Dense Bituminous Macadam Laying Procedure/Complete process of DBM and BC Laying/DBM Laying Process 

MORTH Section 500
Clause 505. Dense Bituminous Macadam
The Specification describe the design and Construction procedure for Dense Bituminous Macadam (DBM), as a surface course material. laid on approved Primed surface of Base or sub-base. the thickness of DBM in single layer shall be 50 mm to 100 mm
Material - Coarse Aggregate shall consist of crushed rock, crushed gravel or other Hard material retained on 2.36 mm sieve. The aggregate shall satisfy the requirements specified in MORTH section 500 table 500-8
Filler shall consist of finely divided mineral matter such as rock dust, hydrated lime or cement. the filler shall be graded within the limits indicated in table 500-9
Table 500-8 physical requirement for Coarse Aggregate for Dense Bituminous Macadam
AIV - Max 27% as per IS2386 Part iv
EI & FI - Max 35% as per IS 2386 part I
Durability soundness either,
Sodium sulphate 12% IS 2386 part v
Magnesium Sulfate 18%
Water absorption - Max. 2% IS 2386 part III
Coating and striping of Bitumen aggregate mix Min. retained coating 95% IS 6241
Water sensitivity Retained tensile strength
Min. 80% AASHTO 283
Table 500-9
Grading requirements for Mineral Filler
Table 500-10
Composition of Dense graded Bituminous macadam
Nominal Aggregate Size
Grading 1 37.5
IS sieve (mm) passing %
45 100
37.5. 95-100
26.5. 63-93
13.2. 55-75
4.75. 38-54
2.36. 28-42
.300. 7-21
.075. 2-8
Bitumen content % by mass of total mix.
Min. 4%
MiX design as per Asphalt Institute Manual MS-2
job mix formula DBM shall be prepare as per specification
Laying and Rolling
Laying temperature 150•c
Rolling tempreture min. 100•c
Mixing at HMP
Bitumen Temperature 160•c-170•c
Aggregate Temperature 160•c - 175•c
Mixed Material Temperature 160-170•c
Laying temperature min. 150•c
Rolling Tempreture. Min. 100•c
Bitumen used for mix is Viscus grade VG 40 as per IS: 73
RS 1 is used as tack coat material as per IS 8887
rate of spray of tack coat on primed surface before DBM laying is per table 500-5 is 0. 25 kg to 0. 30kg per square meter with the help of specified sprayer distributor with suitable nozzle
Speed of Roller shall be 5km per hour during rolling of mix at site
Rolling should be from edge to center or Lower to higher side.
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