Influence of gadolinium oxide and ulexite on cement hydration and technical properties of mortars for neutron radiation shielding purposes

摘要

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. (C) 2018 Elsevier Ltd. All rights reserved.