Wang, Z.-S.; Li, Y.-K.; Lu, J.-L.; Tian, J.-B., and Zhao, K., 2020. Research on corrosion characteristics and performance degradation of basalt fiber concrete under sodium magnesium sulfate corrosion environment. In: Liu, X. and Zhao, L. (eds.), Today's Modern Coastal Society: Technical and Sociological Aspects of Coastal Research. Journal of Coastal Research, Special Issue No. 111, pp. 56–62. Coconut Creek (Florida), ISSN 0749-0208.As the most commonly used building material for marine structures, concrete is seriously corroded by marine environment. As a green, high-performance material, basalt fiber can improve the mechanical and corrosion resistance of concrete materials. The research conducted experimental research and analysis on the durability and mechanical properties of basalt fiber concrete under the erosion of magnesium sulfate and sodium sulfate. The test block is 100 mm × 100 mm × 100 mm, and the fiber content is 0%, 0.05%, 0.1%, 0.2%, 0.3%, respectively, soaked in the magnesium sulfate and sodium sulfate solution with a concentration of 5.0%. The apparent cracks and water absorption were observed every 30 days. The mechanical properties and the ion concentration were measured every 90 days. The main conclusions are as follows: basalt fiber has a certain increase in the bearing capacity and deformability of concrete. Compared with ordinary concrete in a sulfate environment, basalt fiber concrete has a slower increase in porosity; however, excessive fiber will adversely affect durability. When the basalt parameter is about 0.1%, it is the most economical and reasonable, this study will provide a certain research basis for the application of basalt fiber concrete in marine structures.

Thin-walled concrete-filled steel tubes are efficient and economical with promising applications in civil and light industrial buildings. However, their local buckling resistance and deformation capacity are low, which adversely affects the seismic safety of structures. There are relatively few studies on thin-walled concrete-filled steel tubular columns with ultra-large diameter-to-thickness ratios, and there is also a lack of relevant experimental research on them. In this study, horizontal hysteresis tests were conducted on concrete columns with a large diameter-to-thickness ratio. The seismic performances of regular and straight-ribbed specimens were analyzed and compared, including the analyses of load-displacement hysteresis curves, strain distribution, skeleton curves, ductility, and energy dissipation capacity. Using these results, a restoring force model for concrete columns with a large diameter-to-thickness ratio was established. The findings indicate that under horizontal loading, the ductility of concrete columns with a regular thin-walled steel tube is 3.9, with an equivalent viscous damping coefficient of 1.65. Meanwhile, the ultimate bearing capacity is 201 kN. After adding stiffening ribs, the ultimate bearing capacity reaches 266 kN and the ductility coefficient reaches 4.4, resulting in the stiffeners increasing the ultimate bearing capacity and ductility by >30% and 12.8%, respectively. However, they have a less pronounced effect on deformation and energy dissipation. Building on these research outcomes, we propose a dimensionless three-line skeleton curve model and a restoring force model. The calculation results from these models align well with the test results, offering valuable insights for the seismic safety analysis of real-world engineering structures.

The concrete structure will be seriously eroded in a sewage environment, causing substantial economic losses. Therefore, it is of great significance to repair the existing corrosion structure. In order to quickly restore the mechanical properties and enhance the durability performance of eroded concrete structures, this paper develops a new composite high-durability mortar by adding polypropylene fibers, basalt fibers and impermeable agents, which can achieve the dual requirements of structural repair and protection. For the new material, this test set up a total of five groups of mixing ratios. This test analyzed the water absorption, mass loss rate, compressive strength and other performance indicators of the test block in the corrosive environment, and scanned and studied the microstructure of each mortar test block after corrosion. It was found that the new anti-corrosion mortar has relatively less crystallization, dense internal structure, and significantly lighter erosion. From the mechanical properties, the strength of ordinary polymer mortar after erosion decreased by 6%; high-durability mortar instead improved the strength by nearly 20%, showing better resistance to erosion. Taken together, the use of mineral dopants and water repellents can effectively enhance the strength and corrosion resistance of mortar, and the cost is low, with good prospects for engineering applications.

Reinforcement treatment for the damaged structure can guarantee the continued safe use of the building. This paper proposes a new prestressed column reinforcement technology for traditional steel structure reinforcement technology by using space profile steel structure instead of angle steel and combining prestressing technology and bolt connection. According to different constraint forms, 4 types of members were designed, and the eccentric compression test and finite element parameter analysis were carried out. The experimental study found that, after being reinforced by prestressed lattice steel, the ultimate load-carrying capacity of the specimen was increased by 49.2%, stiffness by 28%, and deformation capacity by 15%. Compared with the traditional angle steel reinforcement, the reinforcement effect is improved by more than 20% under the same cross-section steel consumption condition. Prestressing can significantly improve the utilization of steel, and steel strain increases by about 30%. At the same time, applying prestressing can improve the stress state of the concrete and steel rebar of the core column. The various parts of the reinforced specimen work together better, and the integrity is enhanced. Based on the test, a parametric analysis was carried out, mainly considering the effects of material strength, eccentricity and steel plate thickness. It was found that increasing the thickness of lattice steel can effectively improve the specimen bearing capacity and ductility, and the strength ratio of reinforcement to lattice steel is about 0.16. However, increasing the strength of steel does not have a significant effect on the bearing capacity. The deformation capacity occurs to be reduced, and using high-strength steel is not recommended. By applying prestressing, stronger restraint can be provided to the reinforced columns, and the reinforcement effect is significantly better than that of angles, which has better engineering application value.