Comprehensive evaluation of microparticle-modified cement mortars: microstructural analysis, thermal fatigue, and mix-field radiation shielding

This study investigates the multifunctional performance of cement mortars modified with microparticles of boron oxide (B2O3), lead oxide (PbO), bismuth oxide (Bi2O3), and tungsten oxide (WO3) at varying dosages (1-5 wt.%), with a goal to improve mechanical strength, thermal fatigue resistance, and radiation shielding against both primary and secondary products. Among all additives, mortar modified with 3 wt.% PbO exhibited the highest 28-day compressive strength of 47.6 MPa (55.56% more than the control) due to its dense particle packing. WO3 addition resulted in a 35.94% increase in strength at 2 wt.%, attributed to its fibrous morphology and improved matrix interlocking. Under thermal fatigue testing, WO3-modified mortars exhibited superior durability with only 12.36% strength loss after 400 cycles, compared to 20.26% for the control. Radiation shielding study revealed that 2 wt.% B2O3 achieved the lowest Total Effective Dose Rate (TEDR) of 17.20 mSv/min, a 70.88% reduction compared to the control. WO3 also showed balanced shielding effectiveness (TEDRs: 26.43-28.27 mSv/min). Microstructural analysis confirmed the inert nature of PbO, Bi2O3, and WO3, while B2O3 exhibited chemical interaction, forming boric compounds. WO3 emerged as the most balanced additive, offering a synergistic enhancement of structural integrity, durability, and comprehensive radiation protection under realistic mixed-field conditions.