Quieter, tougher and greener roads

Manufacturers, pressed by an industry pushing for quieter, tougher and more environmentally friendly roads - constructed partly from recycled materials - continue to throw out new ideas for their construction and repair.

Mowlem's fixed form paving train, supplied by Belgian firm SGME, and modified to lay 9.3m wide sections of dual carriageway in a single pass, has done much to put concrete paving back at the forefront of contractors' minds.

Used in 1993 to lay 'whisper' concrete on the M18, and in 1994 for the A564 Foston Hatton Hilton Bypass in Derbyshire, Mowlem's machine - reputedly one of the largest paving trains in Europe - has helped produce a road surface the British Cement Association (BCA) claims is quieter than conventional hot rolled asphalt.

David Jones, spokesman for the BCA, reports that in recent tests carried out on the M18 by the Transport Research Laboratory - on behalf of the Highways Agency - 'whisper' concrete was the quietest of four materials being tested.' Other materials involved in the tests, which measured surface noise levels, were: brushed surface concrete, hot rolled asphalt and Burlap and Tine concrete.

Results from similar tests on the A564 - a road comprising continuously reinforced concrete pavement and an exposed aggregate surface - are due in the autumn. If the results prove as positive as those for the M18, UK contractors may again return to using concrete - a product which has been rejected in the past owing to its unacceptably high surface noise.

Recent developments in asphalt pavers are marked by the return of tracked machines to the UK market. Ingersoll-Rand's latest tracked paver, the Titan 323, four of which have been sold to two UK-based contractors, provides paving widths from 2.5m - 9.0m.

Standard features include a new synchromatic electronically controlled drive system, hydraulically extendable screeds and high capacity hoppers.

Attractions of the synchromatic system, according to I-R, include its ability to ensure straight line or smooth curve steering is maintained, even in the case of extreme load variations, and minimum forward speeds of less than 1m/min.

Two axial variable displacement piston motors for each side of the pavers have a pressure cut-off device to prevent overheating, and a two-stage adjustment for the paving speed range, 0-16m/min, and a travel speed range of 0-3.6km/h. A toggle switch on the control panel changes speed while driving.

Blaw Knox offers a new tracked paver. On show this week at Hillhead, the PF-451, a 106kW tracked machine, weighs in at around 17t. As well as a Cummins engine, the machine is fitted with a tamping-only Omniscreed V.

Alternatively, for those contractors favouring wheeled pavers, ABG, I-R's European Road Machinery Division, marked this year's BAUMA with the launch of the Titan 255 wheeled paver. Innovative features of the 255 include: optional front-wheel-drive and load-dependent torque control on the front wheels. The torque control on the front wheels modifies the torque according to the material load in the hopper. Standard features include: height adjustable augers to adapt the screed to produce various layer thicknesses, and ultrasonic sensors for contact-free material control.

Conscious of a burgeoning market in compaction, Caterpillar has stepped into the market with a comprehensive range of state-of-the-art equipment. Set to ruffle the feathers of existing players, Cat's line-up includes the 10t articulated roller, the CB-534B, and the 10.7t CB-544 drum steering machine.

Attracted by Caterpillar's foray into compaction, LPH Plant Hire recently opted to add 50 of the company's CB-244C double drum soil compactors to its plant fleet.

Design engineers have been busy at Bomag. New equipment includes AD-130 and BW-151 rollers. Of special interest for surface contractors is Bomag's new Vario Vibration system for its heavy tandem roller range. The system's advantage is its ability to handle a range of materials from coated chippings through to thick layers of asphalt or sub base.

Describing Bomag's AD-130, Alex Ferris, md of Bomag UK, said: 'This 130 isn't just heavier and wider than its predecessors, its hugely more productive. On a big road job this would be ideal. Price may be up by around 15-20% but productivity is twice that. Once contractors twig there will be a huge demand. On certain asphalt specifications an eight pass finish can be achieved with only three passes using this machine - and that is very significant.'

Ingersoll-Rand's DD-74 tandem roller, shares space with other newcomers. Suitable for compaction applications on road and motorway construction projects, for base and wearing courses, the DD-74 offers: a split drum, independently operated drives on all four drum sections, and three different modes of steering - front, both drums or crabbing. Particularly suited to narrow and curved job sites, according to I-R, the DD-74 weighs in at 7,200kg and has a forward travel speed of 0-9km/h. The unit's low noise and low emission Deutz BF4L 1011F diesel engine, giving an output of 48kW at 2650rpm, powers the DD-74's hydrostatic drum motors and vibration system. Each pair of split drums provides a total rolling width of 1500mm and has a diameter of 1200mm. Operating at two frequencies, notably 33 and 55Hz, the DD-74 roller produces a centrifugal force of 45kN.

Already in use on the M25 road widening project, the RT560 articulated steer double drum vibratory trench roller from Wacker - this year's winner of the SED Gold medal award - is notable for its ability to give smooth turns without scuffing. Vibrators and motors are in each drum giving significant reduction in stress. Since its April launch a number have been bought by Kent-based Hewden Hire.

Power is supplied by a twin cylinder, air-cooled Lombardini electric start diesel, driving transmission and vibrator circuits. Frequency is set to 40Hz, and centrifugal force can be changed quickly from 31kN to 62kN at the flick of a switch on a control panel.

Carriageway repair technology is central to German manufacturer Wirtgen's 50% growth in sales since BAUMA '92. Wirtgen, famous for its cold planers, offers contractors a number of pieces of plant for the recycling of worn roads.

As well as its WR2500 recycler/ stabiliser unit, designed to handle soil stabilisation and cold recycling, Wirtgen has introduced the MS400 mobile slurry mixer. Described as a match for the company's CR4500 and 2100 DCR units, it lays cement prior to recycling.

Road repair/ rehabilitation is, claims South African manufacturer Landpac, something it has plenty of experience of, albeit in Kenya.

Armed with a comprehensive range of impact rollers, which have been developed and used in South Africa for the past 20 years, Landpac claims its recent introduction to the UK market represents a cost-effective road rehabilitation solution for contractors.

Unlike conventional 'low-cost' rehabilitation methods, where layers are added to the top of the existing pavement, Landpac claims its technique relies on adding layers to the bottom of the pavement structure by in-depth compaction. In less than four hours, the company claims, two of its machines can fully compact a 500m section. The rollers, of which there are many, all have one thing in common - that is specially-shaped compaction drum or drums. Each drum comprises a series of flat compacting faces alternating with a series of rounded points. As the machine moves over the site surface, the compacting drums, rotated by contact with the ground, rise on their points then fall downward and forward so that the compacting faces strike the ground. It is a revolutionary concept for the UK, full of potential.

Whatever the task, whether road construction, repair or recycling, manufacturers have plenty of solutions. The skill lies in spotting the most pragmatic and cost-effective.