2019 CSCE Annual Conference - Laval (Greater Montreal) Conference
Mr. Martin Gagné, International Zinc Association
Dr. Frank Goodwin
Mr. Gary Dallin, Galvinfo Centre
Corrosion of steel reinforcing bar (rebar) is the most significant cause of concrete failure, resulting in expensive repairs and premature replacements across the country. This presentation will discuss proven low-cost zinc coating processes for reinforcing steel. The properties of this new coated rebar and its contribution to improvement of concrete performance will be presented together with the status of related national and international standards.
Hot-Dip Batch Galvanizing of steel is a proven technology that has been in use for over 100 years, protecting structures exposed to marine and deicing salt environments from deterioration. This technology has been applied to reinforcing steel for over 50 years, with most structures still operating and in good condition today.
The Continuous Galvanized Rebar (CGR) coating process is similar to galvanizing of sheet steel. As an in-line process, the bar is fluxed, induction heated and coated with a uniform zinc layer in a matter of seconds. With reduced production time, CGR requires shorter lead times than current corrosion resistant bars. The zinc coating applied is durable and resistant to abrasion that is routine during transport and construction.
Additionally, the coating is also highly ductile and can be bent without cracking to diameters of less than 4x the rebar diameter. This property ensures the bars can be pre-fabrication, reducing cost and accelerating construction schedules.
Once in the concrete, the zinc coating protects the rebar both as a barrier coating and with the well-known sacrificial properties of a galvanized coating. Test results indicate that the use of galvanized rebar with high quality concrete and customary depths of concrete cover will enable rebar to be protected for 100 years.
The ability to greatly extend the life of concrete bridges by using galvanized rebar is important to maximize the public investment in infrastructure projects. Life cycle cost analysis confirms that using a zinc coated bar from the beginning of a project reduces the future maintenance needs of the bridge and significantly reduces cost over the life of the project. Many bridge maintenance plans require zinc anodes to be used to extend bridge life. Bridges that use zinc from the beginning already benefit from the sacrificial properties of the metal, delaying the need for maintenance programs to prolong bridge life.
From coating to placement to maintenance, CGR contributes positively to accelerated bridge construction and offers extended corrosion protection, extending bridge life and reducing life cycle costs.