Sand can melt ice if it is heated naturally from the sun or a warm temperature--just like any other substance that is warmer than ice. The actual texture of sand does not cause ice to melt, which is why you would have to place a blanket of warm sand on ice for it to melt. The sand could similarly cause the ice to melt faster if it was placed on ice and then in direct sunlight, as sand heats very quickly.
Though sand cannot melt ice on its own unless it is heated by the sun, it may prevent more ice from forming. Placing a thick layer of sand on icy roads may reduce the amount of ice that can form on top of the sand. This is because sand particles are extremely small and mobile, making them hard to keep down with substances such as ice. Elements such as wind or rain may cause sand to move continuously, keeping the surface of the road from becoming substantially covered in ice. Though it may not prevent any ice from forming on the road, it can slow down the buildup.
Because many highway patrols place sand on ice during the winter, many people have come to believe that it is put there to melt the ice. This is not the case. The sand is put there to provide some traction on the ice. Without sand, an icy road would be extremely slick, leading to numerous accidents. However, by placing a rough layer of sand on the ice, the highway patrol is able to provide a make-shift form of gravel during cold spells. People mistakenly think that sand and salt perform the same functions on ice, but they do not. When salt is placed on an icy road, it is done so to melt the ice, creating a slick-free road. If salt is mixed into the sand, however, it may be able to melt the ice to a certain degree.