Effect of stay-in-place metal forms on performance of concrete bridge decks

The primary objective of this research was to investigate the effect of stay-in-place metal forms (SIPMFs) on corrosion of steel reinforcement in concrete bridge decks. The study included 12 concrete bridge decks located within the Interstate 215 corridor in the vicinity of Salt Lake City, Utah. All decks were subject to similar traffic loading, climatic conditions, and maintenance treatments, including applications of deicing salts during winter months, and had been constructed during 1984-1989 with epoxy-coated rebar. Test methods included visual inspection, chain dragging, hammer sounding, Schmidt hammer testing, half-cell potential testing, and chloride-concentration testing. An analysis of covariance (ANOCOVA) was performed to evaluate the effect of SIPMFs on each of the 13 deck properties measured. Five of the 13 analyses yielded significant results, including age, cover, Schmidt rebound number, half-cell potential, and chloride concentration at 2-in. depth. While differences in age and cover resulted from limitations associated with the deck selection process and were accounted for in the ANOCOVA, the differences in Schmidt rebound number, half-cell potential, and chloride concentration were attributed to elevated moisture contents in decks with SIPMFs. While higher moisture contents lead to enhanced curing conditions that ultimately provide higher concrete strengths, they also facilitate greater ionic current flow necessary to sustain higher reinforcement corrosion rates and cause accelerated diffusion of chlorides into the concrete. Given these findings, SIPMFs should be used with caution in concrete bridge deck construction.