Use of Rapid-Hardening Cement for Controlled Low-Strength Materials for Pavement Applications

Controlled low-strength materials (CLSMs) are engineered, cement-based mixes that are of growing interest in all trench backfilling and bedding applications in which low stiffness, strength, and density are required. Although 50 years have passed since its first application, CLSM technology has been the focus of continuous innovation. The challenge today concerns the excessive long-term gain in strength of current CLSMs that leads both to difficulties in the event of future removals and to unbalanced stress–strain behavior with surrounding soils. In this investigation, the authors present a long-term laboratory study aimed at the creation of new CLSM formulations for pavement applications with the objective of avoiding or limiting any gain in stiffness and resistance over time. For this purpose, a rapid-hardening cement that presented distinct advantages in rapid-set, high early-strength development, and insignificant long-term gain in strength was used as a substitute for portland cement. All the mixtures studied were subjected to static and dynamic triaxial tests for which the mechanical characteristics of a reference granular soil were taken as the mix design target for new CLSM formulations. The results derived from the use of different admixtures and mixing procedures in mixing time, batching sequence, and mixer type were also investigated.