Development of Pervious Concrete by Using Bottom Ash as Supplementary Cementious Material

Abstract

AbstractUrbanization has reduced ground water level and flooding of roads due to extensive use of non-permeable paving method. To continue urbanization while preserving ground water and to mitigate street flooding will require a pervious concrete (PC). Although the pervious concrete has lot of environmental and economic benefits, its uses are still limiting in Sri Lanka. This research provides a background for developing a mix design using BA as a supplementary material and also achieving optimum balance between porosity and strength is essential with use of locally available materials. This study investigated the potential of using coal BA, waste product of coal combustion, as a substitute for sand which is scarce, in an optimum PC mix design. Concrete cubes 150 mm × 150 mm × 150 mm were manufactured in both mix design 1 (MD1) and 2 (MD2). In MD1 coarse aggregate replaced in 5–10 mm and 5–12.5 mm aggregate sizes with BA. In MD2 aggregate sizes of 5–12.5 mm and 14-20 mm studied in two separate arms by serial replacement of cement 0%, 7%, 12%, 15%, 20% and 30%. Compressive strengths were measured in day 7, 14 and 28. Effective porosity, permeability, flexural strength and abrasion have been measured. Cost analysis performed with the selected mix design versus conventional methods. Both 5–12.5 mm and 14–20 mm coarse aggregate mix designs—28-day percentage increase in compressive strength show linear increase and effective porosity inversely proportionate with the percentage replacement of cement with BA. In series replacement with BA both arms showed compressive strength inversely proportionate to percentage increase in effective porosity. Although it decreases the effective porosity with the percentage of BA, the effect on porosity is relatively lesser compared to the increase compressive strength. Optimum mix design of this study was concluded for PC as a paving method is 5–12.5 mm aggregate size with 12% BA replacement. When compared with the conventional paving methods, proposed PC mix design was cost-effective.KeywordsPervious concrete (PC)Bottom ash (BA)Mix design (MD)