Design Of Controlled Low Strength Material For Bedding And Backfilling Using High Plasticity Clay

Abstract

Flowable fill or Controlled Low Strength Material (CLSM) is a self-compacted cementitious material used in the field in the place of compacted fill. It is also known as unshrinkable fill, controlled density fill, flowable mortar, plastic-soil cement, soil-cement slurry, and others. The advantages of this material include lesser soil settlements, elimination of compaction, and lower costs when compared to chemically treated and compacted subsoils. CLSMs have a wide range of applications such as using them as a backfill, bedding material, trench filling material, void filling material, bridge abutment and embankment materials and also in pavement bases. Current research is aimed at the design of CLSMs using native soils that can be used as bedding and backfilling materials to support a large pipeline project. Native soils were selected as fine material mainly due to excavation in the site will lead to large amounts of excavated fills and hence any reuse of this material will enhance sustainability components of the projects. This will also result in significant cost savings to the construction project. Several mix designs using native high plasticity clays were attempted to establish the optimum quantities of binders and water. Set accelerator was also used to lower the setting time of some of the mix designs. All these mix designs were evaluated for their flowability, density, compressive strength and setting time properties as per the available ASTM standards.Finally, six mix designs were formulated with setting time as limitation based on the property specifications for their use as a pipeline fill material at different zones. Test results and analysis indicates that high plasticity clay can be successfully used as aggregate in CLSM mixes. Further recommendations were made to study the durability of strengths achieved.