Effects of calcium sulfate whiskers and basalt fiber on gas permeability and microstructure of concrete

Abstract

This paper aims to investigate the influence of introducing calcium sulfate whiskers (CSW) and basalt fiber (BF) on the gas permeability coefficients of concrete. Employing the Cembureau method, the research quantifies gas permeability while utilizing Nuclear Magnetic Resonance (NMR) to precisely measure pore structure parameters. The results highlight that the incorporation of CSW leads to a substantial reduction in gas permeability, exhibiting a remarkable 57.6% decrease when utilized at a dosage of 3.0 kg/m³ compared to the standard concrete. In contrast, the introduction of BF at the same dosage does not yield a commensurate reduction in permeability. Notably, the combined application of CSW and BF at 3.0 kg/m³ each yields the most effective mitigation of gas permeability. Furthermore, the judicious addition of either CSW or BF demonstrates the capacity to diminish the overall porosity of concrete, alongside a reduction in the proportion of harmful pores (R100, featuring diameters larger than 100 nm). Optimal outcomes manifest when both CSW and BF are introduced at the 3.0 kg/m³ dosage, effectively minimizing R100 and the gas permeability coefficient. It is interesting to find that in comparison to the correlation observed between the total porosity and gas permeability of concrete, the relationship between the proportion of R100 and gas permeability emerges as more statistically significant (R2 approximately 0.800), especially for CSW concrete. This can reveal the interconnection between the concrete's pore structure and its gas permeability characteristics more appropriately.