Hiway Stabilizer's new Wirtgen WR 2000 is a state of the art Pavement Recycler equipped with Foamed Bitumen capability. Hiway Stabilizers can now offer Foam Bitumen technology providing clients with the benefit of this process for specific pavement rehabilitation applications.

Wirtgen WR 2000

Overview

Over the past three years Hiway Stablizers have carried out extensive research and development in the field of Foam Bitumen Recycling (FBR). Extensive foamability, mix design and field trials, including a section of Wainui Road in the Rodney District, have been undertaken using this technology. Based on the successful outcome of these trials has prompted Hiway Stabilizers has invested in Wirtgen's latest, state of the art, WR 2000 Pavement Recycler and a WR 2500 Pavement Recycler, both fitted with their world leading Foam Bitumen injection system.

Wirtgen is the leading manufacturer in the world for Foam Bitumen injection systems and has been developing this technology since the late 1980's. The WR 2000 Recycler is new to the market and has been developed to fill a gap in the industry for a mid range Pavement Recycler. The WR 2000 weighs in at 22 tonnes, has an engine output of 295kw, a rotor width of 2.0m and a mixing depth of up to 500mm. This versatile, high performance machine is ideally suited to New Zealand's conditions is proving an integral part of the Hiway Stabilizers fleet fleet which also includes the WR 2500 as aback up machine and for large scale projects.

The Principle

Foamed Bitumen Recycling is a pavement rehabilitation process involving the mixing of foamed bitumen with an existing pavement to produce a high quality, durable and flexible pavement with exceptional performance and which is resistant to the effects of climatic extremes.

Foamed Bitumen is created by by the computer controller injection of a predetermined amount of cold water (usually around 2.5%) into hot bitumen in the mixing chamber of a pavement recycling unit. The principal is based on the bitumen being at such a temperature that, when a small quantity of water is added the water instantly vaporises and the bitumen foams, expanding up to 15 times its original volume. This expansion process occurs inside the rotor chamber where the Foamed Bitumen can then be thoroughly mixed with the pavement material.

Within 10 to 20 seconds the Foamed Bitumen subsides during which time mixing with the pavement material has been achieved. While foamed, the bitumen doesn't completely coat all aggregate surfaces but has an affinity for finer particles, those of 75 microns or less, and forms a mortar or glue which effectively bonds the pavement materials together.

In its expanded state the bitumen offers good dispersion properties and results in viscoelastic pavement performance with some characteristics similar to asphalt.

WR 2000 and bitumen tanker - Waitakere Road, Rodney District

The Process

The process involves coupling a bitumen tanker to the stabilizing hoe. The hot bitumen is pumped into the stabilising hoe where it is injected along with a small quantity of water through a spray bar fitted to the rotor chamber of a stabilising hoe. The water causes the hot bitumen to expand and foam inside the rotor chamber where it is mixed with the pavement material prior to re-compaction.

The FBR process has a proven track record internationally having been used extensively in places such as Australia, South Africa, North America, the Middle East and Europe. It is a very versatile method of pavement rehabilitation and has proved successful on heavily trafficked roads in many extreme environments including hot, cold, freezing, dry and humid.

The Main Benefits

Benefits of the Foamed Bitumen process:

• Is an effective treatment for pavement freeze thaw deterioration.
• Is a cost effective pavement reconstruction process and is considerably cheaper than deep lift asphalt.
• Produces a strong, durable and flexible pavement which exhibits viscoelastic behaviour resisting permanent plastic deformation with reduced deflections.
• Reduced maintenance requirements and costs when considering whole of life costs.
• Significantly reduces or eliminates excavation volumes and the requirement for imported pavement material.
• Conserves aggregate resources and is an environmentally responsible pavement rehabilitation choice.
• Minimises inconvenience to the public by speed and efficiency of the process.
• The FBR pavement is able to be trafficked immediately.
• Is resistant to moisture and pumping of fines due to bitumen coated fines, tensile capacity and lower permeability.
• No risk of shrinkage cracking due to low volumes of binder and water.

Services

Hiway Stabilizers can offer a full design build service for all FBR projects.

Allen Browne, Hiway Stabilizers Technical Manager, is a chartered engineer with extensive pavement design and consulting experience. Allen heads the design team which can undertake:

• Pavement investigation
• Subgrade analysis
• Pavement sampling
• Laboratory grading analysis
• Bitumen foamability testing
• Foam bitumen laboratory mix design
• Modulus testing
• Pavement design using TNZ recognised Circly design software
• Production Quality Assurance
• Post construction testing
• Completion reporting

Hiway Stabilizers have the expertise and plant resource to offer the following construction services:

• Pavement pre-treatment
• Grading modification
• Foam bitumen recycling
• Heavy compaction
• Final trimming and seal preparation

Summary

Foam Bitumen Recycling is proving its worth around the world in many extreme environments and is now available in New Zealand. Unbound pavements and semi bound pavements that have reached their use by dates can be effectively rehabilitated using FBR technology.

Hiway Stabilizers have the expertise and track record in FBR and can now offer:

• State of the art Foam Bitumen technology providing clients with the benefit of this process for specific pavement rehabilitation applications.
• Wirtgen WR 2000 Pavement Recycler offering high performance and versatility.
• Wirtgen WR 2500 Pavement Recycler offering high performance and production.
• Full technical support, pavement investigation, assessment and Foam Bitumen pavement design and quality assurance.
• Sub-contract or full delivery service.

WR 2000 Foam Bitumen Recycling - Coronet Peak Road, Queenstown Lakes District