The road to prosperity

25 April 2008

Vogele claims that its Inline Pave dual asphalt system allows asphalt to be laid in thinner layers a

Vogele claims that its Inline Pave dual asphalt system allows asphalt to be laid in thinner layers and, due to the retained heat, can be used during a longer surfacing season.

Road development is the road to development,” according to Manfred Swarovski, chairman of the International Road Federation. Mr Swarovski highlighted the link between road investment and economic growth during his speech at the last IRF World Meeting in Bangkok, Thailand.

Figures from the World Bank suggest that road journeys account for 80% of passenger kilometres and about 50% of the freight tonne-kilometres, adding weight to Mr Swarovski’s view. The World Bank has also said that roads form the backbone of a country’s economy and provide essential links to both local and rural road networks.

Each year trillions of dollars are handed out in loans and grants by development banks, including the World Bank, to fund road construction and improvement in South America, Asia, China and Africa. The aim is to help develop road networks to give these countries the opportunity to develop trade links and the ability to improve their economic situations.

The Inter-American Development Bank (IDB) extended a US$ 70 million loan to Panama last month as the first phase of a programme to improve the country’s road infrastructure and increase competitiveness. A specific goal of the programme is to cut costs and travel time for the transportation of passengers and cargo on highways linking Panama’s production centres with its local and external markets, boosting the competitiveness of a key sector for the country’s economy.

The programme also aims to help Panama sustain its network of paved highways through long term, standards-based rehabilitation and maintenance contracts designed to maximise the service life of the road infrastructure. Under the deal, contractors must maintain roads in better conditions than the base levels required by the government.

“The idea is to establish maintenance as a priority. This would represent a radical change for Panama but it will preserve the value of their road network and contain the costs of future investments in highways,” said IDB project team leader Jose Agustin Aguerre.

“Contracts based on standards have had excellent results in Argentina, Brazil, Colombia and Uruguay, and have led to the introduction of new technologies and improvements in the efficiency and quality of road maintenance work,” he added.

The programme’s first phase is expected to rehabilitate around 315 km of paved highways and ensure the constant maintenance of around 1135 km of priority roads.

But maintenance is not just an issue for roads in developing countries, it is also a vital consideration for continued economic prosperity of developed countries. But its not the need for maintenance that is the challenge, it is finding techniques that are efficient, cost effective and cause minimal disruption to traffic flow.

Recycled benefits

The rising cost of raw materials such as oil and aggregates means that recycling techniques are coming increasingly under the spotlight. Methods vary around the world, but most were pioneered on minor roads and are now being accepted as a viable option for rehabilitating major roads. The growing acceptance now includes use on a busy interstate in California, US.

“Many of the major roads in California were built in the 1950s and 1960s, when traffic volumes were much lower. Since then the roads have been hemmed in by development and traffic volumes have grown, leaving the roads in need of repair but no room for new construction or detours during reconstruction,” said State of California head of materials Joseph Peterson.

Problems on California’s east-west I-80 highway were particularly acute. The road carried up to 100000 vehicles per day and was showing visible signs of distress, with cracking rutting, potholing, cracking and oxidation.

“The I-80 had well and truly exceeded its design life and was designed for lower traffic and lighter loads,” said Mr Peterson.

“The original plan was to mill out 100 mm and replace it with 100 mm of new material, placed in two layers. But with the nearest asphalt plant was 40 km away, which combined with the all-time high cost of bitumen and our reluctance to slow the traffic, meant we needed to look for an alternative.”

Mr Peterson’s solution was to use in-situ recycling to rehabilitate the top 100 mm of the carriageway using a slurry mixer to add 1.5% cement and 2.5% foamed bitumen to the mix. The mixture was then compacted by two drum rollers followed by a pneumatic roller and then allowed to ‘cure’ for four hours before being trafficked.

The work was carried out overnight with lane closures to minimise the impact on traffic flow. Tests showed that the recycled surface could be trafficked for up to 30 days without damage, which allowed the site team to complete the recycling work before overlaying it with HRA.

“Recycling saved around 102 tonnes of aggregate and avoided 9200 lorry trips, which would have produced 7200 kg of NOx and used 204000 litres of fuel,” said Mr Peterson. “In total the technique cut the cost of the work by US$ 0.5 million. We’re now looking at using the same method on another highway which carries around 150000 vehicles per day.”

Maintenance matters

Maximising service life and reducing the need for future maintenance is also the focus of some of the latest innovations in the road construction sector. However, these new techniques are not only improving the quality of the finished surface but are also helping to speed up the construction phase.

