| This article from the TianJin BinHai metro line B1's geographical location,environmental conditions and environmental water on concrete and steel bar corrosion study,the purpose is to develop to meet the project and the indicators of high performance concrete durability.According to the relevant domestic specifications and the relevant literature at home and abroad,the basic durability parameters such as strength,electric flux and chloride ion diffusion coefficient of subway engineering concrete were discussed.The research results show that:Chloride environment for the durability of the project control environment,the environmental effects grade according to the working environment of concrete structure is divided into?-C and?-D;The main corrosive ions in ambient water are Cl-,SO42-and Mg2+.It is weak to strong corrosive to concrete and medium to strong corrosive to steel bar under dry and wet alternating conditions.Identified the project for C45 and C50 concrete strength,the main structure of station using cast-in-place concrete for C45,interval of shield lining segments using C50 concrete,C45 concrete chloride ion diffusion coefficient?28d?DRCM?5×10-12 m2/s.The chloride ion diffusion coefficient?28d?DRCM of C50 concrete is less than or equal to 3×10-12 m2/s.The quality of concrete raw materials was tested and analyzed by selecting 5concrete mixing stations which could provide concrete for the project.The results show that the quality of cement,fly ash,mineral powder,sand and stone used in the five concrete mixing stations meet the requirements of relevant specifications.According to field investigation,the sand in most concrete mixing plants is too fine,and the mud content varies greatly from high to low.The content of pebbles varies greatly,sometimes they are very clean,sometimes the soil is mixed,and the pebbles are not well shaped,and there are many needle-like particles.The reasonable composition of cementitious materials was determined by the experiments of clean slurry fluidity,mortar fluidity and strength.Then through the strength and durability test of concrete,the concrete mix ratio satisfying the requirements of the project is determined.The test results show that:?1?Beads and?grade fly ash has the water reducing effect,but?grade fly ash+cement+Slag powder composite water reducing effect than beads+cement+Slag powder,contribution to the strength is also similar.?2?When the dosage of air attractant is constant,the air content of concrete is closely related to the fluidity of concrete,and the air content of high-fluidity concrete increases significantly.When the gas content is too large?more than 6%?,the strength of concrete is significantly weakened.There is no positive correlation between the total amount of glue material and the compressive strength of concrete.?3?The amount of cement was controlled at 300kg,and the amount of air attractor was reduced to 1/10,000th of the design level,so that the air content of concrete was controlled at 4%of the design level,and the strength of each proportion was significantly increased.28d measured cube compressive strength in?5871?MPa.The diffusion coefficient of 28d chloride ion varies between?0.72.2?×10-1212 m2/s.The56d electric flux varies from 200C to 300C.?4?By controlling the amount of gelled material,420420 kg/m3,mineral admixtures for?level grade fly ash and S95 Slag powder,mineral admixture proportion is 40%and 50%,it is possible to prepare high-performance concrete with a slump of over 200mm,good cohesion and water retention,and a chlorine ion diffusion coefficient of 28d at?1.22.2?×10-12m2/s. |
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