Utilization of Cordia Africana wood sawdust ash as partial cement replacement in C 25 concrete

Abstract

Partial replacements are being explored for cement in concrete to reduce the environmental negative effect of their use. This study aimed at investigating the effect of Cordia Africana sawdust ash (SDA) as a partial replacement of cement, on the fresh and hardened properties of concrete. For this purpose, different concrete mixes were designed at a constant water-to-binder ratio of 0.42. The SDA content of 0%, 5%, 10%, 15% and 20% were used to replace cement. The workability and compressive strength of SDA concrete decreased as greater proportions of cement were replaced by the SDA. The initial and the final setting time of concrete increased as the SDA replacement increased. Consistency varied with the increase of water content by weight of cement within an increment of SDA replacement but both are within the acceptable limits of Ethiopian standard. The optimum compressive strength and density for the modified concrete achieved were 33.9 N/mm2 and 2569.3 kg/m3 respectively after 21 days for the sample with 5% replacement. The experimental results of this work are showed that the SDA can be used successfully as a cement replacement in C 25 concrete up to 5% replacement. The study was also able to quantify the environmental benefits of SDA partial replacement by showing a 2.19% reduction of virgin material utilization.

Keywords

• Cement
• Concrete
• Sawdust
• Environment
• Supplementary cementitious material