Fatigue Tests of Bituminous Mixtures with Inclusion of Initial Cracks

Abstract

The method of testing asphalt mixtures including initial cracks appearing in pavements is presented in this paper. The main aim of the study was a determination of the durability of asphalt mixtures in regard to crack sizes. For this purpose, the four-point bending test was performed according to the technical standard PN-EN 12697-24. The test was conducted with selected asphalt mixtures under the controlled strain and with the application of different crack sizes. Specimens with cracks were analyzed. Moreover, a model based on finite-element method (FEM) calculations was worked out, which allowed for the verification of conditions of the asphalt mixtures’ response to strains and the assessment of the state of stresses and strains at the crack tip. The wide range of studied conditions helped to determine the fatigue criterion for the “cracked” beam in the fatigue tests. The presented fatigue condition is very useful in the estimation of fatigue durability of asphalt mixtures. The results of analyses clearly showed the influence of cracks on the decrease in stiffness modulus. This effect has a nonlinear behaviour in the case of larger cracks. The proposed FEM model of beam including cracks is very useful in studies of stresses and tensile strains concentrated at the crack tip.