Investigating the Use of Kiln Dusts in Stabilization of Expansive Clay Soils for Use as a Subgrade Material in Road Construction

Abstract

The general objective was to investigate the use of kiln dusts in the stabilization of expansive clay soils for use as a subgrade material in road construction. This study focused on stabilizing in situ expansive clay soils found in three different road construction projects in Nyandarua County using cement and lime kiln dusts. The preparations involved the acquisition of soil materials from the road projects and CKD and LKD materials from Machakos (Athi River) and Nakuru (Salgaa). The tests carried out were chemical tests on CKD and LKD, and mechanical tests on NEAT expansive clay soils and kiln-dust-stabilized expansive clay soils. The study established that stabilization with cement kiln dust (CKD), lime kiln dust (LKD), and their 50:50 blend significantly improved the soil’s engineering properties. Plasticity index reduced to 6.8%, 6.3%, and 5.5% for CKD, LKD, and CKD-LKD, respectively, while swell potential decreased by up to 97%. Compaction characteristics improved with reduced optimum moisture content and increased maximum dry density. Strength performance also improved, with the soaked CBR increasing from 4.8% in untreated soil to 7.5% with CKD, 6.5% with LKD, and 45% with the CKD-LKD blend. The study recommends that road agencies and contractors consider incorporating the kiln dusts in subgrade designs and promote the use of locally available kiln dusts as a sustainable stabilization material for subgrades.