Chloride Ion Corrosion Pattern and Mathematical Model for C60 High‐Strength Concrete after Freeze‐Thawing Cycles

Abstract

In this study, the porosities of C60 high-strength concrete after 0, 30, 60, and 90 freeze-thaw cycles determined via the water retention method are 1.30%, 3.65%, 5.14%, and 7.34%, respectively. Furthermore, a mathematical model of porosity varying with the number of freeze-thaw cycles is established. Using an artificial environment simulation experimental system and the natural diffusion method, the chloride diffusion law of C60 high-strength concrete after 0, 30, 60, and 90 freeze-thaw cycles is obtained. The corresponding diffusion coefficients are calculated based on the experimental results and Fick’s law, where 0.3431 × 10−12, 0.5288 × 10−12, and 0.6712 × 10−12, and 0.8930 × 10−12 m2/s are obtained, respectively, and a mathematical model of diffusion coefficient with freeze-thawing is established. Transport control equations comprising solution flow and solute migration control equations are established for chloride ions in concrete after freeze-thawing cycles. The equations consider the effects of freeze-thawing, solution pressure, solution concentration, solution density, convection, mechanical dispersion, and chemisorption on chloride ion transport in concrete. Using COMSOL numerical software, the transport control equations for chloride ions are solved using a real concrete numerical model, and the chloride ion corrosion process in concrete after freeze-thaw cycles is simulated. The simulation results are consistent with the experimental values.

Experimental Study on Durability of Hybrid Fiber-Reinforced Concrete in Deep Alluvium Frozen Shaft Lining

“…Frozen shaft lining concrete in deep alluvium has been used under a harsh engineering environment for a long time [14][15][16]. In addition to bearing loads, such as high ground pressure and freezing pressure, the built shaft was also faced with problems, such as water seepage, freezing, and thawing, and the erosion of harmful ions in groundwater [17][18][19][20]. Traditional high strength concrete has obvious deficiencies in impermeability, frost resistance, and corrosion resistance, which is difficult to be applied to such formation conditions as deep alluvium.…”