Effect of unprocessed rice husk ash as a cementitious material in concrete

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME
240
EFFECT OF UNPROCESSED RICE HUSK ASH AS A CEMENTITIOUS
MATERIAL IN CONCRETE
(A COMPARISON WITH SILICA FUME)
Mohammad Qamruddin1
, Prof.L.G.Kalurkar2
1
Master of Civil Structures, Civil Engineering, Faculty of Engineering, Jawaharlal Nehru
Engineering College Aurangabad
2
Professor at Jawaharlal Nehru Engineering College Aurangabad Dr.Babasaheb Ambedkar
Marathwada University, Aurangabad,431001, Maharashtra
ABSTRACT
Fast depleting natural resources, huge consumption of energy, and environmental
hazards involved in the production of cement has inspired for searching the substitution by
other material with similar material, especially in developing countries. Rice husk ash
(RHA), an agricultural waste, is classified as “a highly active pozzolan” because it contains a
very high amount of amorphous silica and a large surface area. The objective of the study is
to investigate the mechanical properties of concrete with different replacement levels of
ordinary Portland cement by rice husk ash and silica fume individually and in combination.
The cylinders (150mmdia x 300mmheight) were cast. The splitting tensile strength at 7days
and 28 days have been obtained with normal curing regime. For RHA a maximum increase in
splitting tensile strength was 10% whereas for silica fume it was 17% compared with nominal
mix when used individually. Combination of RHA and silica fume did not show any exciting
results.
Keywords: Rice husk ash, Silica fume, cementitious material, concrete.
INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND
TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 4, Issue 2, March - April (2013), pp. 240-245
© IAEME: www.iaeme.com/ijciet.asp
Journal Impact Factor (2013): 5.3277 (Calculated by GISI)
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IJCIET
© IAEME

241
1. INTRODUCTION
With growing environmental consciousness at all levels of society, the pollution and
health hazards especially associated with the concrete and cements industries, is coming
under intense scrutiny from environmentalists and the governments. The developed countries
are farther ahead in tackling the problem by using industrial and agricultural wastes in their
industries. These industrial and agricultural wastes are mostly the by-products of oil and coal
burning by-products, slag, rice husk ash, bagasse, fly ash, cement dust, stone crusher dust,
marble dust, brick dust, sewer sludge, glass, tires, etc. Million tons of these waste materials
are abundantly available and discarded every year in the world. They pose environmental
problems like air pollution and leaching of hazardous and toxic chemicals (arsenic, beryllium,
boron, cadmium, chromium, chromium(VI), cobalt, lead, manganese, mercury, molybdenum,
selenium, strontium, thallium, and vanadium, along with dioxins and polycyclic aromatic
hydrocarbon compounds, etc.) when dumped in landfills, quarries, rivers and oceans [1,2].
Consequently air and water pollution have been inextricably linked to environmental
problems and climate change. The production of cement (key binding component of
concrete) is costly, consumes high energy, depletes natural resources and emits huge amounts
0of greenhouse gases (1 ton of cement production emits approximately 1 ton of CO2).
Consequently, environmental degradation, serious pollution and health hazards associated
with cement and concrete industries.
Rice Husk is one of the waste materials in the rice growing regions. This not only
makes the purposeful utilization of agricultural waste but it will also reduce the consumption
of energy used in the production of cement. Therefore Rice Husk is an agro based product
which can be used as a substitute of cement without sacrificing the strength and durability.
Generally the Rice Husk Ash is used while burning the raw clay bricks in the Brick Kilns.
Till recently it is also used in Hotels for cooking but now it is replaced by LPG Gas. Since
Rice Husk has negligible protein content, it is not useful for animal feeding. 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 Rice Husk is burnt, about 20
percent of the Rice Husk or 40 kg would become RHA. Rice Husk Ash contains as much as
80-85% silica which is highly reactive, depending upon the temperature of incineration. Due
to relative high water demand, the lime Rice Husk Ash cement developed lower compressive
strengths. However, the strength characteristics are considered adequate for general masonry
work. The water demand for normal consistency tends to increase with increasing Ash
content of the blended cements. However, this can be corrected by application of certain
water reducing admixtures. The investigations as outlined above point towards encouraging
trend. Normally fly Ash may be used for partially replacing cement to the extent of about
25% of cement. Reactions that take place in the preparation of Rice Husk Ash concrete are;
Silicon burnt in the presence of Oxygen gives Silica.
Si + O2 SiO2
C3S (Cement) + H2O CSH + Ca (OH) 2

