Influence of fineness of rice husk ash and additives on the properties of lightweight aggregate

In this paper, the preparation of lightweight aggregate (LWA) from rice husk ash (RHA) obtained from a biomass power plant was studied. As-received and ground RHAs were mixed with sodium hydroxide solution (NaOH) and cured to obtain the hardened sodium silicate paste. The samples were then crushed and heated to form LWA. The LWA was tested for acid and base solubility and for disintegration in boiling water. The results showed that ground RHA–LWA gave better performances in terms of expansion, solubility, and disintegration than the as-received RHA–LWA. However, the disintegration of LWA in boiling water was the main problem. It was found that the incorporation of 2–7% boric acid by weight of RHA alleviated this problem and no sign of disintegration was observed. The density of LWA of 0.20–0.40 g/cm3 was achieved.