High-consistency heavyweight concrete containing magnetite and steel shot for ion therapy shielding in a full-scale mockup: dynamic segregation, microstructure analysis, and thermal monitoring
摘要
The land costs and spatial limitations in urban areas often prevent the use of thick concrete elements in particle therapy facilities. Hence, heavyweight concrete (HWC) is a practical solution. This study evaluates the production feasibility of high-consistency magnetite and steel shot heavyweight concrete with 4200 kg/m3 and 4500 kg/m3 target dry densities in full-scale mockup. The results showed that for section with 2.5 m height and 4500 kg/m3 target dry density, the dynamic segregation was allowable up to 1 m height, and for section with 4200 kg/m3 target dry density was allowable up to 4. Also, variations in density have more effects on HWC dynamic segregation than variation in height. Thermal analysis results during hydration process revealed that HWC with 395 kg/m3 cement, 2 m thick, and containing steel shot and magnetite can be act as not mass HWC. The microstructure analysis results based on visual inspection showed that a new ITZ zone surrounding steel shot which is quite different from magnetite and tentatively termed a " two-part ITZ". In addition, it seems that steel shot with looser ITZ compare with magnetite is the reason for reduction in HWC mechanical properties.