Proportioning of CLSM Containing Class C Fly Ash, GGBS, Quarry Dust and Processed Slag Sand

Abstract

Controlled low strength materials (CLSM) is a backfill material which is neither concrete nor soil cement but it has properties similar to both. CLSM is a fluid mixture usually made of Portland cement, water, and fine aggregate or fly ash or both. However, other industrial by-products & recycled materials are also incorporated & encouraged as long as they are considered to be easily available, cost-effective for specific application along with the necessary characteristics of the mixture such as flow ability, strength, and density. Consistency of CLSM is similar to that of a slurry or lean grout, however several hours after placement the material hardens enough to bear loads without settling. Nowadays proper disposal of waste materials which are produced from various industries is a severe problem in many countries causing environmental hazards and raises the potential to contaminate water, air and soil resources and carbon emission. The present experimental research aims to arrive at suitable mix proportion combinations for CLSM by the incorporation of waste industrial by products such as Class C fly ash and GGBS (Ground-granulated blast-furnace slag) as partial replacement for cement. Quarry dust (QD) and Processed Slag Sand (PSS), was utilized in total replacement to natural river sand as fine aggregates, for proportioning of CLSM. Variations were considered in binder ratios and water contents. The fresh and hardened properties of CLSM in terms of flow, unconfined compressive strength were investigated. An attempt has been made to develop predictive flow and strength models known as phenomenological models to assist Engineers in the design of CLSM mixes with these material combinations at a future date or some other place. The findings from this study would benefit Engineers to adopt sustainable practice through incorporation of the above waste or by-products in CLSM – in large quantities unlike concrete or any other material.