Mechanical properties, radiation shielding and thermal resistance of UHPC containing colemanite aggregate and PVA fibers

Nuclear energy provides a vast application which includes energy generation and medical imaging that benefits hugely on our livelihood. However, this energy emits harmful radiation which requires shielding material for safe handling. Concrete has been widely used in nuclear-related structures and there is a gap of knowledge in the application of ultra-high performance concrete (UHPC) as radiation shielding concrete, especially in terms of shielding against neutron sources and thermal resistance. Colemanite and polyvinyl alcohol fibre (PVA) improve the neutron shielding and thermal resistance of UHPC but the combined effect of these materials requires further investigation. Hence, this research aimed to study this effect and coined the term ultra high-performance dense concrete (UHPdC) for UHPC with radiation shielding properties. Based on previous studies that produced UHPC against radiation shielding, three types of UHPdC are studied which include magnetite, barite and sand UHPdC. Aggregate of these UHPdCs are replaced with colemanite by 1, 5 and 10 %. Results show highest compressive strength and neutron shielding are achieved with 5 % replacement with colemanite in magnetite, barite and sand UHPdC despite the reduction in gamma radiation. Based on this mixture, PVA is introduced in the composition of each UHPdCs and exposed to heat of 800 oC. The inclusion of 0.5 % PVA fibre by-volume improve thermal resistance of all UHPdCs with reductions in residual mechanical and radiation shielding properties. Based on the survivability of a certain mix of UHPdCs atD 800 oC, a new batch of samples is exposed to 400 oC and tested for flexural and splitting tensile strength. Samples are also scanned using X-ray computed tomography (X-ray CT) to evaluate the effect of heat on the internal structure of UHPdC. Computer simulations using ANSYS and PHITS are conducted to validate the experiment and its application as dry cask storage. Results are compared with experimental based on the deflection and radiation shielding trend among the different type of UHPdCs.

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