Study On The Crucial Influence Factors Of The Erosion Resistance Of Guangzhou Metro Concrete In Carbonic Water

Carbonic water solution lurks the underground circumstance, which can cause a serious damage to the metro concrete. In this article, a real carbonic water solution was simulated. Additionally, the raw materials and concrete in-site were utilized. Considering of internal causes of concrete with a high erosion resistance, three key influence factors (complementary cementing materials, water cement ratio and curing regimes) were consequently captured to study the effect on the performance of erosion resistance. In order to acquire the measures that can improve the erosion resistance of metro concrete in carbonic water, which can guide the metro concrete engineer designing.Firstly, the influence of supplementary cementiting materials (SCMs) on the durability of erosion resistance in carbonic water was deeply investigated. It can be found that erosion depth depends on CH contentest and pore structure closely. If erosion depth is the only consideration,20% dosage unary mixed grounding granuluated blast slag (GGBS),10% dosage unary mixed fly ash (FA) and 20% dosage ternary mixed GGBS and FA pastes have the minimum erosion depth. If only taking the erosion shrinkage into consideration,20% dosage unary mixed GGBS,30% dosage unary mixed FA and 20% dosage ternary mixed paste have a better erosion shringkage resistance. While if taking the balance between erosion depth and shrinkage,20% dosage ternary mixed paste has the best erosion resistance in cabonic water. Then a calculation equation that shows the relationship between erosion depth 2tDe0(w-wc/W0-Wc)n[CO2]0/[CH] erosion depth depends not only on the paste CH content, but also on the effective porosity.Secondly, the influence of water cement ratio on the performance of erosion resistance in cabonic water was studied. Results show the influence of CH content is lower than that of pore structure when the water cement ratio are in the range of 0.45-0.60, for the reason of low water cement ratio of specimens show a better erosion resistance in carbonic water.Thirdly, the degradation process of two pastes cured in different regimes was compared. Results show that steam curing with 4 hours has the higher effective pore content than the normal cured paste with a duration of 28 days, while the steam curing pastes show a better erosion resistance:smaller the erosion depth and shrinkage, which shows that the differences resulting from curing regimes between pore structure of hardened cement paste is not the main factors that affecting the erosion resistance, while CH content is. According to the combination analyses of ionization equilibrium of carbonic water and the phenomenon of erosion depth and shrinkage, the erosion process can be divided:when pH value is higher than 10.5, CO3 is in domination of ions balance, the main reaction is precipitation of CaCO3; when pH value is less than 10.5, HCO3 controls the ions balance of pore solution, dissolution is the main reaction.Finally, the degradation process of Guangzhou metro concrete (C35P8-10) and mortar prepared by getting rid of coarser aggregates were studied. By introducing the reliability theory in evluating the service life of concrete in-site, in the concentration 40mg/L of carbonic water, a 115-year of service life of metro concrete was calculated, which can satisfy the design requirement of 100-year.