DURABILITY STUDIES ON CONCRETE WITH WOOD ASH ADDITIVE
C Sashidhar*, J.N.T.U.A College of Engineering, Anantapur, India
H Sudarsana Rao, J.N.T.A. University, Anantapur, India
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DURABILITY STUDIES ON CONCRETE WITH WOOD ASH ADDITIVE
C Sashidhar*, J.N.T.U.A College of Engineering, Anantapur, India
H Sudarsana Rao, J.N.T.A. University, Anantapur, India
Abstract
Concrete is an artificial material in which the aggregates both fine and coarse are
bonded together by the cement when mixed with water. The concrete has become
so popular and indispensable because of its inherent in concrete brought a
revolution in applications of concrete. With the advancement of technology and
increased field of applications of concrete and mortars, the strength workability,
durability and other characters of the ordinary concrete need modifications to make it
more suitable for a by situations. Added to this is the necessity to combat the
increasing cost and scarcity of cement. Under these circumstances the use of
admixtures is found to be an important alternative solution. Hence an attempt has
been made in the present investigation to study wood waste ash addition (0 – 30%)
in concrete. Wood ash concrete is tested for compressive strength, acid attack with
concentrated acids like H2SO4 and HCL and water absorption.
1. Introduction
Concrete has unlimited opportunities for innovative applications, design and construction
techniques. Its great versatility and relative economy in filling wide range of needs has made it is very
competitive building material. With the advancement of technology and increased field of applications
of concrete and mortars, the strength workability, durability and other characters of the ordinary
concrete need modifications to make it more suitable for a by situations. Added to this is the necessity
to combat the increasing cost and scarcity of cement. Under these circumstances the use of
admixtures is found to be an important alternative solution. Though a lot of research is focused in the
last decade on use of various admixtures in producing concrete, very little information is available on
Wood Ash Concrete (WAC). Wood ash is generated as a by-product of combustion in wood-fired
power plants, paper mills, and other wood burning facilities. Since wood is a renewable source of
energy and environmentally benign friendly material, there will be increased use of wood in energy
production in the future. As a result, there will be increased amount of wood ash generation.
In the light of these, it has become essential to develop beneficial uses of wood ashes to solve
the problems associated with their disposal. Wood ashes were divided in to two major classes of fly
ash and bottom ashes. Knowledge of various properties of wood ashes such as physical, chemical,
and microstructural properties would be necessary to establish beneficial applications for them. These
properties depend heavily upon several factors including type and source of wood, design and
operating parameters of the boiler (especially combustion temperature), and ash collection technique.
This investigation was performed with a view to establish various physical properties of wood ashes
and to determine potential uses of wood ashes in cement-based construction materials. Wood ash is
an admixture: a pozzolana. Wood ash is obtained from the combustion of wood. It can be related to
fly ash since fly ash is obtained from coal, which is a fossilized wood. Rice husk ash is also of plant
origin. This implies that wood ash could be used as a pozzolana in concrete.
Tarun et al.[1] reported the following elements in wood ash: carbon (5% to 30%), calcium (5% to
30%), carbon (7% to 33%), potassium (3% to 4%), magnesium (1% to 2%), phosphorus (0.3% to
1.4%) and sodium (0.2% to 0.5%). Pascale Coatanlem et al. [2] in their report, they aimed at
examining the durability of a wood fibre lightweight concrete. Samples have been stored in humid and
dry environments, compressive and flexural strength were measured and the microstructure
examined using SEM analysis. The material properties are improved when wood chippings are
saturated with a sodium silicate solution, this is due to the improved bond between chippings and
cement paste, resulting from the formation of CSH I and ettringite. Felix et al. [3] in their research,
wood waste, saw dust and wood shaving ash, wood waste ash (WWA) of pretreated timber of 0, 5,
10, 15, 20, 25, and 30% by weight of cement was added as a supplement to a concrete of mix
proportion 1:2:4:0.56 cement: sand: Coarse aggregate: water cement ratio, and the strengths and the
water absorption of the matrix were evaluated. Also, the metal leachability of WWA was analyzed.
The compressive and the flexural strengths of WWA concrete for the ages investigated ranged from
12.83 to 28.66 N/mm2, and 3.65 to 5.57 N/mm2, respectively, with the lowest values obtained at 30%
additive level of ash. When compared with the strength of plain concrete control, the compressive and
flexural strengths of WWA concrete were between 62 and 91% and 65 and 98%, respectively, of the
former. Abdullahi [4] (2005) has studied the behaviour of wood ash / OPC concrete. Chemical
analysis of wood ash, bulk density, sieve analysis and specific gravity of wood ash and aggregates,
consistency, setting time and slump test of the fresh paste were conducted to determine the suitability
of the materials for concrete making. Test result indicates that the wood ash is slightly pozzolanic,
water demand increases as the ash content increases and the setting time of the paste increases as
the ash content increases. Compressive strength of wood ash / OPC concrete it increases with age at
curing with optimum replacement of cement by wood ash of 20%. Kurashige Isao et al. [5] reported
the mechanism of scaling-off of hardened cement due to sulfuric acid attack, aiming to establish a
deterioration-predicting method of concrete under such environments as sewage facilities, hot
springs, etc. It was learned that the solid volume increased during the corrosion reaction of hardened
cement. As a result, in high sulfuric acid concentrations (pH 0.5-1.0), the lower the water-cement ratio
is, the higher the scaling rate. These results were confirmed by using SEM, XRD, etc. Further more, it
was found from the experiments that the neutralization progress was highly affected by the scaling
rate due to sulfuric acid attack. Little information is available on wood ash concrete. Thus this new
admixture has lot of potential for use in concrete. Hence, there is need to study the strength and
durability characteristics of Wood Ash Concrete (WAC).
