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

Specification 12 Hot Rolled Asphalt and Macadam for Airfields 1 Introduction
1 Introduction
1.1 BACKGROUND
1.1.1 The unique characteristics of military
aircraft, in terms of speed, weight, tyre pressures,
etc., create specialist requirements in the surfacing
of MOD airfields. As such, specialist materials
specifications are required to meet these needs.
1.1.2 This Standard, for Hot Rolled Asphalt and
Asphalt Concrete (Macadam), is one of a series
being produced by DE to lay down specification
requirements for airfield pavement works. The
following clauses in this Section are intended to set
out the applications of Hot Rolled Asphalt and
Asphalt Concrete (Macadam) in the construction
and refurbishment of MOD airfield pavements.
1.1.3 The use of this Standard does not absolve
a Project Manager from any responsibility for his
designs, neither does its existence constrain him
from using alternatives, provided such alternatives
can be demonstrated to provide a result of equal
quality.
1.2 FUNCTIONAL REQUIREMENTS OF
AIRFIELD PAVEMENTS
1.2.1 The pavements must facilitate safe aircraft
ground operations. In order to do this they must
meet certain specialist performance requirements.
The following sets out the main requirements, the
relative importance of which will be dependent on
the function of the pavements and the nature and
type of aircraft operations:
a. Good rideability.
b. Good friction characteristics.
c. High strengths and stability to withstand the
shear stresses induced by heavy wheel loads
and high tyre pressures.
d. A durable, hard-wearing weatherproof surface
free from loose material and sharp edges which
might endanger aircraft.
e. Resistance to fuel spillage and jet blast.
Depending on the nature and type of aircraft
operations, these requirements are likely to be
too onerous for asphalt surfacings in certain
areas of the airfield.
f. Facilitate economic maintenance.
1.2.2 Main Length of Runways
It is important on the main length of a runway to
have good rideability and wet weather skid
resistance. Asphalt surfacings generally give better
rideability than PQC. Good skid resistance/friction
characteristics are achieved by a combination of
good surface shape to effect efficient surface water
run-off and also surface texture to increase friction
and allow water to disperse from under the tyre
contact area. The technique of providing texture on
asphalt road surfacings by the provision of rolled-in
chippings is not acceptable on airfield pavements
because materials which are likely to pluck out or
spall on the surface of a pavement are a potential
FOD (Foreign Object Damage) hazard to aircraft,
particularly with regard to ingestion by jet engines.
The methods currently favoured for providing
suitable friction characteristics on new asphalt
surfacings on MOD runways are as follows:
a. The provision of a 20 mm thick Porous Friction
Course (not included in this Standard) on asphalt
surfacing. This is the most favoured
construction option but it would not be specified
in certain situations including dusty regions, very
cold climates, runways used for STOL (short
take-offs and landings) operations and where
night-time construction work necessitates
numerous transverse construction joints.
b. By grooving an asphalt surface with continuous
grooves cut perpendicular to the centre-line of
the runway.
c. By the provision of a coarse graded slurry seal
over an asphalt surfacing. This is the least
favoured option.
1.2.3 Runway Ends and Adjoining Aircraft
Holding Areas
Service conditions can be severe in these areas
where jet blast and fuel spillage are likely to be
most damaging and aircraft carry out sharp turns.
To avoid excessive tyre wear being caused to
turning aircraft, it is usual to reduce the friction
properties at runway ends compared with that
provided on the main lengths. The material most
frequently used on runways ends and holding areas
at MOD airfields is PQC. However with certain
aircraft, the effect of jet blast on the pavement
surface is not critical (e.g. piston engined aircraft,
turboprops or turbojets where the jet exhaust is
located at a safe height above the pavement). In
these instances, asphalt provided with a fuel
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