Laboratory Investigation on Lateritic and Black Cotton Soils Stabilised With GGBS and Alkali Solutions

Abstract

The natural aggregates are depleting in developing countries due to the excessive usage in road and building construction. The present work investigates the improved properties of lateritic and Black cotton (BC) soils stabilized with Ground Granulated Blast Furnace Slag (GGBS) and alkali solutions such as sodium hydroxide and sodium silicate. The lateritic and BC soils are stabilized with 15, 20, 25 and 30% of GGBS and the alkali solutions consisting of 4, 5 and 6% of Sodium Oxide (Na2O) having Silica Modulus (Ms) of 0.5, 1.0 and 1.5 at a constant water binder ratio of 0.25. The Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) are obtained for both untreated and stabilized soils from standard and modified Proctor tests. The stabilized samples were air-cured for 0 (immediately after casting), 3, 7 and 28 days at ambient temperature. In case of stabilized lateritic soil, the maximum strength is achieved at 30% of GGBS and alkali solution consisting of 6% Na2O and 1.0 Ms whereas, in case of stabilized BC soil, the maximum strength is achieved at 30% GGBS and alkali solution consisting of 6% Na2O and 0.5 Ms at both standard and modified Proctor densities. The stabilizedlateritic soil with 25 and 30% of GGBS and alkali solution consisting of 5 and 6% of Na2O having 0.5 and 1.0 Ms is found to be durable after 28 days curing at both densities. Whereas, the stabilized BC sample having 25 and 30% of GGBS and alkali solution consisting of 5 and 6% of Na2O with Ms of 0.5 only at modified Proctor density have passed durability. The stabilized lateritic soil with 30% of GGBS and alkali solution consisting of 6% of Na2O having Ms of 1.0 at both densities and the stabilized BC soil with 25% of GGBS and alkali solution consisting of 5% of Na2O having Ms of 0.5 only at modified Proctor density achieved the highest flexural strength, fatigue life and the densified structure. Thex formation of calciumsilicate hydrate and calcium aluminosilicate hydrate structures resulted in a remarkable improvement of compressive strength, flexural and fatigue life of the stabilized soils due to the dissolved calcium ions from GGBS, silicate and aluminium ions from alkali solutions. The design of high and low volume roads is proposed by replacing the conventional granular layer with the durable stabilized soil and stress-strain analysis is carried out using pavement analysis software. The comparison of the cost of the conventional material with the proposed stabilized soils are carried out.