Access viaducts to the drawbridge of Leixões Harbour: diagnosis of concrete deteriorations

Abstract

The two access viaducts to the drawbridge of Leixões harbour are connected with the metallic structure of the drawbridge and allow the passage between the two towns, Leça da Palmeira and Matosinhos. The viaducts are concrete structures, composed of wall-columns and abutments, in reinforced concrete, supporting longitudinal beams placed side by side and braced by transversal beams, all of prestressed concrete. The slab is also in reinforced concrete. The viaducts built between 1957 and 1960, were repaired between 1991 and 1993. As the drawbridge was inadequate for both the road and the harbour traffic, it was replaced and some of the spans of the viaducts were demolished and all the concrete was repaired between 2006 and 2008. The aim of this work was, before this last rehabilitation, to make a diagnosis of the deterioration of the concrete viaducts. After collecting and analyzing all the information about the characteristics of the different materials used in concrete and its composition and properties, a visual inspection of the structure was made, and all relevant evidence of deterioration was recorded and photographed. Some samples of apparently non-deteriorated concrete and visually deteriorated concrete were extracted for analysis. The carbonation and the chloride ingress were determined in samples of apparently nondeteriorated concrete. All samples were observed and analyzed by scanning electronic microscopy (SEM) and energy dispersive spectrometry (EDS).