INVESTIGATION OF SOFTWOOD ASH,HARD WOOD ASH AND RICE HUSK ASH AS A PARTIAL REPLACEMENT OF ORDINARY PORTLAND CEMENT IN CONCRETE

Abstract

Cement is known globally to be the most expensive constituents of concrete. During its course of production, the CO₂ which is released has negative impacts both on human’s health and other inhabitants in the community. These problems however have called for sourcing suitable and effective waste products as an alternative to cement in concrete. Hard wood ash(HWA), Soft wood ash (SWA) and Rice husk ash(RHA)were investigated experimentally to know their suitability as cementitous materials partially replaced for cement in concrete. The calcination was done under controlled temperature 450 ºC andSWA,HWA and RHA were found to belong to class N pozzolaniccementitous materials. The design concrete mixed was 1:2:4 at water cement ratio 0.6, and 0%. 5%, 10%, 15% and 20%percentage replacement were used. The results revealed a general trend of decrease in compressive strength of the concrete as percentage replacement with SWA, HWA and RHA increased but increased as curing age of concrete increased from 5% to 20%. All the samples had highest compressive strength at 5% replacement with 19.3N/mm², 19.1N/mm²and 16.3N/mm² for SWA, HWA and RHA respectively at curing age 28 day while the lowest values were observed when percentage replacement was 20% with 12.7N/mm², 12.5N/mm² and 9.7 N/mm² at the curing age 28 day for HWA, SWA and RHA accordingly.The type of used was found to have played major role in affecting the compressive strength and other parameters obtained for the concrete produced. However, 5% percentage replacement with the highest compressive strength at the curing age 28 day and the lowest water absorption values were observed to be the most suitable. The SWAwas therefore found to be the most suitable cementituous material followed by HWA and RHA was the least.