May 2013. Vol. 3, No. 3 ISSN2305-8269 International Journal of Engineering and Applied Sciences © 2012 EAAS & ARF. All rights reserved www.eaas-journal.org 57 STRUCTURAL PROPERTIES OF RICE HUSK ASH CONCRETE. Godwin A. Akeke, Maurice E. Ephraim, Akobo, I.Z.S and Joseph O. Ukpata. Department of Civil Engineering, Cross River University of Technology, Calabar, Nigeria. Abstract This research was experimentally carried out to investigate the effects of introducing Rice Husk Ash (RHA) as a Partial Replacement of Ordinary Portland Cement (OPC) on the Structural Properties of Concrete. Rice Husk Ash which is an Agro-Waste and known to be a Super Pozzoland have been used for mass concrete and found to have compressive strength ranging from 33-38.4N/mm 2 at replacement percentages of 10-25% in a mix of 1:1.5:3. A further study was carried out on its flexural properties to determine their moduli of rupture as well as its tensile strength characteristics for the determination of cracking, the values obtained at 28days are 3, 2.5 and 2.4N/mm 2 while the tensile strength values are 1.94, 1.17 and 0.91N/mm 2 at replacement percentages of 10%, 20% and 25%. This research has proved that RHA Concrete can be used as a Structural Concrete at suitable replacement percentages. This research therefore is an investigation of the performance of the concrete made of partially replacing OPC with RHA on the structural integrity and properties of RHA concrete. Keywords: Rice Husk Ash, Structural Properties and Concrete. INTRODUCTION This research is aimed at putting into effective use Rice Hush Ash (RHA) a local additive which has been investigated to be super pozzolanic in a good proportion to reduce the high cost of structural concrete. Rice Husk Ash (RHA) is an agricultural waste product, and how to dispose of it is a problem to waste mangers. While Concrete today has assumed the position of the most widely used building material globally. The most expensive concrete material is the binder (cement) and if such all-important expensive material is partially replaced with more natural, local and affordable material like RHA will not only take care of waste management but will also reduce the problem of high cost of concrete and housing. There is an increasing importance to preserve the environment in the present day world. RHA from the parboiling plants is posing serious environmental threat and ways are being thought of to dispose them. This material is actually a super pozzolan since it is rich in Silica and has about 85% to 90% Silica content. A “pozzolan” is therefore defined as “a siliceous or siliceous and aluminum material, which itself possess little or no cementing property, but will in a finely divided form and in the presence of moisture chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementite’s properties. A good way of utilizing this material is to use it for making “high performance concrete” which means high workability and very high early strengths, or consider high workability and long term durability of the concrete. Materials Rice Husk Ash (RHA); Rice Husk was burnt for approximately 48hrs in an open air and uncontrolled burning process. The temperature was in the range of 400- 600 0 C. The ash collected was sieved through BS standard sieve size 75μm and its colour was grey. Batching was done by volume at replacement percentages of 10, 20, and 25%. Cement Ordinary Portland cement (OPC) was used in which the composition and properties is in compliance with the Nigerian standard organization defined standard of cement for concrete production.