Restoration of Macro Texture (Retexturing)

As a result of natural in - service wear, or binder migration, road surfaces can become very
smooth and exhibit very low friction values which, particularly in wet conditions, can give rise
to dangerously slippery surfaces that may cause vehicles to skid or aquaplane (hydroplane)
exposing national and local Government authorities to potential liability for claims. The
historical method of overcoming this problem has been to apply a new wearingcourse or to
surface dress.
Studies regarding surface texture and Retexturing methods began in the mid-1980’s in the
UK but until the mid-‘90’s, these were limited to mechanical processes.
In 1995, the TRL produced Reports 298 & 299 following process trials. DMRB-Volume 7
contains standards and tables concerning skid resistance levels and Chapter 11 covers
Retexturing techniques.
Chapter 11 also sets out objectives and main ‘stated’ advantages of Retexturing as a Primus
Operandi of highway maintenance. These are as follows:
• Conserves natural resources
• Preserves infrastructure
• More economical than traditional surfacing methods
• Most processes are weather independent
• Disruption to traffic is reduced
• Useful ‘stop-gap’ measure to treat small – high-risk sites
TRL reports 322 & 367 indicate the importance of texture depth even on low speed
carriageways, being important for drainage and low acoustic values and for ensuring that the
micro texture provided by the aggregate is sufficiently exposed to optimize skid resistance
values.
With the development of hydrotechnology it is now possible to re-texture pavement surfaces
quickly and efficiently and affordable.

In the above example, the working width of the unit is 2300mm (maximum working width is
2800mm and minimum 500mm.) Water at a pressure of between 200 and 550 bar was
applied via a hydraulically driven rotating arms containing variable angle nozzles, which are
completely contained within their own housing to prevent egress of water and for safety.
Traffic management is established at the limits of the working site and whilst operational,
traffic is controlled by mobile ‘stop’ and ‘go’ operatives, who are linked by two-way radio sets.
Because rates of progress are routinely achieved of 8-10 linear meter’s/minute, delays to
traffic are minimal.

 

Located immediately behind the cleaning unit is the high power vacuum extraction system,
which removes the water and arisings at the point of treatment, leaving the surface clean and
virtually dry, in a single-pass operation. The required degree of ‘roughness’ is achieved by
the use of different nozzles that are matched to the surface being treated and the required
result.

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