Research On Technology And Quality Control Of Highway Structural Concrete In Seasonal Frozen Regions

In seasonal frozen regions, natural environments for concrete bridge structures are complicated. Serious damages are prone to appear which influence the durability of bridge. In this thesis, anti-freezing, durability evaluation and construction quality control of concrete were conducted and demonstrated.The main research contents are as follows:(1) Disease investigations of express way and ordinary highway bridge in Jilin Province were carried out, and the causes were analyzed. The main influence factors for concrete durability included improper design of anti-permeability and anti-freezing abilities, loosely control of construction process and freeze-thaw effects.(2) Aiming at the limitations of mixture design method for ordinary concrete, a skeleton dense packing theory-based method was proposed for anti-freezing design.Taking air content and compressive strength as evaluation indices, the optimal dosages of mineral admixtures were determined according to orthogonal test method.(3) Water freezing test and salt freezing test are carried out. Torrent Permeability Tester and Autoclam Osmotic Pressure Tester were adopted to measure the relationship between air permeability, water permeability and concrete durability, the field NDT methods of concrete durability was then proposed which provide a technical support for fast and quantitative evaluation of the durability of the in-service concrete structures.(4) The effects of the main factors on construction quality of structural concrete in seasonal frozen regions were analyzed. Based on the labiratiry tests and site investigation,the key technology of construction quality control for structural concrete was proposed. For comparision, the performance of quality control in the field concrete project were conducted as well.(5) Ning-jiang Songhua River Bridge on the highway from Daqing to Guangzhou was selected as the actural project. Concrete mix ratio was optimized with fly ash and efficient air-entraining superplasticizer. The field permeability testing and two-year follow-up observations verified the validity and accuracy of the proposed techniques.