This study aims to investigate the use of ground pumice powder (PP) in cement production and to monitor void developments in mortars by X-ray Computerized Tomography (CT) which is a nondestructive test method. PP-blended cements were produced by replacing ordinary Portland cement with PP at 0% (control), 5%, 10% and 15% by weight. Paste and mortar specimens were manufactured by these blended cements. Some of the physical and mechanical tests are carried out on these mortar specimens. Experimental results showed that macro void developments in 100-day period for mortars with different PP replacement ratios exhibited different reduction in void ratios. (C) 2014 Elsevier Ltd. All rights reserved.