Effect of waste rice husk ash on structural, thermal and run-off properties of clay roof tiles

•Waste rice husk ash contains 84% of silica, which are more amorphous and reactive.•10% replacement of clay shows 45.97% increment in the transverse breaking load.•Light-weight roof tiles could be achieved by replacing clay with RHA.•With 10% RHA mixed clay tiles, indoor temperature is reduced by 4 °C.•Rain water harvested from RHA mixed clay roof tiles can be utilized.

Rice Husk Ash (RHA), a waste from firing process of clay products, has no proper usage. For this study, roof tile specimens were manufactured by replacing clay with different RHA percentages (i.e., 0%, 5%, 10%, 15% and 20%) in an industrial scale plant, so as to determine the effect of waste RHA from a brick firing process on structural, thermal properties and run-off qualities of clay roof tiles. For 10% replacement of clay with RHA, transverse breaking load was increased by 45.97% indicating higher ductility compared with that of the conventional tiles. Bulk density is reduced with the percentage of RHA added, promising a light-weight roof tile, a favourable tile for a roofing material. With increasing RHA content, water absorption increases. RHA replacement up to 15% is desirable, satisfying the water absorption limit according to standards. RHA replacement up to 20% doesn't affect on the water penetration property. RHA mixed roof tiles can reduce the indoor temperature, feeling more comfortable for inhabitants. Collected runoff coming along the 10% RHA mixed clay roof tiles has a pH value of 7.22 and total solid concentration of 118.67 mg/L, indicating RHA mixed roof clay tile will not cause any severe impact on the runoff. Hence this harvested runoff can still be utilized for non-potable activities while enhancing the strength and thermal properties of clay roof tiles.