US-based Bergkamp’s latest microsurfacing/slurrysurfacing machine, the M1, is designed to operate continuously to reduce the number of construction joints in the finished surface. The machine mixes the aggregate, bitumen emulsion, water and additives and applies this in a thin layer over the existing surface, which can extend the life of the pavement by up to 7 years. Bergkamp claims that the new surface can be trafficked in less than an hour and the jointless finish means that the integrity of the completed pavement is improved.

According to Dynapac, its F300C/S - AM300 Compact Asphalt Paver not only speeds up the surfacing phase of the work but can also double the service life off the new pavement. In addition to a longer service life, Dynapac has also said that surfaces laid by the paver are up to +70% more resistant to deformation and uses less material than conventional pavers.

The Compact paver was launched at Bauma in 2004 and has been used on a number of German and Polish road projects but the machines has just made its US debut at the National Center of Asphalt Technology test track at Auburn University in Alabama, US.

The paver is based on Dynapac’s F300C/S paver and has two hoppers - the upper 25 tonne capacity one holds the surface wearing course, while the lower 45 tonne capacity hopper holds the binder course - and a screed for each hopper. The machine is also supplied with a mobile feeder and specially adapted static rollers. Both courses of asphalt are laid simultaneously ‘hot-on-hot’ with the lower screed not only placing the binder course but also compacting it to 92% density.

The design of Vögele’s ‘Inline Pave’ system is based on the design of the company’s conventional pavers and, Vögele claims this opens the method up to a wider circle because it doesn’t call for high capital investment.

Like the Dynapac system, the Vögele Inline Pavers use a compacting screed to compact the lower binder course as it is laid and is followed immediately after by laying of the surface course over the top. Unlike the Dynapac machine, the Vögele Inline system ‘links’ two modified conventional pavers together.

Vögele’s Inline Pave system can surface roads up to 8.5 m wide in one pass. The paving train consists of a Super 2100-2 IP paver, which is fitted with an AB 600 IP high compaction screed, to place the binder course with a Super 1600-2 or Super 1800-2 paver to lay the surface course and an MT 1000 IP mobile feeder to ensure a continuous supply of asphalt.

According to Vögele, the ‘hot-on-hot’ technique retains more heat than conventional single layer surfacing which allows it to be used in colder or wetter conditions than is normally possible.

Vögele also claims that asphalt laid ‘hot-on-hot’ can be laid thinner to give the same performance characteristics than when using conventional surfacing methods. The ‘hot-on-hot’ layers can be laid at 15 to 20 mm thick, instead of 35 to 40 mm, which reduces the amount of raw materials needed to construct the new pavement.

But while faster surfacing reduces the impact of the work on traffic, getting the compaction right is essential to achieve the design characteristics.

“Modern asphalts need careful compaction to ensure they achieve the right properties,” said Hamm product manager Ralf Schröder. “Our HD rollers were developed specially for use with open/porous asphalt, which must not be over compacted or it loses the negative texture that allows it to drain surface water. Porous asphalt needs a large drum with a low static load but high vibration to achieve the right level of compaction and the HD series has been developed to meet this demand.”

According to Mr Schröder, one of the biggest development in the compaction sector in recent years has been oscillation technology.

“Thin asphalt layers are best compacted using static loads or oscillation,” he said. “Use of vibration on thin asphalts usually results in cracking.”

Hamm has carried out extensive testing with its oscillating rollers and thin asphalt layers to gain a better understanding of compaction control. The company is now working on developing the Hamm Compaction Quality (HCQ) system, which was originally developed for sub-base compaction, for use with asphalt.

“In its standard format, the HCQ measures stiffness of the sub-base and combines it with GPS data to provide accurate information on the compaction and minimise the number of passes needed,” said Mr Schröder. “Now we want to bring this technology to the asphalt sector but it’s not as simple as measuring stiffness, because the stiffness of asphalt is influenced by the ambient temperature, temperature of the material, frequency of the compaction and so on.

“We are currently testing a prototype system and new software, which we hope to be able to launch during 2007. Last year we used the system over a 20000 m2area at our factory and undertook 8000 pavement quality indicator tests over the area to evaluate the results. Now we’re ready to test it on a live job site and we are currently looking for a suitable project.”

Accuracy is also a vital ingredient in modern road construction and the sector is starting to benefit from the GPS technology, which has already revolutionised the earthmoving industry. GPS machine control is already being used on asphalt pavers to add accuracy to surfacing work but systems are now also being developed for concrete pavers.

