Methodology for the Construction of Bituminous Road Works
The construction of Bituminous Road Works in India is governed by the Indian Standards and guidelines provided by the Ministry of Road Transport and Highways (MoRTH). Here is a general methodology to be followed for the construction of Bituminous Road Works as per Indian Standards:
The subgrade is prepared by excavating the soil and removing any debris or organic material. It is then compacted to achieve the required density and level. The subgrade should have a minimum CBR (California Bearing Ratio) of 2% for rural roads and 5% for urban roads.
Granular Sub-Base (GSB):
The GSB layer is constructed on top of the subgrade to provide a stable base for the bituminous layer. The GSB layer is typically 200-300 mm thick and consists of crushed stone or gravel. The material is compacted to achieve the required density and level.
Bituminous Concrete (BC) Layer:
The bituminous layer is constructed on top of the GSB layer. The thickness of the bituminous layer varies based on traffic volume and climatic conditions. The bituminous layer consists of a binder course and a wearing course. The binder course is typically 50-75 mm thick and consists of coarse aggregates and bitumen. The wearing course is typically 20-40 mm thick and consists of finer aggregates and bitumen.
Construction of Drainage Structures:
The construction of drainage structures like side drains, cross-drains, and culverts should be done before laying the bituminous layer.
Construction of Kerb and Channel:
The construction of kerbs and channels should be done before laying the bituminous layer. The kerbs and channels are constructed to provide a smooth flow of water along the road and to protect the bituminous layer from damage due to water stagnation.
Application of Tack Coat:
Before laying the bituminous layer, a tack coat is applied to the GSB layer. The tack coat is a thin layer of bitumen that helps in bonding the bituminous layer with the GSB layer.
Laying of Bituminous Layer:
The bituminous layer is laid using a paver machine. The bituminous material is heated and mixed in a hot mix plant and transported to the site in trucks. The paver machine spreads the bituminous material and compresses it to achieve the required density and level.
Compaction of Bituminous Layer:
After laying the bituminous layer, it is compacted using a roller. The roller should have a minimum weight of 8 tonnes for the binder course and 10 tonnes for the wearing course. The bituminous layer should be compacted to achieve a minimum density of 92%.
Quality control tests should be conducted at every stage of construction. The tests include the Marshall Stability test, bulk density test, and compaction test. The test results should conform to the specifications provided by the MoRTH.
After the bituminous layer has been compacted, a thin layer of bituminous material is sprayed on top to provide a smooth surface finish. The surface dressing is typically 6-8 mm thick.
These are the general steps to be followed for the construction of Bituminous Road Works as per Indian Standards. The specific details may vary based on the project specifications and site conditions.