How to Perform and Report Half Cell 腐蚀 Mapping

Half Cell corrosion mapping is an effective method for assessing the severity of corrosion in reinforced concrete structures. 这种快速, cost-effective and non-destructive survey method provides key information in corrosion evaluations. 腐蚀 of steel reinforcement is a major factor in the deterioration of highway and bridge infrastructure and half cell corrosion mapping can be used to detect corrosion, as well as being the first step towards its rehabilitation. It can also be used as a quality assurance tool in the repair and rehabilitation of concrete structures and as a predictor of remaining service life.

The most practical way to determine the severity of corrosion in reinforcement steel is to measure its corrosion potential. This is done with the use of a standard portable half-cell, 正常情况下 a copper/copper sulphate (Cu/ CuSO4) standard reference electrode. The reference electrode is connected to the negative end of a voltmeter and the positive end of the voltmeter is connected to the reinforcement steel. Depending on the measured half cell corrosion potential value, the probability of active corrosion is determined.

ASTM  C876 provides a half cell potential range . Depending on the measured half cell corrosion potential, the probability of active corrosion is determined.

How to Perform Half Cell 腐蚀 Mapping

1-测量点

The first things is to know the test locations. 在一般情况下, a schematic grid will help you with smoothly taking the measurements, 管理测试结果. There is no general rule about the grid spacing. A finer mesh will be more precise, but also more expensive. Wide spacing can reduce the resolution of test results, and may result in inaccurate half cell potential measurements. A suitable spacing should be selected with regards to the area under investigation.

2- Rebar Connection / Connectivity Test

Half cell potentials at each test point is measured to an identical reference point. An electrical connection to the rebar network is required at this reference location. 正常情况下, concrete cover should be locally removed (this can be achieved by drilling into concrete), to establish a sound electrical connection to rebar. To do so, one needs to locate the rebar first (this can be done by using a rebar locator). Rebar network 正常情况下 provides a connected mesh. 然而, 在更大的范围内, 例如甲板板, one needs to check if the steel rebar network is connected.

3- Electrical Connection to Voltmeter

The connecting lead cable from the negative terminal should be connected to the reference electrode, while the other lead wire should be connected to the rebar network at the reference location. The voltmeter should be able to measure direct current (dc) voltage, and have the capacity to be battery operated. The voltmeter should have a variable input impedance ranging from 10 to 200 MΩ may be used to determine the input impedance required to obtain precision readings.

4-预湿表面

If the surface of concrete is too dry, the pre-wetting is required. Pre-wetting can either be achieved by spraying the water over the location to be tested, 或者用湿海绵. ASTM C 876 describes how suitable pre-wetting condition can be achieved.

5-进行测量

At each location, the value of half cell potential should be recorded to the nearest 0.01 v (astm c 876). For each point, record the coordinates of the test point, as well as the corrosion potential value. 如果天气状况, including the temperature has changes, the values of the half-cell measurement should be adjusted for temperature variations.

Presentation of Half-Cell potential measurements

A Half-Cell potential equipotential contour map is widely used to report Half Cell potential data. Results can also be reported as a cumulative frequency distribution of corrosion potential.

参考:
FC Prime解决方案网址:www.fprimec.com 'Half Cell 腐蚀 Mapping for 混凝土'