Matteo Gastaldi

Prevention of steel corrosion in concrete exposed to seawater with submerged sacrificial anodes

This paper presents the results of a study of the effectiveness of submerged sacrificial anodes in preventing the onset of pitting corrosion in the emerged part of marine piles. Experimental tests were carried out on reinforced concrete columns with steel embedded both in chloride free concrete and chloride contaminated concrete in order to compare the effects of sacrificial anodes on passive steel and on corroding steel. Results have shown, at least under the present testing conditions, that sacrificial anodes may be more effective in preventing corrosion initiation (i.e. in providing cathodic prevention) than in controlling ongoing pitting corrosion (i.e. in guaranteeing cathodic protection). Monitoring criteria for this type of prevention are also discussed.

Electrochemical techniques for the repair of reinforced concrete suffering carbonation-induced corrosion

Abstract The use of electrochemical techniques in the repair of reinforced concrete suffering carbonation-induced corrosion is increasing thanks to advantages connected with the possibility of preserving carbonated concrete and minimising the alteration of the surface, which make these techniques attractive for facades or monuments that have a high cultural, historical or architectural value. Electrochemical techniques allow repassivation of the steel through the application of a temporary or permanent cathodic current. These techniques have been used for several decades, although some aspects connected with their application have not been clarified yet. This paper presents a state-of-the-art on the techniques of electrochemical realkalisation and cathodic protection used in carbonated concrete, and describes the recent developments in this field, with particular reference to experimental investigations and on-site applications carried out in Italy in recent years.

Binders alternative to Portland cement and waste management for sustainable construction—part 1:

This review presents “a state of the art” report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1—the present paper—focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Performance parameters for the durability design of reinforced concrete structures with stainless steel reinforcement

Abstract Stainless steel reinforcing bars can be a suitable choice to guarantee the target service life of reinforced concrete structures exposed to aggressive chloride-bearing environments. Usually, the choice of the stainless steel grade is based on experts’ opinion or practical codes, whilst the adoption of performance-based approaches would allow to quantify the service life. To apply these models, when stainless steel reinforcement is used, the evaluation of the parameter which describes its performance when used in a chloride-bearing environment, i.e. the critical chloride threshold for the initiation of corrosion, is an indispensable requirement. This parameter cannot be easily determined since it is influenced by many factors and a standardised methodology for its evaluation has not been proposed yet. This paper describes the results obtained in an experimental research aimed at developing a test methodology which allows to evaluate the cumulative density function of the critical chloride threshold for the corrosion initiation. A test procedure based on mixed-in chloride and potentiostatic polarisation was proposed and applied to a duplex stainless steel reinforcement (1.4362). Corrective factors, which have to be applied in order to use these data for the design of structures in different exposure conditions, are discussed.

Corrosion behaviour of stainless steel reinforcement in concrete

Abstract In Europe, stainless steel rebars have been used since the mid-80s, whilst in North America, their use has been progressively growing only since the mid-90s. Due to their higher resistance to corrosion in comparison to ordinary black steel bars, they have been employed in a wide number of applications worldwide to achieve the durability performance of reinforced concrete structures, especially in extremely corrosive marine environments or when long service lives are required. In this paper, a state of the art on the corrosion resistance of stainless steel bars is reported. In particular, the contribution of Professor Luca Bertolini in this research field is considered. Initially, different testing methods are presented to point out their advantages and limitations and then the results on corrosion behaviour of different grades of stainless steel bars (i.e. austenitic, ferritic and duplex), obtained especially with tests in concrete, are analysed. Afterwards, some of the recent applications of stainless steel bars are illustrated.

Corrosion of Steel in Concrete and Its Prevention in Aggressive Chloride-Bearing Environments

This keynote paper deals with the durability of reinforced concrete (RC) structures exposed to aggressive environments characterized by high concentration of chloride ions, namely, marine environments or the use of de-icing salts. The mechanism of chloride-induced corrosion of steel in concrete is introduced, and its influence on the service life of RC structures is analyzed. Factors affecting the time to corrosion initiation are described with regard to both concrete properties and environmental exposure conditions. Design approaches available for achieving durability targets associated with the design service life are analyzed, focusing on studies carried out by the authors in recent years at the mCD Concrete Durability lab of Politecnico di Milano, which were aimed at improving the protection provided to the steel bars by the concrete cover, investigating the advantages of using corrosion-resistant stainless steel bars and developing the electrochemical technique of cathodic prevention.