Hydration kinetics and microstructure development of normal and NaAlO2‐activated Al‐doped β‐C2S pastes

Abstract Sodium aluminate (NaAlO 2 ) can be used to accelerate hydration of Portland cements. Here, we compare the use of NaAlO 2 solutions with deionized water on the hydration of Al‐doped β‐C 2 S. The microstructure development of hydration product C‐S‐H obtained from hydrated Al‐doped β‐C 2 S was investigated. NaAlO 2 significantly improved the hydration kinetics of Al‐doped β‐C 2 S due to the enhancement in the precipitation of calcium hydroxide and stimulation of C‐(A)‐S‐H nucleation and increased the early‐age mechanical strength of Al‐doped β‐C 2 S pastes. NaAlO 2 promoted the incorporation of Al in the C‐(A)‐S‐H structure and accelerated the formation of C‐(A)‐S‐H phases containing tetra‐, penta‐ and hexa‐coordinated Al in its composition. The alkali cations modified the electrostatic equilibrium of the C‐(A)‐S‐H, thus promoting the development of the nano‐mechanical properties.