Abstract:
Strength of weak soils present significant geotechnical, road pavements, and structural
engineering challenges the world over, with costs associated with expansive behavior
estimated to run into several billion dollars of damage annually. Expansive soils are
soils that experience significant volume change (swelling and shrinking) associated
with changes in water contents. These problems need a wider application of cost effective and environmentally friendly technology for improving soil properties to be
adapted to the current road construction trend. The general objective of this research is
to investigate the suitability of MCA and WBP for stabilization of Weak subgrade soils.
To achieve the objectives of the research to based on the properties described under
field investigations:- Four samples were taken from different locations. A free swell
test, high plastic index and low load bearing were carried out for each sample, one
sample with high free swell, high plastic index and poor soil values had been selected.
Tests were performed on natural and treated soil samples as per the ERA, AASHTO,
and ASTM laboratory test standards. The selected soil samples were characterized and
were found A-7-5 category of soil based on the AASHTO soil classification system and
CH as per the USCS soil classification system which is clay soil of poor engineering
properties. The soils were treated with varied proportions of MCA (5%, 10%, 15%, and
20%) and WBP (10%, 20%, 30%, and 40%). and (5%MCA + 40 %WBP, 10%MCA +
30 %WBP, 15%MCA + 20 %WBP, 20%MCA + 10 %WBP ) by dry weight of the soil.
The laboratory tests carried out to evaluate the stabilized soil sample were; Atterberg
limits, free swell, compaction tests, and CBR tests. Analysis of the results shows that
improvement on the engineering properties of MCA-WBP stabilized soil. As the MCA WBP content adds, reduces plasticity index and swelling potential, increase MDD and
the OMC is decrease and the CBR strength also increased and the better improvement
was found when using 10% MCA and 30%WBP. It can be concluded from the present
investigation that weak subgrade soil could properly be treated for use as subgrade
material. Adequate strength was achieved with 10% MCA mixed with 30%WBP, and
which is found to be the optimum Maize cob ash and waste brick contents for improving
the engineering properties of the weak subgrade soils.
