Review of Galvanized Rebar Performance on G-109 Specimens after 9 Years

As part of the efforts toward achieving bridges with a service life of 100 plus years, a study was initiated almost nine years ago to assess the use of galvanized rebars. Three different reinforcing steel bars were used in this study: regular carbon steel rebar, galvanized rebar and Zn-4.9Al-0.1 misch metal bath bar “GF” (the last two are Zn coated bars). The specimens used to rank the rebars were ASTM G-109. Several concrete-mixes-series were prepared. Parameters varied: two water/cement ratios and the effect of two admixtures pozzolanic admixtures. Another variable was the shape of the top rebar. In some specimen sets, the specimen had an initial simulated crack. Selected series with galvanized rebars were prepared with the rebar intentionally damage before exposure. Forensic and metallographic examinations were conducted on selected specimens after being exposed for almost nine years. Results of this examination will be presented. As a general summary, a number of the data sets indicated that galvanized bars out-performed black bars, but in certain conditions the performance difference was marginal. The GF bars have exhibited excellent corrosion resistance in the standard and simulated concrete cracked configurations (the only conditions tested for GF bars).