Abstarct: Grouted Macadam mixture is a composite consisting of two phases of asphalt matrix and cement slurry, which has been used as a pavement coating material due to its favorable advantages such as: high capacity of static load, high rutting resistance, good durability and resistance to chemical attacks and fossil fuels. However, due to the large difference between the characteristics of the two phases of asphalt and cement, as well as the weak interface (connection) between them, these mixtures do not have a suitable performance against cracks caused by environmental conditions and frequent traffic loading. If it is possible to improve the interface between two phases of asphalt and cement of grouted Macadam mixtures, the performance of these mixtures against the appearance of cracks can be improved. For this purpose, in the present study, TegoAddibit L 300 additive was used as an adhesion improver of bitumens used in the asphalt matrix of grouted Macadam mixtures in contents of 0.2, 0.3 and 0.4% by weight of bitumen. In order to evaluate the effect of this additive on the behavioral characteristics of bitumen, the penetration degree, softening point and kinematic viscosity tests were used at a temperature of 135 degrees Celsius. Also, in order to check the adhesion properties of bitumen, sessile drop tests and semi-circular bending (SCB) adhesion strength were used. The performance of grouted Macadam mixtures was evaluated in two situations of 1-short-term: after the 28-day processing period and 2-medium-term: by applying temperature conditions of 60 degrees Celsius for 16 hours on the samples. For this purpose, indirect tensile tests at ambient temperature and low temperature: -10 degrees Celsius, three-point bending strength at low temperature: -10 degrees Celsius and Marshall stability were used. The results showed that the adhesion ability of asphalt binder has a direct effect on the performance of grouted Macadam mixtures in both short-term and medium-term conditions. It was observed that the addition of TegoAddibit in the short-term condition can increase the ductility and fracture energy of grouted Macadam mixtures in the ambient temperature of indirect tensile test by 53.9% and 45.2%, respectively, compared to the control samples. Also, the indirect tensile strength of grouted Macadam mixtures at medium situation under the effect of this additive can increase up to 12.1% compared to the control samples. The overall results of the tests showed that the optimal amount of TegoAddibit additive in order to improve the performance of grouted Macadam mixtures is 0.3 percent by weight of asphalt binder of asphalt phase.