Research Paper Mechanical properties and durability assessment of rice husk ash concrete Rahmat Madandoust a, *, Malek Mohammad Ranjbar a , Hamed Ahmadi Moghadam b , Seyed Yasin Mousavi a a Department of Civil Engineering, University of Guilan, P.O. Box 3756, Rasht, Iran b Department of Civil Engineering, Lashtenesha-Zibakenar Branch, Islamic Azad University, Lashtenesha, Iran article info Article history: Received 23 May 2010 Received in revised form 4 July 2011 Accepted 25 July 2011 Published online 24 August 2011 The effect of rice husk ash (RHA) on concrete properties and durability was studied. To establish the suitable proportion of RHA for the partial replacement of cement, concrete mixtures with 0e30% RHA were produced and their mechanical properties were deter- mined. The effect of RHA on the uniformity of concrete was also examined. The durability of the specimens exposed to aggressive environments (5% NaCl with wet-dry cycling) was evaluated for a total of eleven months. The degree of damage was studied by determining the percentage of reduction in compressive strength and chloride ions penetration as compared with control specimens that had cured normally. The results indicate that the partial replacement of cement by RHA improved durability and homogeneity but did not increase the early age compressive strength of concrete. However, concrete containing RHA showed higher compressive strength at the later ages. The scanning electron microscopy (SEM) studies of the microstructure of mortar specimens showed that the RHA filled up the pores and this explained the superior mechanical performance of the mortar with RHA. ª 2011 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction A large number of researches have been directed towards the utilisation of waste materials (Bui, Hu, Stroeven, 2005; Mehta, 1977). For the construction industry, the development and use of blended cements is growing rapidly. Pozzolans from industrial and agricultural by-products such as fly ash and rice husk ash (RHA) are receiving more attention now since their use generally improves the properties of the blended cement concrete, the cost and the reduction of negative environ- mental effects. Rice husks, sometimes called rice hulls, are one of the major agricultural by-products and are the shells produced during the de husking operation of paddy rice. It constitutes 20% of the 500 million tons of paddy produced in the world (Bhanumathidas & Mehta, 2004). Due to the low nutritional properties of rice-husk, it is not appropriate for use as a feed for animals. Moreover, its siliceous composition is resistant to natural degradation, which can produce a large environ- mental load (Zerbino, Giaccio, Isaia, 2011). Hence, adequate alternative disposal arrangements must be considered to avoid environmental effects. In some countries, rice husk has * Corresponding author. Tel.: þ98 9113314970; fax: þ98 1316690271. E-mail addresses: rmadandoust@guilan.ac.ir (R. Madandoust), ranjbar@guilan.ac.ir (M.M. Ranjbar), h.ahmadimoghadam@lziau.ac.ir (H.A. Moghadam). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/issn/15375110 biosystems engineering 110 (2011) 144 e152 1537-5110/$ e see front matter ª 2011 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2011.07.009