A restricted finite element study has been made to verify whether uniaxial cyclic compression creep tests are representative of stress path conditions in asphaltic concrete top, secondary and base courses. In top and secondary courses, unfavourable stress conditions occur under edge of truck tyres. These cause large principal stress variations in one direction combined with small principal stress variations in other direction, resulting in large more or less horizontal shear loads. For top courses these conditions can be schematised as cyclic compression. Maximum ratio between deviatoric and compressive stresses in secondary courses is considerably higher than in top courses. This should be borne in mind when an overlay is applied to a wearing course. For base courses, the most unfavourable stress conditions occur under centre of truck tyre, consisting of horizontal cyclic tension-compression combined with limited vertical tension-compression. Further research is necessary before final decisions are made concerning test conditions. Availability of material model parameters and available computer program imposed restrictions on the analysis. The results presented must be treated with reservation. Further determination of material model parameters, further development of finite element code and practical verification of theoretical results is necessary to establish performance test procedures.
Samenvatting