Effect of addition of lime on coir fiber admixed BC soil

Abstract

Expansive soils, having predominantly montmorillonite clay mineral, pose acute construction problems for many civil engineering structures. Admixing lime is popular and cost-effective which is used widely. However, BC soil has inherent low tensile strength but a high compressive strength. Incorporating fiber reinforcement that is capable of absorbing tensile loads or shear stresses will address the problem. In this context, the use of cheaply and abundantly available natural coir fibers as soil reinforcement in the BC soil along with lime is investigated. The effect of lime reaction and associated heat of hydration on coir fiber was investigated in terms of unconfined compressive strength (UCC) of BC soil. XRD and SEM studies on surface characteristics of coir fiber were studied. It was found that, at longer curing periods after addition of lime, plate-like particles are replaced by foil-like membranes and fine filaments due to flocculation–agglomeration of soil particles along with carbonation. XRD confirmed that these fine filaments are foils consisted of calcium silicate hydrate gel that increases strength due to cementation. It was observed that admixing both untreated and treated coir fibers in lime-stabilized BC soil beyond 7 days of curing causes decrease in the UCC due to heat of hydration of lime reaction that seems to affect the fiber characteristics.