Modelling and optimization of different pozzolanic materials in the durability of cement composite by central composite design

Abstract

The production of Ordinary Portland Cement (OPC) requires high temperatures and significant energy consumption, leading to environmental pollution and posing challenges to the sustainability of green cementing materials. To address this, numerous researchers have explored replacing cement with various supplementary cementitious materials, such as blast furnace slag, active limestone, and bentonite, in concrete or mortar. However, optimizing the combined use of these materials to achieve maximum durability in mortar remains a novel area of study. This research models and optimizes the effects of replacing OPC with blast furnace slag, active limestone, and bentonite in mortar using the central composite design method. The findings reveal that increasing the content of bentonite along with either blast furnace slag or limestone from 0% to 20% significantly minimizes strength degradation due to sulfuric acid exposure, improves heat resistance, and lowers water absorption at 28 days. The optimal substitution levels were found to be 20% for both blast furnace slag and limestone, and 18.54% for bentonite. The optumal result reduced damage from sulfate attack by 33.4%, strength loss under high temperatures by 69.04%, and water absorption by 98.58% when compared to the control sample. These outcomes were validated experimentally with a 95% confidence level. Overall, incorporating these SCMs not only improves the durability of mortar but also supports environmental sustainability by reducing CO₂ emissions due to OPC production.