Feature: Quality drive in road building
By Helen Wright10 May 2011
Road building contractors can allow themselves to be cautiously optimistic on the prospects for the sector over the next few years, after positive signals in the budget plans of key international markets.
In India, for example, the government's 2012 five-year plan provides INR 6.3 trillion (US$ 139 billion) for a string of ambitious investment programmes in national, state and rural roads. And both political parties in the US have indicated they would like to spend more on transport and road building in particular, with the initial proposal for the 2012 budget providing US$ 556 billion to modernise the country's transportation and highways infrastructure over the next six years.
Manufacturers are reacting by improving the productivity and quality of the latest generation of machines. Vögele has given a lot of consideration to the robustness of its equipment, for example, and showcased the new VR 600-2 extending screed for its Vison Pavers at ConExpo which it claims stands out from the crowd in terms of structural stability.
It has a basic width of 10 ft (3 m) and it can be extended hydraulically to up to 19 ft 8 in (6 m) and up to 28 ft (8.5 m) with bolt-on extensions. Equipped with vibration across its full paving width, the screed can also take on sloping pavements as its guide system remains horizontal at all times, and only the frame of the screed extension is sloped, contributing to its high rigidity.
Sumitomo, too, is pushing the limits of screed technology with the development of two new asphalt screeds, the largest of which can pave up to 7.5 m without the use of bolt-on extensions. The minimum paving width of the smaller Jpaver2360 is 2.3m - which can be increased to a maximum of 6 m by extending the rear screed.
The Jpaver's wide extension options allow it to be used on more applications on a range of widths from very narrow to wide roads.
Similarly, the larger model, the Jpaver3075, can pave a
minimum of 3 m and a maximum of 7.5 m without bolt-on extensions, and up to 9 m with bolt-ons. Sumitomo said it believed that 9 m was the maximum advisable paving width that could be offered by screeds, given that the asphalt mix has a tendency to separate longer the screed becomes.
The company has enjoyed success in its domestic Japanese market with the Jpaver series, claiming a 70% share. Since 2010, Sumitomo has been targeting expansion in China and other Asian markets, as well as promoting the Jpaver in Europe.
Breaking the mould
And the latest pavers on the market have also been designed to break the mould. In March, Caterpillar introduced two new machines - the AP500E asphalt paver and the tracked AP555E model - featuring more compact and lightweight designs that can take on paving widths as narrow as 2.5 m. The AP500E when equipped with the new AS4252C electric heat screed has an operating weight of 16.1 tonnes, while the tracked model has an operating weight of 16.7 tonnes with a screed.
The wheeled model was put to the test this year by contractor Varesco on two confined Italian sites with plenty of manholes as well as slopes so steep the transport trucks struggled to contain their loads.
Varesco's paver operator, Heinz Serra, praised the machine's performance after the two tests. "The machine is quite easy to move according to your needs in any working environment. I appreciate the electronically controlled traction, the recovery of fumes, the perfect operation of the electric screed and the easy access to all major service points for daily maintenance," he said.
VT LeeBoy, meanwhile, has also launched a new paver line. The B Series features three conveyor-style models - the 8500B, the 8510B and 8515B - that can pave from 1 ft to
15 ft (0.3 m to 4.6 m). The machines also feature LeeBoy's Legend Screed System, which includes hydraulic screed extensions as well as dual vibrators to eliminate seams.
And Terex also showcased new concrete and asphalt pavers at ConExpo. The new CR652RX remix asphalt machine can pave widths up to 9.1 m and features Terex's new generation remix anti-segregation system for ensuring against variations in the temperature of the material as it is being laid.
The system includes two sets of counter-rotating augers with interleafing shafts that draw down material from all areas of the hopper in a uniform way. This material is then re-blended in order to virtually eliminate thermal segregation at the last stage of the paving process.
