Induced Corrosion Techniques for Two-Way Slabs

Accelerated corrosion techniques are used to assess the structural performance of corroded reinforced concrete elements. This paper aims to illustrate the use of various techniques by showing their advantages and disadvantages. Two different corrosion techniques were investigated: constant voltage and constant current. Each technique was used to corrode a full-scale structural element. Two reinforced concrete two-way slabs were prepared and cast for this purpose. The slabs had identical dimensions of $\mathrm{1,900}\times \mathrm{1,900}\times 150\mathrm{mm}$. Each slab had a column stub with a cross-sectional area of $250\times 250\mathrm{mm}$ and a height of 200 mm. The two slabs were corroded to the same level of 25% mass loss. The setup and procedure for each technique is described in detail showing its appropriateness and difficulties. The corrosion of each corroded slab was evaluated on the basis of the experimental results of current measurement, half-cell potential readings, crack patterns, natural frequency, chloride content, and mass loss. The theoretical mass loss was calculated on the basis of Faraday’s equation for both techniques. After the induced corrosion process was completed, the concrete cover was carefully removed and the corroded bars were extracted, cleaned up, and weighed. It was found that the actual mass loss for the corroded bars showed a close agreement with the theoretical mass loss for both techniques. The corrosion causes cracks on the concrete surface, which facilitate the flow of electricity between the anode and the cathode. In the case of the constant current technique, the cracks do not affect the current intensity because the current is kept constant under controlled conditions, whereas in the case of the constant voltage technique, the cracks cause fluctuation in the current value. Thus, the current intensity could reach extreme values, which affect the damage that occurs in the corroded element. Hence, constant voltage may cause more damage than would occur under uniform corrosion conditions when a constant current is used.