPERTIES OF RICE HUSK ASH:

Table 1.3: Chemical Composition of RHA

Constituents % Composition

Fe2O3 1.38

SiO2 90.20

Al2O3 0.85

CaO 1.18

MgO 1.21

Loss on ignition 3.95

1.7 REACTION MECHANISM

1.7.1 Pozzolanic reaction

A pozzolanic reaction occurs when a siliceous or aluminous material get in touch

with calcium hydroxide in the presence of humidity to form compounds exhibiting

cementitious properties. The calcium silicate hydrate (C-S-H) and calcium hydroxide

(Ca(OH)2, or CH) are released within the hydration of two main components of cement

namely tricalcium silicate (C3S) and dicalcium silicate (C2S) where C, S represent CaO and

SiO2. Hydration of C3S, C2S also C3A and C4AF (A and F symbolize Al2O3 and Fe2O3)

respectively, is important. Upon wetting, the following reactions occur:

2(3CaO.SiO2) + 6H20 3CaO.2SiO2.3H20 + 3Ca (OH) 2 …………… (1)

2(2CaO.SiO2) + 4H20 3CaO.2SiO2.3H20 + Ca (OH) 2 …………… (2)

3CaO.Al203 + 3H20 + 3CASO4

3CaO.Al203. 3CaSO4. 3H20 …………… (3)



4CaO.A1203.Fe203 + 10H20 + 2Ca (OH) 2

6CaO Al203. Fe203. 12 …………… (4)

The C-S-H gel generated by the hydration of C3S and C2S in equations (1) and (2) is

the main strengthening constituent. Calcium hydroxide and Ettringite (3CaO.3CaSO4.31H20,

equation 3) that are crystalline hydration products are randomly distributed and form the

frame of the gel-like products. Hydration of C4AF (equation 4), consumes calcium hydroxide

and generates gel-like products. Excess calcium hydroxide can be detrimental to concrete

strength, due to tending the crystalline growth in one direction. It is known that by adding

pozzolanic material to mortar or concrete mix, the pozzolanic reaction will only start when

CH is released and pozzolan/CH interaction exist. In the pozzolan-lime reaction, OH- and Ca

2+ react with the SiO2 or Al203-SiO 2 framework to form calcium silicate hydrate (C-S-H),

calcium aluminate hydrate (C-A-H), and calcium aluminate ferrite hydrate:

Tobermorite gel:

SiO2 + Ca (OH)2 + H20 CaO.SiO2.H20 ……… (5)

Calcium aluminate hydrate:

Ca (OH)2 + H20 + Al203 aO.A1203.Ca(OH)2.H2O ……. (6)

Calcium aluminate ferrite hydrate:

Ca (OH)2+ Fe203 + A1203 + H20

Ca(OH)2.A1203.Fe203.H20 ……… (7)

The crystallized compound of C-S-H and C-A-H, which are called cement gel,

hardened with age to form a continuous binding matrix with a large surface area and are

components responsible for the development of strength in the cement paste. Pozzolan-lime

reactions are slow, generally starting after one or more weeks. The behavior of the delay in

pozzolanic reaction will result in more permeable concrete at early ages and gradually

becomes denser than plain concrete with time. This behavior is due to two reasons: Firstly,

pozzolan particles become the precipitation sites for the early hydration C-S-H and CH that

hinders pozzolanic reaction. Secondly, the strong dependency of the breaking down of glass



phase on the alkalinity of the pore water which could only attain the high pH after some days

of hydration. Pozzolan can partially replace cement in mortar or concrete mix without

affecting strength development.

1.7.2 Pozzolanic reaction of RHA

Data from reaction results between RHA and CH indicates that the amount of CH by

30% RHA in cement paste begins to decrease after 3 days, and by 91 days it reaches nearly

zero, while in the control paste, it is considerably enlarged with hydration time. The addition

of pozzolan decreases the formed CH by the pozzolanic reaction to produce more C-S-H gel

that can improve the strength and durability of concrete. Amorphous silica that is found in

some pozzolanic materials reacts with lime more eagerly than those of crystalline form. The

most essential asset of RHA that identifies pozzolanic activity is the amorphous phase

substance. The RHA is an approximately 85% to 95% by weight of amorphous silica.

As a consequence of this extremely reactive pozzolanic substance appropriate for use

in lime-pozzolan mixes and for Portland cement substitution. The reactivity of RHA

associated to lime depends on a combination of two factors: namely the non-crystalline silica

content and its specific surface. Cement replacement by rice husk ash accelerates the early

hydration of C3S.