For the concrete market, Terex had its Bid-Well 5000 Automatic Roller Paver on display at the show, featuring a self-widening leg design that enhances paving efficiency on complex applications. Capable of paving widths from 2.4 m to 20.7 m, the 5000's sturdy truss construction also affords quick set up and machine width changes in a matter of hours - a fraction of the time it takes to make width changes on a slipform paver.
Another new paver on display at ConExpo came from Gomaco. The company introduced its GP-2400 concrete slipformer in March, available in two- or four-track models. It can slipform widths of up to 7.3 m wide and is capable of turning in a tight radius.
Bomag, meanwhile, used March's Samoter exhibition in Italy to launch its new BF 800 paver finisher, which offers a 6 m paving width with its hydraulically extendable screed and up to 10 m with quick-fix bolt-on extensions.
In fact the 20 tonne BF 800 comes with a choice of screeds, which can also be used on the smaller BF 600. The S 500 screed offers 2.5 m to 5 m of working width with its hydraulic extenders, and can be increased up to 9 m with quick-fix extensions. The S 600, meanwhile, offers a range of 3 m to 6 m, with extensions of up to 10 m.
Operators will also appreciate the visibility that can be achieved with the sliding seats and canopy - the cab can be moved laterally to overhang either side by up to 500 mm.
Innovations in compaction technology have also been debuted this year. During ConExpo, Wirtgen group's compaction subsidiary Hamm unveiled what is thought to be the first soil compactor in the world to feature a Tier 4 Interim compliant engine.
A pre-production 20 tonne class H20i was on display, with full production of the 18, 20 and 25 tonne class models due to start in September. The H20i features a 160 kW Deutz engine and offers a 2.1 m compaction width and a maximum centrifugal force of 331 kN.
And in April, Bobcat launched five new vibratory rollers featuring widths from 1.2 m to 2 m. Designed for use on the company's skid-steer loaders, compact tracked loaders, all-wheel steer loaders and telehandlers, Bobcat claims the new vibratory rollers offer the highest dynamic force in the industry, with enhancements to the machines' isolators providing consistent forces regardless of the carrier.
Dynapac has also launched a new roller, the CA 250. Designed to be a compaction workhorse for operating long days in tough conditions, the machine is powered by a Cummins 4BT 3.9C diesel engine, rated at 82 kW (110 hp), has an operating weight of 12.7 tonnes and sports a 2.1 m wide drum.
Dynapac has also launched new wheeled compact planers - the PL1000T with 1 m cutting width and its sister model, PL600T with 600 mm cutting width.
The new 13 tonne machines feature +20% more power at a maximum milling depth of 300 mm. They complete Dynapac's range, offering cutting widths from 350 mm to 1 m and cutting depths from 100 mm to 300 mm.
And Wirtgen showcased two new large cold milling machines, the W200 and W210, at ConExpo. Both machines can be equipped with milling drums with working widths of 1.5 m,
2 m and 2.2 m, but while the W200 is fitted with a single,
550 hp (410 kW) engine, the W210 uses two diesel engines which generate a total 671 hp (501 kW).
Both models have three selectable engine speeds for broad range of applications including large-scale surface course rehabilitation, complete pavement removal at full depth and fine milling.
Bomag, meanwhile, has also launched new milling equipment. Also on display at the Samoter show, the new BM 500/15
500 mm milling machine features quick-change milling drums - the product of three years of research and development.
Significantly, Bomag said it would start selling its new
BM 500/15 compact planer and Bomag milling drums for other makes of 500 mm class milling machines.
New tooth patterns mean vibration is reduced during cutting, and a new geometry at the edge of the drums means there is minimal damage to neighbouring surfaces during cutting. Bomag said the drum drive and mounting have also been improved, cutting fuel costs and extending the service life, and a new range of diagonal cutters protect the drum shell when working around bends.
