|主題||A Study on Chloride Penetration in Concrete|
|筆頭著者||Sudhir MISRA （University of Tokyo）|
|連名者1||Taketo Uomoto （University of Tokyo）|
Even though the exact role played by the chloride ions in the initiation and propagation of reinforcement corrosion is not fully understood,it is generally accepted that they are one of the critical factors in,at least,damaging the passivating film protecting the reinforcing bars. It can also be assumed that this passivating film is disrupted only when the chloride concentration in the neighbourhood of the reinforcing bars exceeds a certain "threshold" level. The question as to what type of chlorides are really detrimental from the view-point of reinforcement corrosion,has not been resolved. Basically, the chloride content of concrete is said to be made up of the following two parts：1.Bound:These are chemically "trapped" in the hydration products of the cements. Generally,the tri-calcium aluminate content of cement is regarded as a measure of it's chloride binding capacity. The ability of other hydration products e.g.those of silicates to bind the chlorides is not presently taken into account. And since the hydration of the aluminates is completed very rapidly, the ability of the hardened concrete to "bind" the chlorides that penetrate can be considered to be nominal. 2.Free： These are not chemically "bound" in the sense explained above, and are free to move through the pore water within the concrete on account of concentration gradients, etc.,and thus travel towards the reinforcing bars through the covering concrete. However, the state in which such chlorides actually exist within the matrix is not known.
1)The chlorides penetrating into concrete with permeating water lead to higher and deeper contamination of the concrete. And therefore,the chloride penetration along with the water is perhaps more important than chloride penetration occurring under concentration alone.2)Concrete apparently maintains some sort of binding ability to hold penetrating chlorides even after sufficient curing and hydration. This mechanism has been modeled as a surface adsorption process in this study. The experimental values obtained for the chloride concentrations are too high to be accounted for if the pore walls are assumed to be inert.