The increase in the early hydration ratio of C3S is attributed to the high

specific surface area of the rice husk ash. This phenomenon specially takes place with fine

particles of RHA. Although the small particles of pozzolans are less reactive than Portland

cements, they produce a large number of nucleation sites for the precipitation of the

hydration products by dispersing in cement pastes. Consequently, this mechanism creates the

more homogenous and denser paste as for the distribution of the finer pores due to the

pozzolanic reactions among the amorphous silica of the mineral addition and the CH. Mehta

(1987) reported that the finer particles of RHA speed up the reactions and form smaller CH

crystals. (2001) have exposed that pozzolanic reaction can be characterized by the Jander

diffusion equation based on Fick's parabolic law of diffusion assuming the interface is a

contracting sphere. The Jander equation for three dimensional diffusion in a sphere is (1- (1 –

x) 1/3)2=(D/r2)kt where x is the fraction of the sphere that has reacted, r is initial radius of

the starting sphere, and k is the diffusion constant.



1.8 ADVANTAGES OF USING RICE HUSK ASH IN

CONCRETE

The use of RHA in concrete has been associated with the following essential assets:

Increased compressive and flexural strengths.

Reduced permeability.

Increased resistance to chemical attack.

Increased durability.

Reduced effects of alkali-silica reactivity.

Reduced shrinkage due to particle packing, making concrete denser.

Enhanced workability of concrete.

Reduced heat gain through the walls of buildings.

Reduced amount of super plasticizer.

Reduced potential for efflorescence due to reduced calcium hydroxides

1.9 APPLICATIONS

Portland cement manufacturing.

Road base / Sub base.

Landfill cover or hydraulic barriers.

Parking lot construction.

High quality RHA can be used as a super pozzolanic additive for HSC.

Low quality RHA can be used as filler for concrete



CHAPTER 2

LITERATURE REVIEW

Many researchers have studied the effect of replacement of Cement by Rice Husk

Ash which increases the mechanical and durability properties of concrete.

2.1 “Effect of Rice Husk Ash on Properties of High Strength

Concrete”byDAO VAN DONG, PHAM DUY AND NGUYEN NGOCLAN

(2008)

Rice Husk is an abundant waste generated from agricultural product in Vietnam. This

is a potential source to produce RHA for construction applications in Vietnam. Low quality

RHA can be used as filler for concrete. The acceptable content is 15% to replace for cement

with an acceptance of reduction in compressive strength. High quality RHA can be used as a

super pozzolanic additive for HSC. HSC used 15% RHA to replace for cement obtains

substantial improvements in properties, especially, compressive strength, and water and

chloride resistance. Investigations in manufacturing high quality RHA in Vietnam are

necessary.

The replacement of RHA for cement results in decreases in compressive strength

compared to the control samples. At age of 28 days there is no big difference between

compressive strength of 10% and 15% RHA samples. However, the use 20% RHA leads to a

significant reduction of compressive strength. Additionally the rate of development of

compressive strength of the RHA concrete samples tends to decrease the age of curing. These

could be due to that RHA does not act as a cement replacement because of its coarse particle

size and low reactivity. From these data it is designed that 15% RHA is an acceptable

percentage of RHA as cement replacement.



2.2 “Experimental Study on Strength of Concrete by Using Artificial

Fibers with Rice Husk Ash” by SANDESH D. DESHMUKH,

PRAVINV.DOMKE, SATISH D. KENE, R.S.DEOTALE(2008)

Husk ash Properties studied include workability of fresh concrete, compressive

strength, flexural tensile strength, splitting This paper reports on a comprehensive study on

the properties of concrete containing rice tensile strength, modulus of elasticity for hardened

concrete. Rice husk ash content was use from 0% to 20% in the interval of 2.5% in weight

basis. It was found that the strength of concrete reduces after further addition of 12.5% of

rice husk ash. The laboratory results Shown that steel fiber addition either into Portland

cement concrete or rice husk ash concrete, improve the tensile strength properties. However,

it reduced workability. Although rice husk ash replacement reduces strength properties. The

performed experiments show that the behavior of rice husk ash concrete is not similar to that

of Portland cement concrete when rice husk ash is added.

Compressive strength of concrete mixtures was measured at the ages of 7, 14, 28 and 90 days

and shown in Table 2.1. There was an increase up to 10% and reduction up to 6%

compressive strength of cube concrete specimens produced. This may be due to the physical

difficulties inproviding a homogeneous mix within the concrete causing rise or drop in

thecompressive strength as compared to the plainconcrete. The addition of rice husk ash to

the concretemixture did not improve compressive strength of 7days and 14 days of curing

specimen, but after28days and 90 days only small increase (up to 10%) in compressive

strength was observed. The presence of rice husk ash, whencompared with plain concrete,

decreased the averagecompressive strength by 10% and 14% for 15% and30% rice husk ash

replacement ratio, respectively.If the amount of mixing water was reduced on the basis of

equal Vee-Bee workability, it appears that thereduction in compressive strength due to

addition ofrice husk ash can be recovered significantly.



