EFFECT OF SILICA FUME AND SAND SIZED COAL BOTTOM ASH AS BINARY ADDITIVES ON PROPERTIES OF PERMEABLE CONCRETE PAVER BLOCKS

Abstract

This research investigates the effect of silica fume and sand-sized coal bottom ash (CBA) as binary additives on the performance of permeable concrete paver blocks (PCPBs). The study was motivated by the challenges of urban flooding caused by impermeable surfaces and the need for sustainable pavement solutions that balance structural strength with water permeability.Ten concrete mix designs were prepared with varying proportions of silica fume and CBA, and tested for compressive strength and permeability after 28 days of curing. Results showed that silica fume significantly enhanced the compressive strength of PCPBs up to an optimum level, while CBA maintained permeability through its rough, porous texture. When used together in moderate proportions, the two additives produced a balanced microstructure that improved mechanical strength without excessively reducing infiltration capacity.The findings suggest that an optimal mix can be achieved by combining silica fume and CBA, making PCPBs more suitable for urban applications such as parking lots, sidewalks, and light-load pavements. Beyond these optimum levels, however, strength gains diminished and permeability dropped below recommended ranges. This study highlights the potential of using industrial by-products in sustainable concrete technology, contributing both to improved stormwater management and to environmental conservation through waste utilization.