Shear performance of recycled asphalt mixture based on contact interface parameter analysis

The mechanical characteristics, quantity, and distribution of contact interfaces in the composite skeleton of recycled asphalt mixture affect the consistency of deformation of new and old aggregate composite skeleton, further affecting the macroscopic mechanical properties of material. To quantitatively analyze the effect of reclaimed asphalt pavement (RAP) content on the mechanical characteristics of contact interface and shear performance of recycled asphalt mixture, the tangential elastic stiffness of interface of new-new, new-old, and old-old contact types is defined as k(snew-new), k(snew-old), and k(sold-old), respectively; interfacial shear tests were carried out for new-new, new-old, and old-old contact types. Digital image technology and statistical analysis were used to obtain the proportion distribution of alpha(new-new), alpha(new-old), alpha(old-old) of three aggregate contact types under different RAP contents. Combined with the calculation results of interface tangential elastic stiffness and shear modulus with different RAP contents, an interface tangential elastic stiffness estimation model and a shear modulus calculation model were established, and the rationality of the model was verified. The results show that different interface contact types significantly affected the shear test results. The tangential elastic stiffness of old-old contact type is the highest, 0.3416 x 10(6) N/m. The tangential elastic stiffness of new-old and new-new contact types are 0.2254 x 10(6) N/m and 0.0992 x 10(6) N/m, respectively. The results of contact interface shear test of recycled asphalt mixture with different RAP contents show that the overall trend of shear curve is similar, and the peak value and mean value of shear force do not change consistently with the increase of RAP content. Using the least square mathematical analysis method for overdetermined equation, the goodness-of-fit of k(s) regression model with different RAP contents is 0.85. There is a good correlation between the shear modulus calculation results and uniaxial penetration test results, and the correlation coefficient is 0.80. (C) 2021 Elsevier Ltd. All rights reserved.