Table 2.1: Compressive Strength test

Fig.2.2 Effect of RHA on compressive strength

No RHA(%)

Byweight

7Days

(N/mm2)

14 Days

(N/mm2)

28 Days

(N/mm2)

90 Days

(N/mm2)

A1 0 23.56 24.89 40.00 42.22

A2 2.5 22.67 23.02 36.89 40.00

A3 5.0 22.22 22.89 36.44 37.78

A4 7.5 21.56 22.67 35.56 36.44

A5 10.0 21.33 22.22 34.22 34.67

A6 12.5 20.89 21.11 33.33 33.78

A7 15.0 16.44 16.89 17.78 18.22

A8 17.5 15.56 16.00 16.44 16.89

A9 20 15.11 15.56 15.56 16.44



2.3 “The Possibility of Adding the Rice Husk Ash (RHA) to the Concrete”

by MAURO M. TASHIMA, CARLOS A. R. DA SILVA, JORGE L.

AKASAKI , MICHELE BENITI BARBOSA.

This paper evaluates how different contents of rice husk ash (RHA) added to concrete

may influence its physical and mechanical properties. Samples were tested, with 5% & 10%

of RHA, replacing in mass the cement. Properties like simple compressive strength, split

tensile strength were evaluated. The results were compared to control sample and the

viability of adding RHA to concrete was verified.

The compressive strength is shown in Table 2.2. The addition of RHA causes an

increment in the compressive strength due to the capacity of the pozzolana, of fixing the

calcium hydroxide, generated during the reactions of hydrate of cement. All the replacement

degrees of RHA increased the compressive strength. For a 5% of RHA, 25% of increment is

verified when compared with mixtures.

The resultsof splittingtensilestrengthare shown in Table 2.3. All the replacement degrees

of RHA researched, achieve similar results in split tensile strength. According to the results,

may be realized that there is no interference of adding RHA in the split tensile strength.

The use of RHA in civil construction. An increment of 25% was obtained when was

added 5% of RHA. Moreover, a reducing on waste Portland cement was verified, obtaining

the same resistance of control sample. According to the results of split tensile test, all the

replacement degrees of RHA researched, achieve similar results. Then, maybe realized that

there is no interference of adding RHA in the split tensile strength. All the samples studied

have a similar results in elasticity module. A decreasing in the module is realized when the

levels of RHA are increasing.



2.4 “Use of Ultrafine Rice Husk Ash with high-carbon content as pozzolan

in high performance concrete” by GUILHERMECHAGASCORDEIRO,

ROMILDO DIAS TOLEDO FILHO, EDUARDO DE MORAESREGO

FAIRBAIRN (2008).

Rice husk ash (RHA) has been generated in large quantities in rice producing

countries. This by-product can contain non-crystalline silica and thus has a high potential to

be used as cement replacement in mortar and concrete. However, as the RHA produced by

uncontrolled burning conditions usually contains high-carbon content in its composition, the

pozzolanic activity of the ash and the rheology of mortar or concrete can be adversely

affected. In this paper the influence of different grinding times in a vibratory mill, operating

in dry open-circuit, on the particle size distribution, in order to improve RHA’s performance.

In addition, four high-performance concretes were produced with 0%, 10%, 15%, and 20%

of the cement (by mass) replaced by ultrafine RHA. For these mixtures, rheological,

mechanical and durability tests were performed.

For all levels of cement replacement, especially for the 20%, the ultra-fine RHA

concretes achieved superior performance in the mechanical and durability tests compared

with the reference mixture. The workability of the concrete, however, was reduced with the

increase of cement replacement by RHA.



2.5 “Study on Properties of Rice Husk Ash and Its Use as Cement

Replacement Material” byGHASSAN ABOOD HABEEB, HILMI BIN

MAHMUD (2009).

This paper investigates the properties of rice husk ash (RHA) produced by using a

ferro-cement furnace. The effect of grinding on the particle size and the surface area was first

investigated, and then the XRD analysis was conducted to verify the presence of amorphous

silica in the ash. Furthermore, the effect of RHA average particle size and percentage on

concrete workability, fresh density, superplasticizer (SP) content and the compressive

strength were also investigated. Although grinding RHA would reduce its average particle

size (APS), it was not the main factor controlling the surface area and it is thus resulted from

RHA’s multilayered, angular and microporous surface. Incorporation of RHA in concrete

increased water demand. RHA concrete gave excellent improvement in strength for 10%

replacement (30.8% increment compared to the control mix), and up to 20% of cement could

be valuably replaced with RHA without adversely affecting the strength. Increasing RHA

fineness enhanced the strength of blended concrete compared to coarser RHA and control

OPC mixtures.

In terms of the replacement level, the 5% replacement level achieved slightly lower

values of compressive strength at early ages for up to 7 days except for the mixture where the

compressive strength was higher due to the increased reactivity and the filler effect of RHA.

Based on that, it can be noticed that the amount of RHA present when 5% replacement used

is not adequate to enhance the strength significantly.

