Influence of waxes on bitumen and asphalt concrete mixture performance

The influence of different kinds of wax on bitumen and asphalt concrete properties was studied. Experimental parts involve mainly 160/220 penetration bitumens from different sources, four commercial waxes and one polyphosphoric acid. Binder properties were evaluated using laboratory equipment such as dynamic shear rheometer, bending beam rheometer (BBR), differential scanning calorimeter and force ductilometer. Asphalt concrete properties were evaluated using the tensile strain restrained specimen test (TSRST) and creep test at low temperature. At higher temperatures, dynamic creep testing and complex modulus tests were performed. Binder test results indicated that the magnitude and type of effect on bitumen rheology depend on the bitumen itself, type of crystallizing fraction in the bitumen and/or type and amount of additive used. Bitumen composition was found to be of decisive importance. For instance, adding FT-paraffin decreased the physical hardening index for all bitumens. Also polyethylene wax and montan wax showed this effect for some bitumens. Slack wax showed a large increasing effect on physical hardening. Addition of commercial waxes used showed no or marginally positive influence on bitumen ageing properties. Comparing asphalt mixture test results to the corresponding binder test results, the effects on asphalt mixtures from adding commercial wax or polyphosphoric acid were less evident. Significant binder physical hardening by BBR was not confirmed by TSRST. For the covering abstract see ITRD E157233