Preparation And Properties Of Anti-disturbance Super Early Strength Concrete For The Repair Of Expansion Joints

Bridges,as one of the important infrastructure facilities in modern transportation,play a crucial role in the development of the transportation industry.However,bridge expansion joints,as one of the important structures of bridges,are prone to serious damage and premature failure under complex environmental conditions and traffic loads,which seriously affects the service life of bridges.Therefore,the maintenance of bridge expansion joints is an important challenge in modern infrastructure maintenance and construction.To reduce the impact of maintenance on traffic,the construction method of half-open traffic is usually adopted during the repair of bridge expansion joints,which involves the deterioration of newly mixed concrete due to vehicle-bridge coupled vibration.In view of this,the development of disturbance-resistant materials for repairing bridge expansion joints is of great significance for improving the level of maintenance and repair technology and reducing traffic interference.The paper proposes simulation standards for vehicle-bridge coupled vibration and a quantitative evaluation index for concrete disturbance.From the perspective of the influence and synergistic mechanism of multi-component cement on the hydration process of composite cementitious systems,the paper explores the strength development law of multi-component composite cement and auxiliary cementitious materials,introduces a regulating component to optimize the composite cementitious system,designs a mix proportion for disturbanceresistant ultra-high early strength concrete,and further evaluates the mechanical and durability performance of disturbed concrete,investigating the evolution law of performance damage of early strength concrete under different disturbance mechanisms.Finally,the composition of disturbance-resistant ultra-high early-strength concrete is optimized again,and reasonable suggestions for the construction of bridge expansion joints are proposed based on actual engineering.Experimental studies have found that:(1)SAC content has a great influence on the early strength of the SAC-P·O compound cementitious system.With the increase of SAC content,the early strength of the SAC-P·O composite system increased significantly,but the later strength increased slowly.After that,50 % SAC compound system was selected,and an appropriate amount of retarder was added to meet the construction requirements.It was found that tartaric acid had the best retarding effect on the compound cementitious system in the range of 0.1 % ～ 0.4 %.(2)The influence of early disturbance on Anti-disturbance super early strength concrete is much less than that of ordinary concrete,so the Anti-disturbance super early strength concrete has good anti-disturbance performance.For ordinary concrete,the disturbance in the setting and hardening period can improve the compressive strength of concrete,reduce the bending and tensile strength,and bond strength,and increase the segregation phenomenon.Especially,the disturbance in the middle stage of setting and hardening has adverse effects on the flexural strength and segregation degree of concrete.However,applying disturbance from the initial stage of concrete setting and hardening can reduce the influence of disturbance on the deterioration of concrete in the middle stage of setting and hardening.(3)Compared with ordinary concrete,anti-disturbance ultra-early strength concrete has poor frost resistance due to rapid hydration and loose structure,but adding 0.02 % air entraining agent can significantly improve its frost resistance.At the same time,it is found that the disturbance environment has little effect on the frost resistance,chloride ion penetration resistance and wear resistance of disturbed ultra-early strength concrete,but has a great influence on ordinary concrete,and the disturbance deterioration in the middle stage of setting and hardening is the most significant.