Pore size distribution modification of OPC paste through inclusion of fly ash and sand

This paper presents a study into the modification of pore size distribution of ordinary Portland cement (OPC) paste due to inclusion of fly ash (FA) and sand as determined through mercury intrusion porosimetry. Cement–sand mortar specimens were prepared from two different grades of OPC with water to cement (w/c) ratios of 0·2, 0·3, 0·4, 0·5 and 0·6 and tested at different curing ages from 1 day to 90 days. Cement–FA paste and mortar specimens were also prepared by incorporating FA at four levels of FA to cement (f/c) ratio (0·1, 0·2, 0·3, 0·4) and a control mix along with four w/(c + f) ratios (0·25, 0·35, 0·45 and 0·55). These specimens were tested at 7, 28 and 90 days. The relationships involving w/c ratio and age with mean distribution radius (r_0·5) and coefficient (d) representing dispersion of pore sizes are presented for both types of OPC–sand mortar. The relationships involving w/(c + f) ratio, f/c ratio and age with r_0·5 and d are also presented separately for cement–FA paste and mortar.