Effect of Initial Timing of Scarification and Overlay Treatment on Chloride Concentrations in Concrete Bridge Decks

Scarification and overlay (SO) procedures are often performed on concrete bridge decks to minimize the corrosion of reinforcing steel caused by chloride ingress. The objectives of this research were to collect information from personnel of state departments of transportation (DOTs) about their SO procedures and to recommend the timing of initial SO procedures on concrete bridge decks to prevent the accumulation of corrosion-inducing levels of chlorides and to extend deck service life. A survey of state DOTs was conducted; numerical modeling of SO treatments was performed for decks both with and without stay-in-place metal forms (SIPMFs). Full-factorial numerical modeling was performed through a service life of 50 years to determine the recommended initial timing of SO treatment in each case. Research results showed that bridge decks without SIPMFs could endure longer delays in SO treatment timing than those with SIPMFs. The allowable delay in SO timing ranged from 2 years to 6 years for decks with SIPMFs, while the allowable delay ranged from 6 years to 18 years for decks without SIPMFs. In addition, results showed that the allowable delay also depended on the original cover depth (OCD). On average, for each additional 0.5 in. (12.7 mm) of OCD, the period of additional allowable delay for decks with SIPMFs was 2 years; for decks without SIPMFs, however, the additional allowable delay was 5 years with each additional 0.5 in. (12.7 mm) of OCD.