CHARACTERISTICS OF CEMENT-MODIFIED ASPHALT-ENIULSION LATERITE MIXES

Abstract

The influence of the physical characteristics and composition of three selected laterite samples on their engineering behaviour in the natural untreated state and on their responsiveness to treatment with chemical additives was determined in the laboratory. The additives used are cement; asphalt-emulsion; and mixtures of cement with asphalt-emulsion in various proportions. The percentages of cement and asphalt emulsion. used are 2,4,6 and 8% for soil cement and soil-asphalt emulsion. For cement modification of asphalt-emulsion mixtures, the percentages of cement used are 1/2, 1 and 2 % with each percentage of asphalt-emulsion. Adding chemical stabilizers to the samples generally increase their strength, the rate of increase depending on the type of soil. Sample A increased from its natural eBR value of 20% to 120% using 4% cement; sample B gave a CBR value of 88% with 4% cement from its 18% eBR value and at 6% cement it gave a eBR value of 150% while sample C increased from its natural eBR value of 8% to 102 % using 8% cement content. Using asphalt-emulsion to treat the samples gave CBR values of 110% and 80% with 6 % emulsion for samples A and B respectively. Sample C gave a eBR value of 60 % using 8 % emulsion. Beneficial results were obtained using 1 - 2 % cement with asphalt-emulsion for treating all the samples especially the highly plastic and organic soil types such as soil sample C which is often detrimental to successful stabilization with the use of only cement or asphalt-emulsion thus bringing to enlightenment a new technology improving the strength of locally available weak soils by pretreating the soil with small amount of cement before the addition of asphalt-emulsion for required strength characteristics. For the modified samples, the proportions of cement to asphalt emulsion are 1:2, 2:2 and 2:6 for samples A, Band C respectively. The cost comparison of using cement; asphalt emulsion and combinations of cement with asphalt -emulsion was carried out and results show that the soils can be stabilized economically with well designed mixes of asphalt-emulsion and cement.