Séni Tamba

Origin of the pozzolanic effect of rice husks

Abstract Rice husk ash has been used in many countries as a low cost concrete admixture because of its role as a filler and a pozzolan. A study is made of an ash produced in Senegal to establish the existence and origin of silica. Two calcinated rice husk ashes were studied. X-Ray diffraction analysis revealed the presence of quartz whose origin may be attributed to contamination and/or re-crystallisation of silica in the calcination. Amorphous silica was detected by scanning electron microscopy and microanalysis, its presence is concentrated on the interior and exterior surfaces of the uncalcinated husk which may promote a pozzolanic action on the surface of the husk and therefore enable its use in lightweight concrete.

Properties of cement—rice husk mixture

Abstract The properties of lightweight mortar using rice husk can benefit from pozzolanic reaction and from organic fibre reinforcement. The effect of curing and storage on 40×40×160 mm 3 OPC rice husk mortar specimens is described. Two conditions are studied; one-year storage at 50% RH and at 95% RH. The final specimen properties were characterised by density, strength, SEM, EDS and XRD. It is concluded that at high humidity storage, pozzolanic reaction is well developed but husk fibres deteriorate. The mortar stored at 50% RH has a lower compressive strength and higher flexural strength, indicating inferior pozzolanic reaction and active fibre reinforcement.