A Two-Year Evaluation of Corrosion-Induced Damage to Hot Galvanized Reinforcing Steel B500SP in Chloride Contaminated Concrete

Abstract

Corrosion-induced damage to concrete reinforced with bars is a serious problem regarding technical and economic aspects and strongly depends on used materials, corrosion environment, and service life. Tests described in this paper refer to a two-year evaluation of the effectiveness of protection provided by zinc-coated low-carbon reinforcing steel of grade B500SP in concrete against chloride corrosion. Performed tests were comparative and included measurements conducted on four groups of concrete test elements with dimensions of 40 mm × 40 mm × 140 mm reinforced with a bar having a diameter of ϕ8 mm. Particular groups were a combination of different types of concrete with or without chloride additives, with galvanized or black steel. Chlorides as CaCl2 were added to the concrete mix in the amount of 3% of cement weight in concrete. Reinforced concrete specimens were periodically monitored within two years using the following techniques: linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Polarization measurements were conducted in a three-electrode arrangement, in which a rebar in concrete served as a working electrode, stainless steel sheet was used as an auxiliary electrode, and Cl−/AgCl,Ag was a reference electrode. Comparative tests of changes in the density of corrosion current in concrete specimens without chloride additives basically demonstrated no development of corrosion, and possible passivation was expected in case of black steel. Higher densities of corrosion current were observed for galvanized steel during first days of testing. The reason was the dissolution of zinc after the contact with initially high pH of concrete pore solution. Six-month measurements demonstrated a higher density of corrosion current in concrete specimens with high concentration of chlorides, which unambiguously indicated corrosion in concrete reinforced with galvanized or black steel. Densities of corrosion current determined for selected specimens dramatically decreased after an 18-month interval in measurements. Corrosion was even inhibited on black steel as an insulating barrier of corrosion products was formed. The above observations were confirmed with structural studies using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. Results obtained from corrosion (LPR, EIS) and structural (SEM, EDS) tests on specimens of concrete reinforced with steel B500SP demonstrated a very favorable impact of zinc coating on steel by providing two-year protection against corrosion in the environment with very high chloride content.

Influence of the Type of Cement and the Addition of an Air-Entraining Agent on the Effectiveness of Concrete Cover in the Protection of Reinforcement against Corrosion

“…For this reason, research is constantly being carried out to maximize the protection of steel bars against corrosion or to assess the possibility of replacing black steel with more corrosion-resistant reinforcement. The effectiveness of reinforcement made of galvanized steel is tested [ 6 ], including in an aggressive chloride environment [ 7 , 8 ]. Experimental tests also concern specimens and elements of the structures in which steel bars are replaced with a non-metallic reinforcement made of glass fiber (GFRP) [ 9 , 10 ], carbon (CFRP) [ 11 ], basalt [ 12 ] or even aramid (AFRP) [ 13 ].…”

“…The conducted tests prove the effectiveness of the use of alternative forms of reinforcement in order to reduce corrosion in concrete elements. However, at the same time, the authors point to other problems, e.g., related to the limited adhesion of rods to concrete [ 7 , 11 ], a different (rapid, uncontrolled) damage mechanism of elements in which such reinforcement was used [ 11 , 13 ], the difficult workability of the concrete mix with the addition of fibres [ 14 , 15 ], high performance requirements [ 7 , 8 ] or the high cost of such reinforcement.…”

An 18-Month Analysis of Bond Strength of Hot-Dip Galvanized Reinforcing Steel B500SP and S235JR+AR to Chloride Contaminated Concrete

“…100 µm in thickness. The detailed analysis of the quality of the zinc coating on ribbed rebars of the same batch and made of steel grade B500SP is presented in the paper [ 38 ]. It also includes the effects of chloride-induced degradation of the coating.…”

“…45° with reference to the axis of the reinforcement [ 31 , 34 ]. It should be emphasized that hot-dip galvanization usually generates a thicker layer of zinc in the ribbed area, which can slightly affect the inclination of the ribs [ 38 ]. Then, a small change in the stress values f b can be noticed compared to the rebar without zinc coating.…”

Corrosion performance of steel rebars by application of electroless Ni-P-W coating: An optimization approach using grey relational analysis

“…Open circuit potential (OCP) and tafel polarization revealed that the rebars were in passive state. Remarkable corrosion performance in severe chloride contamination was also seen over a period of 2 years [44]. Nevertheless, porosity of concrete increased due to the formation of hydrogen during reaction of zinc coating with fresh cement during the initial stages [45].…”