Specification 49 Stone Mastic Asphalt for Airfields - Ministry of Defence

Specification 49 Stone Mastic Asphalt for Airfields 6 Plant and Workmanship
6 Plant and Workmanship
6.1 REDUCTION IN SURFACE LEVEL OF
ASPHALT SURFACES
Where the surface level of an existing asphalt
surface is being reduced, thicknesses shall be
removed with a planing machine that has been
approved by the Project Manager. The machine
shall be provided with control devices that enable
the rapid adjustment of blades to fine depth-of-cut
settings while the machine is operating.
6.2 REDUCTION IN SURFACE LEVEL OF
CONCRETE SURFACES
6.2.1 Where the surface level of an existing
concrete surface is being reduced, thicknesses from
fine fractions up to the limits as specified hereafter
shall be removed by scabbling or planing.
Scabbling or planing shall be carried out by
machines operated in a manner that results in a
minimum of over-cutting and uniform exposure of
the aggregate, without shattering or otherwise
damaging the concrete slabs.
6.2.2 Unless directed by the Project Manager,
such reductions in level shall be bounded by joints
in the concrete pavement. Where they are not and
where the scabbling or planing is not tapered to
zero depth, the area to be reduced in level shall first
be defined by saw cuts, 5 mm deeper than the
depth of the scabbling or planing.
6.2.3 The surface treated as above shall be
thoroughly cleaned with hand brooms and all loose
debris shall be collected and removed.
6.2.4 Before the area is surfaced, a tack or bond
coat appropriate to the surfacing material shall be
applied as specified in Clause 6.10 and the
exposed vertical edges shall be painted with hot
bitumen. The new surfacing shall be made to firmly
adhere to the vertical edges.
6.2.5 The whole of the concrete layer shall be
removed for its full depth where the thickness
required to be removed is greater than the lesser of:
• 100 mm; and
• one third the depth of the slab.
Where the concrete is in bays less than 4.5 m
square, the boundary of the area to be removed
shall be defined by bay joints. Where the bays are
larger, part bays may be removed such that the
remaining portion shall not be less than 2.25 m by
the full length or full width of the bay.
6.2.6 Care shall be taken to ensure that all
concrete remaining in the vicinity of cutting-out
remains sound and without fracture and that
disturbance to sub-bases and underlying layers is
minimised.
6.3 PREPARATION OF EXISTING
ASPHALT SURFACES
6.3.1 Before the tack or bond coat is applied, all
vegetable growth and loose aggregate or other
particles shall be removed from all cracks in the
existing asphalt surfacing on which new surfacing is
to be laid. Loose laitance and other spalling or
debonded slurry seal shall be removed from the
surface. The surfaces shall be swept until standing
water, mud, grit and all other extraneous matter has
been removed. Immediately ahead of tack or bond
coating, all dust shall be removed by vacuum
extraction cleaning, with or without high-pressure
water at the discretion of the Project Manager.
(NOTE 1. Cleaning machines applying high-pressure
water and vacuum extraction are very effective in
removing debris and cleaning the surface. Water
pressures about 50 Bar are adequate for general
cleaning, but higher pressures may be used subject to the
Project Manager’s discretion. At very high pressures,
damage to the surfacing can result.)
(NOTE 2. Vacuum extraction after high pressure
cleaning generally results in a sufficiently dry surface for
application of a tack or bond coat.)
6.3.2 Existing overbanding of the surfacing shall
be removed when required by the Project Manager.
(NOTE. When resurfacing comprises only a surface
course, it will normally be a requirement to at least
remove thick depositions of overbanding.)
July 2008 13