| Crack is a common problem in concrete project which is difficult to solve, and also is thefocus performance of concrete structure diseases and defects. Alpine region has low annualaverage temperature, a large diurnal temperature range, strong ultraviolet radiation and dryclimate. These factors greatly exacerbate the plastic shrinkage, autogenously shrinkage,drying shrinkage, cold contraction of concrete.Therefore, the study of repair materials, technologies and processes of concrete crack inalpine regions and how to take effective repair techniques to prevent cracks in the furtherdevelopment to maintain the use performance of concrete structures has important practicalsignificance in the process of improving the durability and service life of concrete structure.The main work and achievements of the paper include the following aspects:（1）By the field investigation and classification, we can say that, non-structural crackmainly exists in the pier of the bridge and the shrinkage crack has a large proportion in thesenon-structural cracks. Either structural cracks or non-structural cracks exist in the tunnel. Inthis paper, we put forward the hazard of the concrete crack and how to control it. And tonon-structural crack, it could lead to the corrosion of the reinforcement、 the carbonation ofthe concrete and reduced the service life of the concrete. While to the structural crack, it maydo harm to the bearing capacity of the concrete structure. So, to the control of the concretecrack, we should consider from three aspects at the same time, including material、design andconstruction, and this shoud control from start to end.（2）Width and depth of typical crack in bridges and tunnels in the alpine region aretested, and also make statistical analysis and characteristic analysis of crack width, depth andalignment. Through the method used in the determination of PH value, This paper sets up thecorresponding relationship between crack width and the durability of carbide, and putsforward that0.21mm is the allowable width limit of railway bridge in cold area,on the basisof steel passivation membrane failure with PH=12.0.Influencing factors includingenvironmental factors, moisture curing, freezing and thawing, chlorine environment andconcrete material were analysed respectively.（3）Compared with the ordinary commercial flexibility fluorocarbon aging, modifiedFEVE fluorocarbon coating for crack closure is good aging, and has strong adhesion, hightensile strength and elastic characteristic; polymer cement composite coating has goodelasticity, strong cohesive force, good durability, etc. Flexible epoxy resin and polyurethanewhich is used in crack grouting satisfy the requirements of grouting materials technology under the special circumstances in alpine region, especially improve the elongation at breakand adhesive strength obviously.This paper puts forward an overall repair scheme aboutconcrete crack of bridge piers in alpine region. Concrete cracks are dynamically monitored fora long-term; and plateau adaptability of crack repair materials is made selective experiments.（4）Compressive strength and tensile strength of colloids are studied, thoughcomparative analysis of the experimental results we can know that: the compressive strengthof modified concrete perfusion colloid decreases, but its influence on compressive strength ofcolloid is not very big. The tensile strength and elongation of modified perfusion are allimproved. According to the study of reasons of concrete cracking and repair technology ofpiers and tunnels in alpine region, concrete cracks of piers and tunnels in alpine region aremade on-site repairing experiments. |
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