Properties of Sawdust Concrete

This work examined the structural properties of concrete obtained by partially replacing cement with sawdust ash. The sawdust ash which is a pozzolan was obtained by burning sawdust which is a waste product from processing of timber in an open air. The burnt ash was passed through a 150 µm metric sieve to obtain the ash used. Physical and chemical analysis were performed on the ash to verify its suitability as a partial substitute for cement in concrete. Chemical analysis was also carried out on the Ordinary Portland Cement (OPC) sample. Concrete mixes were produced by replacing OPC with 0%, 5%, 10%, 20% and 30% of Sawdust Ash (SDA). Both fresh and hardened properties of the concrete produced were investigated. The chemical investigation on the ash showed that it contained most of the basic compounds found in OPC making it suitable to serve as a partial substitute for OPC in concrete. Investigation on the concrete showed that both the workability and density of the concrete reduce as the SDA content increases. Analysis on the hardened concrete revealed that the compressive strength of the concrete decreases as the ash content increases for the early ages of curing. However, from 21 days curing age upwards, the compressive strength decreases as SDA increases up to 10% of SDA at which the compressive strength rose to a maximum value, and then starts reducing again as the percentage SDA increases. Thus, the SDA concrete gained rapid strength at later ages indicating its pozzolanic activity.