Setting time and compressive strength of geopolymer concrete with variations in the addition of cement

The increasing demand for cement in the world of construction can have an extraordinary effect, especially in the production of cement which produces CO2. So we need an alternative material as a substitute and even replace the role of cement. Utilization of coal waste in the form of fly ash is in the spotlight to be maximized. Therefore this research was conducted as an alternative contribution to the solution using geopolymer concrete in terms of setting time and compressive strength with variations in the addition of cement. The method used is experimental in the laboratory which produces qualitative data for further numerical calculations. Tests focused on the setting time and compressive strength of concrete using 5 mix designs with cement variations ranging from 10%, 20%, 30%, 40% of the use of fly ash. The results of the setting time with the highest duration, namely 100% FA=1.5, 95 minutes initial setting time and 225 minutes final setting time, then decreased to the lowest duration, namely 60% FA: Pc 40%=1.5. The initial setting time is 15 minutes and the final setting time is 37 minutes. The highest concrete compressive strength results in the MD 4 mix design with 70% FA mixture: Pc 30%=1.5, which is 43.3 MPa. While the lowest compressive strength is the design mix MD 1 with a mixture of 100% FA=1.5 of 21.8 MPa.