Role of Filler Effect and Pozzolanic Reaction of Biomass Ashes on Hydrated Phase and Pore Size Distribution of Blended Cement Paste

Abstract

The role of filler effect and pozzolanic reaction of biomass ash on hydrated phase and pore size distribution of blended cement paste was studied. Rice husk ash (RHA), palm oil fuel ash (POFA), and river sand (RS) were ground to two fineness values, and used to replace Type I portland cement (OPC) at 0, 20, and 40% by weight of binder. A water to binder ratio of 0.35 was used. The compressive strength, pore size distribution, and thermogravimetric analyses of the blended cement pastes were investigated. Partial replacement of OPC with fine RHA and POFA at a dosage of 20% by weight of binder resulted in pastes with higher compressive strengths than that of OPC paste. The compressive strengths of RHA paste were slightly higher than those of POFA pastes at the same age. The differences between mass losses (at 30–450°C) of RS and RHA (or POFA) blended pastes at the same fineness, curing time, and replacement rate were due to the pozzolanic reaction, which increased in accordance with particle fineness and cement replacement rate. In addition, the weight losses (at 30–450°C) due to the pozzolanic reaction were higher than those due to the filler effect. The use of fine RHA and POFA enhanced the pozzolanic reaction, and reduced the average pore diameters of pastes.