Slurry-Micro Surfacing

What is Slurry-Micro Surfacing?

These materials are cold-applied, thin bituminous surface courses incorporating bitumen emulsion and fine graded aggregate with fillers.

What are they used for?

These materials can be used to restore the surface condition on roads, footways, cycleways, car parks, playgrounds, central reservations, traffic islands, amenity areas.

Is there a difference between Slurry and Micro Surfacing? Slurry Surfacing is normally a single coat application laid mechanically or manually up to a dried film thickness of 6mm. Micro-surfacing incorporates a polymer modified bitumen emulsion and is often a two-coat application and can be laid mechanically or manually to a maximum dried film thickness of 15mm. These materials are usually referred to as Micro-Asphalts.

What are the benefits?

Rapid curing characteristics - Able to receive traffic within twenty minutes.
High daily output means less traffic disruption.
Restores surface texture and improves skid resistance.
Impervious membrane prevents ingress of water into the pavement structure.
Seals and preserves existing surfaces.
Suitable for overlay on wide range of existing surfaces.
Micro-surfacing has the ability to reshape and re-profile existing surfaces.
Able to provide smooth or textured finish.
Can be available in a range of coloured finished.

When to Use Slurry-Micro Surfacing

Before the footway or carriageway surface deteriorates to the stage at which expensive major patching and/or reconstruction is required.
Before surface skidding levels fall below the nationally accepted intervention level for the class of road in question.
When the road surface profile needs minor restoration.

Cost effectiveness

Lower cost compared to hotmix asphalt - in the region of £2.50 for Slurry surfacing and £3.00 - £4.00 m2 for Micro-Surfacings, towards the higher end if the process involves surface regulating and ironworks
Typical in service performance of 7-12 years if carefully designed and installed.

Where can Slurry-Micro Surfacing be Used?

Slurry surfacing is ideal for any type of surfacing receiving mainly pedestrian traffic e.g. footways and cycleways.
Micro-Asphalts are ideal for use on urban roads and roads carrying up to 250 commercial vehicles per lane per day.

Some important considerations

Slurry-Micro Surfacings can be specified in accordance with The Specification for Highway Works Clause 918.
The Slurry-Micro surfacing must be designed by the contractor to meet the requirements of the road surface on which it is to be laid.
The work should be carried out by a fully experienced contractor who can demonstrate that he has a record of quality work.
All Slurry-Micro Contractors who are members of RSTA have achieved accreditation to the National Highway Sector Scheme No 13b - Slurry-Micro Surfacing. Clients are urged to specify such quality accreditation requirements in their Contract Documents.
Good "aftercare" is essential. This, together with the correct material design will minimise the risk of early life failure.

Environmental considerations

Compared to re-laying hotmix asphalt, slurry-micro surfacing provides a very low carbon footprint solution typically at least 2 times less embodied carbon compared to asphalt.
The rapid speed of the process means that disruption to road uses, local businesses and emergency services is minimised.

Life expectancy

Careful attention to material design and execution has provided in service performance of typically 7 - 12 years on trafficked sites.

Summary

Slurry-Micro Surfacing is an established, proven process.
It is an extremely cost-effective surface maintenance treatment when carefully designed, specified and executed.
Developments in materials, techniques and equipment and improved operator training mean there is a very low risk of early life failure.