Research On The Attack Of CO₂ And Sulphate On Tunnel Lining Concrete

As a passage through mountains and waters,tunnels are impacted by traffic loads and environmental factors,which enhance a great challenge on their durability. Common durability diseases of tunnels are:lining crack,lining deterioration (including carbonation,chloride ingress,sulphate attack etc),tunnel freezing.Basing on the transportation mechanisms of aggressive ions in concrete,research on the lining carbonation and sulphate attack were carried.The following work has been performed.(1) The commonly disease of tunnel lining in China has been classified and analyzed.Further study were carded on carbonation and sulphate attack.(2) A multi-factor carbonation prediction formula was developed using basing on Least Square Method.(3) The sulphate source in lining concrete was analyzed and the effect of different sulphate was studied.(4) Different diffusion models for sulphate ingress were developed considering different factors,for example,the effect of adsorption on diffusion.(5) Basing on classic Similarity Theory,the similarity between the natural carbonation and accelerated carbonation,between different sulphate ingress were studied.Different similarity rule were deduced.(6) The expansion of concrete under sulphate attack was studied basing on cement chemical composition.The volume expansion of concrete considering porosity,shrinkage,ultimate strain of concrete were calculated.The threshold values of sulphate content in concrete were also calculated.This research was supported by the National Education Ministry Special Funds for College Doctor Station "Research of the Influence of Early Time Dehiscence Sensitivity and Micro Crack Evolution Rule to Service Performance for Modern Concrete Structure"(Authorized NO.20070335087) and "863" program of National Hi-Tech Research Development "Durability Test Technology of Large-Scale Civil Engineering Infrastructure under Combined Environment"(NO.2006AA04Z415).