The strength increased with RHA for up to 10% which resulted in achieving the

maximum value. For example, 10% mixture resulted in 30.8% increment compared to the

OPC control mix tested at 28 days age, that is due to the pozzolanic reaction of the available

silica from the RHA and the amount of C-H available from the hydration process and also

due to the microfiller effect when fine RHA is used.

The strength values when RHA was replaced by 15% were found to be similar to 5%

replacement except that at the age of 7 days, the strength was higher than the control for all

RHA mixtures, in this case, the amount of silica available in the hydrated blended cement

matrix is probably too high and the amount of the produced C-H is most likely insufficient to



react with all the available silica and as a result of that, some amount of silica was left

without any chemical reaction.

When 20% of OPC was replaced for RHA, the strength of concrete achieved

equivalent values to the OPC control mixture. Increasing the replacement to a level above

20% was avoided in this study due to the fact that the increased water demand would lead to

SP content higher than the manufacturer recommendations (maximum of 2% by weight of

the cementitious materials) which can give an adverse effect on the produced concrete by

acting as a retarder and increasing cost. Furthermore, the strength would decrease to a value

that is lower than the control. The released amount of C-H due to the hydration process is not

sufficient to react with all the available silica from the addition of RHA and thus, the silica

will act as inert material and will not contribute to the strength the RHA used in this study is

efficient as a pozzolanic material; it is rich in amorphous silica (88.32%). The loss on

ignition was relatively high (5.81%). Increasing RHA fineness increases its reactivity.

Grinding RHA to finer APS has slightly increased its specific surface area, thus, RHA APS is

not the main factor controlling its surface area. The dosage of superplasticizer had to be

increased along with RHA fineness and content to maintain the desired workability. The

compressive strength of the blended concrete with 10% RHA has been increased

significantly, and for up to 20% replacement could be valuably replaced by cement without

adversely affecting the strength. Increasing RHA fineness enhances the strength of blended

concrete.



CHAPTER 3

MATERIALS AND METHODOLOGY

3.1 MATERIALES USED

3.1.1 CEMENT

In this experiment 43 grade ordinary Portland cement (OPC) with brand name ultra

tech was used for all concrete mixes. The cement used was fresh and without any lumps. The

testing of cement was done as per IS:8112-1989. The specific gravity of cement was found to

be 3.15.The physical properties of cement used are as given in table.

Table 3.1 physical properties of cement

Particulars Experimental result As per standard

1.Fineness 6% 10%

2.Soundness

a)By Le Chateliers apparatus 1.00 mm 10 mm

3.Setting time (minutes)

a) Initial set 195 minutes 30 minutes

b) Final set 255 minutes 600 minutes

4.Comp strength (M Pa)

a) 3 days 32 23 MPa

b) 7 days 41 33 MPa

c) 28 days 52 43 MPa

Temperature during testing 27.810 C 27° C 2%



3.1.2 COMPOSITION OF ORDINARY PORTLAND CEMENT

Table 3.2 Composition of Ordinary Portland cement

INGRADIENTS COMPOSITION PERCENTAGE

Lime CaO 62

Silica SiO2 22

Alumina Al2 O3 05

Calcium Sulphate CaSO4 04

Iron Oxide Fe2O3 03

Magnesia MgO 02

Sulphur S 01

Alkalies --- 01



3.1.3 FINE AGGREGATE

The sand used for the experimental program was locally procured and was

conforming to zone-II according to code IS 383:1970. The specific gravity of fine aggregate

was found to be 2.89.

Table 3.3 Sieve Analysis of Fine Aggregate

3.1.4 COARSE AGGREGATE

Locally available coarse aggregate having the maximum size of 20 mm were used in

the present work. The specific gravity of coarse aggregate was found to be 2.82.

3.1.5 RICE HUSK ASH

Rice husk ash is obtained from the local rice mill in Davanagere. Which is burnt in

furnace and the process of burning is uncontrolled.The specific gravity of rice husk ash was

found to be 2.3.

3.1.6 WATER

Portable tap water was used for the preparation of specimens and for the curing of

specimens. Portable water as available in GMIT campus was used for the preparation of

mortar mix. The PH value of water is 6.8.

SL

NO

IS SIEVE

SIZE

Weight

Retained

(Kg)

Cumulative

Weight

Retained

(Kg)

Cumulative

Percentage

Retained

Cumulative

Percentage

Passing

1 4.75 6 6 0.6 99.4

2 2.36 42 48 4.8 95.2

3 1.18 229 277 27.7 72.3

4 600 µ 348 625 62.5 34.5

5 300 µ 225 880 88 12.0

6 150 µ 115 995 99.5 0.5

7 Pan 5 1000 100 0



3.2 METHODOLOGY

The main objective of this work is to study the suitability of the rice husk ash as a

pozzolanic material for cement replacement in concrete. However it is expected that the use

of rice husk ash in concrete improve the strength properties of concrete. Also it is an attempt

made to develop the concrete using rice husk ash as a source material for partial replacement

of cement, which satisfies the various structural properties of concrete like compressive

strength and split tensile strength.

