METHODOLOGY FOR CONSTRUCTION OF WET MIX MACADAM

               CONSTRUCTION OF  WET MIX MACADAM

1. Scope:

Laying and compacting of well graded granular aggregate on prepared granular sub-base for flexible pavement.

2. References:

MORT & H specifications clause No:406 and technical specifications of contract.

3. Equipments:

Paver, Motor grader, Dumpers, Vibratory roller, water tanker, Auto level,

4. Tools:

Measuring Tape ,Line rope, lime powder, pegs, String wire etc…

5.  Materials:

 The aggregate shall be produced from the multiple stage crushing and screening plant.

Physical requirements:

~ The aggregate blend for WMM for roads shall confirm to grading requirements mentioned in table 400-11 in MoRTH specification. The material to be used shall have Los Angeles abrasion value not more than 40% or aggregate impact value not more than 30%, combined flakiness and elongation Indices not more than 30%, PI value not more than 6%, and if water absorption is more than 2% soundness test shall be carried out.

6. Procedure:

Wet Mix Macadam shall be prepared, as per the approved design proportion, in the Pug mill plant with controlled addition of water.

Gradation of the mix shall be checked as the production starts for the day at the site laboratory itself.

Generally 1.0 to 2% extra moisture shall be maintained in the mix to compensate the evaporation losses depending up on lead and season. 

Mix shall be transported from the plant to the laying site by dumpers.

Water shall be sprinkled on the entire GSB surface, before placing the WMM.

Before laying and spreading of material, the shoulder on both sides shall be constructed in advance. This will laterally confine the wet mix macadam while compacting.

The wet mix shall be spread uniformly and evenly upon the prepared granular sub-base by a paver finisher / motor grader.

The required camber, grade, and thickness shall be checked. The high and low spots are to be rectified by removing or adding new material.

The number of heavy vibratory passes shall be established after doing trial stretch to achieve required density.

Vibratory pass shall overlap 1/3 of preceding pass, and make sure the speed of the roller shall not exceed 5km/hr. The places not accessible to roller shall be compacted with mechanical tampers or by a plate compactor

All the depressions and segregated portions if any will be rectified during initial rolling it self.

After the rolling is completed the stretch is to be tested for degree of compaction with respect to MDD of design mix of WMM.

Field compaction test shall be conducted as per MORTH clause No. 406.3.5.

Surface levels will be maintained as per table no. 900-1, and recorded in the specified format.

All the Field density readings / results will be recorded in the specified format.

Any rectification in WMM layer will be done after scarifying the layer for proper bonding.

After final compaction of Wet Mix Macadam the surface of road shall be allow to dry 24 hour and no vehicle traffic will be allowed till dried and the wearing course laid.

7. 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.