Effect of Mix Ratio and Curing on Compressive Strength of Sandcrete Hollow Blocks

Abstract

The standards of the materials used in a building’s construction greatly influence its strength and durability. In Nigeria, hollow sandcrete block is the most common material used in buildings. This study evaluates the effect of the water-cement ratio and then the aggregate-cement ratio (mix ratio) on the compressive strength and density of hollow sandcrete blocks of size 9" (225 X 225 X 245mm). Six water–cement ratios (0.35, 0.40, 0.45, 0.50, 0.55 and 0.60) and five mix ratios (1:6, 1:7, 1:8, 1:9 and 1:10) were used and the compressive strength and density of the blocks were determined. The results were checked for compliance with the Nigerian Industrial Standard (NIS) (2004) and BS 2028 (1983). The results revealed that 0.45 is the optimum water-cement ratio with the highest compressive strength value of 3.34N/mm². Furthermore, the 28-days compressive strengths of the 1:6, 1:7, 1:8, 1:9 and 1:10 were found to be 2.88 N/mm² , 2.85N/mm²,  2.71N/mm², 2.49N/mm2and 2.46N/mm² respectively. The study samples have a density range of 1527kg/mm³ to 1815kg/mm³ meeting  the minimum requirement of 1500kg/mm³ by BS 2028 (1983). For commercial purposes mix ratios of 1:8 and below should be used  because they meet the minimum requirement of 2.5N/mm² compressive strength specified by NIS (2004).