Utilization of waste materials and by-products in producing controlled low-strength materials

Controlled low-strength material (CLSM) is a self-compacted, cementitious material used primarily as backfill in lieu of compacted fill. It is also known as flowable fill, unshrinkable fill, controlled density fill, and flowable mortar. ACI 229R defines it as materials that result in a compressive strength of 8.3 MPa or less at 28 days. CLSM is generally used in backfills, structural fills, conduit bedding, erosion control, void filling, etc.Use of several waste materials and by-products such as coal combustion products (fly ash, bottom ash), spent foundry sand, cement kiln dust, wood ash, and scrap tire rubber have been used in making controlled low-strength material. This paper presents an overview of the work published on CLSM made with coal combustion products (fly ash, bottom ash), spent foundry sand, wood ash, cement kiln dust and scrap tire rubber.