Vol. 4(9), pp. 275-284, December 2013 DOI 10.5897/JCECT2013.0286 ISSN 2141-2634 © 2013 Academic Journals http://www.academicjournals.org/JCECT Journal of Civil Engineering and Construction Technology Full Length Research Paper Strength properties of groundnut shell ash (GSA) blended concrete Raheem, S. B. 1 *, Oladiran, G. F. 1 , Olutoge, F. A. 2 and Odewumi, T. O. 1 1 Civil Engineering Department, the Polytechnic, Ibadan, Oyo State, Nigeria. 2 Civil Engineering Department, University of Ibadan, Oyo State, Nigeria. Accepted 6 November, 2013 This research work detailed the report of an experimental study into the strength of modified concrete produced from mixes containing partial replacements of Ordinary Portland Cement (OPC) with groundnut shell ash (GSA). The experiments were designed to include two main mixes (with variations in the water/cement ratios) with different percentages by weight of OPC to GSA in the order of 100:0, 95:5, 90:10, 85:15 and 100:0, 90:10, 80:20 for mixes 1:2:4 and 1:2.3:2.6 respectively. For the ratio 1:2:4 mix, a total of 32 concrete cubes of sizes 150 × 150 × 150 mm and 32 cylindrical concrete specimens (100 mm diameter and 200 mm long) were cast and tested. Also, for the 1:2.3:2.6 mix, 24 concrete cubes and 24 cylindrical concrete specimens, with the same sizes as above, were cast and tested at 7, 14, 21, 28 days of curing. Compressive and splitting tensile tests were conducted to assess the strength of concrete. Generally, strengths of modified concrete increased with curing period but decreased with increased GSA percentage. For mix ratio 1:2:4, the highest compressive and tensile strengths were 24.06 (2.67) and 21.34 (2.11 N/mm 2 ) at 28 days for 0 and 10% GSA respectively. While mix ratio of 1:2.3:2.6 gave the highest compressive and tensile strengths of 35.11 (4.21) and 27.33 (4.01 N/mm 2 ) at 28 days for 0 and 10% GSA respectively. It was observed that 10% GSA replacement was appropriate for both mixes. GSA therefore seems to be a promising and local partial replacement material for cement in concrete making. Key words: Concrete, pozzolana, partial replacement, groundnut shell ash (GSA), concrete strength. INTRODUCTION Due to increasing industrial and agricultural activities, tones of waste materials are deposited in the environment with little effective method of waste managing/recycling. Some of these deposits are not easily decomposed and the accumulation is a threat to the environment and people at large. Some of these waste materials are rice husks, maize combs, snail shells, palm-kennel shell, coconut shell, saw dust, groundnut shell etc. Global pollution coupled with resource depletion has challenged many researchers and engineers to seek locally available materials with a view to investigating their usefulness wholly as a construction material or partly as a substitute for conventional ones in concrete making. In search for new materials which address the issues aforementioned and which are cost effective and more efficient, pozzolans attract much interest. Malhotra and Mehta (1996) define "pozzolan" as "a siliceous or siliceous and aluminous material, which in itself possesses little or no cementing property, but will in a finely divided form – an in the presence of moisture - *Corresponding author. E-mail: talk2deleola@gmail.com.