Compressive and tensile strength properties of pre-compressed and soaked natural fiber reinforced lime—fly ash stabilised soil

Abstract

In this study, the effects of pre-compression, fiber inclusions and capillary soaking on the compressive and tensile strength properties of lime-fly ash stabilised soil were investigated. Randomly distributed 25 mm sisal fibers were mixed with stabilised soil at the percentages of 0.25%, 0.5% and 1% by dry mass of the soil. Both unreinforced and fiber composite specimens were subjected to the pre-compression stresses equivalent to 10% and 20% of the strength mobilised by the un-precompressed specimens. The pre-compression stresses were applied after 4h and 24h of accelerated curing at 40°C, after which the conditioned specimens were allowed to continue curing under constant conditions. The results revealed that capillary soaking in un-precompressed specimens caused average compressive strength reduction of 38% and 42% for unreinforced and reinforced specimens, respectively. Pre-compression caused loss of strength of 20% for both tension and compression due to fiber slippage and debonding at the fiber-matrix interface. Soil-fiber composite specimens performed better in compression than in tension however, there existed proportionality between tensile and compressive strengths beyond optimum strength indices $$\left(\frac{\text{q}_{\text{t}}}{\text{q}_{\text{u}}}\right)$$ 0.1 to 0.17 for both pre-compression scenarios. Fiber inclusions endowed soaked stabilised soil with higher average compressive residual strength (90%) than tensile residual strength (50%). Fiber inclusions significantly improved ductility of the composite in both compression and tension due to the deformability of natural fibers.