The Sustainable Application of Fly Ash in Bridge Abutments

Fly ash is a by-product of the coal combustion in electric power generating plants and can be used efficiently in controlled low strength materials (CLSMs). This paper presents an experimental study using locally available class F fly ash to produce a suitable CLSM mixture as a backfill for construction of a laboratory full-scale bridge abutment. The ability to use large volumes of by-product fly ash in the CLSM backfill translates into the potential for a sustainable design by reducing the demands on landfills, where these materials might otherwise be deposited, and conserving the natural aggregate resources. The required time for building bridge abutments can be shortened using CLSM as a flowable and self-compacting backfill material because they do not require controlled compaction of soil layers. The main performance properties for selection of a potential CLSM mixture were compressive strength to support the bridge loads, and flowability to fill the entire abutment in one continuous pour.