en Research Paper Research Paper Abstract: The use of alkali-activated cementitious materials especially over the past decades has significantly been increased. The goal of this research is to investigate the effects of silica modulus and alkali concentration on alkali-activation of blast-furnace slag. In this research, the most important physical characteristics of cementitious systems, i.e. the 28-day compressive strength and final setting time, were studied by changing influencing parameters such as silica modulus, i.e. SiO2/Na2O, (0.44, 0.52, 0.60, and 0.68) and Na2O concentration (4, 6, 8 and 10% by weight of dry binder) at a constant water-to-dry binder ratio of 0.25. Final setting time of the studied systems varies in the range between 55-386 minutes. The obtained results show that systems cured at an atmosphere of more than 95% relative humidity at room temperature exhibit relatively high 28-day compressive strengths up to 107 MPa. Alkali-activation, Blast-furnace Slag, Setting Time, Compressive Strength. 32 35 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-3-26&slc_lang=en&sid=1 A. Allahverdi ali.allahverdi@iust.ac.ir 180031947532846001649 180031947532846001649 Yes E. Najafi Kani 180031947532846001650 180031947532846001650 No S. Esmaeilpoor 180031947532846001651 180031947532846001651 No