Cement cohesion from the structuring of ions and water

Reducing the environmental impact of cement production is central to reducing greenhouse gas emissions of the construction industry. However, any modification of cement is hindered by an incomplete understanding of the setting process due to its complexity at the nano- and meso-scales. During setting, the precipitation and non-equilibrium aggregation of charged particles into a percolating, porous network is responsible for the overall mechanical properties. But what is the origin of adhesion between these particles? Previous studies suggest that spatial organization of multivalent ions can lead to attraction between highly charged surfaces, but the role of the solvent is largely overlooked. The solvent itself can also exhibit a great deal of structure due to confinement and strong electrostatic forces. To investigate these effects, we combine a primitive model for ions and surfaces with an explicit representation of water. We find that the presence of water proves to have a strong impact on the ordering of ions and greatly enhances the strength of attraction between two surfaces. By identifying quantitatively the link between chemistry and cohesive forces in cement, these results may open new paths for designing stronger cements, more durable and more sustainable.