Environmental degradation of reinforced concrete structures

It is well known that corrosion is the greatest phenomenon of metal degradation. It represents a problem in terms of both socio-economical costs and safety, especially in cases where metals are used as structural elements. Since the beginning of the last century, steel was used as a structural component for reinforced concrete in order to support, above all, shear and bending loads. At that time, concrete was considered to be an endless material, but soon reinforced concrete showed numerous issues in terms of reliability and durability.

A survey of the scientific literature since the 1950s revealed some surprising knowledge and studies as far as corrosion in concrete is concerned, as reported below.

Stratfull carried out pioneering studies on bridges during 1957 (Stratfull, 1957). In 1963, Wood published the first study about the protection of reinforced concrete (Wood, 1963). In 1965, Frazier (1965), Gouda and Monfore (1965), and Scott (1965) published their articles about the use of galvanized steel in reinforced concrete, corrosion inhibitors and anti-corrosive proprieties of Portland concrete, respectively. These authors provided the first basis for the understanding of the urgent need to protect steel (and reinforced concrete in general) from corrosion. In 1966, Mather published the first study about concrete cracking due to environmental effects (Mather, 1966). In 1967, Hannsmann published Steel corrosion in concrete (Hannsmann, 1967). In 1968, Stratfull, published a study about chlorides effects on reinforced concrete and some months later Spellman and Stratfull started to publish results obtained from performing tests on laboratory specimens (Spellman & Stratfull, 1968; Stratfull, 1968). In 1969, Brezny and Kemp published the first studies related to the bond loss of corroded steel in concrete (Brezny & Kemp, 1969). In 1974, Ost and Monfore published a paper about chloride penetration into concrete (Ost & Monofore, 1974), while in 1976 Rosa published (in Italian) a study about a correct analytical evaluation of the aggressiveness of chlorides towards the reinforcements of reinforced and pre-stressed concrete in the journal Cemento (Rosa, 1976). In 1977, O’Neil, published the Army Engineer Waterways Experiment Station report no. 4 about the durability of pre-stressed concrete beams (O’Neil, 1977). Recently, however, Pedeferri, Andrade, Cairns and Broomfield, among others, have conducted and published studies aimed at the prevention, protection, diagnostics and restoration of reinforced concrete structures affected by corrosion, evaluating chemical and structural aspects of the corrosion of reinforced concrete (Andrade et al., 1993; Broomfield, 1997; Pedeferri & Bertolini, 2000; Cairns et al., 2007).

The scientific community, therefore, took up the challenge to find methods of prevention, protection, investigation and restoration of these kinds of structures in order to give them the adequate durability and the necessary safety up to the service life expected.

Nowadays, the knowledge on the problems related to corrosion of reinforced concrete has reached very high levels with the creation of additives and codes that allow the achievement of the expected service life for new structures.

The new, real challenge of this field of research is surely represented by existing structures built before techniques and technologies allowed reaching good levels of durability during the construction stage. The restoration and the evaluation of the residual load capacity of corroded structures are of essential importance for the safeguard of existing reinforced concrete both in terms of seismic safety along a structure’s life and in economic terms.

This special issue collects recent studies by experts from all over the world that capture the various aspects of corrosion of reinforced concrete structures, from its casting up to the evaluation of the seismic behaviour of corroded buildings. Castel et al. (Australia/France) present a paper about new service life criteria for concrete in chloride environments comparing the new reinforcement stress limitation to the Australian Standards AS3600 concrete building code and AS5100.5 concrete bridge code provisions. The have found out that the existing AS3600 and AS5100.5 code provisions are more conservative than the new limitation for lightly to normally reinforced concrete cross-section. Pantazopoulou et al. (Canada/Cyprus) have written a paper about the behaviour of corroded lap splices in reinforced concrete beams in order to evaluate the bond trend of corroded structural elements. Loreto et al. (USA/UK) present a case study about the assessment of reinforced concrete structures in marine environments estimating a failure probability associated with the steel corrosion initiation. Bossio et al. (Italy) have analysed the seismic behaviour of corroded reinforced concrete structures by performing finite element method(FEM) analyses. Last but not least, Lollini et al. (Italy) write about the use of stainless steel in reinforced concrete in order to increase durability and sustainability of such kinds of structures. The latter article comes from the group of Prof. Luca Bertolini one of the pioneering researchers in the area of corrosion in concrete, to whom the paper is dedicated.

Finally, this special issue offers be a starting point for all young researchers who want to accept the challenge that corrosion of reinforced concrete has started.