Laboratory and field investigation of grouted macadam for semi-flexible pavements

Grouted macadam (GM) made of an open-graded asphalt skeleton whose air voids are filled with a cementitious grout, is used as wearing course in semi-flexible pavements. GM stands out for its high stiffness and rutting resistance, as well as for its chemical resistant and jointless surface. Although it could satisfy all the engineering properties requested by ports, airports and industrial pavements, there are still few applications worldwide and the mechanical characteristics have rarely been investigated in depth. The main objective of this paper is to compare the stiffness, fatigue resistance and the cracking propagation resistance of GM mixtures manufactured in the field and in the laboratory. The thermal susceptibility and the ravelling resistance of laboratory specimens were also evaluated. The findings show that the stiffening contribution of the grout improves the fatigue life especially at high deformation levels. However, due to the hardening of the asphalt skeleton caused by the ageing of the bitumen, GM mixture may exhibit a brittle behaviour. Considering the validation and correspondence between laboratory and field results, the data could be useful for establish some analytical pavement design criteria.