There has been researched on the optimization of fly ash Baturaja as a cement additive PCC. The purpose of this research is to know the optimal percentage of fly ash, which can be added to the process of making PCC cement, which still produces excellent quality cement and fulfills SNI and knowing the effect of adding fly ash to physical testing and chemical testing. The test was done physically, Blaine test, setting time test and compressive strength test for three days, seven days, and 28 days. Meanwhile, chemical testing is the Loss of Ignition (LOI) test, Free Calcium Oxide (FCaO) test, and Insoluble Residue test (IR). Based on the result of research, the most optimal percentage is when adding 6% ash fly proportion. The higher the ratio of fly ash, will result in an unstable Blaine value. The higher the proportion of fly ash is added, the compressive strength will be smaller, and the setting time will be longer. Meanwhile, the higher the addition of fly ash, the value of loss of ignition, Free Calcium Oxide, and insoluble residue value will be higher.

Research has been carried out on the optimization of the use of Lahat Fly Ash as an Additive Portland Composite Cement (PCC) which aims to determine the optimum conditions for adding Lahat fly ash to produce cement with physical and chemical requirements in accordance with SNI 7064:2014 and discover the ideal composition of cement with fly additions Lahat ash from various cement compositions. The quality analysis in making PCC cement is chemically in the form of Insoluble Residue (IR), Loss of Ignition (LOI), and free lime (FCaO) as well as the quality of physics in the form of Blaine, setting time, and cement mortar compressive strength. The results obtained after the process of making PCC cement with the addition of 14% Lahat fly ash, namely PCC cement in optimum conditions with physical and chemical requirements in accordance with SNI 7064: 2014 where the ideal composition of PCC cement manufacture is 14% Lahat fly ash, clinker 62%, 3% gypsum, 18% limestone, and 3% pozzolans in making PCC cement. Therefore, Lahat fly ash can be used as an alternative mixture in making PCC cement.