Frequently Asked Questions

	Kerbing Operation - rear View
	Kerbing Operation - Plan View

What is the kerb extrusion process?
Asphalt kerb extrusion can be simply compared to squeezing toothpaste from a tube.  The actual process is rather more complex but the principle is similar.

Adhesion of the kerb to the surface upon which it is laid is achieved as a result of the high pressure and temperature at which the asphalt kerb material is extruded.

At the heart of the process lies the Patented Extrudakerb asphalt machine.  A machine which has evolved over many years and many thousands of kilometres of kerbing, been unsuccessfully copied but never equalled.  The machine is able to automatically vary extrusion pressure and forward propulsion to adapt to different locally available asphalt mixes changing inclines and different mould profiles yet maintain a perfectly formed product extruded at pressure of around 2,500psi with an expected minimum life of 15 years.

The extrusion machine is supplied with Kerb asphalt from a network of proven suppliers local to each project.

The asphalt is mechanically conveyed from the supply truck to the extrusion machine by a separate feeding machine.

The entire process is fully mechanised and free from the risks associated with heavy manual lifting.

Our typical kerbing set up is detailed on the following pages, although this standard configuration can be amended to suit project specific requirements.

Kerbing set up
Alignment of the extrusion machine and therefore the kerb produced is controlled by an offset string line set by us to datum’s given by you.

These datum’s are usually as simple as marks on the road surface at 30 linear metre intervals indicating the position of the front face of kerb.  It is also helpful if the start and stop locations of each kerb run are clearly indicated together with any required termination detail.

The road surface must be clean and free from debris.

A proprietary bituminous emulsion is supplied and sprayed by us on the road surface directly under the intended kerb line.

The level of the kerb is directly dictated by the surface upon which is extruded.

As the kerb mould runs directly on the road surface, the wearing course must be constructed beyond the proposed line of the rear face of the kerb - this width can be as little 20mm.

How many different sections of kerb are available?
Over 75 different kerb sections are currently available “off the shelf” including the typical profiles detailed in the latest edition of the Highway Construction Details together with splay sections, heights varying from a minimum of 50mm and channel details.

Bespoke sections are available to order.

What daily output can be expected?
Daily output is dependent on jobsite conditions and preparation, up to 1500 linear metres is not uncommon and is equivalent to two 16 tonne loads of asphalt.

Output as high as 3500 linear metres per shift has been achieved.

What type of asphalt mix is required?
Extruded asphalt kerbing is detailed and specified within The Manual of Contract Documents for Highway Works.

Where typical road and kerb design are provided within drawing references B9 and B10 of the Highway Construction Details and material specification and construction guidelines are provided within Clause 1103 of the Specification for Highway Works.

Our works are undertaken within the strict control of ISO9001 and 14001 Quality and Environmental accreditations. This demands the inclusion of detailed mythology, rigorous safety procedures and audited quality control.

An asphalt kerb mix design complies with the recommendations of BS 5931.

What typical closure is required for the asphalt kerbing operation?
A two lane closure is required for the asphalt kerbing operation. Normally Hard Shoulder and Lane 1. See the PDF downlaods (left) for typical set up.

What if a short section of asphalt kerb needs replacing?
Although asphalt kerb is not easily damaged and frequently outlasts the road upon which it is laid minor repairs are sometimes necessary.

Short lengths of damage are repaired by replacement with pre-laid asphalt kerb sections, fixed with Bitukold.  We carry a large stock of pre-laid asphalt kerb available ex works in 1.0 linear metre lengths.

We are also able to offer a supply and fix service.

How are outfalls/gullies constructed?
Drainage gully outfalls can be accommodated in a wide variety of asphalt kerb details.

Wherever possible it is desirable to provide insitu machine formed kerb around the grate whether the grate be located on or off the kerb line.

Pre-laid kerb may also be used to form off line mitred outfall details.  The kerb is affixed to the apron surround using Bitukold.

Additional gangs may be supplied to ensure that the benefits brought about by the high speed application of machine produced is not lost by the reduced output of the more labour intensive production of hand formed outfall details.

What preparation is required before the extrusion process can begin?
Alignment of the extrusion machine and therefore the kerb produced is controlled by an offset string line set by us to datum’s given by you.

These datum’s are usually as simple as marks on the road surface at 30 linear metre intervals indicating the position of the front face of kerb.  It is also helpful if the start and stop location of each kerb run are clearly indicated together with any required termination detail.

The road surface must be clean and free from debris.

A proprietary bituminous emulsion is supplied and sprayed by us on to the road surface directly under the intended kerb line.

The level of the kerb is directly dictated by the surface upon which is extruded.

As the kerb mould runs directly on the road surface, the wearing course must be constructed beyond the proposed line of the rear face of the kerb – this width can be as little as 20mm.

How long after the extrusion of the kerb until the road can be open to traffic?
Asphalt kerb hardens quickly to a dense resilient material easily able to absorb the day to day impact of adjacent vehicles.

However for the first hour of its life newly laid kerb is vulnerable and care should be taken to protect it from unnecessary damage, usually from other construction activities.

Hot ambient weather conditions during summer months can extend this initial period of vulnerability overnight.