Properties of eco-friendly concrete produced by partial replacement of sand with sawdust with emphasis on water-cement ratio

There is environmental nuisance and degradation occasioned by indiscriminate disposal of sawdust. There is also growing concerns about the depletion of non-renewable natural resources like sand. In response to these problems, researches have been carried out on the usage of sawdust to supplement sand as fine aggregate in concrete. This research examines the effects of water-cement ratio on the engineering properties of concrete produced using sawdust as partial replacement for sand. Standard mixes were prepared without sawdust to serve as control and then sawdust mixes were prepared using 20% replacement of sand with sawdust. The mixes were prepared for varying water cement ratios of 0.4, 0.45, 0.5, 0.55 and 0.6 with the corresponding mix ratios of 1:1.1:2.6; 1:1.3:3; 1:1.5:3.4; 1:1.6:3.8 and 1:1.8:4.2 respectively. A total of 120 cubes of concrete were cast in triplicates for each water-cement ratio and each curing period for both 0 % and 20 % replacement. The results revealed that the slump values increased as the water-cement ratio increased. The results indicate that for a water cement ratio of 0.4 and 0.5, the sawdust concrete attains good properties with compressive strength values of 22.82 N/mm2 and 21.56 N/mm2 respectively at 28 days. However, by increasing the water cement ratio to 0.6, the sawdust concrete recorded a low value for the various properties of concrete with compressive strength value of 14.15 N/mm2 at 28 days. This is due to the decomposition of lignocellulolytic components such as carbohydrates, lignin, cellulose, etc. Therefore, at 20% replacement of sand with sawdust, it is recommended to use water-cement ratio not exceeding 0.5 due to the water absorption rate of the sawdust concrete