Radon emission characteristics and pore structure evolution of self-compacting concrete with silica fume-molybdenum tailings under different curing environments

Reducing the radon emission rate on the surface of self-compacting concrete prepared from industrial solid waste is crucial to lowering the risk of human lung cancer. This study prepared four types of self-compacting concrete with a composite cementitious system of silica fume and molybdenum tailings. The effects of various curing temperatures (0 °C, 20 °C, 40 °C, and 60 °C) and amounts of molybdenum tailings substitution on the pore structure, microstructure, compressive strength, and radon emission characteristics of self-compacting concrete were studied. Additionally, using Low-Field Nuclear Magnetic Resonance (LF-NMR), a segmented fractal analysis of the pore structure of self-compacting concrete within various pore size ranges was carried out. The findings suggest that raising the curing temperature and using a suitable quantity of molybdenum tailings enhance self-compacting concrete's compressive strength and the microstructure's density, while decreasing the porosity and radon emission rate. The variation in the micro-pore structure resulting from the aggregation of C-S-H gels strongly correlates with the radon emission rate. This association is evident through decreased porosity and increased fractal dimensions D₁ and D₂. This results in a denser microstructure of self-compacting concrete, weakening the connectivity of microcracks and pore throats, thereby reducing the transport pathways for free radon and lowering the radon emission rate.