Backfill Corrosivity around Corrugated Steel Plate Culverts: Fid-Bau Portal

Backfill Corrosivity around Corrugated Steel Plate Culverts

Beben, Damian

Corrugated steel plate (CSP) culverts are exposed to the risk of soil corrosion because of the location in the soil environment. This paper characterizes the most important factors contributing to corrosion in the soil: resistivity, pH, and moisture content. Tests of soil resistivity based on the geophysical electrical resistivity measurements (Wenner array) are presented. This method allows for soil resistivity measurements at various depths. The conducted experimental tests concerned the six galvanized CSP culverts situated on different types of roads (national, provincial, and local). All tests were conducted in two seasons: summer and spring. The minimum resistivity of the soil in the vicinity of the CSP culverts amounted to $30 Ω \cdot m$ and was established near roadway. The pH of the backfill in the tested culverts showed alkaline reaction (8.1–9.3). The largest natural soil moisture of approximately 10% was obtained during the spring. The obtained results indicate the peril of the soil corrosion occurrence in the CSP culverts, especially located on the national and provincial roads. The Pearson’s correlation coefficient was applied to the statistical analysis. A strong correlation between the backfill resistivity and the pH value in summer and spring, and between the resistivity and moisture content in spring, was recorded. Analysis of durability based on the three standards [American Association of State Highway and Transportation Officials (AASHTO), Australian/New Zealand Standard (AS/NZS), and Canadian Highway Bridge Design Code (CHBDC)] shows that the tested culverts meet the requirement for a minimum service life of 40 years (as for culverts), but do not fulfill the required lifetime as for bridges, which is 100 years.