Properties of lightweight alkali activated controlled Low-Strength material using calcium carbide residue – Fly ash mixture and containing EPS beads

This research aims to use of alkali activated binder containing expanded polystyrene (EPS) beads for producing lightweight controlled low strength materials (CLSM). Sodium hydroxide (NH) solution and sodium silicate (NS) were used as alkali activators. NH concentration was set as a constant of 6 Molar. The mixture of fly ash (FA) and calcium carbide residue (CR) at a ratio of 75:25 by weight was used as a binder. EPS beads was used as a lightweight aggregate and the binder to EPS beads ratio was varied from 1:2.50 to 1:3.00 by volume. Workability in terms of flow was controlled between 200 and 300 mm. The compressive strength at 6 h up to 28 d and water absorption of lightweight alkali activated CLSM were determined. In addition, XRD and SEM of lightweight alkali activated CLSM were also investigated. The results revealed that the compressive strengths of lightweight alkali activated CLSM rapidly increased in the first 12 h, which were from 451 kPa to 731 kPa. The ratio of binder to EPS beads at 1:2.50 by volume was the optimum ratio and the ratio of NH:NS at 1:0.4 gave the highest compressive strength of lightweight alkali activated CLSM. Lightweight alkali activated CLSM obtained from this study had the compressive strength of 1,500–3,000 kPa and the density of 750–900 kg/m³ at 28 d, which can be used as structural backlinking.