Bridge Structures Cracks – What Made that Phenomena so Common?

AbstractThe common phenomena – cracks appearance on newly built reinforced concrete bridge structures - is being detected in Poland for several years now. That phenomena is regarded as threatening in case of bridge structures, despite the fact that reinforced concrete theory considers cracks as a standard concrete performance. Cracks are very likely to appear on concrete surface. Cracks are usually detected during concrete surface treatment before protective coating laying. Cracks appear on monolith structures, mainly at the slab spans and foreheads as well as, at support columns in a minor range. Concrete surface cracks openings reach up to 2mm size. The experience gained throughout consulting works on cracked structures are discussed in that paper. The influence of concrete surface mechanical cleaning prior the protective coatings laying on the crack “visual” intensification was also discussed herein. Crack openings measurement rules, as well as the most common mistakes made during the crack measurements and their real value assessment were described in the paper. The maximal crack opening allowances fluctuations in Polish and European concrete Codes were also discussed here. It was proved that the spotted crack opening increase is caused by the codes changes and by bold reinforcing cover. The bold cover is regarded as the corrosion protection of reinforcing bars. The cover bold and crack opening allowance dependency was discussed in the paper. The effect of Euro codes and the Minister of Transport and Maritime Economy Ordnance from May 30th 2000 titled “Technical requirements for highway engineering structures and their locations” simultaneous obligation on reinforced concrete structures cracks assessment was deliberated.At the conclusion the necessary modifications in crack assessment practice were claimed. The cracks should be assessed on the basis of homogenous code system. Their openings are dependent straight forward from the reinforcement cover thickness. One should avoid crack measurement at the sections, at which the crack edges are mechanically shattered. The crack opening assessment should be dependent on cover thickness. The rod anti shrinkage activity reaches the cover depth approximately to the depth equal to the rod diameter only. That fact should be taken under consideration during crack assessment