Process of recycling a bituminous product, preferably a bituminous membrane product containing reinforcement layers comprising the steps of: - Collecting waste bituminous products, preferably waste bituminous membrane products containing bituminous layers and reinforcement layers and sorting the waste bituminous products in a series of n waste bituminous product batch(es), - At least one grinding step of each batch of said series of n waste bituminous product batch(es) or a mixture of n waste bituminous product batch(es), thereby forming a fine ground batch, - Introducing said fine ground batch into a recycling unit (1, 1') having at least a rotor and a stator and an micronization chamber, said fine ground batch being heated and melted by shear strength upon the operation of the stator, rotor and micronization chamber and collecting a melted product. - Feeding said melted product in a mixing tank having a predetermined volume containing fresh carrier at a level comprised between 25 and 75w%, preferably between 30 and 60 w% with respect to the predetermined volume, at a residence temperature comprised between 160 and 200°C, preferably between 170 and 190°C, more preferably around 180°C, said mixing tank being continuously agitated with horizontal screw having mixing blades, said melted product being fed in said mixing tank until the volume of the melted product is comprised between 25 and 75 %, preferably between 40 and 70 w% with respect to the predetermined volume to provide a recycled bitumen having a predefined viscosity at 180°C for pumpability comprised between 500 and 45000 cPS, wherein said at least one grinding step comprises: - A first grinding of each batch of said series of n waste bituminous product batch(es) in a knife shredder for reducing the size of said each batch in a first shredded batch having a mean particle size distribution comprised between 20 and 50 cm, preferably between 20 and 40 cm, - A second grinding of each first shredded batch in a rotor granulator where each first shredded batch is reduced in size to a first crushed batch having a mean particle size distribution between 5 and 25 cm, preferably between 8 and 20 cm, - A third grinding of each first crushed batch in a rotor granulator (8, 9) where each first crushed batch is reduced in size to a first ground batch having a mean particle size distribution between 20 and 50 mm, preferably between 25 and 40 mm, more preferably between 27 and 35 mm. - Collecting waste bituminous products, preferably waste bituminous membrane products containing bituminous layers and reinforcement layers and sorting the waste bituminous products in a series of n waste bituminous product batch(es), - At least one grinding step of each batch of said series of n waste bituminous product batch(es) or a mixture of n waste bituminous product batch(es), thereby forming a fine ground batch, - Introducing said fine ground batch into a recycling unit (1, 1') having at least a rotor and a stator and an micronization chamber, said fine ground batch being heated and melted by shear strength upon the operation of the stator, rotor and micronization chamber and collecting a melted product. - Feeding said melted product in a mixing tank having a predetermined volume containing fresh carrier at a level comprised between 25 and 75w%, preferably between 30 and 60 w% with respect to the predetermined volume, at a residence temperature comprised between 160 and 200°C, preferably between 170 and 190°C, more preferably around 180°C, said mixing tank being continuously agitated with horizontal screw having mixing blades, said melted product being fed in said mixing tank until the volume of the melted product is comprised between 25 and 75 %, preferably between 40 and 70 w% with respect to the predetermined volume to provide a recycled bitumen having a predefined viscosity at 180°C for pumpability comprised between 500 and 45000 cPS, wherein said at least one grinding step comprises: - A first grinding of each batch of said series of n waste bituminous product batch(es) in a knife shredder for reducing the size of said each batch in a first shredded batch having a mean particle size distribution comprised between 20 and 50 cm, preferably between 20 and 40 cm, - A second grinding of each first shredded batch in a rotor granulator where each first shredded batch is reduced in size to a first crushed batch having a mean particle size distribution between 5 and 25 cm, preferably between 8 and 20 cm, - A third grinding of each first crushed batch in a rotor granulator (8, 9) where each first crushed batch is reduced in size to a first ground batch having a mean particle size distribution between 20 and 50 mm, preferably between 25 and 40 mm, more preferably between 27 and 35 mm. - A first grinding of each batch of said series of n waste bituminous product batch(es) in a knife shredder for reducing the size of said each batch in a first shredded batch having a mean particle size distribution comprised between 20 and 50 cm, preferably between 20 and 40 cm, - A second grinding of each first shredded batch in a rotor granulator where each first shredded batch is reduced in size to a first crushed batch having a mean particle size distribution between 5 and 25 cm, preferably between 8 and 20 cm, - A third grinding of each first crushed batch in a rotor granulator (8, 9) where each first crushed batch is reduced in size to a first ground batch having a mean particle size distribution between 20 and 50 mm, preferably between 25 and 40 mm, more preferably between 27 and 35 mm.