SHRINKAGE CHARACTERISTICS OF COMPACTED LATERITE SOIL-FLY ASH MIXTURES

Abstract

Low design tolerance for shrinkage is a critical requirement for soils used in most engineering projects such as barriers and covers in waste disposal facilities. To meet this requirement, emphasis has to be put on the dimensional changes that occur in the material with variations in composition and compaction conditions. In this study, volumetric shrinkage strain of compacted laterite soil admixed with locally generated fly ash subjected to desiccation under laboratory conditions are presented. The tests were conducted on mixtures of laterite soil and varying percentages of fly ash (0-20%) by weight of dry soil prepared at moulding water contents of between 10-20% using three energy levels that represent compaction energies expected in the field at no compaction delay. Experimental data used to explore relationships between shrinkage strain and the identified variables, that was is, plasticity index, moulding water content and compaction energy. Results obtained indicate that volumetric shrinkage strain decreased with increase in fly ash content to values as low as 0.08% for 20% fly ash content. Specimens with fly ash content 15% on the dry side of compaction experienced increase in volume (i.e. swelling) resulting from greater moisture deficiency and random particle orientation. Relatively high shrinkage strain values (up to 8%) were observed at greater moulding water contents. A systematic trend between compaction energy and shrinkage strain could not be established from the data, and for all specimens, no visible cracks were observed regardless of the moulding water contents.