STUDY ON USE OF FLYASH IN BASE/SUB BASE OF PAVEMENTS

Abstract

In the road construction sector, the world is facing a major problem of scarcity of conventional construction materials. On the other hand, there are some materials, which are lying as waste. Some waste products, e.g., fly ash can be utilized as an additive to conventional construction materials. Fly ash is available enormously and almost at free of cost. In India, efforts have been made since the early seventies to utilize this waste product in different fields, but unfortunately nearly 5% utilization has been achieved till date which is far below the world average of 16%. Efforts have been made for maximum utilization of fly ash in embankment construction in bulk quantities. Sub base course can be constructed using pond ash or bottom ash replacing conventional material. The pozzolanic property of fly ash enables it to be used as an alternate binder in place of cement. While coarser fly ash can be used as fill material, the finer ash can be used for replacement of sand and cement in road construction works. The main objective of this study is to utilize fly ash as base/sub base material in road pavements. Fly ash was used in GSB and WMM by replacing the fine aggregate with 0%, 10%, 20%, 30% and 409'o of fly ash and CBR, Field CBR and Plate Load tests were conducted. Based on the results it has been concluded that with the 20% of fly ash in GSB and WMM maximum lab CBR, maximum Field CBR and maximum modulus of subgrade reaction (k) was observed. It was observed that by using fly ash in GSB and WMM 20% of fine aggregate used in base and sub base can be saved. The results of economic analysis shows that by replacing fine aggregate with fly ash there was considerable amount of saving. In this study economic analysis was done without considering the transportation cost.