Physical and strength development in lime treated gypseous soil with fly ash - Micro-analyses

An attempt has been made to examine the role of fly ash content (0-30%) to control undesirable strength loss in lime-treated expansive soil containing gypsum (0-6%) after curing for different periods up to one year. Further, detailed experimental investigations have been performed to assess the plasticity, swell index and compaction behavior of soil treated with these additives. Results of the strength behavior revealed that a significant effect of higher fly ash content in the strength development of lime-treated soil is observed after longer curing periods. Presence of increasing amounts of gypsum accelerates early strength gain initially, but reduces long-term strength gain in soil-lime-fly ash mixes. Fly ash improves the strength of lime-treated gypseous soil. However, beneficial use of fly ash to improve the strength of lime treated gypseous soil depends on the amount of gypsum present in the soil and length of curing periods. Micro-analyses (XRD and SEM) revealed that the strength development is controlled by reaction products formed such as cementitious compounds and ettringite crystals.