  Arguably the most ubiquitous construction material in modern civilization,
concrete is enabling the development of megacities around the globe together
with increasing living standards in developing nations. However, it can be
argued that the concrete industry's somewhat empirical and conservative
approach to change is hampering innovation and associated CO2 reductions, yet
materials engineering of the essential phase(s) responsible for strength and
durability would enable for revolutionary advancements to be achieved. Using a
computational materials engineering approach, we simulate the fundamental
solution-based building blocks of cement hydrates and their propensity to form
larger complexes as assessed from Gibbs free energies of chemical reactions
characteristic of the formation of calcium-silicate-hydrate,
calcium-alumino-silicate-hydrate and sodium-containing
calcium-alumino-silicate-hydrate gels. By accurately simulating the high pH
pore solution chemistry in Portland cements and related systems, along with
discrete solvation of the species, we discover and discuss the dominant early
stage mechanisms controlling gel formation in these systems.
