Swell-Shrink-Consolidation Behavior of Rubber-Reinforced Expansive Soils

This study examines the effects of two types of recycled tire rubber of fine and coarse categories on the swell-shrink-consolidation behavior of a highly expansive soil mixture. Each of the two rubber choices were incorporated into the soil at four different content levels (i.e., rubber to dry soil mass ratio) of 5, 10, 20, and 30 %. The experimental program consisted of consistency limits, compaction, swell consolidation, swell-shrink, and unconfined compression tests. Improvement in the swell-shrink-consolidation capacity was in favor of higher rubber contents; however, when excessively included, it raised strength concerns. The swell-shrink-consolidation properties were also rubber size-dependent, meaning that the rubber of coarser sizes often outperformed finer rubber. In terms of strength, however, the two rubber types promoted similar results with marginal differences. The results of the unconfined compression tests were cross checked with the swell-shrink-consolidation properties to arrive at the optimum stabilization scenarios. A maximum rubber inclusion of 10 %, preferably the rubber of coarser category, proved to satisfy the stabilization objectives (i.e., decrease in the swell-shrink-consolidation capacity as well as maintain or improve the strength) and thus was deemed as the optimum choice. Where context changes and the strength and stiffness are not a primary concern, higher rubber inclusions of up to 20 % may also be considered acceptable.