Umasabor and Okovido, 2017 75 Nigerian Journal of Environmental Sciences and Technology (NIJEST) www.nijest.com Vol 1, No. 1 March 2017, pp 75 - 80 Investigation of the Compressive Strength and Curing Duration of Binary Blend of Groundnut Shell Ash Concrete Umasabor, R. I. 1, * and Okovido, J. O. 1 1 Department of Civil Engineering, University of Benin, Benin City, Nigeria Corresponding Author: *umasaborrichie@uniben.edu ABSTRACT This paper studied the evaluation of the compressive strength of the binary blend of groundnut shell ash concrete and curing period. The purpose of the study was to source for local materials like agricultural waste that could replace some percentages of cement in order to make it more economical in concrete in order to ascertain its usefulness in the construction industry. An experimental (quantitative) method was adopted as the research design in this work. The total concrete specimens of size 100mm x100mm produced in the laboratory were one hundred and twenty (120). The groundnut shells were completely burnt in an electric furnace to obtain the ash and 0%, 5%, 10% and 15% of the ashes were used to replace cement for a designed mix of concrete strength of 20N/mm 2 at w/c ratio of 0.6, after varying the w/c ratios from 0.4 to 1.0, according to basic guidelines stated in Department of Environment method. They were cured at 7 days, 28 days, 30 days, 60 days, 90 days, 120 days, 150 days and 200 days. The concrete cubes were taken to the compression machine for compression test. The result shows that compressive strength of the groundnut shell ash concrete increases as the curing period increases and there was decrease in the compressive strength of the pozzolanic concrete as the percentages of groundnut shell ash increases in the concrete. The binary blend of groundnut shell ash at 5% replacement had the maximum compressive strength of 23.3N/mm 2 at 200 days while the control concrete compressive strength was 22.0N/mm 2 . This represents an increment of 1.06% of compressive strength over the control at 200 days. Keywords: Pozzolans, compressive strength, blended concrete, curing duration, replacement 1.0. Introduction Groundnut shell is an agricultural waste obtained from milling of groundnut. About 5% of ash is obtained when the shells are oxidized by burning (Oriola and Moses, 2010). Nigeria contributes about 7 percent of world groundnut production which makes Nigeria the 3rd largest producer of groundnut in the world (Oriola and Moses, 2010). Oriole and Moses (2010) investigated the effect of groundnut shell ash in stabilization of black cotton soil. They found no improvement on the soil. Adole et al. (2011) studied the effect of groundnut husk ash (GHA) blended cement on chemical resistance of concrete. The authors cured the specimen with MgSO4, NaCl and H2SO4 at 14, 21 and 28 days. The results revealed that Ordinary portland cement/ groundnut husk ash (OPC/GHA) performed best in most of the chemical solutions at 28 days hydration period with compressive strength value of 21.0N/mm 2 in MgSO4 solution and 22.55N/mm 2 in NaCl solution. Nwofor and Sule (2012) worked on the stability of groundnut shell ash (GSA)/ ordinary Portland cement (OPC) concrete in Nigeria. They found out that 10% replacement of cement with GSA is suitable for sustainable construction especially in mass concrete construction. Umasabor (2009) also studied partial replacement of ordinary Portland cement (OPC) with groundnut shell ash (GSA) in concrete and discovered that 10% replacement of cement with GSA in concrete will be more suitable.