Roadbuilding: Highway to sustainability
By Thomas Allen16 January 2018
Sustainability is an important issue for the construction industry to address, and that of course includes roadbuilding.
Companies involved in the construction and maintenance of roads are faced with the challenge of streamlining their machines, materials and processes so that they are not only more environmentally friendly but also ever more efficient and versatile.
In an effort to reduce its reliance on virgin asphalt and aggregates production, Swedish-based project development and construction company Skanska recently started experimenting with the use of large quantities of reclaimed asphalt (RAP) in all layers of the roads it builds.
To develop a way of increasing RAP percentage without compromising the durability of the road, Skanska has been collaborating with US-based Kraton on a number of projects over the past four years.
In 2016, for example, they worked together on a 1km test section of the 694 road near Västerås in Sweden, using 70% RAP in the surface layer.
It was said that the use of such a high percentage was made possible by Kraton’s biobased performance additive Sylvaroad RP1000.
The additive is made from pine chemicals derived from the wood industry.
Bruno Vuillier, market development manager at Kraton, said, “Most important is the long-term durability of the road. We are pleased to see strong results a year after paving the surface layer of high-trafficked road 694.”
He added, “Depending on the reclaimed asphalt content, between 1 and 2kg of Sylvaroad is needed per tonne of asphalt to fully restore the binder properties.”
On the subject of RAP, Swiss-based Ammann recently announced the release of its mobile RSS 120-M, which prepares recycled asphalt for use in an asphalt plant.
It is essentially a three-in-one machine capable of functioning as a shredder, iron separator and screener.
Desired grain size
The RSS 120-M is designed to deal with asphalt that ranges in size from millings to large pieces, and the protective processing maintains the desired grain size.
It was said that the machine could go from installation to production in as little as 30 minutes, and it could process 180 tonnes of recycling materials per hour.
The shredder uses two low-speed, electrically-driven counter-rotating shafts. Also, the milling cutters have three interchangeable teeth that crush the material. This was said to reduce the power required by the machine.
By way of making the RSS 120-M more environmentally friendly, it has been fitted with a dust reduction system, and sound and emission levels have been cut.
The new FS 7000 D floor saw from Swedish-based Husqvarna also claims to minimise emissions, in response to new legislative and environmental demands, while boosting productivity.
Faced with the new Tier 4/Stage IIIB emissions regulations, the development team were set the challenge of upgrading the earlier FS 8400 D model.
So the FS 7000 D was fitted with a 2.9 litre, 55.4kW Deutz turbo diesel engine and equipped with a more efficient transmission. As a result, the floor cutter was said to deliver 50kW to the blade shaft with a torque of 260Nm, which is close to the peak torque of the FS8400 D but is achieved with lower rpm.
The weight distribution has been optimised with the introduction of a longer base plate equipped with a heavy-duty blade shaft, capable of running blade sizes up to 1,500mm.
After a series of field tests were carried out, it was established that the new FS 7000 D performs as well as the FS 8400 D, both with 1,500 and 1,000mm blades.
Erik Edvardsson, global product manager of floor saws, said, “The modern, service-friendly design, ergonomic controls and electronic support systems are highly intuitive, with a focus on operator efficiency and convenience.
“And the modern commonrail turbo diesel engine delivers higher levels of sustainable torque, with far fewer particles and nitrogen oxides in the exhausts.”
A similar challenge was faced by Liebherr, which recently launched the new L 514 and L 518 Stereoloaders. Both pieces of equipment have been designed to comply with Stage IV/Tier 4f emissions standards, while remaining powerful and versatile.
Pollutant emissions have been reduced by combining a diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and selective catalytic reduction (SCR).
The newly developed cooling system directs the cooling air diagonally through the engine compartment, ensuring optimal heat dissipation. By delivering the correct amount of cooling capacity on demand, the system was said to help in the reduction of fuel consumption and noise emissions.
For operations requiring longer driving distances, Liebherr offers Speeder versions of the L 514 and L 518, which are able to travel at up to 40km/h.
The L 514 was said to be particularly well suited to roadbuilding, acting as a reliable assistant. And it comes with a number of innovations, including the new Z-unit bar linkage, which delivers high breakout forces in the lower lift arm range.
This was said to offer an advantage in earthmoving operations.
It also allows for large holding forces in the upper range, which is important when working with heavy equipment such as high-tipping buckets.
A new hydraulic quick hitch is offered with the Z-unit bar linkage for improved versatility because it enables operators to switch tool attachments efficiently.
Liebherr also invested in making various aspects of the L 514 and L 518 models robust. The axles, for example, have automatic self-locking differentials that were said to provide excellent traction even on difficult terrain. Their robust and basic design, along with the use of high-quality steel components, help to guarantee their reliability regardless of what operation is being performed.
Planning for environmental mitigation was an important part of the ongoing £1.5 billion (€1.7 billion) upgrade of the A14 road between Cambridge and Huntingdon in the UK.
Highways England has been in charge of the 35km revamp, half of which is off the route of the current road.
Over a period of four years, the project will include widening a total of 11km of the A14 in each direction, building a major new bypass, widening a 5km stretch of the A1, and demolishing a viaduct.
Project manager Chris Griffin said, “A team of ecologists is creating new habitats for the local wildlife and, in addition, the team will replant twice as many trees as have been felled throughout the project by the time it is completed.”
At another road project in the UK, JCB Hydradig wheeled excavators have been provided by UK-based Hawk Plant Hire for the M6 junction 16 to junction 19 Smart Motorway project.
The £274 million (€311 million) venture will convert the existing motorway into an all-lane running smart motorway. Using the latest technology, it will allow traffic to be monitored and speed limits to be set automatically to maintain flow.
