Components of a Flexible Pavement and Construction Steps

Flexible pavements are generally strengthened in stages by constructing bituminous pavement layers one after another in a certain period of time (Resurfacing). Resurfacing of road means the laying of the DBM and BC layers (Wearing Course) on the existing disturbed bitumen surface of the road.

Common Construction steps of flexible pavement

Cleaning of the surface: - First of all the surface of existing pavement layer is to be cleaned to remove dust and dirt. It is done manually or by using mechanical broom and high-pressure air jet from compressor or any other approved equipment/method.

Prime Coat: - Then Prime Coat is applied on the cleaned surface of existing pavement layer. Prime Coat is the first application of a low viscous liquid bituminous material over an existing porous or absorbent pavement surface like WMM base course. The Prime Coat is sprayed uniformly using a mechanical sprayer at a rate of 7.3 to 14.6 kg per 10 m2 area.

Tack Coat: - After 24 hrs of applying Prime Coat, Bituminous material of higher viscosity like hot bitumen at the rate of 4.9 to 9.8 kg per 10 m2 area Called „Tack Coat‟ is applied and then the laying of Wearing Course (DBM & SDBC/BC) is started. The Tack Coat and Prime Coat should be as per IRC: 16 “Standard Specification and Code of Practice for Prime and Tack Coat”.

Mixing & Transportation: - Mixing of the Bituminous Materials is done at hot mix plant where all the laboratory testing of the bituminous materials are done before mixing and after mixing. The testing report should fulfill all the criteria given in IRC: 111-2009 “Specification for Dense Graded Bituminous Mixes”. The Bituminous Mix is then charged in Truck/dumper and transported to the site for paving. Once the material is charged and transported, it must be paved it must not be postponed. The temperature of the charged bituminous mix is between 150-1650C here or depending on the grades of Bitumen. The Bituminous mix must be paved within Laying Min. temperature 1400C and Rolling Min. Temperature 900C. All specification has been given IRC: 111-2009.

Paving of Bituminous mix/Spreading: - Pavers are used for paving the Bituminous Mixes. In paving operation, the pavers are used for laying the DBM or SDBC/BC layers and to provide the needed thickness and slope/camber.

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