Performance improvement in neutron-shielding ultra-high performance mortar prepared with alkaline-treated boron carbide

Boron-containing compounds are known for their excellent radiation shielding capability against slow neutrons. To prepare an unalkaline and alkaline-treated industrial-grade boron carbide neutron-shielding radiation ultra-high performance mortar (UHPM) with varying cement replacement ratios, a modified Andreasen＆Andersen (A&A) model was employed for ratio optimization based on the tightest stacking design theory. The performance levels, compressive strengths, microstructures, pore structures, and other properties of the specimens were subsequently tested. The researchers utilized Monte Carlo simulation software (MCNP) to simulate the transmission rate, half-value layer, and macroscopic cross-section of the boron carbide UHPM and then evaluate its neutron radiation shielding capability. The results of this study indicate that the addition of unalkalized industrial-grade boron carbide decreased the compressive strength of the specimen, retained good flowability, and increased porosity. In contrast, alkaline-treated boron carbide overcame the adverse effects caused by the acid (at a 10% replacement rate, the strength of the alkaline-treated boron carbide UHPM increased by 20.8% relative to the unalkalized boron carbide) and optimized the pore structure. The addition of boron carbide significantly improved shielding in the UHPM specimens against slow neutrons but had limited effects on the shielding against fast neutrons. Thus, alkaline-treated boron carbide could be an effective and promising material for preparing high-strength neutron-shielding mortars.