Nanomechanical analysis of Gamma-irradiated cement paste exposed to different humidities

The paper characterizes concurrent effects of gamma-irradiation and presence of water in Portland cement pastes. An extensive nanomechanical quantification (Young's modulus, hardness, and creep compliance) at two scales is performed after exposure to two gamma-ray doses and a wide range of relative humidities (RH 0%-100%). Competing microstructural mechanisms such as water radiolysis, hydration, carbonation and drying were identified and their effects de-coupled with the aid of nanoindentation and other supporting techniques. Maximum radiation resistance was found for samples in medium humidities (33%-57%). Samples irradiated below 11% RH exhibited compaction of C-S-H phases at the level of 100 nm, & SIM; 25% increase of Young's modulus and decrease of creep compliance due to water radiolysis and drying. The compaction resulted in microcracking at higher paste scale and caused & SIM; 17% decrease of elastic modulus. Samples irradiated in water showed large (& SIM; 26%) decrease of Young's modulus and increased creep compliance accompanied by 9%-10% Portlandite loss.

Automated summary

This paper characterizes the concurrent effects of gamma-irradiation and water presence in Portland cement pastes. Nanomechanical quantification is performed on two scales to identify competing microstructural mechanisms and decouple their effects. Maximum radiation resistance is found at medium humidities, while samples irradiated below 11% RH exhibit compaction of C-S-H phases, increase of Young's modulus, and decrease of creep compliance. Irradiation in water results in decreased Young's modulus, increased creep compliance, and Portlandite loss.