A new activity index for pozzolanic materials

Cement production is responsible for about 8% of the global carbon footprint. One solution to confront this issue is using cement replacement materials or supplementary cementitious materials. Supplementary cementitious materials or SCMs are materials that can be used as a partial replacement for cement in concrete. These type of materials usually have multiple benefits. In addition to the reduction of cement usage, they may improve concretes characteristics. Pozzolans are among the best supplementary cementitious materials, due to their technical, economic, and environmental benefits. In addition to reducing the cement demand, using pozzolans improves long-term mechanical and durability-related properties of concrete. Nowadays pozzolans are widely used as cement replacement materials in concrete because of their environmental, mechanical and durability benefits. The pozzolans activities vary under the influence of their Nano-structures and chemical compositions. In this paper, molecular dynamics simulations were employed to propose a new method to simply compare the activity of pozzolans. For this purpose, the adsorption of water molecules on the surfaces of pozzolanic minerals was simulated and water/surface interaction energy was used as a criterion to investigate the minerals’ activity. The minerals SiO2, Al2O3, Fe2O3, K2O, MgO, and CaO were studied. Based on the minerals’ activity, an equation was proposed to calculate an activity index for each pozzolanic material. Finally, the presented activity index verified with experimental results of other researches. Additionally, studies showed that, SiO2, Al2O3, and Fe2O3, with an activity index of 15.89, 0.56, and 0.51 respectively have the greatest impact on the pozzolanic activity.

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