METHODOLOGY OF CONSTRUCTION OF PROFILE CORRECTIVE COURSE OVER EXISTING CARRIAGE WAY (BY BM OR DBM)

 

CONSTRUCTION
OF PROFILE CORRECTIVE COURSE OVER
EXISTING CARRIAGE WAY (BY BM OR DBM)

1. Scope:

 The work shall consists of mixing, laying and compacting of Dense bituminous macadam for profile corrective course on existing carriage way.

2.References:

 MoRT & H specifications clause no . 501.8 , 507 and Technical specifications of contract.

3.Equipments:

Sensor paver, Tandom roller, water tanker, dumpers, Asphalt plant, Wheel loader, Auto level, leveling staff.

4. Tools:

  Lime powder, string, sensor pegs, measuring steel tape, straight board, thermometer, steel scale.

5. Responsibility:

Responsibility of Implementation of this procedure lies with Site engineer and Section in charge of Asphalt work.

6. Materials:

·           Binder: The material shall be 60-70 grade bitumen in DBM for profile corrective course.

·           Aggregate: The coarse and fine aggregate shall consist of crushed stone. These shall be clean, hard, durable, dry and free from soft or friable, organic or deleterious matter. These shall satisfy the physical requirement set forth for the individual relevant materials/mixes. Before approval of the source it shall be tested for stripping.

7. Procedure:

This work shall consist of in single course or in multiple course of crushed

                  aggregates premixed in HMP with 60-70 grade bitumen at the rate of as per DBM                           mix  design to the line , level and slopes as shown in drawings.

                 The aggregate blended with coarse and fines shall consist of crushed rock and it Shall                      satisfy the following physical requirements of grading – as per MORT&H.

Aggregate property	Specification
	DBM
Grain size	Max.5% passing in 75mic sieve
Combined FI+EI Index	Max 30 %
Los angles Abrasion Value	Max 35 %
AIV	Max 27 %
Soundness with sodium sulphate	Max 12 %
Water Absorption	Max 2 %
Stripping(Retained coating)	Min 95 %
Sand Equivalent Value	Min 50 %

 

·   The pre-mixed bituminous material shall be prepared in an electronically controlled hot mix plant of adequate capacity and capable of yielding a uniform quality mix

·    At the time of mixing the temperature of aggregate shall be 150-170*C, bitumen shall be 150-165*C and the mix temperature shall not be more than 165*C.

·           The material shall be transported in clean vehicles, a thin coating of lubricating oil may be applied to the interior of the vehicle to prevent sticking.

·           The surface on which the bituminous layer to be laid shall be swept clean of all loose and extraneous materials by mechanical or by any other suitable method.

·           Profile corrective course for correcting the existing pavement profile shall be laid to varying thickness as shown on the drawings or as indicated in the contract documents.

·           Any high spots in the existing surface shall be removed.

·           Where the maximum thickness of profile corrective course not more than 40 mm , the profile corrective course shall be constructed as a integral part of the overlay course. In other cases, the profile corrective course shall be constructed as a separate layer.

·           The material which is to be laid shall be mix designed in accordance with Marshall Method.

·         The material shall be spread by means of self-propelled paver finisher of with electronic sensor device, except in inaccessible areas, to the required thickness, lines and camber as shown in the drawings.

~ The thickness of compacted layer shall not exceed 100mm.

~ In the inaccessible areas the mix shall be laid with suitable hand tools. ~ At the time of laying a minimum temperature of 125~ C shall be maintained.

·           As soon as the material was spread, compaction shall commence and completed within the rolling temperatures.

·           Rolling shall be completed at min. 90*C of Mix. Rolling of longitudinal joints shall commence behind the paving operations, after this the rolling shall start from the lower edge towards upper edge parallel to the centre line of road, and each pass shall overlap 1/3rd preceding pass.

·           All deficiencies in the surface shall be made good behind the paver before the initial rolling commenced.

 ·    The initial rolling shall be done with a smooth wheeled roller of 80-100Kn static weight, followed by intermediate rolling with a vibratory roller of 80-100Kn static weight.

·    The finishing rolling shall be done a smooth wheeled tandem roller of 80-100Kn weight.

·   In uni-directional camber and super-elevated portions the rolling shall progress from lower to the upper edge. Rolling shall be done as per approved rolling pattern, which is decided in trial stretch.

·   All the joints shall have offset of , at least, 300mm from parallel joints in the layer beneath, longitudinal joints shall coincide with either the lane edge or the lane markings and shall not situated in wheel track zones.

8. Acceptance criteria:

~ The tolerance in level shall be in between +6 to -6mm. 

~ The core density shall be more than 98% of lab density.

~ The mix binder content shall be +/- 0.3% of designed OBC.

9. Safety Requirements:

~ All dumpers, rollers, tankers shall be provided with reverse horn & light. ~ Wherever required, Flagman shall be provided

~ The speed of vehicles plying in stretch shall be restricted to 30kmph. Levelling staff shall be fibre or Wooden.

·         Any labour, if being used in the job for surveying shall be screened and trained.

~ All workmen at work area shall wear PPE^·s and reflective jackets. ~ During night work sufficient lighting shall be provided.

~ The tippers when being positioned in front of the paver shall move very slowly as per the directions given by the supervisor or by the helper provided.

·   All workmen who are spreading the hot mix asphalt shall wear shoes and hand gloves.

~   The hot mix paver shall be provided with first aid box containing at least to provide treatment for minor burns.

~   Keep the work area cleared off any person or workmen   before applying tack coat using bitumen sprayer.

~   Mobile phones shall not be used, near and while operating the equipments.