Durability of sea-sand containing concrete:Effects of chloride ion penetration

This paper describes an orthogonal experiment on the effect of water/cement ratio,water consumption per cubic meter,curing time,and type of sand on the response＂resistance to chloride ion penetration＂.A sea-sand containing concrete was used for the trials.An analysis of chloride ion diffusion coefficients at different factor levels was performed.A predictive model of chloride ion diffusion in concrete is developed through regression analysis.The experimental results show that when the water/cement ratio varies from 0.45 to 0.60,and the water consumption per cubic meter varies from 185 to 215 kg,and the curing time varies from 30 to 180 d then the size of the effects fall in the order（most significant first）： curing time,type of sand,water consumption per cubic meter,and water/cement ratio.Chloride ion penetration is reduced,and better durability of the concrete is observed,with longer curing times,less water consumption per cubic meter,and a smaller water/cement ratio.

Modeling Boundary and Edge Effect of Chloride Diffusion for Durability Design of Concrete Structures Exposed in Marine Environment

According to the Fick＇s second law of diffusion, six analytical solutions of chloride profile in concrete were studied and discussed with regard to different boundary and initial conditions. In those analytical solutions, the most prevailing error-function solution which is based on semi-infinite assumption is the simple one, but may under-estimate the chloride content in concrete and over-rate the life time prediction of concrete structures. The experimental results show that compared with other solutions, the chloride content in concrete predicted by error-function model is the minimum, and the calculation difference produced by different analytical models should not be ignored. The influence of models on chloride content prediction is more than other environment and material coefficients in some time. In order to get a more realistic prediction model, modification to error-function model is suggested based on analysis and calculation examples concerning the boundary and edge effect.

Experimental Investigation on Contribution of CFRP Attachment to Durability of Reinforced Concrete Structure Subjected to Chloride Attack

The function of externally-bonded carbon fiber reinforced polymer （CFRP） in preventing chloride from entering into concrete is verified by experiment. The results show that externally-bonded CFRP can be considered as a part of corrosion prevention system of strengthened concrete structures subjected to chloride ingress, and the contribution of CFRP should be considered in evaluation of durability of reinforced concrete structures with externally-bonded CFRP. With the effective shielding function of CFRP considered, an equation for residual lifetime prediction of concrete structures with externally-bonded CFRP is derived from Fick＇s dispersion law. CFRP has two functions for coastal concrete structures, including strengthening and increasing durability as part of corrosion prevention system.