Observations and analysis of a 63-year-old reinforced concrete promenade railing exposed to the North Sea

Abstract

Despite being exposed to the harsh sea-spray environment of the North Sea at Arbroath, Scotland, for over 63 years, many of the reinforced concrete precast beam elements of the 1 . 5 km long promenade railing are still in very good condition and show little evidence of reinforcement corrosion. In contrast, railing replacements constructed in about 1968 and in 1993 are almost all badly cracked as a result of extensive corrosion of the longitudinal reinforcement. This is despite the newer concrete appearing to be of better quality than the 1943 concrete. Statistics for maximum crack width for each of the three populations, based on measurements made in 2004 and in 2006, are presented. In situ and laboratory measurements show that the 1943 concrete appears to have high permeability but it also shows high electrical resistivity. Chloride penetration measurements show the 1943 and 1993 concretes to have similar chloride profiles and similar chloride concentrations at the reinforcement bars. This is inconsistent with the 1943 beams showing much less reinforcement corrosion than their later replacements and casts doubt on the conventional practice for durability design focusing on reducing concrete permeability through denser concretes or greater cover.

Performance of 45-year-old corroded prestressed concrete beams

“…For beam A, corroded wires were found only in bay 5, despite limited external visual evidence. Interestingly, a similar lack of external evidence of internal corrosion on older concrete structures has been described more recently (Melchers et al, 2009 Performance of 45-year-old corroded prestressed concrete beams Pape and Melchers corrosion of steel caused by oxygen, which produces large volumes of red-brown corrosion products such as typically seen at cracks in the concrete parallel to the corroded steel. The corrosion of the wires in beam A could be the result of the aggressiveness of chloride ions in low-oxygen environments (Melchers, 2010).…”

Field experience and the long-term durability of reinforced concrete structures

“…The present review, and earlier examinations of the available data (Melchers & Li 2009), indicates that an alternative approach is to make greater use of limestones and similar alkaline materials as part of the concrete mix. The evidence shows that concretes made with such aggregates can delay reinforcement corrosion initiation considerably in time, provided the concretes also are of high quality including low permeability.…”

“…The other 10% were replaced in 1968 and in 1993. Remarkably, all replacements have been badly damaged by longitudinal cracking from reinforcement corrosion (Melchers et al 2009). Samples of the 1943 elements were selected at random by the local Council for detailed examination.…”

“…Despite these difficulties, the approach does have merits, and can be considered an archaeological one, such that with care useful observations can be made. Several investigations along these lines have been described for reinforced concrete structures ( Melchers et al 2009) as well as for materials of potential use in nuclear waste storage facilities (Chitty et al 2005). …”

Microcell versus galvanic corrosion currents in carbonated concrete

“…On the contrary, no corrosion damage would occur anywhere else nor for a long period because this combination of unfortunate local circumstances would not happen. Taking into account galvanic currents in concrete structures could explain why in some instances heavy corrosion occurs significantly earlier than predicted by existing models (Marchand and Samson, 2009;Melchers et al, 2009). Galvanic corrosion such as that described in this paper is not taken into account in any of the existing models dedicated to active steel corrosion prediction.…”