STABILIZATION OF BLACK COTTON SOIL USING WOODEN ASH

Introduction

Aimed at evaluating the possibility of utilizing wooden ash in the stabilization of black cotton soils

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 wooden ash

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 economical

This is possible only when the underlying soil has greater strength

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 power plant.

It is used traditionally by gardeners as a good source of potash for domestic gardens.

Material Source

Black cotton soil has been collected from a field in Athupalam, Coimbatore

Wooden ash has been collected from Malumichapetti region.

Laboratory tests

The following are the various laboratory tests conducted on the samples collected

Specific Gravity testDry Sieve AnalysisRelative Density TestLiquid Limit TestPlastic Limit TestStandard proctor compaction Test

Natural Moisture Content

NATURAL MOISTURE CONTENT All moisture content determination was done by the oven

drying method 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

(g) m3 = mass of container and dry soil

(g)The natural moisture content was determined

to be 26.95 %

Specific Gravity

The density bottle method The specific gravity of the soil sample was done by using density bottle method.

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 0.01gsing

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 various samples.

Pychnometer

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 fraction

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.

Sieve Panals

Liquid Limit

200g of the air dried BC soil passing 425–μm sieve size was taken and was mixed with water and kneaded for achieving uniformity.

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.

Conclusion

• 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 construction.

References

Study of Geotechnical properties of black cotton soil www.bvmengineeering.ac.in

Electronic Journal of Geotechnical Engineering- www.Ejge.com

Characteristics of wood ash and influence on soil properties www.ncbi.nlm.nih.govpubmed

Wood ash – www.wikipedia.org