New developments in asphalt compaction

New developments in asphalt compaction offer performance gains for contractors, with future innovations being unveiled – Mike Woof writes

Advanced asphalt compactors are offering huge gains in performance over previous generation machines. Better working quality and finish is claimed for the latest machines, while future developments will offer sophisticated solutions.

The new ARX 91 articulated tandem roller from 6791 Ammann is designed as a high productivity compactor that can be used on both thin and thick asphalt layers. A high compaction output is said to ensure that the machine can compact asphalt in fewer passes than earlier machines.

According to the firm, the machine’s combination of its drum dimensions, frequency and amplitude settings help deliver versatility across a range of worksites. The novel drive system and wide range of compaction settings are said to provide a high output and allow optimum compaction results in a minimum number of passes. This high productivity is said to result in achieving the same. compaction output as larger machines from competing firms, while offering lower fuel consumption and operating and maintenance costs.

The machine is designed for use on medium to large jobsites, including both thin and thick layers of asphalt.

The ARX 91 model weighs in at 9tonnes and is powered by a 196 Cummins diesel. Key to the operation of the roller are the efficient hydraulics, traction control system and speed sensors. The company claims that this set-up allows smooth starts and stops, helping to optimise mat quality. The engine is mounted in the rear chassis, which helps to reduce vibration and heat in the operator’s cabin. The design also allows better forward visibility, according to the firm.

The machine has electronic joystick controls and is said to have a tight turning radius, while its water tank has a capacity of 1,000litres and is said to maximise the time between refills. The ARX 91 has maximum working speed of 7km/h, a maximum travel speed of 12km/h and gradeability of up to 40%.

It is also available with the Ammann Compaction Expert (ACE), the firm’s proprietary Intelligent Compaction system as an option. This package monitors density and provides feedback, helping to reduce the number of passes, while eliminating the risk of either over- or under-compaction.

A novel development from 172 BOMAG is the choice of drive systems for its popular BW 120 asphalt compactor, which competes in the 1.2m-wide drum class. In addition to two diesel engine options, the firm is offering a version of the BW 120 that can run on propane gas from cylinders, as well as the potential for an electric variant.

The propane-fuelled variant has the same cost as a standard diesel and runs from standard 11kg gas bottles, which allow a running time of five hours and are readily available in most markets.

The propane-fuelled model is rated at 30kW and cuts overall emissions by around 50%, with no particulates and minimal tailpipe NOx. The 201 Deutz engine meets the Stage V requirements and has a particulate filter but has no need for more complex aftertreatment. The firm says it is testing the market for the gas-fuelled variant but believes demand could develop in urban areas with ultra-low emission zones.

The electric model features four lithium ion cells and two electric motors, allowing an operating time of 1.5 hours and requiring a recharging time of 1.5 hours. Although this model has zero emissions, it costs two to three times that of the standard diesel model. BOMAG believes the lack of mains power for charging on many sites means the market may not be ready for this option yet. However, there may be applications where an all-electric roller may be preferable (such as in tunnels) and BOMAG is testing the market.

On a more conventional note, the firm is also offering the BW 120 with diesels that meet the Stage V emissions requirements. There is a model with a Kubota diesel engine delivering 24.3kW, as well as a lower rated version with an 18.5kW diesel and lower running costs.

The firm is also looking ahead to the future and has unveiled a more radical prototype. BOMAG’s innovative BW 154 compactor is an autonomous machine, with its most obvious feature being the absence of a cab. The machine, developed in partnership with 2122 Trimble, is able to operate on its own without the need for an operator. Sensors around the machine detect whether there is anything in its path and will stop the unit or allow it to steer around obstacles as a safety feature.

Jörg Unger, president of 217 Fayat Road Equipment, said that this 7tonne machine is fully autonomous and features geofencing technology to ensure that it operates in a restricted zone. The machine is also equipped with BOMAG’s proven Asphalt Manager 2 control package, which helps to optimise compaction operations.

This futuristic project will not be available for the market just yet, with the lack of necessary regulations being just one of the many factors preventing its deployment. Unger said: “We don’t expect that autonomous compaction will come in tomorrow but BOMAG and Fayat will be ready for this.”

Dynapac is introducing its sixth generation of asphalt compactors, the CO4200 - CO6200 models. The firm claims that the machines are easy to operate and offer high manoeuvrability and high- quality compaction. Key features include low emission engines and high vibration frequencies, as well as an advanced water system.

An improved driving position and visibility are important upgrades. The new generation Dynapac machines allows the seat and steering module to be swivelled and slide from the left side of the roller to the right. This allows the operator to see the drum edges. The seat can also swivel to be fully rear-facing when working backwards, while the instrument panel has been improved. And the electronic mini-steering wheel is said to make it easier to steer the roller accurately.

The machine also combines articulated steering with a steerable rear drum and now features an offset of up to 500mm. And using the front drum for offset means that the roller operator will have good control of the front drum edges and can follow a curb or other obstacles.

High vibration frequency compaction is said to suit duties in thin layers, which need to be compacted fast because they cool off quickly. The rollers can also be used for thick layers with high amplitude and conventional vibration frequencies.

