The effect of gamma radiation on the mechanical and microstructural properties of Fe-rich inorganic polymers

Inorganic Polymers (IPs) are interesting alternative binder materials to Ordinary Portland Cement (OPC). They could be potentially used in applications such as nuclear safety structures and radioactive waste management since they are highly chemically and thermally resistant. However, their chemical and mechanical stability still has to be proven when irradiated at the very early age. This study investigated the effect of gamma irradiation on the mechanical and microstructural properties of IPs cured for 1 h, 24 h or 28 days. For that purpose, IPs were irradiated using different dose rates (1.6 Gy/h, 7.1 Gy/h, 152 Gy/h and 2 kGy/h) until different absorbed doses with a maximum of 624 kGy. The effects were evaluated by means of compressive strength tests, microstructural analysis by image analysis, porosity analysis (water absorption and MIP), thermogravimetric analysis (TGA) and infrared spectrometry. For each irradiation test, non-irradiated samples were kept as a reference at the same environmental conditions as the irradiated samples. The results were compared with similar studies on OPC-based samples. At low doses (<5 kGy) no statistically significant change has been found. Above 5 kGy however, a significant increase in compressive strength was found for all the samples tested. An increase up to 22% in compressive strength was observed for the samples irradiated at 2 kGy/h. Gamma radiation induced carbonation, Fe ³⁺ reduction and polymerization could explain the strength increase but need further investigation.