Construction Methodology for Dense Bituminous Macadam

Construction Methodology for Dense Bituminous Macadam

1.            Scope:

This covers laying and compacting the mix of clean crushed graded aggregate, with required amount of Bitumen and filler material on a previously prepared base to the requirement.

2.            Procedure:

The work will be executed as per MORT&H specifications for Road and Bridge (Fifth revision).

2.1.1    Safety

Adequate Road safety precautions shall be taken while executing works. Barricading the area, so that no vehicle can play on DBM surface will protect DBM layers.

2.1.2    Setting out & Cross Sections

Setting out will be carried out in accordance with approved drawings and with Auto-level and Total stations. We are going to maintain the required cross-section based on approved drawings.

Required cross section as submitted on the basis of approved survey details and approved construction drawings shall be used to commence work.

2.1.3    Materials

It shall consist of the following materials:

(i)           Aggregate: The aggregate for bituminous work shall be brought from the approved sources. The said material meets the parameter as laid down in MORT&H specifications Table 500-10 (Grading –I & II). The materials are test in accordance with IS: 2386 and approved from the Engineer before the start of the work.

(ii)          Bitumen: Bitumen conforming to VG-40 grade of IS: 73 shall be used. The quality shall be determined as per job mix formula. Bitumen shall be procured and used from approved source.  The bitumen shall be obtained in bulk and stored in storing tank for the daily consumption.

(iii)        Filler: As approved mix design cement OPC-43 grade shall be used as filler.

2.1.4    Equipment:

A.           Hot Mix Plant (160 TPH)                         -           01 Nos

B.           Wheel Loader                                           -           01 Nos

C.           Tipper trucks                                             -           10 Nos

D.           Asphalt Paver                                           -           01 Nos

E.           Tandem Roller                                          -           01 Nos

F.            Pneumatic tyre Roller                              -           01 Nos

G.           Bitumen sprayer                                       -           01 Nos

H.           Water Tanker                                            -           01 Nos          

I.             Generator with lighting arrangement.   -           01 Nos          

2.1.5    Stand by equipment:

There is no need to install one more HOT mix plant and one additional sensor paver for laying of mix as standby arrangement, only stand by equipment requires for transportation and compaction of mix. In case breakdown of bitumen paver, the production will be stopped immediately. The list of stand by equipment for transporting and compacting of Mix are as under

A.           Tipper trucks                                             -           5 Nos

B.           Tandem Roller                                          -           01 Nos

C.           Mini Tandem Roller                                 -           01 Nos

D.           Water Tanker                                            -           01 Nos          

E.           Generator with lighting arrangement.   -           01 Nos          

2.1.6   Job Mix Formula & Plant Trial:

Job mix formula shall be establish in accordance with MORT&H specifications. After the laboratory trail mix and approval of plant trials will be carried out in accordance with MORT&H specification Table 500-10 (Grading 1 & 2) to demonstrate the capability of plant. The plant to be used shall be continuous process plant of Linhoff make of 200 TPH capacities.

2.1.7    Laying Trials:

After the approval of the plant trials, laying trial will be carried out on prepared patch of 100 m length in single lane width in order to establish the following:

1)         Thickness of the mix to be laid in order to obtained the specified compacted thickness.

2)         No. of passes of various compaction equipment to obtain the requisite density.

2.1.8    Preparatory Works:

1)         The surface on which bituminous work is to be laid shall be roughened and cleaned by manual labors and by mechanical broom. High pressure air jet from a compressor shall be use to remove dust or loose material.

2)         Marking of edge with lime for guidance of paver operator so that mix should be laid in the required width

3)         Fixing of sensor wire as per specified line and level

4)         Application of Track coat in accordance with MORT&H specifications

2.1.9    Mixing:

The requisite quality of the material shall be fed into the plant and thoroughly mixed in such manner that of the all particles of the aggregate are completely and uniformly coated. The aggregate shall be surface dry and shall be mixed at 160 C-175 C temperature with binder temperature at 160 C - 170 C. The temperature of mixed material as delivered to the laying site shall be in between 150 C – 170 C.

2.1.10 Transport & Laying:

Work shall be commencing at site after getting and acceptance of the wet mix macadam and prime coating. Tack coat will be sprayed on the surface, to receive the DBM.

The dense bituminous macadam shall be plant mixed as specified in design mix.

The samples of the mix shall be collected at regular intervals as suggested by the Engineer and tested for its compliance with the mix design.

The approved bituminous mix shall be delivered to site by tipper or trucks. To prevent the loss of heat, the mix shall be covered by Tarpaulin.

Rolling shall always commence from the lower to the higher side of the carriageway. The minimum rolling temperature shall be 100 C. Initial rolling will be done by vibratory tandem roller and finish by pneumatic roller. Rollers shall move with 5Km/h and shall not be permit to stand on pavement which is not fully compacted.

The surface of the dense bituminous macadam shall be finished to the grade and lines as required by the drawings, within the specified tolerance limits of + 6mm.

On completion of laying and compaction, checks shall be carried out to verified compliance with the specified requirement.

2.1.10.1         SITE RECORDS:

a)        Date, Time

b)        Weather

c)        Check list

d)        Truck delivery notes

e)        Asphalt temperature at site, on arrival & laying

f)         Field test results

g)        Machinery used at site and period worked

h)        Reasons for delay or obstructions, if any

2.1.11 TESTS REQUIRED:

The control tests on material and work shall be as specified in the MORT&H specifications and as per the contract agreement.

2.1.12 Manpower Assignment to control the work:

For proper controlling of work following personnel are responsible for laying and finishing operation as well as quality control.

1)  Material Engineer   -Responsible for production and transportation of Bituminous Mix.

2)      Highway Engineer -Shall be overall responsible for progress / quality of work.

3)      Site engineer           -Shall be responsible for laying and compaction of mix in proper line and level. He shall be also responsible of progress of work.

4)      Surveyor – Shall be responsible for proper line and level

5)      Mechanical Manager         -Responsible to manage the timely and breakdown free movement of equipment.