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The use of fly ash as cement replacement material in geopolymer is able to overcome the environmental problems caused by the cement production process. One type of fly ash that is widely used is class C fly ash which has a high calcium content. However, the main issue of this materials is the low silicate content which is required in forming geopolymer matrix. The use of zeolite which has a high silicate content is one alternative to overcome this problem. This research aims to identify the effect of zeolit addition in strength of high calcium class C fly ash geopolymer mortar. The ratio of zeolit to fly ash was 5% : 95%, 10% : 90%, 15% : 85%, 20% : 80%, and 25% : 75%, respectively. The specimen was developed using the blended 12 molar NaOH and sodium silicate at room temperature. The results showed that the combination of 95% fly ash and 5% zeolit gives the highest compressive strength. The zeolit significantly affects the strength development rate of geopolymer and accelerates the setting time rate. This can be concluded that the mix of class C fly ash and zeolite can provide an alternative in geopolymer production at room temperature.