2. Experimental Investigation
The present investigation is aimed to study and evaluate the effect of addition of wood waste ash
(0-30%) in concrete with water cement ratio of 0.49 for concrete. The compressive strength ,
resistance of wood waste ash concrete(WAC) to acid attack using 5% concentrated acids like H2SO4
and HCL, and water absorption are studied. Standard cubes of 150 X150X150mm have been cast
and tested for obtaining 28 days compressive strength. For acid attack, the same cubes have been
immersed in solution of 5% concentrated H2SO4 and HCL and the Weight loss. Compressive
strengths were observed after 30, 60 & 90 days curing. Water absorption test is conducted to
determine the amount of water absorbed under specified conditions. For Water absorption test
100X100X100mm cubes have been used.
2.1 Materials used
Cement: OPC Cement of 53 grade was used. The specific gravity is 3.10.
Coarse Aggregate: Crushed granite metal with 50% passing 20mm and retained on 12.5mm sieve
and 50% passing 12.5mm and retained on 10mm sieve was used. Specific gravity of coarse
aggregate was 2.75.
Fine aggregate: River sand from local sources was used as fine aggregate. The specific gravity of
sand is 2.64.
Water: Potable fresh water, which is free from concentration of acid and organic substances, was
used for mixing and curing the concrete.
Wood waste Ash: Wood waste ash is generated as a by-product of combustion in wood-fired power
plants, paper mills, and other wood burning factories. In the present research the wood waste ash
used, is retained from 300 microns.
2.2 Casting and testing
The cement, sand, coarse aggregate and wood waste ash were mixed thoroughly by manually.
Approximately 25% of water required is added and mixed thoroughly with a view to obtain uniform
mix. After that, the balance of 75% of water was added and mixed thoroughly with a view to obtain
uniform mix. The moulds were removed after twenty four hours and the specimens were kept
immersed in clean water tank. After curing the specimens in water for a period of 28 days the
specimens were taken out and allow to dry under shade. Twenty Four concrete cubes of size
150Х150 Х150mm , Three concrete cubes of size 100Х100 Х100mm have been cast from each mix.
2.3 Compression test
Compression test on cubes was conducted on the Compression Testing Machine (CTM). The
pressure gauge of the machine indicating the load as least count of 1kN. The load on the cube was
applied at a constant rate up to the failure of specimen and the ultimate load was noted. Average
compressive strength of three cubes were taken for 28 days water curing. The same procedure is
adopted for determining the compressive strength after 30, 60, 90 days of acid immersion.
2.4 Weight Loss Test
The cubes of 150 Х 150 Х 150 mm were cast. These were immersed separately in each 5%
concentrated solutions of HCl and H2SO4 after normal 28 day curing. The normal weights of cubes
were initially taken and observed the deteriorating effect after 30, 60 and 90 days by taking weights
again. The weight loss due to acid immersion has been noted.
2.5 Water Absorption Test
Water absorption is used to determine the amount of water absorbed under specified conditions.
For the test 100 Х 100 Х 100mm cubes were cast and cured for 28 days in ordinary water.
Immediately upon curing, the cubes were weighed, which is the dry weight. The cubes were then
immersed in water for 24 hours. Cubes were removed, patted dry with a lint free cloth, and weighed,
this is the wet weight. Water absorption is expressed as increase in weight percent.
Percent Water Absorption = [(Wet weight - Dry weight)/ Dry weight] x 100
3. Discussion of Test Results
3.1 Effect of percentage of addition of wood waste ash in concrete in compressive strength
The influence of percentage of addition of wood waste ash in concrete on percentage decrease
in compressive strength is presented in fig 1 for different ages of acid immersion. From these figures,
it can be observed that with addition of wood waste ash content the percentage decrease in
compressive strength decreases. Maximum percentage decrease in compressive strength is
observed for plain concrete mixes with 10% of wood ash. It can be observed from these figures that
the percentage decrease in compressive strength decreases rapidly from 0% to 10 % addition and
from then onwards it decreases very gradually. Similar trend is observed for HCl, H2SO4 acids tried in
the present investigation. Hence it can be concluded that optimum results are obtained at 10%
addition of wood ash concrete. It can also observe from the figures that the percentage decrease in
compressive strength increases with the age of acid immersion. Maximum percentage decrease in
compressive strength is noticed at 90 days age of acid immersion.
