With the permissions process becoming ever more restrictive for the quarrying industry in Europe, the squeeze on the supply of new aggregates for construction becomes ever tougher. As a result, the recycling of materials is an increasingly attractive proposition for the road building industry. There are numerous technologies in use already, such as re-using milled material extracted during road planing.

However, new and even more sophisticated techniques and processes are now coming to market. While many of these systems have been around in prototype form for some time, the methodologies have been refined while the incentives to use them grow stronger every day.

A number of firms are making particular progress in this field, having developed and proven innovative solutions for this growing market based on hot, cold and now warm-in-place technologies. All of these have been used in construction projects or in trials and the results have been positive, although the road construction industry has yet to capitalise on the potential benefits offered by adopting such techniques more widely.

Cold choice
Italian asphalt technology specialist Iterchimica is working closely with the Fayat Group on an advanced cold-in-place recycling technology. There are two Marini trains now operating in Italy and another in Iran and the latter is of particular note. Fayat and Iterchimica have a technology transfer agreement for cold in-place recycling with the Iranian specialist asphalt producer and surfacing contractor Asphalt Nemooneh.

The technology is well proven. A milling machine works in front of the train, removing the old surface using conventional techniques. However the way the material is used is innovative and there is a crusher and a screen mounted on top of the main unit in the train, which mixes this milled material with chemicals, water, cement and emulsion.

There are numerous benefits from using cold-in-place recycling techniques. Using such a system up to 1.5km of road can be paved/day and there are few smoke emissions. There is no need for trucks to carry asphalt from a batching plant to the site and only 10% of the aggregate has to be added into the mix, so the overall energy consumption is considerably lower than for conventional paving methods. Using such equipment cold in-place recycling can be carried out at ambient temperatures of 25-30ºC. Paulo Visconti, export division manager at Iterchimica said: "With milled material you don''t have to heat anything."

The main application for this technique is where existing roads have problems such as cracking or poor mechanical stability. Visconti pointed out that the technique can be used to remove the binder and base courses as well as the wearing course if required.

The contractor is able to mill the surface to different depths, depending on the type of problem encountered in the road surface and the wearing course can be removed separately or along with the binder course. However Visconti emphasised: "The performance of a cold recycled road is exactly the same as for a traditional hot mix layer. It''s not a technique that''s just suitable for secondary roads." He added that one successful application of this technique in Italy has been on the busy main highway linking the cities of Milan and Bologna and this road carries some 220,000-250,000 vehicles/day.

Having bought the cold in-place recycling equipment four years ago, Asphalt Nemooneh has now used it to recycle some 100km of road in and around Tehran as well as paving 150km or so of chip seal paving.

There is a particular need for road resurfacing in Tehran as the city has a population of 12 million and some 5 million cars, so its traffic levels are extremely high and pavement wear is a serious problem. The machine is used at night and the equipment is able to operate in a single lane, so as to minimise disturbance to traffic though. In Iran, the recycling system is being used on cracked or rutted roads and these have shown good performance.

Because it provides a continuously paved surface, the consistency is also good with no bumps. According to Asphalt Nemooneh, at nominal speed the machine can produce up to 250tonnes/hour, although 220-230tonnes/hour is a more normal working range. It is worth noting though that in Iran the cost benefit of cold recycling is not from savings on fuel (diesel prices are incredibly low by world standards) but to the productivity and quality of surface that can be achieved. However in countries where fuel costs are higher, this system can slash fuel consumption and boost the bottom line.

Iterchimica is confident that demand for the cold-in-place recycling technology is set to grow and believes its close relationship with Marini, part of the Fayat Group, will help build an international market for this technique.

Hot option
Another Italian firm, Socotherm, has high hopes for its Pavirec recycling technology, and company president Zeno Soave believes this represents a major business opportunity. The firm intends to increase its presence in the road construction market through innovative technologies and recycling of road materials has been identified by Soave as a market segment that is set to grow.
The Pavirec system has been patented and allows for hot in-situ recycling of asphalt surfaces that have become degraded through heavy use. According to Socotherm it offers major benefits in terms of improving surface durability, reducing transport requirements, cutting traffic disruption and minimising costs.

Alessandro Fracasso, sales manager at Socotherm''s infrastructure division said: "Recycling is today the most important aspect for the environment. It is important to do this to save energy, reduce costs and cut truck transportation."

The thinking within Socotherm is that hot-in-place recycling of road materials offers a good site solution and Fracasso explained: "You don''t break the stone and the molecular connections between the polymers. Our system is most efficient for recycling porous asphalt."
But the lack of forward thinking within Italy''s political quarters in regard to recycling asphalt and other materials for highway construction causes frustration at Socotherm. Fracasso said, "There is no demand (in Italy) because the Government does not understand this activity. It is a question of mentality. When they know they are forced to recycle they will do everything to push for it."

However, Fracasso said that Socotherm is hopeful that the tide will change in Italy, with the authorities opening their eyes to the benefits of recycling road materials. "We are pushing and we are now making tests in some parts of Italy," he said.

Three tests are being carried out during this year on Italian tolled roads and Soave said he is hopeful that these will lead to further trials. Fracasso said, "We are doing a test in Italy for the most important highway concessionaire."

The A28 autostrade between Treviso and Mare has been used as a test site for this process and Socotherm has used the equipment on 7,000m² of the road. Another 7,000m² has been recycled using the system, which Socotherm has now fine-tuned according to Fracasso.

