Comparison Study of Class F and Class C Fly Ashes as Cement Replacement Material on Strength Development of Non-Cement Mortar

Cement is the most widely used material for construction. However, the cement production has a negative impact on the environment, as it is one of the contributors to global warming. The production of one ton of cement also produces approximately one ton of CO2. This encourages to the search for more environmentally friendly materials as cement replacement. The aims of this study are to compare two types of fly ashes, i.e. class F (high silicate, low calcium content) and class C (low silicate, high calcium content) fly ashes, as primary material on non-cement mortar. The strength test was performed at the age of 7, 14, and 28 days according to ASTM standard. Class C mortar was cured at ambient temperature, while class F was cured in ambient and 60°C temperatures. The results show that class C fly ash non-cement mortar demonstrated a higher strength compared to class F fly ash at ambient temperature. In contrast, the class F fly ash non-cement mortars exhibited a better performance than class C when it cured at heat temperature. This might due to the high calcium content of class C fly ash which contribute to the additional hydration reaction on strength development.