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Concrete is one of the environmental pollutants. Cement as a main part of the concrete is one of the largest greenhouse emitters. So, searching for a solution to reduce negative environmental impacts of concrete production can be valuable (Pacheco-Pacheco-Torgal, 2014). Ceramic tile and sanitary ware are among the most commonly used materials in construction. World production of ceramic tiles in 2016 was about 13 billion square meters . The amount of waste in the different production stages of the ceramic industry ranges from 3 to 7 percent of daily production (Meyer, 2009). The nature of construction industry, especially the concrete industry, is such that ceramic wastes can be used safely with no need for dramatic change in production and application process. On one hand, the cost of deposition of ceramic waste in landfill will be saved and, on the other, raw materials and natural resources will be replaced, thus saving energy and protecting the environment.

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Calcium silicate hydrate (C–S–H) gel contains almost 50% to 70% of cement paste, which has a significant effect on the cement paste properties. An attempt is made to assess the atomistic structure of calcium silicate hydrate and the impact of water on it through molecular dynamics simulation. The most similar compositions (tobermorite 14Å, tobermorite 11Å, and jennite) are chosen and the effect of water thereof is studied. This study is presented in two phases: (1) water removal from the structure and simulating difference of water-to-calcium ratios through grand canonical Monte Carlo method. Next, the effect of water on the mechanical properties of C–S–H gel is examined through molecular dynamics method. (2) Defects in the existing molecular structures were introduced, which lead to newer Ca–Si proportions followed by the examination of the effect of water on the new structures. The obtained results revealed that as W/Ca ratio increases, the Young's modulus decreases. An increase in the Ca/Si ratio, owing to the defects in the structure, leads to the reduction in the Young's modulus.

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