A Along with the development of infrastructure to support public activities, causes demand for materials to increase, especially for concrete making materials, which requires portland cement as one of the main constituent materials. The increasing usage of portland cement has a negative impact on the environment, due to it produces CO2 emissions from its manufacture. Therefore, it emerging the innovation of geopolymer concrete, which in making geopolymer concrete does not require cement but can be replaced by fly ash for the mixture. However, for large-scale usage, geopolymer concrete is more complicated to work with and can cost more as well since it requires activators in the form of strong bases NaOH and Na2SiO3 for activating fly ash. CaO and Ca(OH)2 as strong bases are applied as substitutes for fly ash to replace activators which in this study includes varying degrees of substitution 2,5%; 5%; 7,5%; 10% of the weight of fly ash, and the addition of viscocrete 1050 HE superplasticizer at 1% of the binder weight. The tests include setting time and compressive strength of the concrete when the concrete at the age of 3, 7 and 28 days old and curing in an oven at a temperature of 60℃. The test results show that the higher the calcium content added, especially Ca(OH)2, the higher the compressive strength value and the faster the setting time of the concrete. The maximum compressive strength of geopolymer concrete without activator reached 55.17 MPa and the fastest setting time reached 76 minutes with the addition of Ca(OH)2 with a content of 10%.