Experimental study for evaluating crack retardation of asphalt concrete overlays

This paper presents the development of Asphalt Concrete Slab Fatigue Testing Equipment and its use in evaluating crack retardation of AC overlay under opening and mixed modes of displacement. The dense bituminous macadam (DBM) and the unreinforced and geotextile reinforced open graded asphalt concrete (OGA) overlays are investigated under cyclic simulated thermal and traffic loads having 5 mm differential deflection with zero load efficiency factor. Variation of tensile force and deformation in AC overlay with a number of simulated thermal load cycles are observed and cumulative decay of parameters, viz. tensile force, stiffness, and shear modulus, are computed. Overlay life, decay parameters, base isolation, and fabric effectiveness factors (FEF) are also evaluated. It is found that the unreinforced OGAC overlay performed better than that of DBM as a crack relief layer. In purely opening mode of displacement the best performance shown by the geotextile reinforced OGAC overlay becomes worse under mixed mode of displacement