ROAD MARKING WITH WHITE THERMOPLASTIC

INTRODUCTION
THERMOPLASTIC ROAD MARKING MATERIALS
RECIPE OR PERFORMANCE BASED SPECIFICATIONS
PRODUCING QUALITY ROAD MARKINGS
OPERATOR SKILL
BASIC "TROLLY" DESCRIPTION
RETRO-REFLECTIVITY

INTRODUCTION

This page relates to the application of road markings using thermoplastic material that is screeded by hand using a conventional "trolly" built for the purpose. This form of road marking is widely used but takes place mainly on small sites of newly laid road surfacing and more complicated areas of markings, especially in urban locations, where it is not possible or difficult to use a fully automated vehicle.
Also, I do not have any good photographs of fully automated processes.

THERMOPLASTIC ROAD MARKING MATERIALS The thermoplastic is supplied in meltable "poly" bags, i.e. you put the whole bag into the heating unit. The thermoplastic consists of a light coloured aggregate (silica sand), white pigment (titanium dioxide), glass beads and it is all held together with a thermoplastic resin Glass beads of a suitable grade / quality for the contract specification requirements are supplied in bags as shown.  Glass beads are applied to the surface of the still hot thermoplastic to ensure the initial retro-reflectivity requirement of the road markings is achieved. Until quite recently in the UK the thermoplastic was made to a specification that laid down a "recipe" to which the the material must comply, and there will still be many term maintenance contracts where BS 3262 will still be the specification in force. For more information on the BS 3262 Specification, which is both "recipe" and performance based, press,------> HERE

RECIPE OR PERFORMANCE BASED SPECIFICATIONS The new set of British Standards are based purely on "performance" testing and do not include a specification (recipe) for the thermoplastic. However, many suppliers of thermoplastic still produce product to BS 3262 as there is still a demand for a standard, recipe based product amongst their customers. Many clients / specifiers still include a requirement for a basic specification for the formulation of road marking thermoplastic, and usually achieve this in one of two ways. 1) Include the BS 3262 formulation for thermoplastic, often without reference to BS 3262, as it is now withdrawn, although still widely quoted. 2) Specify a road marking thermoplastic to the current basic AASHTO formulation which is more or less accepted world wide, and is a stronger worded document than BS 3262. The thermoplastic is heated in one of the two heaters on the back of purpose built vehicle, when molten it is transferred to the holding tank on the "trolly" which is heated to maintain the thermoplastic in a molten condition. I try to refer to as few commercial sites as possible in compiling my site, but when a site offers particularly useful information about a subject I make an exception. To obtain more information on the properties of road marking thermoplastic, press -----------------------------------------> HERE

PRODUCING QUALITY ROAD MARKINGS The apparatus in the photograph may seem rather basic, but let me assure you that this machine, in the hands of a skilled operator, will produce excellent road markings that will comply with most contract documents. That is providing a well formulated thermoplastic material has been used at the correct temperature, and the correct amount of good quality glass beads have been applied to the still molten surface. This procedure will ensure that good retro-reflectivity will be achieved immediately and during the life of the line as the traffic slowly abrades the line surface. It really is not that difficult to produce good quality road markings providing the contractor uses good product, well maintained machinery and enough correctly trained operators. The factor that is outside the control of everybody is the weather.

OPERATOR SKILL The thermoplastic flows on to the road surface and is spread to the required width and depth by a small screed plate. It is the skill of the operator pushing the "trolly" at the correct speed according to the heat and viscosity of the thermoplastic that will achieve a consistent road marking of the required width and thickness.

BASIC "TROLLY" DESCRIPTION The hopper at the back contains the glass beads. The glass beads are discharged from the hopper on to a flat plate that spreads the beads to the width of the line. The flow of beads is adjusted to a rate to achieve the initial retro-reflectivity requirement stated in the contract document. It is not uncommon to state a rate of beads as 70% of the amount that would be required to achieve shoulder to shoulder cover when tested in the laboratory. But less than this amount may achieve the required retro-reflectivity stated in a performance based specification. RETRO-REFLECTIVITY It is not difficult to test the retro-reflectivity of a laid line, as the cost of the testing apparatus, a retrometer, is not that expensive, and their reliability is much improved compared to earlier models. The difficulty and cost of the traffic management can be the main factor when conducting performance tests on laid road markings. If you are able to conduct the retro-reflectivity testing at the time the road marking takes place you will save on traffic management costs and be able to inform the contractor of the quality of the road markings he is producing. To obtain more information about road markings,  when using the recently introduced performance based specifications, press -------> HERE

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