ORIGINAL ARTICLE Strength and mechanical behavior of soil–cement–lime–rice husk ash (soil–CLR) mixture Younes Bagheri • Fauziah Ahmad • Mohd Ashraf Mohamad Ismail Received: 1 November 2012 / Accepted: 7 March 2013 Ó RILEM 2013 Abstract This study presents results of geotechnical investigations on treated silty sand soil with cement, lime and rice husk ash (CLR) and cement-lime (CL) admixture. Consolidated undrained triaxial test and unconfined compressive test were performed to esti- mate the potential of CLR and CL. The study investigates the influence of the amount of CLR%, main effective stress and curing days on soil strength, deformation, post peak behavior and brittleness. The percentages of the additives of CLR and CL varied from 2.5 to 12.5 % by dry weight of the soil with dry densities of 14.5 kN/m 3 and the curing times of 3, 7, 28 and 60 days were examined. From the results, the stress–strain response is strongly influenced by the CLR contents and effective confining pressure. Strength and post peak strength of the CLR–soil are greatly improved by an increase in binder content. An increase of the effective cohesion c 0 (kPa) and effective friction U 0 (degree) is observed with increas- ing the CLR content, consistently. Brittle behavior observed at lower confining pressures and high CLR content. For both CLR and CL additives, linear trend was observed for variation of the q u (kPa) with respect to the additives percentages. RHA was also found to be effective in increasing the shear strength of CLR–soil mixture. Keywords Silty  Sand soil  Stabilization  Rice husk ash  Shear strength Abbreviations CLR Cement, lime and RHA content CL Cement and lime content UCS Unconfined compressive strength CU Consolidated undrained triaxial compression test PI Plasticity index and RHA Rice husk ash List of symbols D r Relative density G s Specific gravity G sCLR Specific gravity of CLR I B Brittleness index d 50 Main particle diameter q p Peak deviator stress q r Residual deviator stress q u Unconfined compressive strength R 2 Coefficient of determination c 0 Effective cohesion U 0 Friction angle r 0 Effective principal stress Y. Bagheri  F. Ahmad (&)  M. A. M. Ismail School of Civil Engineering, USM Engineering Campus, University Sains Malaysia (USM), 14300 Nibong Tebal, Penang, Malaysia e-mail: cefahmad@eng.usm.my Y. Bagheri e-mail: ybagheri0191@gmail.com M. A. M. Ismail e-mail: ceashraf@eng.usm.my Materials and Structures DOI 10.1617/s11527-013-0044-2