The hydration of tricalcium aluminate (Ca3Al2O6) in Portland cement-related systems: A review

Experiments, simulations and derived theories for the hydration of tricalcium aluminate in Portland cement -related systems are summarized and further conclusions are drawn. Highly reactive calcium sulfates lead to an earlier sulfate depletion, possibly due to their faster dissolution and consequently enhanced sulfate con-sumption by forming more ettringite instead of AFm. Sodium in solid solution decreases the crystal symmetry of tricalcium aluminate and is released over-proportionally during dissolution. When reacting only with water, sodium in solid solution and in the pore solution decreases the dissolution. At lower humidity, hydration starts with a delay, and the minimum humidity that allows a reaction depends on the overall composition of the system. Organic admixtures may interfere with the balance between aluminate phases and calcium sulfates thus disturbing the silicate reaction. The retardations of aluminate phases by sulfate and silicate phases by aluminate are likely due to surface sorption of ions suppressing the dissolution.