Hot Rolled Asphalt and Asphalt Concrete (Macadam) - Ministry of ...

Specification 12 Hot Rolled Asphalt and Macadam for Airfields 4 Design and Composition of Hot Rolled Asphalt
4 Design and Composition of Hot Rolled Asphalt
4.1 GENERAL
4.1.1 All Hot Rolled Asphalt incorporated into
the permanent works shall be CE Marked in
accordance with BS EN 13108-4.
4.1.2 Hot Rolled Asphalt surface course shall
be transported, laid and compacted according to
the requirements of BS 594987 and subject to the
overriding clauses in this Specification. The
production of Hot Rolled Asphalt shall be carried
out by a Contractor (or Supplier on his behalf)
who has Quality Assurance registration to the
BS EN ISO 9000 series incorporating “Sector
Scheme 14”, Production of Asphalt Mixes, with an
appropriate scope of application for those
operations.
(NOTE. Advice for the Project Manager on Quality
Systems is given in Appendix Y.)
4.1.3 The composition of Hot Rolled Asphalt
surface course mixtures shall be selected from the
alternatives in Clause 4.5, according to the
specified thickness. The mixtures shall be
designated ‘recipe’ or ‘design’ according to
Table 4.1 with design mixtures complying with
Clause 4.2 and recipe mixtures complying with
Clause 4.3.
TABLE 4.1 ACCEPTABLE COMPOSITIONS OF
HOT ROLLED ASPHALT SURFACE
COURSE MIXTURES
Location Recipe Design Mixtures
Mixtures Type A Type B
‡, * †, * †, * †, *
‡, * †, * †, * †, *
‡, * †, * †, * †, *
‡ Project Manager to state location(s) with
drawing references as appropriate.
† Project Manager to either tick the relevant box
or state any specific requirements (e.g.
bitumen grade).
* Advice for Project Manager given in
Clauses Z.1, Z.6 and Z.7 of Appendix Z.
4.2 DESIGN MIXTURES
4.2.1 The composition of design mixtures shall
comply with the requirements for either a Type A
or a Type B mixture as directed by sub-
Clause 4.1.3.
4.2.2 Design Hot Rolled Asphalt mixtures shall
be designed by the Contractor in his laboratory,
using the aggregate size appropriate to the layer
thickness as specified in Clause 3.8.
4.2.3 At the target binder content for design
mixtures, the Marshall stability determined in
accordance with BS EN 12697-34 shall conform
to the BS EN 13108-1 Category of *.
* Project Manager to provide Category for
specific job specification; advice given in
Clause Z.7 of Appendix Z.
(NOTE 1. Where 40 mm thick surface course or thinner
is specified, a binder of greater penetration than 40/60
grade bitumen is recommended provided the minimum
stability requirement can be achieved. Extra workability
will be gained and more time for compaction will be
available.)
(NOTE 2. If it is necessary to increase the binder
content to more than the optimum binder content to
achieve the target binder content with an air voids
content of less than 4.0 %, the stability value at the
target binder content shall meet the minimum
requirement above.)
(NOTE 3. The target binder content should be pitched
such that, at the binder content of target + 0.4 %, the
minimum stability value can be achieved and, at the
target -0.4 % binder content, the air voids conforms to
BS EN 13108-4 Category V max 4.)
4.2.4 At the target binder content for design
mixtures, the air voids content determined in
accordance with BS EN 12697-5 shall conform to
the BS EN 13108-4 Categories Vmax4 and Vmin2,0.
(NOTE. A well compacted mat having a design air
voids content of less than 4 % is expected to provide
good durability.)
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