Effect of rice husk ash on structural and thermal properties of clay roof tiles

Utilization of waste matter in building construction is becoming more popular in the world mostly because it not only gives alternative for construction material but also gives a solution for waste management while reducing environmental pollution. Among many waste materials, Rice Husk Ash (RHA), a waste from clay products manufacturing process has no proper usage in many countries including in Sri Lanka. Objective of this study is to investigate the effect of waste RHA collected from a brick kiln on structural and thermal properties of clay roof tiles. Roof tile specimens with different RHA percentages (0%, 5%, 10%, 15% and 20%) were manufactured in industrial scale. Structural properties of clay roof tile such as transverse breaking load, bulk density and water absorption were determined. In addition, thermal behaviour of roof tiles was examined. Furthermore, the physical and chemical properties of RHA and clay were also determined in order to find the reasons for characteristic behaviour of RHA added clay roof tiles. For 10% RHA replacement, transverse breaking load can be increased by 47.24%. Bulk density is reduced with the percentage of RHA added, which is a favourable property for roof tiles as a roofing material. RHA increases water absorption property. However, addition of RHA up to 15% is acceptable, as it satisfies the limits specified in standards. Heat transmitted through the roof clay tile is reduced with increasing RHA percentage. Hence, cooler environment can be built under RHA added roof tiles than under conventional roof tiles. It was found that the brick kiln RHA contains high amount of SiO2 content of 84.14% and that may be the most probable reason for the strength gain property of RHA added roof tiles