No abstract

Gypsum is one of the additive raw materials added to the clinker grinding process that regulate the binding time of cement or commonly known as a retarder. This research aims to observe the effect of gypsum added variation on the compressive strength of mortar and the whole quality of Portland Composite Cement at plant 14 P.T Indocement Tunggal Prakasa Tbk. The PCC compositions did prepare with a variation of the addition of 0 - 5% gypsum where the clinker ratio did fix at 75%, and two other additives, namely limestone, and trass did add with a fixed ratio of 1.2: 1. The effect of adding gypsum to clinker measured by performing a mortar compressive strength test and the binding time at the ages of 1, 3, 7, and 28 days. The results of series observation and analysis show that composite Portland cement has the most optimal quality in the addition of gypsum as much as 3.5%, where SO3 content is 1.7%, the initial setting time is ≥ 90, and the final setting time is maximum at 375 minutes.