3.2 Influence of acid on the residual compressive strength of wood Waste ash concrete
In the present investigation concrete mixes have been subjected to 5% concentrated solutions of
HCl, H2SO4. The influence of these acids on the residual compressive strength for different
percentage of addition of wood waste ash in concrete is presented in fig 2 and fig 3. From these
figures it can be observed that the maximum loss of compressive strength occurred for H2SO4 and
HCL in acid immersion. This is true for all percentage of addition of wood waste ash in concrete.
Similar trend is observed for all ages of acid immersion i.e. 30, 60, 90 days. It is observed attack of
H2SO4 is the most severe on concrete than HCL.
3.3 Effect of percentage of wood waste ash on percentage weight loss
The influence of percentage of addition of wood waste ash in concrete on percentage weight loss
due to acid attack for Two different ages of acid immersion is presented in fig 4 & fig 5. It is evident
from the figures that with the addition of wood ash the percentage weight loss decreased upto 10%
wood waste ash and increased beyond 10% wood ash. However even at 20% replacement the
percentage weight loss is less compared to plain concrete. Thus it can be concluded that, 10% wood
waste ash concrete mixes resisted acid attack better than other mixes. Similar results are observed for
HCL, H2SO4 acids tried in the present investigation.
3.4 Effect of wood waste ash on percentage water absorption
Fig 6 shows the results of tests for the water absorption of Wood waste ash based concrete. It
may be noted from the results that concrete specimens absorb more as the ash content increases. The
water absorption at 0% of wood waste ash is 1.19% and increases to 1.76% at 30% of wood waste
ash. However, these values are less than 10% which is the percentage water absorption value
accepted for most constructed materials.
4. Conclusions:
 The 28 day cube compressive strength of WAC mixes decreases with increasing wood
waste ash content from 0 to 30%. The compressive strength after 30, 60, and 90 days of acid
immersion of concrete decreases with increasing percentage of wood ash content.
 Maximum loss of compressive strength occurred with H2SO4 acid immersion. Hence H2SO4
acid attack is most severe on WAC.
 Percentage decrease in compressive strength increases with the age of acid immersion.
 Maximum Percentage decrease in compressive strength is noticed at 90 day age of acid
immersion.
 For 10% wood waste ash based concrete, the weight loss due to acid attack is minimum.
 H2SO4 has maximum deteriorating effect than other acids used in present investigation.
 The percentage of water absorption of wood ash concrete (WAC) specimens increased with
increase in wood waste ash content from 0 to 30%.
References
[1] Tarun R. N “ Use of Wood Ash in Cement-based Materials”, A CBU Report, (2003) CBU-2003-19
(REP-513), http://uwm.edu/Dept/CBU/report.
[2] Pascale Coatanlem, Raoul Jauberthie and Frank Rendell, “Lightweight wood chipping concrete
durability”,France, 2005.
[3] Felix F. Udoeyo, Hilary Inyang, David T. Young, and Edmund E. Oparadu, “Potential of Wood
Waste Ash as an Additive in Concrete”, 2006, 605-611.
[4] Abdullahi, M. “Characteristics of Wood ASH/OPC Concrete”, Civil Engineering Department,
Federal University of Technology, 2003, P.M.B. 65, Minna, Niger State, Nigeria,
[email protected]
[5] Kurashige isao and Uomoto Taketo, “Mechanisms of scaling-off of hardened cement paste due to
sulfuric acid attack”, 2001, 458-464. W/C ratio 0.49
Residual compressive strength(MPa)
50
48
46
44
42
40
38
0
5
10
15
20
25
30
% of wood ash
Fig 1. Residual Compressive Strength vs % of wood ash
Residual Compressive Strength(MPa)
44
30 days
60 days
90 days
42
40
38
36
34
32
30
0
5
10
15
20
25
30
% of Wood Ash
Fig 2. Compressive Strength vs % of Wood Ash(H2SO4 acid Immersion at 0.49 W/C Ratio)
Residual Compressive Strength(MPa)
45
30 days
60 days
90 days
44
43
42
41
40
39
38
37
36
35
34
33
32
31
0
5
10
15
20
25
30
% Of Wood Ash
Fig 3. Residual Compressive Strength vs % of Wood Ash (HCl acid Immersion)
10.0
30 days
60 days
90 days
9.5
9.0
% Weight Loos
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
0
5
10
15
20
25
30
% of Wood Ash
Fig 4. Weight Loss vs % of Wood ash with H2SO4 acid immersion
9.0
30 days
60 days
90 days
8.5
8.0
% Weight Loss
7.5
7.0
6.5
6.0
5.5
5.0
4.5
0
5
10
15
20
25
30
% of Wood ash
Fig 5. Weight Loss vs % of Wood ash with HCL acid immersion
% Water
Absorption
1.8
% Of Water Absorption
1.7
1.6
1.5
1.4
1.3
1.2
1.1
0
5
10
15
20
25
30
% Wood ASh
Fig 6. % Of Water Absorption vs % of Wood Ash