Influence of fineness of volcanic ash and its blends with quarry dust and slag on compressive strength of mortar under different curing temperatures

•Strength activity index values and compressive strength increased with increasing fineness of VA.•The strength activity index for VUF was highest among all other mortars containing FA, QD, and EAFS.•VUF blends with FA and EAFS (20%) demonstrated comparable 91 days strength to CM under standard curing.•“Cross-over effect” was clear in FA, EAFS, and CM, while not so obvious in VA mortars.•VUF30 demonstrated strength better than CM and FA mortars under moderate and high curing temperatures.

In this study researchers investigated the influence of fineness of locally available basaltic volcanic ash (VA) and its blend with other potential supplementary cementitious materials (SCMs) on compressive strength of mortar. Local quarry sites and steel making industries in the eastern province of Saudi Arabia produces tons of wastes commonly known as quarry dust (QD) and electric arc furnace slag (EAFS), respectively. Including the CM, a total of 19 mortar mixtures were prepared by substituting cement with various SCMs (VA, FA, QD, EAFS), their different percentages in binary mixes, fineness of VA, and blends of ultra-fine VA with other SCMs (ternary and quaternary). After casting, specimens were subjected to different curing temperature (20, 40, and 60 °C) and moisture conditions (continuous and partially moist). Compressive strength was measured according to ASTM C 109 at ages 7, 28, and 91 days and an average value of three identical 50-mm3 specimens was reported. The test results indicated that improved fineness of VA up to 30% mass replacement of cement demonstrated compressive strength comparable to control and reference FA mortars at all ages particularly under high curing temperatures. Moreover, a quaternary blend of ultra-fine VA (20%) with EAFS (10%) and QD (10%) produced strength higher than all other ternary and quaternary blends at all ages and comparable 91 days strength to control mortar.