Effect of Recycled Calcined Alumino Silicate Content on Prope ...

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Abstract

This article presents the engineering properties of controlled low-strength materials (CLSMs) incorporating recycled Calcined Alumino Silicate (CAS) in varying amounts. CLSM, also known as “structural fill,” is a material used as void fill and backfill in construction practices. Primarily used as a replacement for compacted soils, CLSMs provide an advantage for difficult to fill voids by filling them more quickly than by traditional methods. Because the compressive strength requirement is much lower than structural concrete, CLSMs provide a unique opportunity to incorporate recycled materials where the latter may not allow. Specifically, this study evaluates the utilization of recycled CAS in CLSM mixtures containing cement, fly ash, water, and virgin fine aggregate. A thorough review of literature finds little information on the utilization of CAS in CLSMs. The mixture proportions in this study were designed for increasing amounts of recycled CAS content with increments of 25% by fine aggregate weight. The CLSM’s flowability, air content, bleeding, unit weight, and compressive strength were measured and analyzed for suitability in field use. The study found that increasing the amount of recycled CAS in the CLSM mixtures decreases the removability modulus by lowering the unit weight and decreases the compressive strength over the long term. Therefore, the structural fill evaluated in this study was determined to be acceptable as an excavatable flowable material based on the flowability and removability modulus when recycled CAS was included in the mixtures. Further, this study identified CAS as an acceptable alternative material in CLSMs, resulting in a new potential market for utilization of this waste-stream material.