Particle Size Effect of Volcanic Ash towards Developing Engineered Portland Cements

Abstract

Promoting the use of naturally available materials as a partial substitute to portland cement can be a viable solution for producing low carbon footprint and durable cements. This work assessed the chemomechanical behavior of hardened cement pastes with partial replacement of ordinary portland cement (OPC) with volcanic ash up to 5%. Volcanic ash was ground to two different mean sizes (17 and 6 μm) and then used to prepare cement–volcanic ash blends of various proportions. Mixtures were cured for 28 days; then the hardened cement paste specimens were studied for the effects of partial substitution with volcanic ash on mechanical properties, pore structure, and microstructure. The volcanic ash was engineered by decreasing the particle size, thus allowing for a greater extent of OPC replacement with volcanic ash. Strength increase was observed for specimens with up to 4% substitution of OPC with volcanic ash of a mean size of 6 μm, and this increase was attributed to the denser pore structure observed via mercury intrusion porosimetry (MIP) studies. Densification of specimens was attributed to the generation of secondary calcium silicate hydrate (C-S-H) gels when smaller-sized volcanic ash was used. This study provides a multiscale insight into engineering portland cement blends with partial replacement of portland cement with finer volcanic ash.