MICROSTRUCTURAL CHARACTERISATION, PHYSICAL AND CHEMICAL PROPERTIES OF RICE HUSK ASH AS VIABLE POZZOLAN IN BUILDING MATERIAL: A CASE STUDY OF SOME NIGERIAN GROWN RICE VARIETIES

Abstract

Recycling of agricultural wastes such as rice husk ash as pozzolan is being increasingly encouraged, particularly in developing countries. In this paper, preliminary investigation on the physical and chemical compositions of rice husk ash using different techniques was carried out. Scanning Electron Microscopy (SEM) images of the rice husk ash showed residual pores to be distributed within the ash sample, indicating that the silica is a highly porous material with a large internal surface area. Samples burnt at 400⁰C for 6 hours and 600⁰C for 4 hours for ‘Bukus’ and ‘Soro/ Olomo nla’ show aggregates with clearly defined layers of loose flakes compared to ‘Faro 58’. The Energy dispersive x-ray spectroscopy (EDX) analysis of rice husk ash performed to determine percentages of silica present in the samples were graphically represented. Nine elements (Al, Si, K, Ca, Br, Fe, Mg, Na, Mn) and their corresponding oxides (Al₂O₃, SiO₂, K₂O, CaO, Br, Fe₂O₃, MgO, Na₂O, MnO) were detected with varying concentrations. The three varieties, on the average possess good silica content of over 50% considering the two varied temperature and time. Therefore, the chemical analysis results show that burning at combustion temperature of 600⁰C for 4hrs, gives optimal result than at 400⁰C for 6hrs because all the samples show high Silica content (Faro 58; 61.9, Bukus; 62.6 and Soro/Olomo nla; 59.5).

http://dx.doi.org/10.4314/njt.v37i1.10