Radiolysis of Portland cement and magnesium phosphate cement: Effect of the content and state of water on the Physicochemical properties and the mechanism and kinetics of hydrogen formation

The radiation stability of Portland cement and magnesium phosphate cement on γ-irradiation was studied up the absorbed dose of 100 MGy. The radiation chemical decomposition of water contained in the cements was accompanied by hydrogen evolution. The evolution was retarded as the dose increased, with the limiting gas concentration, ∼2.6 L and ∼0.7 L kg−1 of Portland cement and magnesium phosphate cement, respectively, being attained at ∼20 MGy. Oxygen was not released to free volume, but was entrapped by components of the materials. In the case of magnesium phosphate cement, the formation of MgO2 was established. A formal model for cement radiolysis was proposed, and an equation describing the hydrogen accumulation was derived. The formation of hydrogen did not induce swelling or destruction of the cements. The results can be used to assess the level of activity of radioactive waste that may be immobilized in these matrices. •PLC and MPC are resistant to radiation up to 100 MGy.•The decomposition of pore water is accompanied by the evolution of hydrogen.•Oxygen does not enter the free volume.•The proposed radiolysis model describes the accumulation of hydrogen.•The results are useful for assessing the activity of the waste for immobilization.