Other benefits of the machines include reduced emissions and fuel consumption and extended service intervals. Different engines are available to suit local market requirements with Stage IV/Tier 4 Final units for Europe and North America and StageIIIA/Tier 3 for segments without the availability of low sulphur fuels.

206 Dynapac is also offering its latest oscillation compaction system. The firm says it has focused on wear resistance and serviceability. The Dynapac CO4200 has one vibrating drum with two vibration amplitudes and one oscillating drum. This allows the operator to select the system that is most suitable for the application on hand.

Using oscillation ensures 100% ground contact and eliminating vertical vibration limits risk for damage also on less qualitative aggregates. Meeting state specifications requires that oscillations should be used while compacting on bridge decks, near foundations or concrete structures.

The oscillation system is suited to use when compacting thin lifts, bridge decks or in urban areas. The effect of the oscillating drum is to knead the asphalt surface rather than compacting it from above, resulting in the compaction forces being localised. This reduces disturbance in the area around the worksite as the resonances do not travel.

Arch rival 228 Hamm has also been carrying out development work on autonomous compaction systems. The firm has been doing testing at its own proving ground, which lies alongside the factory.

On a rather more conventional note, Hamm is improving the performance of one of its oscillatory type asphalt compactors. The DV+ 90i VS-OS model is now be able to cope with tighter turns due to the fitting of split drums. As a result, the machine can make a tighter turn while the exciter system is in use, without risk of damaging the surface being compacted.

A key feature of the machine is its new exciter configuration for the oscillator drum at the rear of the machine. This now has a separate, mechanically-independent oscillation unit that operates in each half of the split oscillation drum. Belt-driven, the system is also said to be maintenance-free, allowing it to last the lifetime of the compactor. Although the exciter units are separate, they are synchronised electro-hydraulically so that the same forces are applied. The system is said to react quickly and precisely, helping to optimise compaction performance.

The DV+ 90i VS-OS model also has a vibration system on its front drum, again with a split drum. Other features include the latest Easy Drive system, which is said to make the machine easier to use than earlier generation models.

Hamm is also introducing its HP series of rubber tyre rollers, which are now based on a common platform. This new generation of compactors is said to combine both proven and new features, with the Tier 3, Tier 4 and Stage V compliant models all sharing the same basic structure. The machines feature an asymmetrical frame design that is said to allow high compaction performance along with good all-round visibility.

One important feature is the large water reservoir, with a special quick filling system that allows water to be loaded in just two minutes. The improved ballast system allows weight to be changed speedily using a forklift truck, while the large water tank can also be used for ballast. Another important feature is the new additive tank and mixing system, with mixing now being carried out just before spraying to prevent separation.

Operating weights can vary from 8-28tonnes and the machines are available with various options, including a tyre inflation system, the edge pressing and cutting equipment and the new anti-slip system to maximise traction.

Other features include the firm’s proven Easy Drive system, as well as Hamm’s braking system and the ergonomic operator station.

Meanwhile, Mecalac is introducing its redesigned TV1200 tandem vibrating compaction. The roller is driven by a joystick on the right console, rather than a wheel on the steering column which is the usual set-up. This improves its efficiency, safety, comfort and ease of operation.

The normal position of the wheel on the steering column of a compact roller means the driver must contort himself just to get into the seat. Once in position, the driver operates the roller with one hand on the wheel and the other on the lever. 2441 Mecalac’s design creates more space for the driver to climb onto the roller, reducing the chance of accidents. It also allows better visibility and makes operation easier on the driver. The firm has a six-model roller range, with the TV1200 being the first to be redesigned and updates due to follow for the others in due course.

From 2624 Sakai comes the SW774 model, now being offered in North America. The machine has been upgraded significantly in comparison with the earlier SW770, with improved all-round visibility for the operator and better ergonomics being key factors. The operator’s seat can be rotated through 180°, allowing the machine to be used in forward and reverse more easily. The engine was previously mounted transversely but this has now been relocated so that it sits longitudinally in the chassis. This has helped improve operator visibility and a spokesperson for the firm said, “It gave us the opportunity to make the machine narrower. It has better drum visibility and also has a more comfortable operator seat.”

Power comes from a 1265 Kubota diesel rated at 82kW, which meets the Tier 4 Final emissions requirements and the model tips the scales at 10.5tonnes. As with other Sakai rollers, the machine is designed to meet demand for high frequency compaction. Its drums are 1.68m wide and have diameters of 1.25m, operating at 4,000vpm. Spring-loaded scrapers are fitted to the drums, as well as a water spray system featuring brass and stainless steel components. The spokesperson commented, “We never use plastic components because in winter if it freezes, the operator will want to use heating to unfreeze the sprays.”

The firm’s SW774ND model uses a similar chassis, but offers the choice of either vibration or oscillation on both of its 2m-wide drums, as with the larger SW888ND-1. The compaction systems for both machines are gear-driven, a design said to lower maintenance needs. The operator can use the machines in oscillation or vibration modes, depending on the job to be carried out. According to Sakai, having both drums equipped with both vibration and oscillation means that the number of passes can be halved, increasing productivity.