There are various types of road markings in use today. Among the most common are:

• cold spraying paint;
• hot spraying paint (thermoplastic);
• roller coating paint.

Each one of these types paints have individual characteristics, are used on different types of support (concrete, asphalt, etc.) and different modes of application.

All of these factors can influence the system of removal to be used.
Briefly it may be pointed out that:

COLD SPRAYING PAINT
can be of various types: water based, with polymers, two component with glass beads such as used in thermoplastic paint.

HOT SPRAYING PAINT
is usually applied in widths varying from 12 to 40 cm , used as well as for direction arrows, speed warnings, numbers, etc. Generally the paint has an additive consisting of glass beads which allows for good reflection even with the passing of time.

ROLL COATING PAINT
is generally used for a temporary application, for example when road construction is underway and momentarily indications are changed.

Road marking can be either removed or cancelled out.

Generally cancelling means covering with a black material such as tack-coat which does not totally cover the markings.

Removal is a more complete effect carried out by mechanical means, leaving the surface without any marking and sufficiently rough for applying a new marking. This system has proven to be more secure insomuch as the system, by a for of abrasion, removes the paint as well as the glass beads impregnated in the paint.

The two most common techniques of removal are:

• SHOT BLASTING;
• SCARIFYING

SHOTBLASTING
With shot blasting small steel shot balls, from 1 to 2mm in size, are mechanically launched at high speed against the surface. With the impact against the surface, the steel shot bounces back into the machine along with the material removed. The shot is separated from the material, cleaned and returned into cycle for re-use while the removed material is deposited into an air tight dust drawer ready for disposal at the proper time. Consequently no dust is created during the operation which is a major important factor for protection of the invironment. This operation also creates a micro roughness of the surface and macro roughness on the aggregate itself creating a proper bond for the new markings to be applied. One of the most positive effects of this system is that “groves” are not created nor micro cracks in the aggregate itself.

SCARIFYING
Scarifying, or abrading, utilizes cutter flails which are placed on free moving (lasky) mounted shafts which in turn are on a rotating drum. These cutters have an insert in tungsten and are available in various sizes and shapes. These tools “scrape” against the surface permitting a “total” removal of the paint or type of marking which can often be in strips, bubbles or tacks when speaking of sound indicators and the like. In these cases the thickness to remove can be as much as from 0 to 3mm. Depth control can be controlled on most all scarifying equipment. In the case of thick paint or poor condition surface, scarifying is recommended while shot blasting could cause small grooves on the side of the marking width. If the surface is very “crumbly”, there would not be sufficient rebound for the blasting procedure. In addition on self draining asphalts, blasting would be inadequate insomuch as the steel shot would remain for the most part embedded in the bitumen. For this type surface, a multi drum scarifier is recommended using light star shaped steel cutters. However the paint which has been absorbed by the surface would not be removed.

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