What is AR Bitumen?
AR Bitumen test based on the viscosity of aged residue from the rolling thin film oven test. AR grading system also is an attempt to simulate asphalt binder properties after it undergoes a typical HMA manufacturing process. In addition, AR Grade Bitumen should be more representative of how asphalt binder behaves in HMA pavements.
Furthermore Viscosity grade have a thermoplastic property which causes material to soften at high temperatures and to harden at lower temperatures. This unique temperature/ viscosity relationship is important when determining performance parameters like adhesion, rheology, durability and application temperatures of bitumen. VG Bitumen spec, emphasis is on Bitumen ductility.
RTFOT Viscosity Grade Bitumen Binders (AR Bitumen) include
Viscosity Grade Bitumen AR-1000, 2000, 4000, 8000 and 16000.
RTFOT Viscosity Grade Bitumen (AR-Grades), in which the Viscosity of bitumen (asphalt) is measured at 60oC(140oF) after the roll on thin film oven test. Also Viscosity grade bitumen have a thermoplastic property which causes the material to soften at high temperatures and to harden at lower temperatures. This unique temperature/ viscosity relationship is important when determining the performance parameters such as the adhesion, rheology, durability and application temperatures of bitumen. Viscosity Graded Bitumen specifications further special emphasizes is placed on the Bitumen ductility.
Asphalt Rubber (A-R) Binder Specification
A-R binders used in surface treatments, ingredients are PG or AC binder and a minimum of 15% crumb rubber modifier (CRM), with the blend to meet the requirements of Item 300, Table 16. (CRM is recycled granulated tire rubber from passenger and truck tires. The requirements for CRM are in Section 300.2.G. and Table 13.) Manufacture of A-R requires mixing the asphalt and rubber in specialized tanks at high temperature and digesting or “cooking” for an hour or more to partially dissolve the rubber. This imparts a rubbery gooey characteristic to the blend. Types I, II, and III are the designations. For A-R Binders, as the number (Type) gets higher, the material gets softer (opposite other designation nomenclatures).
Asphalt rubber (AR) is defined by American Society for Testing and Materials (ASTM) as a blend of hot paving grade asphalt cement, reclaimed tire rubber and additives in which the rubber content is at least 15 percent by weight of the liquid asphalt binder and has reacted to cause swelling of the rubber particles.