Study On Appearance Quality Control And Evaluation System Of Precast Concrete T Beam

The application of prefabricated T-beams in bridges is extremely common,and the requirements for the appearance quality and durability of concrete structures are also increasing.However,there are common defects in appearance quality of domestic concrete bridge structures.Therefore,how to quickly and systematically evaluate the appearance quality of prefabricated beams can provide a basis for appearance quality control.Combined with the prefabricated T-beam project of the North Approach Bridge of Guandu Yellow River Bridge,this paper studies the appearance quality evaluation system of precast beams,aiming to propose an appearance quality evaluation method with good systemacity and strong maneuverability.The main contents of this paper are as follows:(1)Appearance quality control technology has been formed throughout the entire process of prefabricated T-beam construction.Combined with the prefabricated T-beam construction process,the paper has formed 6 patents including the T-beam ribbed slab reinforcement binding limit device,the T-beam truss plate steel positioning jig,the T-beam reinforcing steel classification storage device,the T-beam wing plate steel hoisting truss,the T-beam hoisting corner guard devices and prefabricated beam storage and transported frames.In combination with the construction process,the "1+6" intelligent spray energy curing method and the large circulating grouting method are formed for the T-beam health.The two construction methods have been awarded provincial level construction methods in Henan Province and were promoted in Henan.The formation of the prefabricated T-beam construction process appearance quality control technology has based on the selection of concrete raw materials,optimization of concrete mix ratio,template system selection,steel engineering,proper concrete pouring,reasonable maintenance,prestress control and other prefabricated T-beams such as beam preserving and transporting girder.(2)A prefabricated T-beam concrete appearance quality assessment system has been established.Through reviewing a large number of documents,visiting experts,and communicating with the site,based on the "Standards for the Assessment of Highway Bridge Technology Status"(JTG/T H21-2011),a prefabricated T-beam concrete appearance quality assessment system has been built.The system includes the contents concerning structure level,appearance level and appendages.Among them,the structural level focuses on the five aspects,that is,concrete rebound strength,protective layer thickness(leakage),cracks,structural line shape and structure size and they need to be measured by means of portable equipment.The appearance level includes four aspects: concrete honeycomb surface,peeling off angle,hole cavity,sand line and chromatic aberration(including rusty spots),which can be observed by visual observation.In addition,the appearance quality of the reserved steel bars and embedded parts is included to comprehensively reflect the appearance quality of the prefabricated beams.According to the results of these 10 categories of individual assessments,the quality of the concrete appearance is finally assessed.The evaluation system is used to evaluate the appearance quality of the prefabricated beams on site.There are no five types of beams in the prefabricated beams of the North Approach Bridge.The fourth type of beams only accounts for 0.1% whereas the first type of beams takes up more than 80%.Besides,the first type of beams and the second type of beams account for more than 90%.This shows that the prefabricated beam on site is of good quality.(3)The Guide for Appearance Quality Control of Prefabricated Beams of Guandu Yellow River Bridge has been compiled.The guide has been successfully applied in the production of this project,which effectively guarantees the appearance quality of precast T-beams and improves the pre-production efficiency.Moreover,the guide is promoted and applied within the bureau.This paper provides a strong technical support for the successful construction of the North Approach Bridge of Guandu Yellow River Bridge,and can also provide reference for the appearance quality control of similar prefabricated structures.