Institute of Fundamental Technological Research

Gadolinium oxide (Gd2O3) is a potentially effective mineral additive that improves neutron shielding properties of cement based composites. The paper presents the influence of Gd2O3 and ulexite (a boron compound) on Portland cement hydration evaluated by isothermal calorimetry measurements and strength. The progress of hydration was investigated on mortar specimens at water to cement ratio w/c = 0.5 and sand/cement ratio 0.75. The addition of Gd2O3 generates a slight retardation of cement hydration, however it accelerates aluminate activity at the same time. The hydration of cement was completely hindered for mortars containing a substantial content of ulexite. The strength test results show that addition of Gd2O3 to Portland cement mortar mix caused a decrease of early age (3 days) flexural and compressive strength. The optimum content of Gd2O3 in respect to the long term compressive strength and the hydration kinetics was 5% in relation to the mass of cement. Good long term strength was also obtained for specimens with 3% of ulexite.

gadolinium oxide, boron compounds, isothermal calorimetry, bending strength, compressive strength, mortar, neutron radiation, radiation shielding, radioactive waste