The salt content within the asphalt automatically melts ice without the need for grit spreaders. The formulation mixed a salt (potassium formate) with a hydrophobic (water-repelling) polymer known as styrene-butadiene-styrene. That mixture was in turn added to bitumen, which is the main binding ingredient in asphalt. The resulting composite material was found to be just as tough as regular bitumen, yet its salt content "significantly delayed" the formation of ice on its surface. (Source: Gelation-Stabilized Functional Composite-Modified Bitumen for Anti-icing Purposes. 2015. Ind. Eng. Chem. Res., 2015, 54 (50), pp 12587–12596. Derya Aydın, Riza Kizilel, Ramazan O. Caniaz, and Seda Kizilel.)