This drive for increased efficiency is also mirrored in a new Mobile Stockpile machine that has been launched by Bergkamp. The machine is a material transfer and storage trailer that Bergkamp claims can increase the amount of time available for paving, reduce costs, simplify job management and eliminate overweight truck citation risks. The onsite stockpile also reduces the need for multiple longer distance trips so fewer pavers can do more work in less time, lowering overall production costs.
Aggregate is dumped into the inlet hopper located at the rear of the Mobile Stockpile unit and transferred to the 16.4 m3 main hopper on an enclosed conveyer at a speed of up to six tonnes per minute. The main hopper can either store the material or simultaneously transfer it during filling via a 610 mm discharge conveyor.
In addition to the stockpile unit, Bergkamp has also introduced a new Variable Width Spreader Box (VSB), which can expand and contract while paving so the operator does not have to stop when the road changes. A replacement for standard boxes, the VSB can be connected to the paver's hydraulic system and adjusts by using the levers located on the handrails of the box.
Available in 2.4 to 4 m, 2.7 to 4.3 m and 3 to 4.6 m models, each VSB model has four augers - the first two feed the material to the centre of the box while the other two evenly distribute the mix during placement. As the box adjusts, the augers remain equally spaced apart to achieve an even placement and a smooth finish. This technique is also said to eliminate unwanted construction joints and increasing pavement driving quality.
Meanwhile, much attention is also being paid to the quality and longevity of new road surfaces. Tackling premature failure as a result thermal segregation during paving, for example, has been at the forefront of new technologies.
Moba has developed a real-time method for detecting heat dispersion using infrared sensors to produce a profile for a project. The company's Pave-IR system uses coordinates from global positioning systems (GPS) and a temperature scale to deliver data to the operator on a colour touch screen. Paving speed and paver stops are also recorded, allowing contractors to adjust their paving operations to maximise profits while helping to ensure the surface is free of segregation.
Similarly, the 'hot-to-hot' paving technique, which involves combining both the asphalt binder and wearing courses in one single, hot-to-hot, operation, is growing in popularity outside Europe, where the method was first developed.
Indeed, Dynapac has high hopes for the uptake of the 'hot-to-hot' process in North America and showcased the technique at ConExpo. Initial testing with a Dynapac DF145CS fitted with a CM2500 module to allow two material hoppers and two screeds to be operated simultaneously was undertaken at the company's NCAT test site in Germany.
The results suggested the wearing screed on the road surface could last up to 25 years, while construction times could be reduced by up to -50%.
Another increasingly popular technique is spray paving, used for laying low-noise surfaces and typically requiring less material and causing less mess. Vögele's SprayJet technology, for example, was used in April by contractor Franz Schelle to pave low-noise asphalt on a 550 m road in Munich. Using a Vögele super
1800-2 with a SprayJet Module and an AB 500-2 extending screed for the wearing course, the contractor said it saved up to 50% on material costs.
Franz Schelle site manager Klaus Fihn praised the high precision nozzle, which sprayed material only where it was needed. He described spray paving as "the future for inner-city road projects".
As well as improving the quality of new roads, techniques for prolonging the life of existing surfaces are also being championed in the road building sector. For example, the US International Slurry Surfacing Association (ISSA), this year launched an outreach program to educate federal, state and local transportation agencies about the value of preservation. The trade association is lobbying for slurry and micro surfacing, chip sealing and crack treating processes to be included in state and federal road programmes.
The trade body claims that slurry and micro surfacing, chip sealing and crack treatments can extend the life of roads by up to seven years, save money and are less harmful to the environment than traditional road maintenance techniques. The ISSA also claims that such preservation processes use half as much of a city's budget when compared to reactive maintenance techniques.
But whether it is preserving road surfaces or laying new roads altogether, the sector's equipment manufacturers are well-positioned to benefit from a global resurgence in demand. The flurry of new machines and technology launched this year alone are testament to the dynamism and innovation in the market, and all eyes now are on opportunities in both developing markets and more mature markets to drive home the recovery.