GB604993A - Improvements relating to road metals and methods of making the same - Google Patents

Abstract

Natural stone or chippings of rock or mineral or mixtures thereof for road metalling are coated by bitumen of a penetration at normal temperature of less than 300, and in which there are embedded small grains mainly of a size between 0.1 and 1.0 mm., consisting of hard and strong rock or minerals, or mixtures thereof, a portion or all of the grains being preferably entirely coated by the bitumen. The stones or chippings together with the small grains embedded in the bitumen may be covered with a bituminised binding agent of low viscosity or with bitumen in emulsified form before being laid out on the road surface, or may be provided with one or several layers of small grains and a bituminised binding agent of low viscosity or bitumen in emulsified form. The material may be produced by mixing the stones or chippings with the coating, e.g. hard asphalt, tar pitch, oxidised asphalt at a temperature at which it has a low viscosity, and adding the small grains to the mixture when the coating has cooled to a tough and tenacious condition. The small grains to which fillers such as burnt lime, hydrated lime, cement, kieselguhr, moler or fly ash may be added may be covered prior to their becoming embedded in this coating by road tar or mixtures of bituminous substances that include road tar as an essential component.