Performance-based procedure for the definition of controlled low-strength mixtures

Controlled low-strength material (CLSM) is a self-consolidating cementitious material used as backfill in narrow trenches. The high content of aggregates and water in CLSM leads to a special behavior that is closer to soil than concrete. Consequently, mixture proportioning methodologies for conventional concrete do not apply to CLSM. The objective of this paper is to propose a new methodology to achieve the optimal composition that fulfills the flowability and compressive strength requirements of the material. Instead of computing the aggregate or the cement separately, all solid particles in the mixture are considered concurrently to estimate the water content in terms of water-to-solid ratio (W/S). In this way, the compressive strength can be modified without compromising the desired flowability. An example application is presented and an experimental program is conducted to validate this philosophy. The results confirm that the methodology proposed provides compositions that satisfy the main requirements of CLSM, thus representing a contribution to the use of more economical and adequate materials.