Comparative Study of Fly Ash Stabilized by Lime and Gypsum Phosphogypsum Binder Admixtures Sub Bases for Rural Roads

Abstract

This major project report presents the comparative study of durability characteristics of a class F fly ash stabilized with lime and modified with gypsum/phosphogypsum. The content of lime, gypsum and phosphogypsum was varied from 2 to 14 %, 0.5 to 2 % and 0.5 to 4 % respectively. The curing period was varied from 7 to 28 days. The results of this study reveals that the durability characteristics of the fly ash-lime mix modified with gypsum/phosphogypsum improved with dry and wet cycles. Further, the durability characteristics improve with the increase in curing period. The results further reveal that the improvement in durability of fly ash-limegypsum was more in comparison to the fly ash-lime-phosphogypsum mixes. The improved durability characteristics make the materials suitable for use in base/sub base courses in road pavements. Three pavement models: (i) without fly ash – lime - gypsum/phosphogypsum admixture, (ii) with fly ash – lime - gypsum admixture, (iii) with fly ash – lime – phosphogypsum admixture have been developed to gain an insight into the effectiveness of load bearing capacity of each model.