Mix design of grouted porous asphalt concrete for wearing course layers

A road is a multi-layer load-bearing structure, whose mechanical behavior depends on the design and arrangement of the layers. Asphalt surfaced pavements require resurfacing every 10 to 15 years and traditional repairs don’t last at long. Recent advances in pavement design suggest the use of a combi-layer (grouted porous asphalt) instead of the traditional asphalt concrete for the wearing-course in case of heavy or low-speed channellized traffic. With the aim to provide a guidance pertaining to combi-layers design, the Authors developed a research program for evaluating the performance of mixtures of asphalt concrete filled with cement mortar, produced using a soft modified bitumen and calcareous aggregates, adopting different particle size distributions. Traditional tests (Marshall and Indirect Tensile Strength tests) were executed on the grouted mixtures in order to evaluate the performance varying different parameters, referring to the curing of the samples (1, 7, 28 days) and to the testing temperature (25, 45, 60, 70°C). Moreover, the mechanical characterization was assessed by triaxial tests performed with an original apparatus (UNIBAS-M.P.T.), patented in Italy, achieving interesting results. In particular, the usefulness of the device for the evaluation of the structural response of the road pavements was shown on the basis of the rupture domains obtained analyzing the mixtures.