A non-destructive and quantitative investigation system for corrosion of reinforcing steel in concrete | |
| Author | Nguyen Xuan Hoang |
| Call Number | AIT Thesis no.ST-00-30 |
| Subject(s) | Steel--Corrosion Reinforced concrete--Corrosion |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | The occurrence time of chloride induced reinforcement corrosion in concrete needs to be anticipated so that appropriate protection methods can be applied before corrosion occurs. In Japan, a new probe system is proposed detecting progress of chloride penetration and the start of corrosion of steel in concrete structures, where the probe is placed, is firstly proposed. This probe is developed such that four very thin wires are coiled in separate four ditches at different distances from the concrete surface. The probe does not measure the corrosion of rebar directly but resistance of its steel wires. As the chloride content in concrete reaches the critical value, the steel wire is anticipated to break because of corrosion. Consequently, the abrupt increase of resistance reading can indicate the depth where chloride content has reached the critical value. In this study, the effectiveness of the probe installed in concrete specimens is experimentally investigated under cyclic chloride wetting and drying. In this experiment, the probe successfully shows the progress of chloride penetration into concrete structure. When chloride content at 5 mm from the concrete surface reaches a certain level, the steel wire at that location breaks and its dramatic large resistance reflects the corresponding high chloride concentration. However, the chloride content around the broken wire is more than 10 kg/m3 by volume of concrete, which is much larger than 2.4 kg/m3 assumed as the critical chloride content. Resistance of a wire on the probe does not change even though chloride content at the corresponding depth is over the critical value. To improve the sensitivity of the probe the wires in the probe are charged anodically by a small-imposed current so that it can indicate the depth of the critical chloride content. The experiment also proves that the presence of the probe does not increase the chloride penetration into concrete significantly. Stain or other evidences of corrosion of the steel wire in the probe does not appear on the concrete surface. Thus, the probe does not influence the aesthetics of the structure representing an advantage over other probe systems. This study clearly shows that the probe has high possibility to detect the depth of the critical chloride content in concrete with respect to time. |
| Year | 2000 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Takewaka, Koji; |
| Examination Committee(s) | Pichai Nimityongskul ;Zhu, Hongping; |
| Scholarship Donor(s) | Government of Australia; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2000 |