RELIABILITY ESTIMATE OF STRENGTH CHARACTERISTICS OF BLACK COTTON SOIL PAVEMENT SUB-BASE STABILIZED WITH LOCUST BEAN WASTE ASH AND CEMENT KILN DUST

Abstract

Reliability estimates of strength characteristic values for compacted locust bean waste ash treated black cotton soil using cement kiln dust (CKD) as an activator for road sub-base material were generated from laboratory results for specimens compacted at the energy levels of British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy (BSH). A Model was developed by incorporating data obtained from unconfined compressive strength (UCS) test obtained from the laboratory test to produce a predictive model. Data obtained were incorporated into a FORTRAN-based first-order reliability program to obtain reliability index values. Variable factors such as optimum moisture content (OMC), hydraulic modulus (HM), locust bean waste ash (LBWA) content, cement kiln dust (CKD) content, Di-calcium silicate (C2S), Tetra Calcium Alumino-Ferrite (C4AF), and maximum dry density (MDD) produced acceptable safety index value of 1.0 at the energy levels of WAS and BSH compactive effort and they were achieved at coefficient of variation (COV) ranges of 10-100%. Observed trends indicate that the CKD content, OMC and MDD is greatly influenced by the COV and therefore must be strictly controlled in CKD/LBWA treated black cotton soil for use as sub-base material in road pavements....