MECHANISMS OF CHLORIDE PENETRATION INTO CONCRETE
To avoid early steel corrosion and expensive repair measures within the intended service life of reinforced concrete structures several concepts for durability design have been developed in recent years. In most of these recommendations and codes chloride penetration is simulated by means of Ficks second law. This approach would be approximately valid if diffusion would be the only or at least the dominating transport mechanism for chloride ions in concrete. In reality,however,many structural elements are in contact with chloride containing water temporarily as for instance in the tidal zone or the splash zone,and in structures exposed to de-icing salt during winter time. Under these conditions several transport mechanisms have to be taken into account. During contact of the surface of structural elements with chloride containing water for hours or weeks,capillary suction will take place first. Once chloride ions have reached a distance from the surface of about 30 mm by capillary suction,they will slowly penetrate deeper into the porous material by diffusion. Next to capillary suction and diffusion,water migration due to drying has to be taken into account. Part of the penetrated chloride will be washed out again by evaporable water or at least hindered from further penetration. Experiments have been carried out to simulate all three major mechanisms of chloride transport in concrete,i.e. capillary suction,diffusion and convection. Chloride profiles as measured on real structures will be interpreted on the basis of the obtained results. Elements of a realistic service life prediction will be presented.
Chloride ions Capillary suction Diffusion Convection Diffusion coefficient
Ling Cui Folker Helfrid Wittmann Tie-Jun Zhao
Qingdao Technological University,Qingdao 266033,P. R. China,Centre for Durability and Sustainability Qingdao Technological University,Qingdao 266033,P. R. China,Centre for Durability and Sustainability Qingdao Technological University,Qingdao 266033,P. R.China,Centre for Durability and Sustainability
国际会议
The Eleventh International Symposium on Structural Engineering(第十一届结构工程国际研讨会)
广州
英文
1238-1244
2010-12-01（万方平台首次上网日期，不代表论文的发表时间）