<![CDATA[This study was conducted to determine the effect of temperature on the chemical content and crystal structure on clinker of cement with 20% substitution of basalt stone on the mass of limestone and 20% of coal against total mass. The raw material used is basalt stone from East Lampung and anthracite coal. The percentage of limestone used is 80%. All raw materials are milled, sifted, then formed pellets with a diameter of 0.8 - 1.4 cm. Pellets are dried at room temperature, then heated and burned with temperature variations of 1000 ° C, 1100 ° C and 1200 ° C for 1 hour. XRF results showed that basalt rock had a content of SiO2 + Al2O3 + Fe2O3 of 79.293% so that basalt could be said to have pozzolanic properties. The CaO content for cement clinker decreased, the results of XRF with combustion temperatures of 1000 ° C, 1100 ° C and 1200 ° C respectively were 62,329%, 55,606%, and 54,148%. Materials A, B and C respectively were burning at 1000°C, 1100°C, and 1200oC for 1 hour. The crystalline phase formed in material A is calcium iron oxide with the highest peak belonging to Ca at position 2θ which is 26.6627° and another crystal phase, gehlenite, syn. The crystalline phase formed in material B is akermanite-gehlenite syn with the highest peak belonging to Ca at position 2θ which is 31.2747° and other crystalline phases namely and wollastonite, ferroan 1A. While the crystalline phase formed in material C is akermanite-gehlenite with the highest peak belonging to Ca at position 2θ which is 31.3051° and syn and other crystalline phases namely wollastonite, ferroan 1A.]]>