It is also expected that the final outcome of the project will have an overall beneficial

effect on the utility of rice husk ash concrete in the field of civil engineering construction

work.

Following parameters influences behavior of the rice husk ash concrete, so these

parameters are kept constant for the experimental work.

Percentage replacement of cement by rice husk ash

Fineness of rice husk ash

Chemical composition of rice husk ash

Water to cementitious material ratio (w/c ratio)

Type of Curing

Also from the literature survey, it is observed that the parameters suggested by

different researchers and their results are not matching with each other. It was due to

variation in properties of different materials considered in the work. Therefore the percentage

replacement of cement by rice husk ash and method of mix design is fixed after preliminary

investigation.



3.3 CONCRETE MIX DESIGN

We have designed the mix as per the mix design in accordance with the Indian

standard recommended guide lines for concrete mix design.

The mix design procedure adopted to obtain a M20 grade concrete is in accordance

with IS 10262- 2009.The specific gravities of the materials used are as tabulated in the table

a) Design Stipulations:

i. Characteristic Compressive Strength of cement:43N/mm2

ii. Maximum size of the aggregates: 20 mm

b) Test data for Materials:

i. Specific Gravity of Cement: 3.15

ii. Specific Gravity of Coarse Aggregate: 2.82

iii. Specific Gravity of Fine Aggregate:2.89

iv. Concrete Designation: M20

v. Characteristic Compressive Strength (fck):20 N/mm2

vi. Water Absorption:

a. Coarse Aggregates:0.5%

b. Fine Aggregate:1.04%

vii. Free (Surface) Moisture

a. Coarse Aggregate:0.5%

b. FineAggregate: 2.0%



The design steps are as follows

Step 1: Determination of the target strength for mix proportioning

fck = fck+ 1.65s

Where, fck = target mean compressive strength at 28 days

fck = characteristics compressive strength at 28 days

s = standard deviation.

From IS 456-2000, Table 8, s = 4MPa

Therefore target strength = 20 + (1.65 4) = 26.6 MPa.

Step 2: Selection of water /cement ratio

Referring IS 456-2000, Table 5, W/C ratio = 0.55

Step 3: Selection of water content

From Table 2 IS 10262-2009, maximum water content = 186 liter (for 25to 50 mm slump

range) for 20 mm aggregate. Estimated water content for 100 mm slump

=186+6/100*186=197 liter.

Step 4: Calculation of cement content

W/C ratio = 0.55

Therefore, cement content = 197 / 0.55

= 358.18 Kg/m3.

Referring to IS 456- 2000, Table 5, Minimum cement required = 320 Kg/m3< 358.18 Kg/m

3

Hence the cement content is adequate.

Step 5: Determination of the volume of coarse aggregates

Referring IS 10262- 2009, Table 3, volume of coarse aggregate per unit volume of concrete

corresponding to a maximum size of coarse of 20mm and fine aggregate corresponding to

grading zone II,

Volume of coarse aggregate= 0.62-0.01= 0.61

Volume of fine aggregate content=1-0.61= 0.39



Step 6:Mix Calculations

Volume of concrete = 1 m3

Volume of cement = Weight / Specific gravity

= (325 / 3.15) (1 / 103)

= 0.116 m3

Volume of Water = Weight / Specific gravity

= 197 / 1000

= 0.197 m3

Volume of Coarse aggregate = 0.61 m3

Volume of Fine Aggregate = 1 – 0.116 – 0.197 – 0.62

= 0.067 m3

Total quantity of aggregates = 1 – 0.116 – 0.197

= 0.687 m3

Mass of coarse aggregate = 0.687 0.61 2.82 103

= 1186.9 Kg/m3

Mass of fine aggregate = 0.687 0.39 2.82 x 103

= 777.69 Kg/m



Step 7: The mix proportion obtained are as shown in the table 3.3.

Table 3.4 Mix Proportion

W/C Ratio Cement Fine Aggregate Coarse Aggregate

0.55 358.18 kg/m3 777.69 kg/m

3 1186.9 kg/m

3

0.55 1 2.17 3.31

Table 3.5 Mix Proportion for Different % of RHA

Mix

Designation

Rice husk

ash

Cement

Kg/m3

Coarse

Aggregate

Kg/m3

Fine

Aggregate

Kg/m3

Water

Liters/m3

M0 0% 358.18 1186.90 777.69

197

M1 5% 340.28 1183.20 775.3

197

M2 10% 322.37 1181.77 774.31

197

M3 15% 304.45 1178.83 772.06

197

M4 20% 286.55 1174.89 769.8

197



3.4 CONCRETE MIX DESIGNATION

Table 3.6 Concrete Mix Designation

Mix Designation

Description

M0 control concrete of grade M20

M1 5% RHA + 95% Cement

M2 10% RHA +90% Cement



3.5 CASTING OF SPECIMENS AND TESTING PROCEDURE

Cement, sand and aggregate were taken in mix proportion 1:2.17:3.31 which

correspond to M20 grade of concrete. 0%, 5%, 10%, 15%, & 20% of cement was replaced by

