Impact of Compaction Delay on the Engineering Properties of Cement Treated Soil.

Abstract

In a bid to harness some of our local soils at the expense of expensive good quality materials for geotechnical and highway construction gave rise to this study; i.e impact of compaction delay on cement treated soil. Cement was chosen as stabilizer following its efficiency as it improves the mechanical properties of soil .The natural soil sample was obtained manually from a borrow pit that has been left fallow for a long time at a depth of about 1m. The sample was thereafter divided into 4 portions where a portion being natural soil (untreated) and 3 other portions treated/stabilized with cement at 3%, 5%, and 8% by weight of soil were subjected to laboratory analysis (Natural Moisture Content, Atterberg Limits, Particle Size Analysis, Compaction (West African Standard & Standard Proctor), California Bearing Ratio (CBR), Unconfined Compressive Strength test) in order to determine their engineering properties. But during compaction, the treated samples were delayed for 0,1,2,3 hours respectively in order to determine effect of compaction delay on the samples. The residual lateritic soil was classified based on AASHTO and USCS classifications. The residual lateritic soil was classified as A-7-6(7) according to AASHTO and CL according to USCS. Specimens treated with maximum 8% cement and compacted with no delays at energy levels of SP and WAS yielded average 7 day UCS values of 1660KN/m 2 and 2145KN/m 2 respectively. The average UCS value of specimen compacted using SP compactive effort is lower than the conventional 1720 KN/m 2 criterion for adequate cement stabilization. The CBR values of cement treated specimens at 8% cement stabilization with no delays recorded for the two compactive efforts of SP and WAS are 90% and 180% respectively. The compaction and the strength characteristics of the cement stabilized lateritic soil specimens compacted at the two energy levels decreased with increase in compaction delays. At 8% cement content and maximum compaction delay of 3hours, losses of 12%, 23%, 31% and 20% in MDD, OMC, UCS and CBR respectively were recorded for specimens prepared at energy level of SP, while losses of 10%,20%,32% and 39% in MDD,OMC,UCS and CBR respectively were recorded for specimens prepared at energy level of WAS. Keywords: UCS (Unconfined Compressive Strength), CBR (California Bearing Ratio), MDD(Maximum Dry Density), OMC (Optimum Moisture Content),SP (Standard Proctor), WAS(West African Standard)