242
The highly reactive silica reacts with Calcium hydroxide released during the hydration of
cement, resulting in the formation of Calcium Silicates responsible for strength.
SiO2 + Ca (OH)2 CSH + SiO2
Mehta, P.K., (1) has conducted investigations on Portland Rice Husk Ash cements up to
50% of Ash showed higher compressive strength than the control Portland cement even at as
early as 3 days. Mehta, and Pirtz (2) in a concrete mixture, when 30% Rice Husk Ash by
weight of the total cementing material was present, the 7 days and the 28 days compressive
strengths were higher. Subba Rao.et.al (3) studied the reaction product of lime and silicate
from Rice Husk Ash and showed that it is Calcium Silicate Hydrate (C-S-H) which accounts
for the strength of lime Rice Husk Ash cements.
2. MATERIAL PROPERTIES INVESTIGATED FOR THIS RESEARCH
Table 1:- Material Properties
1 Nominal Max.Size of coarse aggregate 20 mm
2 Slump range (Medium) 50-75 mm IS 10262-2009
(Pg.02)
3 Finness Modulus Of Fine Aggregate 2.88 Confirming to zone II (IS 383-1970)
4 Finness Modulus Of Steel Slag
aggregate
2.86 Confirming to zone II (IS 383-1970)
5 Finness Modulus Of Coarse Aggregate 5.12 Confirming to zone II (IS 383-1970)
6 Specific Gravity Of Fine Aggregate 2.65
7 Specific Gravity Of Steel Slag aggregate 2.67
8 Specific Gravity Of Coarse Aggregate 2.75
9 Specific Gravity Of Cement 3.15
10 Water Absorption of fine aggregates 4.7 %
11 Water Absorption of coarse aggregates 1.65 %

243
3. CHEMICAL COMPOSITION AND PHYSICAL PROPERTIES OF RICE HUSK
ASH USED IN THE STUDY
Table 2:- Chemical Composition of rice husk ash:
Constituent SiO2 Al2O3 Fe2O3 CaO MgO SO3 Na2O K2O
Percentage ( % ) 94.84 0.39 0.54 1.32 0.40 0.01 0.11 1.45
Table 3:- Physical Properties of rice husk ash
Physical Properties Steel Slag
Colour Grey
Appearance Amorphous
specific gravity 2.17
3.1 RHA characteristics
A residual RHA obtained from open filed burning from local resource was used. The
material was carefully homogenised packed to enhance the transport to the laboratory.
Grinded RHA (GRHA): after drying and homogenization process the RHA was ground in a
laboratory ball mill by one hour for optimization. The size and shape of the natural rice husk
ash particles make difficult the development of pozzolanic reactions and the water demand
strongly increases. The GRHA was passed through IS 90 micron sieve and this was used for
the research. Adopting an adequate sequence for concrete mixing process, where the RHA
and the coarse aggregates are mixed during a certain time and after that the rest of component
materials are incorporated, the RHA characteristics can be improved. Table 2 and 3 presents
some chemical composition of the ash and the physical characteristics.
4. EXPERIMENTAL PROGRAM
Materials used in this study were OPC 53 grade cement confirming to IS 8112 and
fine aggregate and coarse aggregate confirming to IS 383-1970.The cement and aggregate
were tested to fulfill the IS requirements.
Rice husk ash was replaced with cement as 10%, 15%, 20% and 25%, similarly silica
fume was also replaced with cement in different batches with percentage replacements
as10%, 15%, 20% and 25%. In the third step rice husk ash and silica fume were replaced in
combination as
Rice husk ash and silica fume were replaced according to following table

