A flyover built in the 1970s along the district road in Zakopane caused concern of the facility administrator who commissioned the technical opinion on its conditions. According to the prepared opinion, it was necessary to perform an extensive and expensive repair of the structure, that is, demolition and restoration of externally corroded bridge supports. In 2009, prior to the final decision, the administrator commissioned the professional corrosion tests of the pointed flyover support to verify finally the future repair works. The tests were contracted to the Department of Building Structures at the Silesian University of Technology. I was the member of a team of three people who performed the advanced corrosion tests. Their results positively surprised the administrator and consequently, costs of the planned repair works could be considerably reduced.
Problem outline, purpose and scope of tests
The advanced corrosion tests were performed on the flyover support pointed by the employer. The flyover consists of 22 spans made of prefabricated prestressed concrete beams of "Płońsk" type of 18 m and 16 m in length, operating in the freely supported arrangement. All the supports were reinforced concrete, monolithic, one-column supports with top plates. The facility administrator was concerned about concrete defects observed in upper parts of the supports with corroded reinforcement and the presence of flora.
Cylindrical concrete cores with embedded pieces of reinforcement were drilled to evaluate the corrosion risk for the support subjected to tests. Polarization measurement (EIS and LPR techniques) of corrosion rate in the concrete specimens, tests on concrete protective properties (pH, chlorides) to reinforcement, and tests on compressive strength of concrete were performed under laboratory conditions.
Summary and conclusions
The complex corrosion tests showed that severe corrosive defects of the flyover supports, visible to the naked eye, were only superficial. Deeper layers of concrete and reinforcing steel of support were in very good conditions. The technical opinion recommended repairing a few-centimetre external layer of concrete and reprofiling top plates using PCC systems. Results of the above tests were presented in several scientific and technical articles in Poland and abroad.