Influences of Environmental Temperature and Relative Humidity on Critical Chloride Content and Depassivation Time of Reinforcing Steel in Concrete

Taweechai Sumranwanich; Aunchana Kijjanon

Authors

Taweechai Sumranwanich Department of Civil Engineering, Faculty of Engineering, Burapha University, Chonburi, Thailand
Aunchana Kijjanon Department of Civil Engineering, Faculty of Engineering, Burapha University, Chonburi, Thailand

Keywords:

Critical Chloride Content, Depassivation Time, Temperature, Relative Humidity, Fly Ash, Silica Fume

Abstract

This research aimed to study the effects of environmental temperature and relative humidity on critical chloride content and depassivation time of steel in concrete. Environmental temperatures of 30°C and 50°C and relative humidity values of 30% and 90% were studied. Fly ash was used as partial replacement of the binder at ratios of 0.20 and 0.40. Silica fume was used to replace the binder at a ratio of 0.075. The water-to-binder ratio of 0.50 was maintained in all concrete mixes. Based on the experimental results at a constant relative humidity of 90%, concrete exposed to 30°C had longer depassivation time than concrete exposed to 50°C; the former possessed a lower critical chloride content. On the other hand, at a constant temperature of 50°C, concrete exposed to 30% relative humidity exhibited longer depassivation time than concrete exposed to 90% relative humidity; the former again possessed a lower critical chloride content. When considering the corrosion resistance index (CRI), it was found that concrete exposed to a low-temperature environment had higher CRI than concrete exposed to a high-temperature environment. Concrete exposed to a lower relative humidity environment also had higher CRI than concrete exposed to a higher relative humidity. Concrete containing fly ash at 40% replacement had the highest CRI, while concrete containing silica fume had higher CRI than the control concrete.

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