Study On Key Techonoioies Of Fair-faced Concrete In Subway Station

Fair-faced Concrete is gradually being valued and applied by virtue of the environment-friendly,low overall-cost,good artistic perception of the advantages.However,reinforced concrete structures are standing acid tests such as gas permeability environment of very high temperament,by using of concrete structures,from wind,temperature changes,rich in chloride ions and other corrosive ions under the common action of the atmosphere and water environment,there are serious problem to Fair-faced Concrete structure.The conventional design based on bearing capacity limit states as well as normal deformation and the crack checking cannot meet the requirements.The durability of material and structure must be considered during design and construction.In view of this situation,the quality of the concrete is evaluated in this paper.Methods were analyzed and studied.This article combines the construction needs of Qingdao subway station,we carried out the following research work:Firstly,The experiment uses a large amount of mineral admixture system,according to the regression analysis of the compressive strength of concrete and the amount of cementitious material used,the linear relationship between the amount of concrete cementing material and the compressive strength of each cementitious material system is obtained,and the reference ratio of concrete is calculated.According to the price of concrete materials in Qingdao area,the cost of concrete in each cementitious material system is calculated,and to choose which one is the best in project costs.The results show that C series is the best cost concrete series.Secondly,We have studied the durability of the series of Fair-faced concrete with the optimized ratio.The research results shows that The hydration reaction rate of cementitious material has the greatest influence on the chloride ion permeability of concrete during the curing of concrete to 28 days.The total amount of cementitious material has the greatest influence on the chloride ion permeability of concrete;In the concrete carbonization test to 28 d,the hydration reaction rate of cementitious material has the greatest impact on the carbonation resistance of concrete.When the carbonization test is carried out to 56 days,the alkali storage capacity of the concrete structure has the greatest influence on the carbonation resistance of the concrete.In the freeze-thaw cycle to 400 times when the concrete appearance integrity is better,the cementitious concrete system under the solid concrete modulus relative to the elastic modulus of more than 85%,the mass loss rate of 3% or less,frost resistance performance good;The relationship between the shrinkage of concrete in different cementitious materials is as follows: D> C> B> A.Thirdly,The paper puts forward the framework of evaluation of the appearance quality of clear water by using image gray-scale analysis technique and bubble content.The surface quality of C50 strength grade concrete model wall of C series cementitious material system is analyzed.The results show that the color consistency of the wall is good,but there are occasional large pore holes appears,and the quality of vibrator needs to be improved.