The diffusion of sulfate (SO₄²⁻) and chloride (Cl⁻) ions from rivers, salt lakes and saline soil into reinforced concrete is one of the main factors that contributes to the corrosion of steel reinforcing bars, thus reducing their mechanical properties. This work experimentally investigated the corrosion process involving various concentrations of NaCl-Na₂SO₄ leading to the coupled erosion of concrete. The appearance, weight, and mechanical properties of the concrete were measured throughout the erosion process, and the Cl⁻ and SO₄²⁻ contents in concrete were determined using Cl⁻ rapid testing and spectrophotometry, respectively. Scanning electron microscopy, energy spectrometry, X-ray diffractometry, and mercury porosimetry were also employed to analyze microstructural changes and complex mineral combinations in these samples. The results showed that with higher Na₂SO₄ concentration and longer exposure time, the mass, compressive strength, and relative dynamic elastic modulus gradually increased and large pores gradually transitioned to medium and small pores. When the Na₂SO₄ mass fraction in the salt solution was ≥10 wt%, there was a downward trend in the mechanical properties after exposure for a certain period of time. The Cl⁻ diffusion rate was thus related to Na₂SO₄ concentration. When the Na₂SO₄ mass fraction in solution was ≤5 wt% and exposure time short, SO₄²⁻ and cement hydration/corrosion products hindered Cl⁻ migration. In a concentrated Na₂SO₄ environment (≥10 wt%), the Cl⁻ diffusion rate was accelerated in the later stages of exposure. These experiments further revealed that the Cl⁻ migration rate was higher than that of SO₄²⁻.

Chemical erosion of reinforced concrete by Cl⁻, SO₄²⁻ and Mg²⁺ in saline soil is the main factor of steel corrosion and concrete damage. In this study, the effects of different molar ratios of aqueous NaCl-MgSO₄ on concrete macroscopic properties (appearance, weight change, compressive strength, and dynamic elastic modulus), ion content, microstructure, and porosity of concrete were investigated. The effects of different molar ratios on the macroscopic characteristics and erosion depth of concrete were revealed through concrete appearance, weight, mechanical properties, and SO₄²⁻ and Cl⁻ content. Analysis of the microstructural evolution process and complex mineral composition of concrete using various microscopic testing methods. The results showed that with increased salt concentration and erosion time, the weight change rate, compressive strength change rate, and relative dynamic elastic modulus of concrete samples had a trend of first increasing and then decreasing. The evolutionary process of transition from large pores to medium and small pores and then to large pores. In the early erosion stage, with increased MgSO₄, corrosion products were deposited in pores and cracks, which refined the concrete pore structure and reduced ion diffusion speeds of Cl⁻, SO₄²⁻, and Mg²⁺. In the later erosion stage, corrosion products caused matrix damage and produced intersecting cracks, which promoted ion diffusion rates and induced deterioration of concrete macroscopic properties. During experiments, the binding ability of SO₄²⁻ and Mg²⁺ ions to hydration products was found to be higher than that of Cl⁻.

Rock wool board (RWB) is widely used in construction of exterior insulation worldwide. Fiber diameter, solid volume fraction (SVF), and contact degree among the fibers significantly influence the RWB physical properties. Herein, the effects of these factors on the mechanical properties of RWB were investigated using the GeoDict software. First, the fiberization process resulted in a finer fiber diameter, and the SVF of RWB increased with decreasing pore sizes. In addition, both the fiber diameter and SVF significantly influenced the RWB shear strength. Furthermore, in compliance with the Chinese standards of compression, tensile, and shear strength, the SVF of RWB with a 10.5 μm fiber diameter did not exceed 4.72%, 4.04%, and 5.4%, respectively. The novel method proposed herein can be used for optimizing the RWB manufacturing process.

Traditional rock wool fibres are susceptible to crystallization and pulverization. To mitigate this, glass fibres were produced from iron ore waste (IOW). When the ratio of Fe²⁺ and Fe³⁺ is 1:3 and the Al₂O₃ content is 10 wt.%, increasing the Fe_xO_y content enhances the thermal stability.At an Fe_xO_y content of 17–19% and an Al₂O₃ content of 10–13%, the glass transition temperature (Tg) peaked. Increasing the Fe_xO_y content from 10% to 20% enhanced the stability of Si-O and Al-O bonds and increased bridged oxygen, stabilizing the structure. Here, Fe²⁺ balances structural charges, while Fe³⁺ replaces some Al atoms in the network. When the Al₂O₃ content is 10–13% and the Fe_xO_y content is 17–19%, the thermal stability of the IOW rock glass reaches its optimal level. At 20% Fe_xO_y content, the structure becomes three-dimensional and cyclic, increasing polymerization. Consequently, incorporating Fe_xO_y alongside a 10% Al₂O₃ content improves thermal stability, supporting the development of high-stability rock wool from IOW. This approach also enhances the refractory properties of rock wool fibres within the Fe_xO_y-Al₂O₃-SiO₂-MgO-CaO system.

Prediction of Thermal Conductivity of a Rock Wool Board by Computer X-Ray Tomography Technique Scanning and Random Generation-Growth Model: Thermal conductivity of rock wool boards was investigated in this study. Although distribution of fibers in a realistic rock wool board is unclear, it can be simulated by computer X-ray tomography technique (CT) followed by rearrangement through the random generation-growth (RGG) model. An ideal CT-RGG structure model of rock wool boards (CT-random generation-growth model) was established by simplifying material properties based on the mesostructure parameters of the RGG model. Thermal conductivity of rock wool boards with different apparent densities and fiber diameters was studied, and the CT-RGG model was analyzed by explicit jump (EJ) diffusion equations solved by the fast Fourier transform method. We found that thermal conductivity of a single rock wool fiber can be successfully determined. Simulation and measurement results show that thermal conductivity increases consistently with the increase of apparent density and fiber diameter, particularly when the apparent density of rock wool board is greater than 140kgm⁻³. Compared with the existing theoretical models, the proposed method does not depend on the empirical parameters; therefore, it is useful in designing and optimizing the thermal conductivity of rock wool boards.

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