The effect of curing conditions on properties of mortars with and without ground granulated blast furnace slag (GGBFS) was studied. In the present work, cement was replaced by ground granulated blast furnace slag 0% (control), 30%, and 60% by weight, and mortars were produced. One of the two groups of mortars was kept in water at 20 degrees C standard conditions, and the other was kept in moisture cabinet at 40 degrees C temperature and approximately at 100% relative humidity (RH). Flexural strength, compressive strength, ultrasonic pulse velocity, capillarity coefficient, and volumetric water absorption were investigated at the ages of 7, 28, 56, 90, and 180 days. The results obtained indicate that elevated temperature increases performance of mortar at early ages but decreases at later-age, and this affect is more significant at slag replaced mortars. (C) 2006 Elsevier Ltd. All rights reserved.