PSI - Issue 64

Fritz Binder et al. / Procedia Structural Integrity 64 (2024) 175–182 Fritz Binder/ Structural Integrity Procedia 00 (2019) 000 – 000

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3. Field-Study This section outlines the basic design of the monitoring system and the installation of sensors in the supports. Measurement data are complemented by on-site environmental data as well as data from a nearby weather station. The uniform exposure of a row of 21 columns between two lanes ensure consistent conditions for all components, facilitating on-site evaluation of repair methods' efficacy and durability. To date, corrosion indicator assessment for evaluating repair methods performance has not been conducted in this manner. 3.1. The Structure For an in-situ determination of the corrosion of the reinforcement, the environmental impact has also been monitored. Such a monitoring system was installed on columns in different heights on an overpass located in the Austrian motorway network of ASFiNAG (see Fig. 2(a) and Fig. 2(b)). The overpass which was planned in 1980 has a length of about 100 m and shows a tunnel-like characteristic. The beams are supported by the abutment and the columns are situated between the direction lanes of the motorway. In 1994, concrete spalling was patched, and the 21 columns were coated with an epoxy-based coating up to a height of 2.0 m. The substructure, especially the columns, showed severe damage to the concrete structure at the time of investigation in 2010, such as spalling and cracks over 0.3 mm wide as well as traces of rust in the contact and splash zones. During the renovation in 2014, the substructure of the structure was comprehensively renovated. Different repair systems were used for the columns. In the course of this project, some additional sensors were installed to better assess the effect of the individual repair methods.

Fig. 2(a): Portal view of the structure.

Fig. 2(b): View of the colums to which the monitoring applied.

3.2. Results and Discussion Figures 3 and 4 show the course of the corrosion potential in the spray and splash zone overtime. The seasonal variation can be clearly observed. Figure 3 shows the measured values of a column whose concrete surface was sealed with a coating after intervention whereas Figure 4 shows the results from a hydrophobic treatment. In the figures, the time of intervention is marked by a gray shadowed area and is also clearly recognizable by the increase of the el. potential. Since this time a significant reduction of the corrosion potential occurred. The marked limits are taken from ASTM C876 15 (2015) and indicate an improvement from below -438 mV, the level with high corrosion possibility, to approximately -350 mV. This can also be seen in the box plots of the two measured exposure zones (see right section of the figures), while the variation of the values has remained approximately equal.