It may take some time but once the Italian Government changes its attitude towards recycling road materials, Soave said that he believes that the market will develop quickly and in Italy there is some 50,000,000m2 of permeable asphalt, so the potential is vast. In the mean time other European countries represent a more immediate opportunity. Fracasso is optimistic though that its Pavirec system will find customers in other parts of Europe and said, "We are also working to bring the system to Spain."

RAP resource provides aggregate answer

He explained that there has been considerable interest from Spain''s highway industry, which is more open to technical innovations like recycling while some 30-40% of Spanish highways feature porous asphalt. He said, "This system is very necessary in Northern Spain where there is high rainfall."

This system doubles the pavement life and reduces the need for materials transport to a site to just 20% of that required for conventional construction techniques. However, Fracasso added that the Pavirec system is versatile as it can also be used in conventional asphalt.

There are rival road recycling technologies but Soave believes the Pavirec system offers benefits over its competitors, most notably that it does not require a drum to do the mixing. Fracasso said, "We do the mixing directly on the ground."

Socotherm says its technology is more efficient than conventional recycling methods, as it can re-use 100% of the road material, carrying out the milling and mixing operation together and Fracasso said, "The result has been positive."

Soave says that the efficient heating system is another benefit of Pavirec. The hot air is generated by a diesel burner and the company moved to this method because it is safer than using LPG. Giorgo Bedogni is divisional manager at Socotherm''s infrastructure division and explained: "We have a hot air system that is more efficient for heating permeable asphalt than the gas burners used by others. The hot air system does not damage the polymers in the asphalt. It is more efficient and less expensive to run."

The company has built one new machine at the moment, although a number of older trains using gas heating are in existence and some of these have been used in Eastern Europe. Meanwhile the paver is a special unit that has been developed by Socotherm for the task but uses a Vögele screed. Fracasso says that Socotherm will be ready in 2008 to market its hot-in-place recycling technology outside of Italy.

Production solution
French contractor COLAS is proving that effective and cost-efficient use can be made of recycled materials in an asphalt plant. Continuous hot recycling of asphalt is traditionally carried out using a TSM-type of parallel-flow dryer drum with a normal theoretical limit of 30-35%, which can rise to a maximum of 50% for a Rétroflux-type counterflow dryer drum. Any recycling experiments at higher rates are exceptions to the rule, involving special formulations.

High-rate recycling is now developing rapidly on homogeneous sites where complete deconstruction can be carried out. The asphalt on roads such as these, consisting mainly of surface layers and binder courses approaching the end of their life cycle, has to be replaced.

Mobile RAP plant

Wirtgen''s recycled asphalt (RAP) plant is designed to work on-site. The machine is highly versatile and has been developed closely alongside the firm''s milling machines, which helps optimise throughput and this equipment is track-mounted, for versatility

An understanding of the geotechnical characteristics of these asphalts is used to develop formulae that are suitable for high rates of recycling. This process involves adding reduced amounts of virgin materials and new bitumen, along with controlled quantities of rejuvenators.

However ERMONT, part of the Fayat Group, is now offering an innovative solution to high-rate continuous recycling needs. This can be installed as a new system or as a universal kit to be added on to an existing plant and this technology has now been proven by COLAS.

This system is based on the three-point principle. According to ERMONT, the first stage is overheating of virgin materials in a traditional parallel-flow or counterflow TSM or Rétroflux dryer mixer. This allows accumulation of an energy potential that will later be released, with RAP material then being introduced via the recycling ring. Simultaneous heating of the recycled materials is carried out in a specially adapted TSR dryer mixer for recycled materials and at a temperature of no more than 130°C. The next stage is for mixing of the products in a high-power twin-shaft mixer, followed by injection of bitumen and coating and the product can then be transported and stored using conventional methods.

According to COLAS, this system allows a 70% recycling rate at temperatures of 160°C. In addition, the temperature of the finished asphalt is 160°C while the temperature of asphalt aggregates at the recycling dryer drum outlet is 130°C and the temperature of the cold materials is 10°.

Iterchimica and Marini, part of the Fayat Group, have worked together to develop the methods used in the cold-in-place recycling train as well as the equipment itself

COLAS has already proven this system, having first tested it earlier this year at a site in France (near Chartres). The mobile Marini continuous plant, featuring a parallel-flow dryer mixer and an SAE continuous mixer, was supplemented by a dryer mixer for recycled materials. Production figures of 17,000 tonnes of materials at a recycling rate of 30-50% were recorded for this first test. After transporting the equipment to a second site, COLAS has now started work on a highway project and plans to produce 70,000 tonnes at a recycling rate of 60%.

These applications should develop further, due to the increasingly precise traceability of products. The savings relating to the recycling of bitumen are variable and account for up to 35% of the overall costs, whereas aggregates may account for 40% of this figure, providing an economic solution to asphalt production ·

Fayat
www.fayat-group.com

Iterchimica
www.iterchimica.it

Socotherm
www.socotherm.it

Powerful performer

Benninghoven says its latest recycled asphalt (RAP) plant can produce up to 180tonnes/hour of material. The machine operates at temperatures of 160ºC and a spokesperson for the firm said: "You can use the asphalt directly after it comes out of the plant."

This equipment is aimed at customers investing in the materials recycling market and features a number of innovations for this application. One of these is the special crushing system designed by Benninghoven as conventional crushers are not suited to use with asphalt as this is sticky and can cause internal build-ups of material.

This latest machine joins a proven line-up as Benningoven now has a range of RAP plants available and this includes mobile units, which are designed for versatility.

Benninghoven
www.benninghoven.com