Effect of Compactive Effort and Curing Period on the Compressibility Characteristics of Tropical Black Clay Treated with Rice Husk Ash

Abstract

One-dimensional laboratory consolidation test was carried out on compacted tropical black clay (also known as black cotton soil because the cotton plant thrives well on it) treated with up to 16 % rice husk ash (RHA) to assess the effect of compactive effort and curing period on the consolidation characteristics of the treated soil. Specimens were compacted using three different efforts; British Standard Light (BSL), West African Standard, and British Standard Heavy (BSH). Compacted specimen at BSL effort were also cured for 7, 28 and 56 days before being subjected to one dimensional consolidation tests. The gross yield stress increased with increase in RHA content, curing period and compactive effort, ranging from 5 to 26 % between 0 and 56 days curing period and BSL to BSH effort, respectively. The compression index decreased with increased curing periods (15–40 %), increased compactive energy (10–55 %) and increased rice husk ash treatment; while the effect of compactive effort and RHA treatment was more pronounced in reducing the swell index than the curing period. The variation in coefficient of volume compressibility (Mv) decreases with increased compactive effort and curing period irrespective of the loading pressure and RHA content. The Coefficient of consolidation (Cv) generally decreased with increased compactive energy but showed no observable trend with prolonged curing period irrespective of the RHA treatment.