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 (B 2 O 3 ), lead oxide (PbO), bismuth oxide (Bi 2 O 3 ), and tungsten oxide (WO 3 ) 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. WO 3 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, WO 3 -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.% B 2 O 3 achieved the lowest Total Effective Dose Rate (TEDR) of 17.20 mSv/min, a 70.88% reduction compared to the control. WO 3 also showed balanced shielding effectiveness (TEDRs: 26.43-28.27 mSv/min). Microstructural analysis confirmed the inert nature of PbO, Bi 2 O 3 , and WO 3 , while B 2 O 3 exhibited chemical interaction, forming boric compounds. WO 3 emerged as the most balanced additive, offering a synergistic enhancement of structural integrity, durability, and comprehensive radiation protection under realistic mixed-field conditions.