INVESTIGATION ON THE EFFECTS OF COMBINING LIME AND SODIUM SILICATE FOR EXPANSIVE SUBGRADE STABILIZATION

Abstract

Expansive clay is unsuitable subgrade material
covering about 40% of the area of Ethiopia.
Engineering properties of such problematic soils
can be improved by chemical stabilization. This
study investigated the effects of combining slightly
alkaline liquid sodium silicate with hydrated lime
for stabilization of expansive clay. The
experimental study involved Particle-Size Analysis,
Atterberg Limits, Standard Compaction and
California Bearing Ratio tests. Expansive clay was
combined with 2, 4and 6% of lime; 1, 2.5and 6% of
liquid sodium silicate and the respective
combinations of the two additives by dry weight of
the soil. Test samples were typically soaked for
30minutesto account for strength loss due to
compaction delay. Samples were cured for 3 and 7
days before testing for Atterberg Limits and
California Bearing Ratio values. Additional 28
days of curing were considered for Atterberg
Limits test samples. Test results manifested that
sodium silicate reduced plasticity indexes by
least12% compared to untreated soil. Expansive
soil treated with sodium silicate or combination of
lime and sodium silicate resulted in unusual
compaction curves from which maximum dry
densities and optimum moisture contents could not
be determined. Sodium silicate and its combination
with lime decreased shear strength and increased
swelling properties of expansive clay compared to
the respective lime series. Curing enhanced
strength development and reduced swelling
properties of treated soils. The study revealed that
sodium silicate or its combination with lime is not a
suitable means of expansive clay stabilization