Laboratory assessment of the impact of modified asphalt binder on mechanical properties of grouted macadam mixtures under various performance conditions

Grouted Macadam (GM) mixtures are used for pavement coatings due to their strong load-bearing capacity and rutting resistance. However, weak asphalt-cement interface bonding reduces crack resistance performance of these mixtures. This study aimed to enhance this adhesion through implementing TEGO Addibit L300 additive at concentrations of 0.2, 0.3, and 0.4% by weight of asphalt binder. Various tests assessed additive's impact on asphalt binder properties, including penetration, softening point, and kinematic viscosity. Adhesion properties were evaluated through sessile drop and semi-circular bending bonding strength tests. Additionally, GM mixture performance was assessed with mechanical tests such as 3-point bending strength, indirect tensile strength, and Marshall stability, considering two conditions: samples tested immediately after a 28-day curing period (non pre-conditioned samples), and samples tested after the same period followed by exposure to 60 degree celsius for 16 h (pre-conditioned samples). Results revealed that the adhesion capacity of the asphalt binder significantly affected GM mixture performance in both conditions. Addition of TEGO Addibit L300 enhanced ductility and fracture energy by 53.9% and 45.2%, respectively, in non pre-conditioned samples. In pre-conditioned samples, the additive increased indirect tensile strength by up to 12.1%. The optimal dosage for improving GM materials performance was determined to be 0.3%.