20 - Application of fly ash in flowable fills and self-compacting concretes

Abstract

Controlled low strength material (CLSM) is prominently used as backfill material. It is characterized by its low strength and self-flowable characteristics. Self-compacting concrete (SCC) is a versatile concrete which can flow under its own mass and can fill up the congested reinforcing areas without the aid of manual or mechanical means of compaction. Both CLSM and SCC are characterized for self-flowing and compacting abilities, although they widely differ on their strength parameters. One of the primary materials used in CLSM and SCC is fly ash (FA). FA which was once considered as a waste material is now a material with a lot of economic value. FA through its pozzolanic effect will contribute to the long-term strength of CLSM and SCC. Hence by appropriate proportioning of primary binder and FA along with other constituents, the strength can be controlled. Owing to lower strength requirements, different waste materials have been used in CLSM along with FA, unlike SCC. The performance of CLSM and SCC is mainly governed by its fresh and hardened state (or in-service) properties. This review article summarizes the key fresh and hardened state results of FA-based CLSM and SCC with and without other waste materials as additives. The flow, strength, permeability, thermal, and electrical properties are the fresh and hardened state CLSM and SCC properties included in the chapter. The chapter aids in creating a body of knowledge on CLSM and SCC for further research and industrial application. The review confirms that CLSM and SCC is a unique and sustainable material with large scope for use of different waste materials without compromising on the performance requirements of CLSM and SCC.