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 degrees C, 20 degrees C, 40 degrees C, and 60 degrees 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 D-1 and D-2. 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.