Optimum Mixture Proportioning of Sawdust Ash Blended Sand-Stone Dust Blocks Using Scheffe’s Regression Theory

Abstract

This study carried out an experimental investigation on the compressive strength of sawdust ash blended sand-stone dust block of size 450 x 225 x 150 mm using Scheffe’s (5, 2) regression theory. The compressive strength of sawdust ash blended sand-stone dust blocks obtained based on fifteen trial mix ratios were used to develop the mathematical model while the results of the compressive strength values obtained based on the additional fifteen mix ratios were used to validate the mathematical model. The sawdust ash blended sand-stone dust block specimens were manufactured based on the fifteen first fifteen trial mix ratios and the fifteen control mix ratios. The component materials were properly mixed using a shovel and then compacted into the block mould. Two block specimens were produced per mix ratio, making a total of 60 blocks for compressive strength test at age28 days. A computer program was developed using Visual software based on the model developed to quicken the process of selecting the cheapest mix ratios corresponding to a desired compressive strength value and vice versa. The model has determined that the optimal compressive strength achievable is 6.93372 N/mm2, and it corresponds to a specific mix ratio of 0.56 parts water, 0.86 parts cement, 0.14 parts sawdust ash, 5.28 parts sand, and 1.52 parts stone dust. The compressive strength of sandcrete block obtained at 13.75% replacement is 6.644N/mm2 . This value is far above the minimum value of compressive strength recommended by Nigeria Standard-NIS 87:2000 showing that sawdust ash blended sand-stone dust block can be used as load bearing walls.