Partial Replacement of Fine Aggregate Using Water Purification Sludge in Producing CLSM

This study investigated the mix design and engineering properties of controlled low-strength material (CLSM) by partial replacement of fine aggregate using water purification sludge (WPS). First, an investigation was performed at laboratory scale to assess the effects of the constituent materials and their quantities on the properties of the resulting CLSM. The Taguchi method of experimental design was used to determine optimal parameters for the mix design of CLSM. The parameters investigated included sludge content, water-binder ratio, slag content, accelerator agent content, and coarse aggregate content. Then, a cost analysis of a large-scale production CLSM containing WPS in a commercially available ready-mix concrete batching plant was performed. The results indicated that the water-binder ratio was the most significant factor that contributed to the target value (17.5 cm) of the tube flow of the mixture. The main contributions of experimental factors were water-binder ratio (78.00%), slag content (18.71%), accelerator agent content (2.41%), and sludge content (0.88%). Moreover, the strength of mixtures containing WPS was lower than that of mixtures without WPS. In particular, when the replacement percentage of fine aggregates with WPS was more than 20%, the strength was significantly reduced. The material cost per cubic meter of CLSM containing WPS is about NT$297.42 lower than that of ordinary CLSM, which can reduce the cost by 17.53%.