Preparation Of Quick Repair Concrete For Bridge Expansion Joints And Durability Study

Expansion joint is an important part of the bridge structure and plays an important role in regulating the displacement and linkage between the bridge superstructure caused by factors such as vehicle loads.However,heavy traffic and environmental impacts lead to damage to the expansion joint,in order to reduce the adverse impact of repair works on traffic,uninterrupted traffic is mostly used.However,the coupled disturbance of the bridge can cause deterioration in the performance of the repair concrete,posing a significant challenge to its serviceability.Therefore,it is important to prepare a high performance bridge expansion joint repair concrete and to study the effect of traffic disturbance on its performance.In this paper,a new chlorine-free accelerator（NCA）for bridge expansion joint concrete was prepared through one-component and compounding tests.The effect of NCA on the macroscopic properties of concrete was investigated in terms of concrete setting time,compressive strength and shrinkage performance under the optimal proportion.Preliminary exploration of the mechanism of action was conducted through hydration heat and XRD analysis methods,and a conceptual model of early strength mechanism was established.The orthogonal test was used to optimise the baseline ratio of bridge expansion joint quick repair concrete.The water-cement ratio,fly ash replacement,early strength agent admixture and sand rate were used as the four influencing factors.The results were analysed by the efficacy function method,taking into account the workability,mechanical properties,bonding properties and shrinkage properties,to select the best overall bridge expansion joint quick repair concrete ratio.Concrete shakers were used to simulate coupled axle disturbances,and simulation tests of concrete disturbance for rapid repair of bridge expansion joints under different disturbance mechanisms were carried out.Then,the evolution of the properties of concrete for rapid repair of bridge expansion joints under different disturbance mechanisms was analysed.Finally,based on the fuzzy hierarchical comprehensive evaluation method and mathematical and statistical hypothesis testing principle,the evaluation method and evaluation model of the bridge expansion joint quick repair concrete anti-disturbance performance were established to characterize the magnitude of the concrete anti-disturbance performance.The proposed evaluation model was applied to verify its operability and accuracy.The results show that the optimum dosing ratios of NCA were 0.52%for A,0.46%for B,3.21%for C and 0.07%for D.The incorporation of NCA can promote the hydration of C₃S,provide additional nucleation sites,reduce the crystal precipitation energy barrier,promote the hydration process of cement and increase the strength of cementitious materials.The orthogonal test and the efficacy function method recommended the best ratio for bridge expansion joint quick repair concrete as follows:water-cement ratio 0.34,fly ash replacement 15%,early strength agent 6%and sand rate 32%.The results of concrete performance tests under different disturbance conditions show that concrete subjected to low disturbance during the initial to final setting time didn’t cause damage to performance,but rather improved the uniformity of aggregate distribution,which can increase the early compactness of concrete and improve the overall performance of concrete.When the disturbance energy was higher,the internal homogeneity changed and the concrete performance deteriorated,the higher the disturbance energy,the more serious the deterioration.