Characteristics of Earth Blocks Stabilized With Rice Husk Ash and Cement

Abstract

For construction purposes, soil is usually stabilized using lime and/or cement, both of which are expensive. This study investigated the feasibility of using Rice Husk Ash (RHA) as a partial replacement of cement in the stabilization of black cotton soil (clay soil) for the production of compressed earth blocks. The soil used in this study was excavated from a construction site in Juja. RHA was collected from rice mills in Mwea, where RHA is produced through open fire burning of rice husks. Particle size distribution, Atterberg limits, Standard Proctor Compaction and compressive strength tests were carried out according to British standard procedures. The soil used was classified as A-7-5 in the AASHTO classification system. Stabilization was done using different quantities of RHA and cement. This study established that to achieve minimum strength of soil blocks (2.5 MPa), soil should be stabilized with at least 5% cement and 7.5% RHA. When the quantity of RHA exceeded 7.5%, the compressive strength went below the 2.5 MPa required by Kenya Bureau of Standard. Nevertheless stabilized blocks are generally not resistant to wetting and should be used in situations where there is minimum wetting. Use of RHA can reduce the cost of producing stabilized blocks by as much as 30%.