Compaction delay and its effect on the geotechnical properties of lime treated semi-arid soils

Abstract

Quality construction control requires ensuring that compacted fills are properly placed without any significant delay between mixing and compaction of the wet soil mixture. When chemical treatment is resorted to meet the shortcomings in the use of locally available materials, the delay in compaction (time elapsed between mixing and compaction of the wet soil mixture) plays a significant role as it dictates the final in-site density values achieved. In this study, the effect of delay in compaction on the density and moisture content relationships was evaluated for the delay periods of 1hr, 4hr, 24 hr and 7 days. The study was even extended to lime treated soils (at 2% and 4% by dry weight of soil). The time lag which occurs immediately after the onset of wet mixing and compaction often results in variation in geotechnical properties. Accordingly, an attempt was also made to study the effect of delay in compaction on the hydraulic conductivity, compressibility and unconfined compressive strength (UCS) behaviour of plastic clays sourced from the semi-arid region. In order to understand the variations in microstructure, MIP tests (Mercury Intrusion Porosimetry) were conducted at higher delay periods when treated with lime. From the results, it was observed that delay in compaction led to an increase in the hydraulic conductivity and compressibility of both soils. Furthermore, the UCS of both the soils showed a decreasing trend with the increase in the delay period. The agglomeration of clay particles leads to the formation of clods at higher delay periods which resist the compaction energy resulting in reduced density values which in-turn affect the geotechnical properties.