MICRO–SURFACING
SYSTEM
The works to be carried out consist of supply
materials, labours, transport and other necessity required for the execution,
complete and maintenance of the Micro-Surfacing System.
DESCRIPTION OF WORKS
- Preparation of treatment surfaces on site with sweeping and cleaning the loose materials using the applicable method on site or approved mechanical machine.
- Regulating of surfaces.
- Applying Micro-surfacing by machine.
- Applying Micro-surfacing by hand.
- Protection of newly treated surface.
- Sweeping of loose materials after laying before open to traffic.
- Removal the existing road marking and renewal of road marking.
UNSUITABLE WEATHER
Work
shall stop during the period of heavy rain or when there is stagnant water on
the surface.
PREPARATORY SWEEPING
AND CLEANING
All
vegetation growing within the surface to be covered shall have been removed and
any remaining root growth treated with an approved herbicide. All loose
materials shall be swept and any normal oil spillage shall be removed from the
surface prior the applying of the Micro-surfacing.
APPLICATION OF
MICRO-SURFACING
Before
laying of the surface wearing course, a micro- surfacing regulating layer shall
be laid to fill ruts and depressions enabling a uniform wearing course to be
applied. The average total thickness of the Micro-surfacing should be of 10-
12mm and the application rate between 15kg/ sq.m to 20kg/ sq.m covering both
the regulating and the wearing course layers. The required layer thickness of
the Micro-surfacing materials is followed as per specifications or construction
drawings. In case of extremely deep ruts and depressions, more than one
regulating layer may be required to achieve a satisfactory base for the wearing
course.
LONGITUDINAL JOINTS
Longitudinal
joints shall be feathers lapped such as that the joints do not exceed the
nominal layer thickness. Joints with adjacent surfaces shall be feathered to
neat regular shape appreciate to the layout. Wherever possible longitudinal joints
between the final applications shall coincide with “lane lines”. In every case,
surfacing of the feather lap at joints will be so formed to shed water towards
the lower section of surfaces.
MATERIALS -
Aggregates
All
aggregates shall be cleaned, dry, durable and contain no matter which can
prevent proper coating by the binder or effect the durability of the laid
materials. The type, size and grading of the aggregate may be changed depending
on site conditions with consultation of the Engineer.
BINDER
The
binder shall be Latex-modified quick setting bitumen emulsion.
FILLER
The filler shall be Ordinary Portland
Cement (OPC) and be kept dry.
MIXING
The
materials shall be mixed by a self-propelled application machine with shall be
a continuous flow unit able to deliver and proportion accurately the
constituents and to supply and apply sufficient material to achieve the normal
layer thickness and surface regularity required.
The
surfacing mixing shall be spread uniformly by means of mechanical spreader,
equipped with paddles to agitates and distribute the mixture over the entire
spreader box width.
The
front seal to the spreader box shall ensure no loss of mixture at road contact
points. The rear metal seal shall act as the final strike off and shall be
adequate so as to deliver a uniform consistency of application.
A
sufficient amount for material shall be carried in all parts of the spreader
box at all time to ensure complete coverage. Overloading of the spreader box
must be avoided. No lumping balling or unmixed aggregate will be accepted.
It
is recognized that in some areas particularly on footway laying by mechanical
means may not be possible. Areas that cannot be reached shall be surfaced by
using hand squeegees to provide complete and uniform coverage. If necessary,
the area to be hand worked shall be lightly dampened prior to mix placement.
FINISHED SURFACE
The
finished Micro-surfacing shall be uniform surface texture and appearance
throughout the work, without variations within the lane width or from land and
shall be free from holes, streaks and surface irregularities. Any
Micro-surfacing, which does not comply with the clause, or is non-uniform in
surface texture or appearance, shall be made good by replacement by fresh
material. Any surface which shows continual material loss, or extension
non-adherence to the substrate shall be made good by removal and replacement by
fresh material.
TRAFFICKING /CURING
TIME
The
process shall be such that the laid material may be open to traffic within the
maximum of sixty (60) minutes.
PROTECTION OF NEWLY
LAID SYRFACE
Traffic
shall be kept off newly treated surfaces until materials has set, and further
traffic speeds shall be kept to a minimum until the surface will suffer no
detrimental effects.
SKID RESISTANCE
The
skid resistance value of the laid material on the carriageway shall have a
minimum average (corrected to 20˚C) value of 55 as measured by the SRT pendulum
devise for a number of tests to be agreed by the Engineer.
REMEDIAL MEASURES
Failure
of the treatment for any reason will result in the contractor being required to
propose an appropriate remedial works subject to Engineer’s approval.
SWEEPING OF LOOSE
MATERIALS – AFTER LAYING
Possible
loose material shall be swept using self-propelled “TENNANT SWEEPER” attached
with soft nylon main and side brush.
TESTING
There are a few types of testing required for
the Micro-surfacing works to alleviate strength and capabilities of the
Micro-surfacing system.
The usual testing applied was as follow:-
Skid
Resistance
With using SRT Pendulum Devise Equipment as a
measurement to measure the value of skid resistance.
The value shall have a minimum average
(corrected to 20˚C) value of 55 devise. The number of tests to be done shall as
per required/agreed/instructed by the Engineer.
