Media Migration Properties Of The New And Old Concrete

As the service time of engineering structures extended and then defective concrete structures needed to repair gradually increasing, how to ensure the durability of restored concrete structures has become an important topic for the related. This paper centers on the durability involved in the existing concrete structure repair system; and studies the characteristics of media transpon in new-old concrete, and then analyzes its influencing factors, such as water-cement ratio, mineral admixtures, polyacrylate and concrete interface treatmenting methods, and lastly investigates the correlation between its media transpon and microstructure, by the establishment of the relationship of electric resistivity and chloride ion diffusion coefficient between new-old concrete and the single new and old concrete, and the indoor tests which mainly employ three kinds of methods, capillary absorption, chloride ionic penetration (ASTM C1202), as well as chloride ionic diffusion. Main results are as follows:(1) Whether in new,old or new-old concrete sample, there exists a good linear relationship between the capillary absorption coefficient and the square root time. However, the capillary absorption coefficient of different samples is significantly different, and it in new-old concrete one depends primarily on capillary absorption coefficient of surface absorbent materials.(2) Similar to new,old concrete sample, the capillary absorption coefficient in new-old concrete sample under salt solution environment is much smaller than it in water circumstance.(3) The 6h electric flux and electric resistivity in new-old concrete sample depend mainly on them in new or old concrete sample and the bounding interface. If Coulomb electric charge of new concrete at 6h is not significantly high (e.g. over 4000C), the electric flux in new-old concrete sample will be less than it in new or old concrete sample, besides the electric resistivity will be greater. However, using appropriate interface treatmenting approaches can obviously improve anti-chloride ion permeability.(4) The relationship between the content of internal free chloride ion and the diffusion depth in new-old concrete follows S (Boltzmann) curve distribution. Reducing the ratio of water and cement, doping with mineral admixture, using the coating system can effectively lower the chloride ion diffusion coefficient.(5) The linear correlations between the capillary absorption coefficient, 6h electric flux, electric resistivity, chloride ion diffusion coefficient and its porosity in the new-old concrete sample are significantly worse than them in new or old concrete one.(6) The mathematical relationships between new-old concrete and new or old concrete sample are respectively set up in accordance with theoretical analysis and test results.