Volcanic pumice (VP) is a highly vesicular material derived from acidic lavas. It substantially contains amorphous silica, and widely used in many industry, such as construction, textile, chemical and agricultural industries, due to its physical properties. The study is aimed to evaluate the suitability of finely ground (-20 mu m) and/or heated (at 1000 degrees C) volcanic pumice powder to be used as a supplementary cementitious material. Mortar cylinders were prepared using finely ground natural pumice powder, and heated (1000 degrees C) pumice powder (0-20%) at different mixes ratios as cement replacement. The results from this study showed that the heat treatment significantly affected the pozzolanic activity of VP, and use of heated-ground pumice as a supplementary cementitious material increased the strength of mortar up to 7% in 90 days as well as 7- and, 28-day strengths. (C) 2015 Elsevier Ltd. All rights reserved.