Laboratory and field evaluation of recycled unbound layers with cement for use in asphalt pavement rehabilitation

The use of recycling techniques in the rehabilitation of old pavements has become an important tool for pavement engineering practices. The reduced costs and the scarce natural resources are the main reason for which the development and improvement of recycling processes have been studied by many researchers around the world. The main objective of this paper is to investigate the structural responses of an asphalt pavement after using deep recycling techniques of granular layers with an addition of cement for the rehabilitation of asphalt pavements. Laboratory analysis using resilient modulus, indirect tensile strength (ITS), and unconfined compressive strength (UCS) tests were performed for mixes with 5 and 6 % of cement content, two compaction energies and three curing periods. In the field, two sections using 250 and 300 mm thicknesses of a recycled base layer were constructed with 5.0 % of cement addition. An evaluation of these experimental test tracks was conducted by performing deflections and by mechanical characterization of samples extracted from the test site at different ages. The results indicated differences in UCS and ITS values for the laboratory mixes. Field specimens from the 300 mm-section presented higher stiffness than the 250 mm. Studies have shown that the resilient moduli determined from nondestructive test based on backcalculation procedures are similar from those determined in the laboratory through modulus of elasticity tests.