Strength Studies of Fly Ash Stabilized with Lime and Gypsum

Abstract

An experimental study was conducted to investigate the performance of a composite derived from stabilizing fly ash with lime and gypsum. The initial part of the study examines the effect of lime (4%, 8%, and 12% by mass of dry fly ash) on compaction (in terms of density/moisture relationship) and unconfined compressive strength (UCS) of fly ash. Further the effect of adding small amount of gypsum (1%) on strength was studied. Based on UCS, fly ash stabilized with 12% lime and 1% gypsum was observed as the highest strength mix. The microstructural development in the composite was studied through scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that this composite acquired strength of 4697 kPa at 28 days curing and the strength increase with curing period and composite arrived strength of 6150 kPa at 90 days. Hence it can be beneficially used in civil engineering construction works.
Keywords: fly ash, lime, gypsum, unconfined compressive strength, heavy metals