[01] James E. O. Ovri, Department of Materials and Metallurgical Engineering, Federal University of Technology, Owerri, Imo state, Nigeria. [02] Ovie P. Umukoro, Department of Materials and Metallurgical Engineering, Federal University of Technology, Owerri, Imo state, Nigeria.

The compressive and flexural strengths of concrete using rice husk ash (RHA) as partial replacement for cement is investigated.The RHA substituted in place of cement were 0,10, 20, 30, 35 and 100%RHA. The specimens were cured for a period of 7, 14, 21, 28 and 35- day respectively and it was observed that the control specimen(0% RHA) experienced defects such as efflorescence but the RHA-ordinary Portland cement(OPC) specimens did not. The 100% RHA specimen were unable to set and this is perhaps due to the absence of the by-products of hydration process such as calcium-silicate-hydrate (C-S-H) gel known as tobermorite and calcium hydroxide,Ca(OH)2, and the high SiO2 content compared tothe low content of other important compounds such as Al2O3 and Fe2O3 in the mix. The compressive and flexural strengths of the concrete were found to decreased with increase in RHA contents with the 10% RHA replacement having the optimum value for improved structural performance at 28-day( control: 22.93N/mm2 and 8.73 N/mm2, specimen: 22.22 N/mm2and 6.60 N/mm2)for compressive and flexural strengths. It can be concluded that RHA can be used as a partial replacement for cement in concrete, with the 10%RHA giving the optimum compressive and flexural strengths.

Compressive, Flexural, Rice Husk Ash, Incineration Temperature, Pozzolanic Reactivity

[01] American Society for Testing and Materials (2005) ASTM C618-05: Specifications for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete, ASHM. [02] Atan,M.N. and Awang,H.(2011): The Compressive and Flexural Strengths of Self –Compacting Concrete,Journal of Engineering Science and Technology,Vol.6,No.6,720-732 [03] American Society for Testing and Materials (2005)ASTM. [04] American Society for Testing and Material,ASTMC-150 OPC. [05] ECO-CARE Education, (2005): Building Material: Cement http://www.ecocareeducation.com/building-material.htm. [06] Ikpong, A.A. (1993). “The Relationship Between the Strength and Non-Destructive Parameters of Rice Husk Ash Concrete” Cement and Concrete Research 23 (38):398. [07] Neville, A.M. and Brooks, J.J. (1987) Concrete Technology. Longman Scientific and Technical, England.NIST, Large Scale Structure Testing Facility, retrieved 04-05-2010. [08] Okpala, D.C. (1987): “Rice Husk Ash (RHA) as Partial Replacement of Cement in Concrete” ,Proceedings Nigeria Society of Engineers, Port-Harcourt, pp. 83-90. [09] Okamura,H. And Ouchi, M. (2003): Selt-Compacting Concrete. Journal of Advanced Concrete Technology,1(1),5-15 [10] Ovri,J.E.O.(2000): Determination of the Mechanical Strength of Plain Concrete.GJPAS,Vol.6,No.2,295-300. [11] Powers, T.C. (1958): The Physical Structure and Engineering Properties, Association Research Department Bulletin 90, July 1. [12] The European Project Group,(2005): The European Guidelines for Self-Compacting Concrete. SCC European Project Group. [13] Topcu,I.B. and Uygunoglu,T,(2010): Influence of Mineral Additive Type on Slump-flow and Yield Stress of a Self-Compacting Concrete. Scientific Research and Essays, 5(12), 1492-1500.