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Abstract
The mechanical properties of the static and dynamic compression of concrete eroded by a 15% sodium sulfate solution were explored with a 70-mm-diameter true triaxial static-dynamic comprehensive loading test system, and an analysis of the weakening mechanisms for the degree of macroscopic damage and microscopic surface changes of eroded concrete were conducted in combination with damage testing based on relevant acoustic characteristics and SEM scanning. The experience obtained in this paper is used to analyze and solve the problem that the bearing capacity of concrete buildings is weakened due to the decrease in durability under the special conditions of sulfate erosion. The results showed that, in a short time, the properties of concrete corroded by sulfate solution were improved to a certain extent due to continuous hydration. When the corrosion time was prolonged, the internal concrete structure was destroyed after it was eroded by sulfate, and its dynamic and static strength, deformability, and energy absorption were reduced to differing degrees, thus greatly inhibiting the overall mechanical performance of concrete; the dynamic compressive strength changed with strain that exhibited a significant strain rate effect; and, under the influence of sulfate erosion and hydration, the longitudinal wave velocity increased first and then decreased. The longitudinal wave velocity was slower than that of concrete under normal environment and distilled water immersion condition. SEM and acoustic wave analysis indicated that the internal concrete structure was destroyed after it was eroded by sulfate, and its dynamic and static strength, deformability, and energy absorption were reduced to differing degrees, thus greatly inhibiting the overall mechanical performance of concrete.
Highlights
The erosion of concrete by sulfate is mainly reflected in its destruction of the calcium silicate hydrate gel, which leads to the disruption of the original internal structural balance of concrete
By reducing the erosion of salt for concrete and improving the service time of concrete, it avoids the interference to the normal work of sulfate corroded concrete, reduces the waste of concrete caused by repeated construction of damaged parts due to erosion, and makes a small contribution to the sustainable development and reduction in carbon dioxide emissions to promote green and low-carbon construction mode
The test sample in alcohol concentration for 48 hours soaked in 70% alcohol solution was observed, and soaking by alcohol solution was performed to remove surface impurities affect the follow-up observations to improve the electrical conductivity of the sample surface, and to facilitate follow-up observations, using Leica in Germany production SCD500 type high vacuum coating apparatus coating on concrete specimens
Summary
Concrete is universally used in both industrial and civil construction as a building material due to its low cost, convenience, excellent compressive performance, and easy access to components. Buildings located in coastal areas [6,7] and saline-alkali areas are affected by various factors, such as saline solution and steam, for a long time under special circumstances due to their unique geographical location or environment, among which sulfate erosion is one of the more common erosion factors [8,9] Within these conditions, sulfate erosion will compromise several of concrete’s mechanical indices and, for relevant construction projects and marine works, the durability of the overall structure will be reduced due to the sulfate eroding concrete, leading to a weakened concrete that threatens lives and property. In most current analytical methods for studies on the dynamic effects of sulfate on concrete, SEM or XRD [26,27] was used for analysis and interpretation from a microscopic aspect, or existing damage detection methods, such as acoustic emissions, are used for relevant analyses [28,29]
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