Construction blogs

Lets Achieve Success Together

BITUMEN COARSE

BITUMEN COARSE – Grading, Testing and Method of Construction

Bitumen Coarse is the top layer of pavement and the layer that comes in direct contact with traffic. This layer should be able to withstand traffic and weather (High and low temperature, Rain) without exhibiting various distress like cracking, rutting etc. It may be composed of one or two layers as per the design.

Function

  • Bitumen Coarse provides structural support to the pavement surface.
  • This layer also transmits the load to the subgrade and subbase layer (DBM, WMM, GSB).

Material Required for Bituminous Concrete

  1. Bitumen (Binder)
  2. Coarse Aggregate
  3. Fine Aggregate
  4. Filler
  5. Anti-stripping agent

The individual specifications are already given in the last article of (DBM Layer).

Grading Requirement for DBM

Grading I II
Nominal Aggregate Size 19mm 13.2mm
Layer Thickness 50mm 30-40mm
OBC Min 5.2% Min 5.4%
IS Sieve (mm) Cumulative % by weight of total aggregate passing Cumulative % by weight of total aggregate passing
26.5 100
19.0 90-100 100
13.2 59-79 90-100
9.5 52-72 70-88
4.75 35-55 53-71
2.36 28-44 42-58
1.18 20-34 34-48
0.6 15-27 26-38
0.3 10-20 18-28
0.15 5-13 12-20
0.075 2-8 4-10

In case aggregate have specific gravity more than 2.7, minimum bitumen content can be reduced proportionally.

Grading Requirement for BC

Requirements of Fines in DBM:

Dense Bitumen Macadam (MORTH V):

Layer Thickness Fines Requirement  (75 mic passing) Remarks
40-50 mm               2-8 % Grading 1 (MORTH V Table 500-17)
30-40 mm             4-10 % Grading 2 (MORTH V Table 500-17)

Plasticity Index≤ 4%                                      Sand Equivalent Value < 50%

Quality Control Tests Required for Bitumen and Aggregate

Testing and frequency will be same as of DBM. Therefore we can refer to the given link.

Construction of BC Layer

Construction steps are same as given in DBM layer. Please refer to the link

Productivity

  • BC Productivity              :     21000-25000 MT/month/team/day
  • Paver Productivity        :     50 m³/hr     
  • Roller productivity        :     40 m³/hr