RHA and concrete was produced by dry mixing all the ingredients homogeneously. To this

dry mix, required quantity of water was added (W/C= 0.55) and the entire mix was again

homogeneously mixed. This wet concrete was poured into the moulds which was compacted

both through hand compaction in three layers as well as through vibrator. The specimens

were given smooth finish and taken out of the table vibrator. After the compaction, the

specimens were given smooth finishes and were covered with gunny bags. After 24 hours,

the specimens were demoulded and transferred to curing tanks where in they were allowed to

cure for 28 days.

For evaluating the compressive strength, specimens of dimensions 150x150x150mm

were prepared. They were tested on compression testing machine as per IS 516-1959. The

compressive strength is calculated by using the equation,



F=P/A ………..8

Where, F= Compressive strength of the specimen (in MPa).

P= Maximum load applied to the specimen (in N).

A= Cross sectional area of the specimen (in mm2).

For the evaluating the tensile strength, cylindrical specimens of diameter 150mm and length

300mm were prepared. Split tension test was carried out on 2000 kN capacity compression

testing machine as per IS 5816-1999. The tensile strength is calculated using the equation,

F= 2P/ (πDL) ……….9

Where, F = Tensile strength of concrete (in MPa).

P = Load at failure (in N).

L = Length of the cylindrical specimen (in mm).

D = Diameter of the cylindrical specimen (in mm).

Three concrete cubes and two cylinders are cast for compression test at 7,14 and 28 days .Fig

3.1 shows the test specimens

Fig 3.1 Casting of Cubes and cylinders



Fig 3.2 Testing of Cubes and cylinders

3.6 SLUMP VALUES:

Table 3.7 Slump Values

SL NO MIX DESIGNATION SLUMP VALUES(MM)

1 M0 95

2 M1 85

3 M2 70

4 M3 55

5 M4 40



Fig 3.3 Slump Variation

The slump values decreased upon the inclusion of RHA as partial replacement of

OPC.Thus, it can be inferred that to attain the required workability, mixes containing RHA

will required higher water content than the corresponding conventional mixes.

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20

Slu

mp

va

lue

in m

m

RHA in percentage

Slump Values

slump value



CHAPTER 4

EXPERIMENTAL RESULT

4.1 COMPRESSIVE STRENGTH TEST RESULTS

For each concrete mix, the compressive strength is determined on three 150×150×150

mm cubes at 7, 14 and 28 days of curing.

Following tables 4.1,4.2 & 4.3give the compressive strength test results of control

concrete and RHA concrete produced with 5, 10, 15, & 20 percentages of RHA.

Table 4.1 Compressive strength of RHA concrete for 7 days

Mix

Designation

Curing

period

Failure load

(KN)

Compressive

strength (N/mm2)

Avg

Compressive

strength

(N/mm2)

M0

7 days

640 28.44

29.03 680 30.22

640 28.44

M1 7 days

510 22.66

21.7 475 21.11

480 21.33

M2 7 days

260 11.55

13.55 385 17.11

270 12

M3

7 days

320 14.22

11.77 260 11.55

215 9.55

M4 7 days

280 12.44

10.81 240 10.66

210 9.33



Table 4.2 Compressive Strength of RHA Concrete For 14days

Mix

Designation Curing period

Failure load

(kN)

Compressive

strength

(N/mm2)

Avg

Compressive

strength

(N/mm2)

M0

14 days

790 35.11

35.03 795 35.33

780 34.66

M1 14 days

580 25.77

24.95 575 25.55

530 23.55

M2 14 days

330 14.66

19.44 480 21.33

500 22.33

M3

14 days

390 17.33

18.07 420 18.66

410 18.22

M4 14 days

300 13.33

14.66 365 16.22

325 14.44



Table 4.3 Compressive Strength Of RHA Concrete For 28days

Mix

Designation

Curing

period

Failure load

(KN)

Compressive

strength

(N/mm2)

Avg

Compressive

strength

(N/mm2)

M0

28 days

980 43.55

44.58 1020 45.33

1010 44.88

M1 28 days

770 34.22

36.88 900 40.00

820 36.44

M2 28 days

690 30.66

29.18 620 27.55

660 29.33

M3

28 days

470 20.88

20.07 455 20.22

430 19.11

M4 28 days

320 14.22

14.59 340 15.11

325 14.44



4.1.1 OVERALL RESULTS OF COMPRESSIVE STRENGTH

Following table gives the overall results of compressive strength of RHA concrete

produced with different percentages of RHA. The variation of compressive strength is

depicted in the form of graph as shown in figure 4.4

Table 4.4 Overall Results of Compressive Strength

Mix designation

Compressive strength (N/mm2)

