Evaluation of Paving Bitumen from Waxy Crude of North Eastern Region of India

Bitumen is a binder which acts as an adhesive to bind mineral aggregates together to produce surface courses of road structure. Bitumen obtained from Indian refineries generally meets the current national standards and/or international specifications. However, bitumen meeting all specification still may not essentially give desired service life as the specifications may not sufficiently protect the quality and performance of bituminous mixes on actual road sites. Digboi refinery established in the state of Assam (North Eastern Region of India) produces, bitumen from indigenous crude, which is waxy in nature and is considered unsuitable particularly for construction of heavily trafficked roads. A laboratory study on evaluation of bitumen produced from waxy crude using Vacuum Residue Short Path Distillation (VRSD) unit was taken up. It was found that wax content is higher than the permissible limits and that the viscosity at 600C is lower than the permissible limits for S- 65 grade but it qualifies for S-90 grade bitumen. This bitumen also qualifies PG-58-22 performance grade of SHRP. Therefore, its performance on locations where 7 days average maximum pavement temperature is less than 580C may be acceptable. It was also found that the values of Marshall stability, Retained Marshall stability, Indirect tensile strength and Stiffness modulus (at 150C, 250C, 350C) are comparable with S-65 grade bitumen produced from imported crude (meeting IS-73-1992 specifications), indicating negligible adverse effect of higher wax content. Bituminous mix has adequate resistance to deformation, cracking and stripping. The resistance to temperature susceptibility for waxy crude bitumen is identical or better than the conventional bitumen. Hence, bitumen produced from VRSD unit is considered to be suitable for construction of roads. This paper discusses the evaluation of waxy bitumen produced from VRSD unit at Digboi refinery and also deals with the properties of bituminous mixes (viz., Stiffness modulus and Indirect tensile strength etc) prepared with waxy bitumen and non- waxy bitumen.

Keywords:

Crude , Waxy Bitumen , Marshall Stability , Viscosity , Stripping , Retained Stability , Indirect Tensile Strength , Stiffness Modulus