Impact of gamma-ray irradiation on hardened white Portland cement pastes exposed to atmosphere

Samples of matured hardened cement paste were exposed to an environment with gamma-ray irradiation, which induces a natural carbonation process. After a dose of approximately 5 × 104 kGy, the physical properties, microstructure, and phase composition of the irradiated hardened cement paste samples are compared with those of reference samples exposed to an identical environment without gamma-ray irradiation. Experiments confirm that aragonite and vaterite are preferentially formed under irradiation and that the bending strength is dramatically increased after gamma-ray irradiation. Based on field-emission scanning electron microscopy observations, X-ray scattering profiles, and water vapor sorption isotherm data, it is concluded that vaterite formed on C–S–H plays a role in strengthening the structure of C–S–H via pseudomorphs.