Nanoscale simulations of cement hydrates precipitation mechanisms: impact on macroscopic self-desiccation and water sorption isotherms

Recent experiments show that the nanoscale morphology of cement hydrates can be tuned via solution chemistry and curing conditions. However, it is not known to what an extent a nano-tailored morphology of cement hydrates may translate into improved macroscale properties. This question is addressed here, focussing on water-content-dependent durability properties, in particular self-desiccation and water sorption isotherms. Nanoparticle-based simulations provide the starting point to create model hydrates structures at the micrometre scale, whose formation mechanisms and resulting morphologies depend on solution chemistry and interaction forces at the nanoscale. These nanoscale mechanisms and morphologies are then used to inform a simple model of cement hydration that predicts pore size distribution, water content, internal relative humidity and thus self-desiccation and water sorption isotherms at the macroscale. The results show that the nanoscale morphology of cement hydrates has indeed an important impact on the above-mentioned durability properties, and that hydrates precipitation in current ordinary cements follows a mechanism that is intermediate between the two frequently used models of homogeneous hydrogelation and boundary nucleation and growth.