The Investigation On The Durability Design Method Of Silane Treated Concrete Structures

Due to its superiority in rendering breathability and durability to concrete,silane has been widely used in the surface treatment of marine structures.By reducing the water absorptivity of the concrete,silane impregnation can effectively hinder the chloride penetration process and thus elongate the corrosion-free life.However,its protective effect was not well considered in current design codes and existing studies.Therefore,the design results based on this results are not sufficiently economical and rational.To address this issue,a prediction model was developed to analyze the chloride transport in silane treated concrete structures.Durability design and maintenance scheme design were then conducted with this model.The research contents and major conclusions of this research include:1.A probabilistic model was developed to predict the ion transport in silane impregnated concrete,in which the time-variant protective effect of silane and the statistical distributions of key parameters were specially considered.The model was solved through Monte-Carlo simulation and the sample size was controlled with Latin Hypercube sampling techniques.Through comparisons with some long-term exposure data,the effectiveness of the proposed model can be validated in some degree.Therefore,it was then used to conduct the service life prediction and durability design of silane treated concrete structures.2.Using the validated model,the sensitivity analysis of the corrosion-free life of the silane-impregnated concrete structure was carried out.The results show that the corrosion-free life is mainly af fected by the water-binder ratio and the thickness of the concrete cover,but the service life extension brought by silane impregnation is highly related to the relative humidity when carrying out the treatment.Therefore,how to determine the rational combination of water-binder ratio and cover thickness should be the focus of the durability design.3.Based on the probabilistic model and the well-developed reliability theory,the durability design method of silane treated concrete structures was further investigated.A diffusivity reduction factor is introduced to consider the protective effect of silane in the conventional partial factor method.Further analyses indicate that the factor is sensitive to water-binder ratio,relative humidity and total cover thickness,so its values are determined under various typical combinations of these key parameters.With partial factors derived from the first order reliability method,the proposed method can avoid the heavy computation of the fully probabilistic method.Case studies show that the achieved reliability indexes are higher than the target ones,and therefore the proposed method can ensure the necessary safety margin,as well as improve the design efficiency.4.Using the chloride ion transport model established in the research,the effectiveness of three typical maintenance technologies,including silane reapplication,concrete replacement,and electrochemical chloride extraction(ECE),were investigated.The results suggest that a longer corrosion free life can be achieved when concrete replacement or ECE is carried out right before the occurrence of corrosion initiation.Both technologies can further extend the service life of the structure after being used with silane reapplication,but the effect of using silane reapplication alone is not ideal.