International Journal of Modern Engineering Research (IJMER) www.ijmer.com Vol.3, Issue.3, May-June. 2013 pp-1366-1371 ISSN: 2249-6645 www.ijmer.com 1366 | Page L. O. Ettu, 1 K. C. Nwachukwu, 2 J. I. Arimanwa, 3 T. U. Anyanwu, 4 S. O. Okpara 5 1,2,3,4 Department of Civil Engineering, Federal University of Technology, Owerri, Nigeria 5 Department of Building Technology, AkanuIbiam Federal Polytechnic, Unwana, Nigeria Abstract: This work investigated the compressive strength of binary and ternary blended cementsandcrete and soilcreteblocks containing Afikpo rice husk ash (RHA) and corn cob ash (CCA). 135 solid sandcrete blocks and 135 solid soilcrete blocks of 450mm x 225mm x 125mm were produced with OPC-RHAbinary blended cement, 135with OPC- CCAbinary blended cement, and 135with OPC-RHA-CCAternary blended cement, each at percentage OPC replacement with pozzolan of 5%, 10%, 15%, 20%, and 25%.Three sandcrete blocks and three soilcreteblocks for each OPC-pozzolan mix and the control were crushed to obtain their compressive strengths at 3, 7, 14, 21, 28, 50, 90, 120, and 150 days of curing. Binary and ternary blended cement sandcrete and soilcrete block strength values were found to be higher than the control values beyond 50 days of hydration at 5-20% OPC replacement with pozzolan. The 150-day strength values for OPC-RHA-CCA ternary blended cement sandcreteand soilcrete blocks were respectively 6.10N/mm 2 and 5.30N/mm 2 for 5% replacement, 6.00N/mm 2 and 5.20N/mm 2 for 10% replacement, 5.85N/mm 2 and 5.00N/mm 2 for 15% replacement,5.70N/mm 2 and 4.95N/mm 2 for 20% replacement, and 5.35N/mm 2 and 4.85N/mm 2 for 25% replacement; while the control values were 5.20N/mm 2 and 4.80N/mm 2 . Thus, OPC-RHA and OPC-CCA binary blended cements as well as OPC- RHA-CCA ternary blended cement could be used in producing sandcrete and soilcrete blocks with sufficient strength for use in building and minor civil engineering works where the need for high early strength is not a critical factor. KeyWords: Binary blended cement, corn cob ash, pozzolan, rice husk ash, sandcrete block, soilcrete block, ternary blended cement. I. Introduction Sandcrete and soilcrete blocks are cement composites commonly used as walling units in buildings all over South Eastern Nigeria and many other parts of Africa. The major constituents of sandcrete are water, cement, and sand while those of soilcrete are water, cement, and natural soil, especially laterite. These important construction materials have been greatly investigated by many researchers. Mama and Osadebe (2011) developed a mathematical model for optimizing the strength of laterizedsandcrete blocks. Joshua and Lawal (2011) successfully replaced sand with laterite in suitable optimal percentages to produce laterizedsandcrete blocks with adequate strength and more cost effectiveness than the traditional sandcrete blocks. Wenapereand Ephraim (2009) found that the compressive strength of sandcrete blocks increased with age of curing for all mixes tested at the water-cement ratio of 0.5. Their findings showed that the strength at ages 7, 14, and 21 days were 43%, 75%, and 92% of the 28-day strength respectively. Baiden and Tuuli (2004) confirmed that mix ratio, materials quality, and mixing of the constituent materials affect the quality of sandcrete blocks. Within the past decade researchers in this field have focused largely on finding ways of reducing the cost of cement used in sandcrete and soilcrete block production so as to provide low-cost buildings in the suburbs and villages of South Eastern Nigeria and other places. For this reason agricultural by-products regarded as wastes in technologically underdeveloped societies are increasingly being investigated as partial replacement of Ordinary Portland Cement (OPC) in binary blended cement systems. Manasseh (2010) carried out an elaborate review of some of the commonest agro wastes that have been experimented as cement replacement in sandcrete making and found some of them such as rice husk ash (RHA) suitable. Apata and Alhassan (2012) recently evaluated locally available materials as partial replacement for cement and concluded that partial replacement of these local materials with 10% OPC can be adopted for low cost housing. Okpala (1993) had partially substituted cement with RHA in the percentage range of 30–60% at intervals of 10% while considering the effect on some properties of sandcrete blocks. His results revealed that up to 40% cement replacement would still be suitable for a sandcrete mix of 1:6 (cement/sand ratio) while up to 30%replacement would be suitable for a mix of 1:8. Aribisala and Bamisaye (2006) reported the successful use of bone powder as partial replacement for cement in concrete. Marthong (2012) used sawdust ash (SDA) as partial replacement of cement in sandcrete. Ganesan, Rajagopal, and Thangavel (2008) assessed the optimal level of replacement of OPC with RHA for strength and permeability properties of blended cement concrete. Nair, Jagadish, and Fraaij (2006) found that RHA could be a suitable alternative to OPC for rural housing. Cisse and Laquerbe (2000) reported that sandcrete blocks obtained with unground Senegalese RHA as partial replacement of OPC had greater mechanical resistance than 100% OPC sandcrete blocks. Their study also revealed that the use of unground RHA enabled production of lightweight sandcrete block with insulating properties at a reduced cost. Agbede and Obam (2008) investigated the strength properties of OPC-RHA blended sandcrete blocks. They replaced various percentages of OPC with RHA and found that up to 17.5% of OPC can be replaced with RHA to produce good quality sandcrete blocks. Oyekan and Kamiyo (2011) reported thatsandcrete blocks made with RHA-blended cement had lower heat Strength of Blended Cement Sandcrete & Soilcrete Blocks Containing Afikpo Rice Husk Ash and Corn Cob Ash