In order to ensure the durability and flexibility of the pavement, it is necessary to choose the suitable grade of bituminous binder for a specific section of the National Highway. This decision should be based on factors such as the current loading conditions, ambient temperature, and precipitation.
Considering the above requirements, the following has been mandated by S & R (P&B/ New Technology) Zone, Ministry of Road Transport and Highways, Government of India vide circular bearing reference number RW/NH-35072/05/2018-S&R(P&B) (E165688) dated August 23, 2023:
i. Selection of Appropriate Grade of Bitumen Binder:
- The bituminous binder for conventional pavement courses shall be in accordance with IRC: 37 “Guidelines for the Design of Flexible Pavements”. However, provisions contained in relevant IRC Guidelines/Standards shall be applicable for selection of binder grade for pavement courses such as Stone Matrix Asphalt (SMA), Gap-graded Rubberized Bituminous Mixes (GGRB), High Performance Mixes (HIPER), and Cement Grouted Bituminous Mastic (CGBM).
- Specifications for Bituminous Adhesive 2.2.1 Viscosity Grade Bitumen: Viscosity Grade Bitumen shall conform to the quality characteristics specified in IS: 73 “Paving Bitumen Specification” with the exception that the minimum viscosity at 60°C for VG-40 grade bitumen shall be 3600 Poise as recommended in IRC: 37. In addition to these tests, bitumen shall be examined for wax content in accordance with IS: 10512, and wax content shall not exceed 4.5%.
- Polymer Modified Bitumen (PMB): Polymer Modified Bitumen must meet the requirements outlined in IRC: SP: 53 “Guidelines for the Use of Modified Bitumen in Road Construction.” Furthermore, PMB must meet the standards given in IS: 15462 “Polymer Modified Bitumen (PMB)-Specification” for Multiple Stress Creep Recovery.
- Rubber Modified Bitumen (RMB): Rubber Modified Bitumen must meet the requirements established in IRC: SP: 53 “Guidelines on the Use of Modified Bitumen in Road Construction.”
ii. Source of Procurement of Bituminous Binder:
- Viscosity Grade Bitumen: Due to the shortfall in domestic production vs demand, the use of imported bitumen may be acceptable. The traceability of imported bitumen must be guaranteed. A Manufacturer’s Test Certificate (MTC) must be presented with each tanker load. MTC will also include information such as the name of the origin country, the name of the refinery, the GPS coordinates of the loading and unloading ports, the refining technique used, and so on.
- Modified Bitumen: To reduce the possibility of separation, modified bitumen (PMB, CRMB, and NRMB) should be obtained only from domestic sources. Furthermore, because not all refineries produce modified bitumen, modified bitumen might be obtained from domestic refineries or independent producers.
iii. Quality Assurance & Quality Control of Bituminous Binder:
- Laboratory for Bituminous Binder Testing: Refineries, producers, manufacturers, and suppliers must have ISO: 17025 “General requirements for the competence of testing and calibration laboratories” certification from NABL. Each piece of equipment must have a current calibration certificate.
- Bituminous Binder Quality Assurance and Control: Annexure-1, 2, 3 & 4 provide details of internal quality control by refinery/supplier/producer, repeatability & reproducibility of test results, responsibilities of departmental officers (PD/EE), responsibilities of AE/IE, mandatory testing of sample taken from tankers before unloading, and so on for domestically procured viscosity grade bitumen, imported viscosity grade bitumen, and domestically procured polymer modified bitumen. To ensure the quality of bitumen/modified bitumen, the SOP must be strictly followed.
The above guidelines shall be effective from the date of the circular’s issue.