Suitability of Nigerian Agricultural By-Products as Cement Replacement for Concrete Making

Abstract

This work investigated the strength characteristics of binary blended cement concrete made with Ordinary Portland Cement (OPC) and each of eight agricultural by-products in South Eastern Nigeria, namely Rice Husk Ash (RHA), Saw Dust Ash (SDA), Oil Palm Bunch Ash (OPBA), Cassava Waste Ash (CWA), Coconut Husk Ash (CHA), Corn Cob Ash (CCA), Plantain Leaf Ash (PLA), and Paw-Paw Leaf Ash (PPLA). 105 concrete cubes of 150mm x 150mm x 150mm were produced at percentage OPC replacement with each of the eight ashes of 5%, 10%, 15%, 20%, and 25%. Three concrete cubes for each percentage replacement of OPC with each ash and the control were tested for saturated surface dry bulk density and crushed to obtain their compressive strengths at 3, 7, 14, 21, 28, 50, and 90 days of curing. The compressive strengths of binary blended cement concrete increased with curing age and decreased with increase in percentage replacement of OPC with pozzolans. The 3-14 day compressive strength values were much lower than the control values for all percentage replacements of OPC with pozzolan. However, the 90-day strength at 5-10% replacement of OPC in binary blending with each of the eight pozzolans was higher than that of the control, ranging from 24.50N/mm 2 for 10% replacement of OPC with coconut husk ash (CHA) to 30.2N/mm 2 for 5% replacement of OPC with RHA compared with the control value of 23.8N/mm 2 . Thus, all the eight agricultural by-products investigated in this work could be good for binary blending with OPC in making structural concrete. However, since blended cement concrete take a longer time to attain adequate strength than 100% OPC concrete, major structural elements constructed with blended cement concrete should be allowed a longer time before loading, say 28-50 days for 5-15% replacement of OPC with agricultural by-product pozzolans and 50-90 days for 15-25% replacement of OPC.