SPECIAL ON PROTECTIVE TECHNOLOGIES FOR BRIDGES, HIGHWAYS, INFRASTRUCTURES
ANALYSIS
Polymer Modified Cementitious Coatings on Concrete to Control Chloride-Induced Corrosion of Steel Rebars Fabio Bolzoni, Andrea Brenna and Marco Ormellese CMIC G. Natta Department - Politecnico di Milano, Italy
fabio.bolzoni@polimi.it, andrea.brenna@polimi.it, marco.ormellese@polimi.it
Introduction Corrosion of carbon steel reinforcements may occur because of concrete carbonation, i.e. the reaction of atmospheric CO2 with
cement paste that lowers pH, and by the presence of chlorides in concentration higher than a critical level, that is generally
considered in the range of 0.4-1% by cement weight for concrete structures exposed to atmosphere [1]. Corrosion prevention is primarily achieved in the design phase, by using high quality concrete and adequate concrete cover. Additional prevention methods, as inhibitors, coating, corrosion resistant rebars of cathodic protection, are adopted when severe © Politecnico di Milano
environmental conditions occur as well as on structures requiring very long service life. Concrete surface treatments are of great interest for protection of reinforced concrete structure as an alternative to more expensive preventative techniques, as well as in rehabilitation. Nowadays various surface treatments are available, suitable for maintaining their protectiveness for long-time and for a good service life, providing that a proper application and an adequate maintenance are assured [1-2]. Four main classes of surface treatments are available: a) organic coatings that form a continuous ȴlm; b) hydrophobic treatments that line the surface of the pores; c) treatments that ȴll the capillary pores; d) cementitious layers. Their eect is twofold: they reduce the permeability of aggressive agents in concrete and they decrease the water content of concrete with the resulting decrease of concrete electrical conductivity and corrosion rate. PoliLaPP, Laboratory of Corrosion of Materials “P.Pedeferri” (Politecnico di Milano) studied the long-term eect on chloride-induced corrosion of polymer modiȴed cementitious
Corrosion of carbon steel reinforcements may occur because of chloride penetration.
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mortars applied on concrete surface [3]. These coatings have good adhesion, ȵexibility low elastic modulus and a considerable crackbridging ability. Furthermore, they show low water permeability and