STRENGTH CHARACTERISTICS OF SAWDUST ASH MODIFIED CONCRETE

Abstract

The search for more durable and stronger concrete has led researchers to discover pozzolanas in many aggro-wastes .This research is on sawdust. In Nigeria enormous quantity sawdust are generated yearly in sawmills these sawdust are normally discarded or burnt as a means of disposal. Though this method of disposal to a great extent prevents sawdust from causing serious environmental problems, there is need to recycle the waste to make it economically useful. This work, therefore, studied the possibility of using the ash obtained from burning sawdust as partial substitute for cement content in concrete production. Sawdust ash was added to concrete of grade 20(M20) by substituting the cement with various percentage of sawdust ash of 0%, 10%, 20% and 30% by weight of the original cement content. The resulting compressive strengths were recorded. The oxide compositions of the ash was also obtained through x-ray fluorescence spectrometer test. It was observed that at the later ages of the hydration   of the concrete (21 days and 28 days curing periods) the compressive strengths reduced significantly in direct proportion to the added ash. This reduction was worst at 30% ash content, showing near absence of pozzolanic reaction. The oxide compositions showed very low content of SiO2, Al2O3 and Fe2O3 . However, the 28-days strength for 10% and 20% ash contents do not differ widely from the control mix, so sawdust disposal by substituting part of the cement content of concrete with 10 to 20% was then recommended.

KEYWORDS:   Sawdust, cement, concrete, substitution, disposal method, agro-waste, pozzolana