There are no suitable surface-dressing binders for many road sites where vehicles turn and brake sharply. Conventional tar and bitumen binders cannot be used because they lack the cohesive strength necessary to retain chippings under the shear stresses imposed. On the other hand, alternative epoxy-resin-based binders, which are able to cope with high stresses, are too expensive for all but the most severe sites where large savings from reducing skidding accidents cover their high initial cost. Two road experiments on different scales are reported. In the first the performances of 7 thermoplastic binders have been compared by using cores inserted in the wheel-track at the approach to a roundabout. The best two binders were used subsequently in a full-scale experiment on another roundabout approach, and one of these, a bitumen modified with a linear styrene-butadiene-styrene block copolymer and applied as an emulsion, has performed satisfactorily. (Author/publisher)
Abstract