Damage assessment of a RC bridge structure showing damages at the prestressing steel

Principally, the pre-stressing steel embedded in bridges is comparable exposed to corrosion attacks as ordinary reinforcement. If the sealing of the bridge deck is not tight, the concrete has a low diffusion resistance, the concrete cover is low, chlorides reach the reinforcement/pre-stressed steel via uncracked concrete. If cracks are present chlorides can easily penetrate and reach the reinforcement/pre-stresses steel very quickly. The pre-stressing steel can have damages, pitting and stress corrosion and breaks, even if no signs of damages of the bridges are visible. However, compared to reinforcement bars which are usually completely embedded into concrete the anchorage area of post-tensioned pre-stressing steel is at least temporary exposed. Often these niches will be plumbed with mortar or concrete afterwards. Insufficient sealed construction joints are possible path for chlorides. With regard to post-tensioned pre-stressed steel, serious problems can occur if the injection of the sheath is insufficient. Corrosion attack can occur due to condensed water in the cavity and deposits on the pre-stressing bars. If in addition chlorides are present, they can easily spread along the pre-stressed steel, subsequently lead to pitting and to stress corrosion. The paper reports on investigation performed on existing pre-stressed bridges in Germany with different construction characteristics and corrosion damages. Diagnosis methods are introduced, deterioration mechanisms are illustrated and appropriate are discussed. The final repair action are described.