7 days curing

14 days curing 28 days curing

M0 29.03 35.03 44.58

M1 21.70 24.95 36.88

M2 13.55 19.44 29.18

M3 11.77 18.07 20.07

M4 10.81 14.66 14.59

Fig 4.1 Compressive Strength of RHA Concrete For 7 Days

0

5

10

15

20

25

30

35

0 5 10 15 20

com

pre

ssiv

e st

ren

gth

in

N/m

m2

RHA in percentage

Compressive Strength For 7 Days

7 days



Fig 4.2 Compressive Strength of RHA Concrete for 14 Days

Fig 4.3 Compressive Strength of RHA Concrete For 28 Days

Fig 4.3 Compressive Strength of RHA Concrete for 28 Days

0

5

10

15

20

25

30

35

40

0 5 10 15 20

com

pre

ssiv

e st

ren

gth

in

N\m

m2

RHA in percentage

Compressive Strength For 14 days

14 days

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20com

pre

ssiv

e st

ren

gth

in

N/m

m2

RHA in percentage

Compressive Strength of RHA For 28 days

28 days



Fig 4.4 Overall Results of Compressive Strength

Fig 4.5 Overall Results of Compressive StrengthVGV

Fig 4.5 Overall Results of Compressive Strength

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20

7 days

14 days

28 days

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20

com

pre

ssiv

e st

ren

gth

in

N/m

m2

RHA in percentage

7 days

14 days

28 days



4.2 SPILT TENSILE STRENGTH TEST RESULTS

Test has been conducted after 7, 14 and 28 days of curing. Split tensile is conducted on

150 mm diameter and 300 mm length cylinders as per IS 5816-1999.

Following tables 4.5, 4.6 & 4.7 gives the split tensile strength test results of control concrete

and RHA concrete produced with 0,5,10, 15, & 20 percentages of RHA.

Table 4.5 Split Tensile Strength of RHA Concrete for 7 Days

Mix Designation Curing

period

Failure load

(kN)

Tensile

strength

(N/mm2)

Avg Tensile

strength (N/mm2)

M0 7 days 130 1.89 1.93

140 1.98

M1 7 days 175 2.47 2.01

110 1.55

M2 7 days 110 1.55 1.51

105 1.48

M3

7 days 100 1.41 1.30

85 1.20

M4 7 days 70 0.99 0.91

60 0.84



Table 4.6 Split Tensile strength of RHA concrete for 14 days

Mix Designation Curing

period

Failure load

(kN)

Tensile

strength

(N/mm2)

Avg Tensile

strength

(N/mm2)

M0

14 days 155 2.19

2.29

170 2.40

M1 14 days 180 2.54

2.21

130 1.89

M2 14 days 130 1.83

1.79

125 1.76

M3

14 days 85 1.20

1.13

75 1.06

M4 14 days 135 1.90

1.79

120 1.69



Table 4.7 Split Tensile strength of RHA concrete for 28 days

Mix Designation Curing period Failure load

(KN)

Tensile

strength

(N/mm2)

Avg

Tensile

strength

(N/mm2)

M0

M0

28 days 210 2.97

3.11

230 3.25

M1

28 days 175 2.47

2.43

170 2.40

M2 28 days 170 2.47

2.64

200 2.82

M3

28 days 120 1.69

1.83

140 1.98

M4 28 days 100 1.41

1.58

125 1.76



4.2.1 OVERALL RESULTS OF SPLIT TENSILE STRENGTH

Following table gives the overall results of split tensile strength of RHA concrete

produced with different percentages of RHA. The variation of tensile strength is depicted in

the formof graph as shown in figure.

Table 4.8 Overall results of split tensile strength

Mix Designation

SplitTensile strength (N/mm2)