244
Table 4:-
Batch Cement(%) RHA(%) Silica fume(%)
1 100 0 0
2 90 10 0
3 85 15 0
4 80 20 0
5 75 25 0
6 90 0 10
7 85 0 15
8 80 0 20
9 75 0 25
10 90 5 5
11 85 7.5 7.5
12 80 10 10
13 75 12.5 12.5
14 75 15 10
15 70 20 10
16 65 25 10
Designed concrete mix of M-20 grade having mix proportion 1:1.90:2.96 with w/c ratio 0.5
same for different percentages of rice husk ash and silica fume were used.
The concrete ingredients namely, cement and coarse aggregates and rice husk ash and silica
fume according to batches were first mixed in the dry state and water was added last.
Cylinders of size 150mm diameter x 300mm length for split tensile strength, Cubes of size
150x150x150 mm for compressive strength were cast replacing rice husk ash and silica fume
by weight of cement.
All the samples were watered cured for 7 days and 28 days. For each batch of RHA and silica
fume percentage replacement 6 specimens were cast. Details of the experimental
investigation of effect of different percentages replacement of fine aggregate by steel slag are
given elsewhere.
4.1 Testing Programme
4.1.1 Compressive Strength
The cube specimen was placed in the machine, of 1000kN capacity. The load was
applied at a rate of approximately 140 kg/sq.cm/min until the resistance of the specimen to
the increasing load can be sustained. Results are presented in Tables 5 and 6.
4.1.2 Splitting Tensile Strength
The cylinder specimen was placed horizontally in the centering with packing skip or
loading pieces carefully positioned along the top and bottom of the plane of loading of the
specimen. The load was applied without shock and increased continuously at a nominal rate
within the range 1.2 N/mm2/min to 2.4 N/mm2/min until failure the specimen. The maximum
load applied was recorded at failure.

245
TEST RESULTS FOR SPLITTING TENSILE STRENGTH
4. DISCUSSIONS ON TEST RESULTS
4.1 Splitting tensile Strength of Concrete
As the replacement level increases there is increase in splitting tensile strength at 28
days age of strength. The maximum splitting tensile strength for the replacement with RHA
and silica fume individually was 4.54 and 4.78 respectively. An increase of 14% and 20%
was observed for RHA and silica fume individually. RHA and silica fume in combination
showed a decreasing trend of strength.

246
5. CONCLUSIONS
1. Replacement of cement with Rice Husk Ash leads to increase in the compressive strength
at 14% at 15% replacement.
2. Optimum replacement level for silica fume was found to be 20% where 17% increase in
splitting tensile strength is observed.
3. The strength achieved for the replacement of combination of RHA and SF was even less
than the nominal mix but cannot be authenticated due to less number of tests.
REFERENCES
[1] P.K.Mehta, “Properties of Blended Cements Made from Rice Husk Ash”, ACI
Journal/September 1977 pp. 440-442.
[2] P.K.Mehta and D.Pritz, “Use of Rice Husk Ash to Reduce Temp in HSC”,
Journal/February 1978 pp. 60-63.
[3] James, J., Subba rao .M., “Reactive of Rice Husk Ash”, Cement and Concrete Research,
Vol.16, 1986.
[4] Rahman M.N., “Curing of RHA Mix sand concrete blocks”, International Journal of
Structures, Vol. 8, No.1, 1988.
[5] Seshagiri Rao M.V., Chankravarthi R.K., Narasimha Murthy, “Rice Husk Ash Blend
Cement” National Seminar on “Recent Advances in Civil Engg. With Special. Reference to
Building Industry”, JNTU College of Engg. & Tech., Hyderabad1992.
[6] K. Sasiekalaa and R. Malathy, “Flexural Performance of Ferrocement Laminates
Containing Silicafume and Fly Ash Reinforced With Chicken Mesh”, International Journal of
Civil Engineering & Technology (IJCIET), Volume 3, Issue 2, 2012, pp. 130 - 143,
ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.
[7] Raju Sathish Kumar, Janardhana Maganti and Darga Kumar Nandyala, “Rice Husk Ash
Stabilized Compressed Earth Block-A Sustainable Construction Building Material – A
Review”, International Journal of Civil Engineering & Technology (IJCIET), Volume 3,
Issue 1, 2012, pp. 1 - 14, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.

Effect of unprocessed rice husk ash as a cementitious material in concrete

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