Hiway Stabilizers

Foamed Bitumen Recycling

This specialist process delivers a fast, effective and long-term rehabilitation solution to unbound and semi bound pavements that have exceeded their useful economic life.
The process involves the mixing of foamed bitumen with existing pavement materials to produce a durable, high performance pavement with excellent flexibility.

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Our new Wirtgen WR 2000's are "state of the art" Pavement Recyclers with intergrated Foamed Bitumen capability.

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Overview

Hiway Stablizers have carried out extensive research and development in the field of Foam Bitumen Recycling (FBR), prior to the release of FBR to the New Zealand market. Testing, labroratory based and on site, including; foamability, mix design and a through regime of field trials, has been undertaken to categorically prove this technology. Based on the successful outcome of this successful work, Hiway Stabilizers invested in their first Wirtgen, "state of the art", WR 2000 Pavement Recycler in 2005.

The successful introduction of this technology by Hiway Stabilizers has more recently resulted in further investments to our fleet of a WR 2500 and a second WR2000 Pavement Recycler, all are now fitted with intergrated world leading Foam Bitumen injection.

Wirtgen is the leading manufacturer of Foamed Bitumen machinery and has been developing this technology since the late 1980's. The WR 2000 Recycler is new to the market and includes "state of the art" technology. The WR 2000 weighs in at over 25 tonnes, has an engine output of 295kw, a rotor width of 2.0m and a mixing depth of up to 500mm. These versatile, high performance machines are ideally suited to New Zealand's conditions and proving an integral part of the Hiway Stabilizers fleet.

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The Principle

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

Foamed Bitumen is created by the computer controlled injection of a predetermined amount of cold water (usually around 2.5%) onto hot bitumen in the mixing chamber of the 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 aggressively, expanding up to 15 times its original volume. This controled expansion process occurs inside the rotor chamber where the Foamed Bitumen can then be thoroughly mixed with the pavement material that are being uplifted by the stabilising rotor.

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. This 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.

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The Process

The process involves coupling a bitumen tanker to the pavement recycler. The hot bitumen is pumped into the recycler where it is injected along with a small quantity of water via an intergrated spray bar fitted to the rotor chamber of the recycler. The water causes the hot bitumen to expand and aggressivley 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 conditions including hot, freezing, dry and wet environments.

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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, water and the final pavement remaining flexible.

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Services

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

Allen Browne, Hiway Stabilizers Group 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 NZTA 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 surface preparation

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Summary

Foam Bitumen Recycling is proving its worth around the world in many extreme environments and is available in New Zealand with Hiway Stabilizers. Unbound and semi bound pavements that have exceeded their useful economic life, can be effectively rehabilitated using FBR technology.

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

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