Highway and city maintenance departments began wetting rock saltand abrasives with liquid calcium chloride more than 20 years ago to enhance the deicing performance of these materials on highways andstreets. The newest method for combining rock salt or abrasives with liquid calcium chloride is called stockpile wetting. Stockpile wetting of rock salt consists of the injection of solutions of calcium chloride into the upper sections of piles of rock salt stored for use in highway ice and snow control. In this study, stockpile wetting was simulated by injection of calcium chloride solutions into 6-in.-Diameter by 9-ft-tall columns of salt at temperatures of 50 deg f, 45 deg f, 40 deg f, 35 deg f, and 30 deg f. Concentrations of calciumchloride in the injected solutions ranged from 32 to 42 percent. The following characteristics of stockpile wetting were determined; (a) the extent and rate of movement of liquid downward through the simulated stockpile; (b) the quantity of liquid exiting the bottom of the stockpile as a function of temperature, solution concentration, and time; (c) the distribution of calcium chloride within the stockpile and quantities of calcium chloride in leachates; and (d) the ice melting capacity of stockpile-wetted rock salt compared to that of unwetted rock salt. Test results at temperatures 50 deg f or lower indicate that the preferred wetting parameters consist of injecting 42percent cacl2 at a rate of 8 gal per ton. At 50 deg f and lower, wetting with 32 percent, 35 percent, and 38 percent cacl2 yielded leachates. Quantity of leachates is primarily a function of cacl2 concentrations. Wetted salt that remains in storage during hot summer months may produce leachate based upon test temperature rise to 85 deg f. Stockpile wetted rock salt out-performed dry rock salt in total ice melt at all temperatures and almost all time intervals. This paperappears in transportation research record no. 1157, Deicing chemicals and snow control.
Samenvatting