Prediction of Brine Application for Pretreatment and Anti-Icing

Highway anti-icing strives to prevent the ice—pavement bond by pre-application of chemicals. An effective anti-icing program requires prediction and estimation of the amount, type, and timing of chemicals needed for the expected precipitation event while compensating for time and traffic decay of the chemical on the highway surface. Development of a sodium chloride brine anti-icing methodology was accomplished with an extensive study of brine residual decay on four pavement types. In October and November 2002, brine residual was monitored for up to 3 days after initial application on five sections of four-lane divided highways in Ohio. Four evenly spaced test stations within each highway section were monitored for residual as time passed and traffic accumulated. An instrument that dissolves salt and measures conductivity was used to measure available salt residual. Efficacy of the brine to prevent ice—surface bonding was estimated by using freeze—thaw cycles of various brines. After freezing, the bonds were held vertically as temperature was raised. The appearance of liquid below the interface indicated release. Field and laboratory data were correlated to estimate freezing temperatures for various salt residuals as a function of brine dilution represented by precipitation in depth of rainfall. Results support estimation of brine application requirements for three specific pavements based on expected precipitation and the salt residual models developed in the study. A set of graphs is included to implement the algorithm.