Durability of Concrete Bridges in Belgium--Balance of the Systematic Inspection

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Title: Durability of Concrete Bridges in Belgium--Balance of the Systematic Inspection

Author(s): Van Begin

Publication: Special Publication

Volume: 100

Issue:

Appears on pages(s): 541-554

Keywords: bridges (structures); concrete durability; corrosion; cracking (fracturing); inspection; maintenance; General

Date: 4/1/1987

Abstract:
The Belgian Public Works Ministry manages about 5200 important bridges--3640 (70 percent) of them are concrete bridges of which 40 percent are reinforced and 30 percent are prestressed. The average bridge has a surface of 1200 mý, 22 m long spans, and is 22 years old. After seven years of systematic inspection, it is possible to make a balance of the noticed shortcomings and of the reasons why they appeared. Dirty concrete surfaces (graffiti, water trails, moss, etc.) occur very often but generally don't influence the good behavior of the structures. Geometric faults are noticed in 2 to 4 percent of the cases, mainly for cantilever bridges. Concrete cracks are very frequent (30 to 80 percent of the concerned structures). Most of them don't affect the safety but have an influence on the durability. Corrosion of reinforcements and prestressing steel also occurs frequently (20 to 80 percent of the concerned structures). Steel in concrete is naturally protected, but two main factors disturb that favorable situation: carbonation of concrete by CO2 reduces the pH of the concrete and also the protective effect, and cracks and lack of closeness in the protective coating lead to penetration of corrosive agents like deicing salts and acid rain. The deicing salts (chlorides) also attack hardened cement and transform the surface of the concrete into gravel. Although all our bridges are provided with a protective waterproofing, water containing salts remains the most aggressive element. The maintenance, rehabilitation, and reinforcement of the bridges are an important technico-economical problem in Belgium.