7 Days Curing 14 Days Curing 28 DaysCuring

M0 1.93 2.29 3.11

M1 2.01 2.21 2.43

M2 1.51 1.79 2.64

M3 1.30 1.13 1.83

M4 0.91 1.79 1.58

Fig 4.6 Split Tensile Strength of RHA Concrete for 7 Days

0

0.5

1

1.5

2

2.5

0 5 10 15 20

spli

t te

nsi

le

stre

ng

th i

n N

/mm

2

RHA in percentage

Split Tensile Strength For 7 Days

7 days



Fig 4.7 Split Tensile Strength of RHA Concrete For 14 Days

Fig 4.8 Split Tensile Strength of RHA Concrete for 28 Day

0

0.5

1

1.5

2

2.5

0 5 10 15 20

spli

t te

nsi

le s

tren

tgh

in

N/m

m2

RHA in percentage

Split Tensile Strength For 14 days

14 days

0

0.5

1

1.5

2

2.5

3

3.5

0 5 10 15 20

Sp

lit

ten

sile

str

en

gth

in

N/m

m2

RHA in percentage

Split Tensile Strength For 28 Days

28 days



Fig 4.9 Overall Split Tensile Strength

Fig 4.10 Overall Split Tensile Strength

0

0.5

1

1.5

2

2.5

3

3.5

0 5 10 15 20

Sp

lit

ten

sile

str

en

gth

in

N/m

m2

RHA in percentage

7 days

14 days

28 days

0

0.5

1

1.5

2

2.5

3

3.5

0 5 10 15 20

7 days

14 days

28 days



CHAPTER- 5

OBSERVATION AND DISCUSSIONS

The results of compressive strength of concrete cubes show that the compressive

strength reduced as the percentage of RHA increased. However the compressive strength

increased as the number of days of curing increased for each percentage RHA replacement. It

is seen from table 4.1&4.3 that for control cube the compressive strength increased from

29.03 N/mm2 at 7 days to 44.58 N/mm

2 at 28 days. The 28days strength was above the

specified value of 20N/mm2

for grade M20 concrete. The strength of 5% replacement by

RHA showed increase in compressive strength from 21.7 N/mm2 at 7 days to 36.88 N/mm

2 at

28 day, the 28 days strength was above the specified value of 20 N/mm2 for grade M20

concrete. The strength of 10% replacement by RHA showed increased in compressive

strength from 13.55N/mm2 at 7 days to 29.18N/mm

2 at 28days. The 28days strength was

above the specified value of 20N/mm2 for grade M20 concrete as shown in table 5.1. The

strength of 15% replacement by RHA should increases in compressive strength from

11.77N/mm2 at 7days to 20.07N/mm

2 at 28 days. The 28days strength was above the

specified value of 20N/mm2 for precast products as shown in table. The strength of the 20%

replacement by RHA showed increase in compressive strength 10.81N/mm2 at 7days to

14.59N/mm2 at 28days. The 28 days strength was above the specified value of 10 N/mm

2 for

huge concrete works for foundations, culverts and retaining walls as shown in table 5.1.

Table 5.1 Uses of different grades of concrete

SL No Grade Concrete Mix Uses

1 M10 1:3:6 Mass concrete in piers, abutments,

2 M15 1:2:4 Normal RCC works i.e., slabs, columns, walls.

3 M20 1:1.5:3 Water retaining structures, reservoirs.

4 M25 1:1:2 Long span arches and highly loaded columns

5 M30 - Mass concrete foundations

6 M35 - Post tensioned prestressed concrete

7 M40 - pre tensioned prestressed concrete



CHAPTER -6

CONCLUSION

Based on the limited experimental investigation concering Compressive and split

tensile strength of concrete with rice husk ash as a partial replacement of cement, the

following conclusion can be drawn.

1. As the rice husk ash is a waste material, it reduces the cost of construction.

2. The optimum replacement level of RHA is found to be 0-15% for M20 grade of

concrete.

3. The replacement of cement with RHA results in reduction of density of concrete. This is

due to the fact that the specific density of the RHA is much lower than that of cement.

4. The slump values of the concrete reduced as the percentage of RHA increased.



CHAPTER -7

REFERENCES

1 A.M.Naville and J.J.Brooks, (1999) Concrete Technology, Addison- Wesley, First

Reprint 1999.

2 Dao van dong, Pham duy and Nguyen ngoclan . (2008), “Effect of Rice Husk Ash on

Properties of High Strength Concrete”.

3 Ghassan Abood Habeeb, Hilmi Bin Mahmud., (2009), “Study on Properties of Rice

Husk Ash and Its Use as Cement Replacement Material”, vol.13, pp.2.

4 Monikachanu N ,Dr.Th.Kiranbala Devi(2011)”Contribution of RHA to the properties of

cement mortar and concrete” IJER,volume-2,ISSN:2278-018,pages 3-7.

5 Deepa G Nair ,K..Sivaraman and Job Thomas(2013) “Mechanical properties of RHA –

High strength concrete “,AJER,volume-3,ISSN:2320-0847,pages 14-18.

6 Anil kumarsuman, Anil kumarsaxena, T.R.Arora(2015) “Assessment of concrete

strength using partial replacement of cement for RHA”, international journal,vol-4,ISSN :

2231-2307, pages 131-133.

7 IS:10262-2009 “specification for concrete mix proportioning”, BIS 2009

8 IS:456-2000 “Plain and reinforced concrete - code of practice” BIS 2000

9 IS:9103-1999 “Specification for Concrete admixture” BIS 1999

10 IS:383-1970 “Specification for coarse and fine aggregate” BIS 1970

11 IS 5816-1999 “Specification for splitting tensile strength” BIS 1999

12 IS:8112-1989 “specification for 43 grade ordinary Portland cement” BIS 1989

13 M.S.Shetty “Concrete Technology”, S.Chand and Company Ltd, 2008.

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