Effect of coal and long‐chain polymers on the characteristics of bituminous road binders

Abstract

Bituminous road binders have been prepared containing dispersed long‐chain polymers, including both natural and synthetic rubbers, and also certain South African coals dispersed in them under high temperature conditions. Examination of the rheological properties of these binders has confirmed that both types of additive produce an improvement of the viscosity/temperature characteristics and a reduction in brittleness at low temperature. If both coal and polymer are incorporated together, however, the improvement is greater than that calculated from the sum of the separate effects of the two additives. Some of the polymers studied were found to stabilise mixtures of pitch and petroleum bitumen which are normally not completely miscible. An apparatus is described for assessing brittleness under stress and loading times of the same order as those occurring on the road under traffic. The methods of test used in the investigation are critically discussed.