University of Tehran Civil Engineering Infrastructures Journal 2322-2093 Articles in Press 2025 10 11 The Kinetics Role of Gypsum in Limestone Calcined Clay Cement Exposing to Sulfate solution by the Thermodynamic Study 104162 10.22059/ceij.2025.379265.2096 EN Sama Karkhaneh Department of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran Amir Tarighat Department of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran Saeed Ghaffarpour Jahormi Department of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran 0000-0002-3033-7195 Journal Article 2024 08 15 In current research, the kinetics role of gypsum is evaluated during the sulfate attack by replacing cement with calcined clay and limestone. This study is done by geochemical code PHREEQC along with kinetics consideration. The results similarity of current and other studies indicates the accuracy of the simulation. Kinetics diagrams for samples with different cement replacement content, and calcined clay to cement replacement content ratios are evaluated to get more information about the kinetics path of gypsum production during sulfate attacks. The results show that three stages can be considered for the kinetics change of gypsum. The first stage of gypsum production gets longer as calcined clay to cement replacement content ratio increases. This means that gypsum is produced with delay for the mixture with a greater calcined clay to cement replacement content ratio. The availability of more aluminum ions as a result of greater calcined clay leads to the continuation of ettringite production instead of gypsum formation. In LC3 cement the maximum amount of produced gypsum is reduced as well as the rate of gypsum production. The stress due to the gypsum formation is applied to the cement matrix with delay because of the prolongation of first stage. https://ceij.ut.ac.ir/article_104162_d714b6c9e8c5806f98b0651cf3e86e87.pdf