Stabilization of black cotton soil using wooden ash
STABILIZATION OF BLACK COTTON
SOIL USING WOODEN ASH
Aimed at evaluating the possibility of utilizing
wooden ash in the stabilization of black cotton
Black cotton soils possess low strength and
undergo excessive volume changes, making their
use in constructions very difficult
These soils cause more extensive damage than
even natural disasters
Hence, we must increase the compressive
strength of black cotton soil with using of
Reasons for this Study
Economic progress and growth of a country is closely
dependent on the infrastructural development
Pavements of least thickness are found to be the most
This is possible only when the underlying soil has
Black cotton soil possesses low strength. If the soil is
weak, then the thickness of the pavements increases.
So for such problematic soil, it is essential to stabilize
them in the most economic and affective way.
Feasibility of Wooden Ash
Various research works have been undertaken for
improving the expansive nature of the black cotton
soil using materials like wooden ash, as admixture.
Wooden ash is a locally available material residue
powder left after the combustion of wood, such as
burning wooden in a home fireplace or an industrial
It is used traditionally by gardeners as a good source
of potash for domestic gardens.
Black cotton soil has been collected from a
field in Athupalam, Coimbatore
Wooden ash has been collected from
The following are the various laboratory tests
conducted on the samples collected
Specific Gravity test
Dry Sieve Analysis
Relative Density Test
Liquid Limit Test
Plastic Limit Test
Standard proctor compaction Test
Natural Moisture Content
NATURAL MOISTURE CONTENT
All moisture content determination was done by the oven
For the determination of natural moisture content, samples
were collected in polythene bag and immediately taken to the
laboratory for the test.
The water content is calculated from equation.
Where m1 = mass of container (g)
m2 = mass of container and wet soil
m3 = mass of container and dry soil
The natural moisture content was determined
to be 26.95 %
The density bottle method The specific gravity
of the soil sample was done by using density
The sieved sample was grouped into
approximately four equal parts.
Each part was placed into dried 50cm3 density
bottle of known mass (M1) to the nearest
The mass of each bottle with sample inside
was measured (M2) to the nearest 0.01g.
Each bottle was then filled with water and
mixed thoroughly removing all air bubbles.
The bottle was weighed to a mass (M3).
Finally each bottle was washed and dried.
Water was introduced and the mass of the
bottle with water full taken (M4).
The specific gravity is expressed as :
Gs = =2.941
The average of the values was taken for
Particle Size Distribution
The particle size distribution of the natural
soil was determined using the method specify
by BS 1377 (1990) for cohesive soil.
It specifies the use of both sedimentation
analysis and the dry sieving of the coarse
When the black cotton soil was treated with
2 - 12% wood ash by dry weight of soil at
optimum moisture content (OMC), less than
10% of the material passed through BS No.
200 sieve, and therefore did not meet the
minimum requirement for sedimentation
analysis to be carried out.
200g of the air dried BC soil passing 425–μm sieve size
was taken and was mixed with water and kneaded for
The mixing time was specified as 5 to 10 min. The soil
paste was placed in the liquid limit cup, and leveled off
with the help of the spatula.
A clean and sharp groove was cut in the middle by
means of a grooving tool.
The crank was rotated at about 2 revolutions per second
and the number of blows required to make the halves of
the soil pat separated by the groove meet for a length of
about 12 mm was counted.
• From this project we observed that when
admixture is added to black cotton soil
(wooden ash) there is a increase in strength of
soil and less change in volume of soil.
• Hence its can be used economical in
Study of Geotechnical properties of black
cotton soil www.bvmengineeering.ac.in
Electronic Journal of Geotechnical
Characteristics of wood ash and influence on
soil properties www.ncbi.nlm.nih.govpubmed
Wood ash – www.wikipedia.org