Progress in mechanical properties and frost durability of ultra-low temperature concrete
With the rapid growth in demand for clean energy sources like natural gas,the safe storage of lique-fied natural gas(LNG)has emerged as a significant challenge.Due to its excellent mechanical properties,con-crete has become an important engineering material for LNG storage structures.In recent years,the develop-ment of the LNG industry has also propelled research into the ultra-low temperature performance of concrete.The performance of concrete at ultra-low temperatures greatly differs from that at normal temperatures.Current studies indicate that the compressive and tensile strengths,as well as the elastic modulus of concrete,are signifi-cantly enhanced in ultra-low temperature environments.Scholars have developed various performance prediction formulas based on experimental results and have explained the mechanism behind the enhanced performance by considering the pore water-ice phase transition process.Ultra-low temperature freeze-thaw cycle experiment re-sults show that concrete has poor frost resistance at ultra-low temperatures,with a significant reduction in me-chanical properties after just a few freeze-thaw cycles.The existing conventional freeze-thaw testing methods do not meet the requirements for ultra-low temperature freeze-thaw conditions,and there is a lack of specific stan-dards for testing and evaluating concrete performance under these conditions.Moreover,due to differences in testing equipment and procedures,it is difficult to reference related achievements.Therefore,there is an urgent need to systematically summarize the existing experiment result of concrete performance under ultra-low tempera-ture freeze-thaw conditions,improve the relevant standards for concrete testing under special conditions,and fa-cilitate the development of research on ultra-low temperature concrete through in-depth analysis of a large amount of experimental data.To this end,this paper comprehensively summarizes and analyzes the progress in research on ultra-low temperature concrete testing platforms,mechanical properties at ultra-low temperatures,the mechanism of freeze-thaw damage under ultra-low temperature and large temperature difference conditions,and approaches to enhancing frost resistance and durability,both domestically and internationally.Based on the understanding and contemplation of the current state,future research directions for ultra-low temperature con-crete are proposed,aiming to provide references for experimental studies on ultra-low temperature concrete.
concreteultra-low temperaturefreeze-thaw cyclesmechanical propertymechanism of deterioration
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