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

Abstract

This article describes the comparative analysis of tests on bond strength of hot-dip galvanized and black steel to concrete with and without chlorides. The bond effect was evaluated with six research methods: strength, electrochemical (measurements of potential, EIS and LPR), optical, and 3D scanning. The tests were conducted within a long period of 18 months on 48 test elements reinforced with smooth rebars ϕ8 mm from steel grade S235JR+AR and ribbed rebars ϕ8 mm and ϕ16 mm from steel grade B500SP. The main strength tests on the reinforcement bond to concrete were used to compare forces pulling out galvanized and black steel rebars from concrete. This comparative analysis was performed after 28, 180, and 540 days from the preparation of the elements. The electrochemical tests were performed to evaluate corrosion of steel rebars in concrete, particularly in chloride contaminated concrete. The behaviour of concrete elements while pulling out the rebar was observed using the system of digital cameras during the optical tests. As regards 3D scanning of ribbed rebars ϕ8 mm and ϕ16 mm, this method allowed the detailed identification of their complex geometry in terms of determining the polarization area to evaluate the corrosion rate of reinforcement in concrete. The test results indicated that the presence of zinc coating on rebars had an impact on the parameters of anchorage. In the case of ribbed rebars of 16 mm in diameter, the maximum values of adhesive stress and bond stiffness were reduced over time when compared to black steel rebars. Moreover, it was noticed that the stiffness of rebar anchorage in chloride contaminated concrete was considerably higher than in concrete without chlorides.

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.…”

Special Issue “Corrosion in Concrete: Inhibitors and Coatings”

“…Several authors have delt with the corrosion of the reinforcement bars in presence of chlorides, treating the subject from different points of view. Jasniok et al [ 11 , 12 ] investigated the corrosion behavior and the bond strength of zinc-coated low-carbon reinforcing steel in chloride contaminated concrete in comparison with black steel. Experimental results evidenced the favorable impact of zinc coating on steel by providing two-year protection against corrosion in environments with high chloride content.…”