The works will also include the construction of 18 new emergency areas, the replacement and renewal of existing drainage and manholes, the installation of a ducting system for power and fibre cables, the construction of foundations for new gantries, and the installation of 70 CCTV cameras.
Hawk Plant Hire initially trialled two of the compact wheeled machines earlier in the year. This was followed by an order for a further four machines.
The upper structure of the 11.5 tonne Hydradig 110W can be rotated within a single motorway lane, and yet it can lift a full tonne at maximum reach. This makes it an ideal machine to use in the central reservation of the motorway, according to Hawk Plant Hire.
In Germany, Mexican construction materials company Cemex recently supplied a number of special solutions for the rehabilitation of sections of the A1 and A2 motorways.
For the renovation of approximately 6km of the A1 motorway, near Bremen in northwestern Germany, Cemex supplied almost 1,000m3 of Pervia, a special concrete mix, for the creation of a water-permeable concrete layer under the highway’s new concrete pavement.
In addition, Cemex and a supply partner delivered more than 4,000m3 of air-entrained concrete to replace sections of the A1 motorway’s pavement.
For the A2 motorway, the German government commissioned the reconstruction of both carriageways on the east-west axis, which is said to be one of the busiest sections of the highway. Located 45km southwest of Berlin’s city center, the 5km section comprises six lanes.
Cemex supplied approximately 10,700 tonnes of cement for road paving through a mobile mixing plant located near the construction site.
Elsewhere in Germany, Wirtgen’s W 200 and W 220 cold milling machines were recently used. Working in conjunction with Vögele pavers and a Benninghoven asphalt mixing plant, Wirtgen’s milling machines laid the ground for the pavement rehabilitation and re-profiling of the Sachsenring race track.
According to Wirtgen, the quality of milling has a considerable influence on the quality of overall road rehabilitation works, and this is especially true for race tracks, where precision is key.
In this project, it was necessary to mill off the existing asphalt pavement to a depth of 8cm, and it was specified in the call for tender that 3D levelling was required for the re-profiling of several bends.
The digital terrain model created by the client was communicated to the cold milling machines via two total stations that were set up at the race track.
The W 200 and W 220 achieved an evenness of less than 6mm variation across a width of 4m. The grade of the milled surface did not deviate from the specifications of the digital terrain model by more than 8mm at any point.
The two machines removed the surface and binder courses from the 50,000m2 race track in just four days. Their average advance rate was 7m/min.
Also with an eye to rehabilitating roads at top speed, Vögele – part of the Wirtgen group – recently launched the new Dash 3 generation of its InLine Pave train.
It can lay the binder and surface courses in a single pass, and the excellent bond between the layers was also said to enhance the quality and resistance to deformation of the asphalt pavement.
Product manager Björn Westphal said, “The challenges when rehabilitating roads frequently consist of minimising the impact on traffic while improving economic efficiency for the client at the same time.”
To ensure that the freshly laid binder course can be driven over by the surface course paver prior to compaction by a roller, the Super 2100-3i IP paver for binder course can be fitted with an AB 600 TP2 Plus Extending Screed.
Inside the screed are two high-compaction pressure bars operated by pulsed-flow hydraulics that ensure very high pre-compaction values.
The company said that a key innovation of the Super 2100-3i IP was the new transfer module for conveying the surface course mix to the downstream paver. The module has been extended by 1m.
As with the MT 3000-2i material feeder, a diesel heater now maintains the mix at a constant temperature, preventing it from sticking to the conveyor.
As for the Super 1800-3i, a new camera system improves the view into the material hopper, helping to avoid bottlenecks in the supply of mix. And like its predecessor model, the SUPER 1800-3i is fitted with a water spray system that prevents material sticking to the 40cm-wide crawler tracks.
Portability is also a key concern with a lot of roadbuilding equipment, as contractors like to be flexible.
Caterpillar has introduced a number of new utility compactors that were said to be simple to transport – as well as easy to operate and quick to service.
Typical uses for the new CB2.5, CB2.7, CB2.9, and CC2.6 might include streets, bike paths, courtyards, parking lots and driveways, according to Caterpillar.
The single-point lifting option and durable hitch design are intended to make hoisting the machine onto transport vehicles quick and easy.
In addition, the foldable ROPS (rollover protection structure) option provides a short transport height and which is said to enable the machine to move under and around low structures when performing compaction procedures.
The analogue display on all of the machines allows operators to monitor fuel level, engine temperature and machine hours at a glance.
In terms of serviceability, these new utility compactors have been equipped with fuses and relays that enable service personnel to troubleshoot root causes without the use of specialised equipment.
Caterpillar has also designed the compactors with rental in mind.
Their Product Link capability enables close monitoring to keep owners informed of machine location and condition, and the simple control panel and spacious platform are intended to suit a variety of operators.
Also, durable components and the fuel-efficient engine were said to maximise uptime and minimise lifetime operating costs.
Dynapac – now part of the Fayat Group – has also launched a new range of equipment for roadbuilding that it said had been designed to be easily transportable.
Its CC1100/CC1200 generation VI small asphalt rollers have flexible lifting, tie-down and towing possibilities built into the casted forks. An optional central lifting point is also available.
The ROPS can be folded, and the total length of the machines, including the ROPS, is 2,400mm. This means that they can be cross-loaded on a truck, allowing twice as many rollers to be carried.
The range was also designed to be robust and comfortable for the operator, while providing good compaction results, according to Dynapac.
The company also said that sustainability was a central concern. The latest emissions reduction technology has been used in the rollers to meet worldwide regulations.
The range is powered by Kubota engines, different versions of which are available for specific markets. In North America, for example, a 28kW Tier 4 final Kubota engine with a DPF after-treatment system is available.