Leica has been working with Gomaco to develop its PaveSmart 3D system for curb and gutter paving applications and, according to Leica, it is the world’s first fully automated track grade and steer control system for concrete paving equipment. The system, which is based on a new modular 3D software platform, allows contractors to upload the project to the machine and pave without any time consuming setting out.

GPS systems are also being added to rollers to allow operators to track compaction passes. Bomag’s system combines its Variocontrol and its BCM05 compaction measuring system with a GPS receiver to provide co-ordinate values accurate to 25 mm. The system is linked to an on site GPS reference station, which enables to operator to view the compaction in real-time and adjust the roller accordingly.

The information can also be transferred to the construction office and a graphical display show the areas where the compaction has been achieved in green, while areas which require further work are displayed in red.

New machines

The US Tier 3 and European Stage IIIA emissions regulations for engines in the 130 to 560 kW power bracket came into force in January this year. The change resulted in a wave of new machine launches in the road construction sector earlier this year and many of these were displayed for the first time at the Intermat exhibition in Paris, France. Nonetheless, manufacturers have since added other machines to their product lines and some are beginning to talk about the equipment which will be on display at next year’s Bauma show in Munich, Germany.

Ingersoll Rand’s latest product launch marks the company’s entry into a new area of the road construction market and, according to Ingersoll Rand road development president Gary Michael, the launch give the company “a full complement of products”. The company has launched two milling machines - The MT-2000, which offers a 2 m milling width, and the MW-500 with a 500 mm working width.

Wirtgen has also added to its milling machine range with the addition of the W 100 F, which offers +20% more power than the previous model as well as a more ergonomic, easier to use design. The new W 100 F offers standard working width of between 1 and 1.3 m but can also be used with Wirtgen’s Flexible Cutter System to give working widths of 0.3 to 1 m. The design concept on the W 100 F will also feature on the new W 100 and W 60, which will be launched at Bauma next year.

Paving the way

Next year’s Bauma exhibition will also be the launch pad for Bomag branded pavers, which are currently sold under the Marini name. According to Bomag head of product management Lutz Stallgies, Bomag is not just taking over the paver range but is redeveloping the machines to improve the operation and performance.

As well as Vögele’s new dual asphalt paver, the company has also added four other ‘conventional’ pavers to its line up. The new models follow on from the launch of the other ‘dash two’ pavers - the Super 1900-2 and 2100-2 - at Intermat and also feature the ErgoPlus design, which offers better controls and cab for the operator. Also new on all the models is the Niveltronic Plus Automated Grade and Slope Control.

The Super 1603-2 and Super 1803-2 wheeled pavers offer paving widths of up to 7 m and 8 m, respectively, while the tracker models, the Super 1600-2 and Super 1800-2, can pave widths of up to 8 m and 10m, respectively. Vögele is expected to launch another four models at Bauma 2007 to complete the range.

Compaction

Recent additions to Bomag’s product line include a 22 tonne single drum roller, the BW 222 D-4, which is manufactured to meet the specific needs of the Chinese domestic market. The machines’ on-board software systems, such as BTMprof and BCM05, have been upgraded to display Chinese characters and audible information is given in the Mandarin dialect.

“It is impossible to cover the whole world with one product line,” said Mr Stallgies. “At Bomag, we try to develop a platform which is then specified using common parts to suit the demands of each country.”

Hamm is also planning to show new compaction products at next year’s Bauma exhibition. The company launched the first three models in its small HD range, with operating weights of between 1.5 and 4 tonnes, at Intermat but has said that another three will be added to expand the range.

Sakai has added a new monitoring system to its vibratory compaction products. The ExactCompact System is designed to help the operator maintain a predetermined number of impacts per metre run.

Bomag plans to introduce four new light reversible plate models at next year’s Bauma exhibition, which will extend the range to seven machines in the 120 to 700 kg weight class. The new machines are likely to include measuring technology, which will give operators a display of the increase in bearing capacity of the material they are compacting.

“The system will help to save unnecessary passes and will help to improve the quality of trench/repair work,” said Mr Stallgies.

“It is a very simple to use system.”

Further growth?

New emissions regulations have helped to drive development of new road construction equipment in the last 12 months and a number of manufacturers are already talking about launching new machines at next year’s Bauma exhibition. But the need for more efficient and cost effective techniques is likely to stimulate further innovation in the sector over the next few years.

The current growth in infrastructure investment is also likely result in the current high volumes of construction equipment sales being maintained, or even rising over the next year. Mr Stallgies told iC, “The road construction market is booming everywhere atthe moment. Some countries are performing better than elsewhere but the market in almost every country worldwide is strong and this is likely to continue into 2007.”

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