Abstract:The saw dust (SD) is often used as a fuel which in turn leads to the environmental pollution. So, it must utilize this waste into useful applications to avoid what is known as "air pollution". In this study, the SD was converted to saw dust ash (SDA) by its firing at 500°C. It is then used as a partial substitution for cement. The results showed that the water of consistency (WC), initial setting time (IST) and final setting time (FST) of the Portland cement pastes are decreased with the substitution of SDA due to the presence of Na-lignosulfonate. The bound water content (BW), bulk density (BD) and compressive strength (CS) increased with time of hydration up to 90 days, while the apparent porosity (AP) decreased. The BW, BD and CS of the cement pastes containing 5-15 wt. % SDA are slightly higher than those of the blank (S0) at all hydration ages. The free lime content (FL) of the Portland cement pastes (S0) increased as the hydration progressed onward, whereas the cement pastes with SDA (S1-S5) only increased up to 3 days and then decreased. The FTIR spectra of the OPC without SDA showed that the free lime content increased as the hydration proceeded till 90 days, while that of the optimum cement mix containing 15 wt. % SDA, the FL content increased only up to 3 days and then progressively decreased until nearly disappeared after 90 days.