Roadbuilding: Paving the way ahead

A call was made at this year’s ConExpo for the construction industry to unite against climate change. Volvo CE hosted the latest Construction Climate Challenge (CCC) seminar, Reducing Carbon in Infrastructure Construction, at which it was suggested that we are on the cusp of a step change in sustainable performance.

Opportunities for improvement abound in the construction industry, according to Dave Ross, vice president of advanced engineering at Volvo CE and one of this year’s speakers. Cutting-edge technologies promise to help us seize those opportunities in the roadbuilding sector by significantly improving accuracy and flexibility.

Topcon’s new ZPS concept, for example, aims to reduce waste by affording greater precision in the paving process. Two components, a Z-Robot and a Z-Stack, work in tandem to guide the paver using enhanced Topcon Millimetre GPS technology. The improved vertical accuracy helps to create a surface that is more true to design, minimising any excessive use of materials.

The Z-Robot is a robotic total station with Z-beam laser technology, designed to provide high precision and optically based vertical accuracy control.

Murray Lodge, senior vice president and general manager of the Construction Business Unit, said, “With the ZPS system, only one Z-Robot controls the paver.” According to him, this eliminates the need for multiple robotic total stations, as are used in traditional LPS (local positioning systems), meaning costs are cut.

Time is saved, too, by the fact that this automated concrete paving system supposedly requires fewer instrument transitions, since its working range exceeds that of traditional methods by up to 45 m.

The Z-Robot communicates with the Z-Stack on board the paver, which is a modular unit that brings together GPS, optical targeting and Z-beam reception into a single, multifunctional unit.

The team at GOMACO apparently refers to the Topcon Z-Stack as the ‘sandwich’ because the three interlocking components can be mixed and matched according to the specific requirements of the job.

Needing no separate base station and just a single cable for both power and connectivity, the Z-Stack has, for the first time, begun to feature on GOMACO products. The control system on their new three-track Commander IIIx Xtreme slipform paver is capable of interfacing with various 3D guidance systems, including Topcon’s ZPS.

The GOMACO Commander IIIx Xtreme can slipform a radius of 6.1 cm. This is made possible by the fact that each track is equipped with a rotary-sensored slew drive and smart hydraulic cylinder, so that the G+ controller knows the position of all three tracks and can make steering and speed adjustments as needed.

This intelligent slipform paver comes with G+ Radius software that allows the operator to pre-program the size of the radius. As the paver approaches the turn, the program can be activated and the machine left to carry out the work automatically.

In addition to offering improved fuel efficiency with its load-sensed hydraulic circuits and power-optimised engine, the Commander IIIx Xtreme has been built to accommodate Tier 4 engines and their cooling packages.

It also claims to be one of the quietest pavers on the market today thanks to G+ quiet running technology, which helps to keep sound pollution to a minimum.

An optional accessory is the G+ wireless remote control. It allows the operator to step down off the platform and maintain control while moving around the machine.

Clever slipforming

Wirtgen has replaced its SP 500 slipform paver with the new SP 60 series for creating concrete pavements and monolithic profiles.

The SP 61i, SP 62i and SP 64i models comply with the latest emissions laws. Those machines that meet EU Stage IV and US Tier 4 Final emissions specifications have a 180 kW Deutz engine that provides about 40% more power than the SP 500. Despite the higher output, fuel consumption is reduced by the Wirtgen Eco mode, which automatically adapts engine output to power requirements.

With the new hydraulic concept, more features operate hydraulically, saving energy that is then available for new equipment options, such as a large delivery screw for offset applications or the four swivel arms used to switch the machine from transport to working mode more quickly.

The SP 60 series uses state-of-the-art intelligent machine control systems with interfaces for Wirtgen’s Widiag service diagnosis and WITOS (Wirtgen Group Telematics and On-Site Solutions) FleetView system. The Paving Plus package is an optional extra that enables the swivel arms to circumnavigate obstacles during the paving process.

More flexibility is provided by the modular design of these pavers and the walkway that has now been extended to span the full width of the machines.

In the push for ever-greater efficiency, Power Curbers & Power Pavers is also offering improved accuracy and flexibility with its latest products.

The Power Curber 7700 is a versatile slipform machine that is designed for offset applications and paving widths of up to 6 m. Contractors who carry out a variety of jobs can use the curber in such diverse projects as variable barriers, bridge parapets and ditches.

For paving, the Power Curber 7700 offers hydraulic sides, edge overbuild and crowning capabilities, along with optional tamper bar, auger or plough, and finishers.

Switching from paving to offset mode is made easier by the hydraulic telescoping frame, as well as the Simple Steer Track Positioning System, which aligns all four crawlers.

The company’s latest Power Paver 2400 series includes two new slipform pavers: the four-track SF-2404 and two-track SF-2402.

Designed for residential and intermediate projects up to 7.5 m wide, these two machines provide solutions for conventional and offset paving, as well as custom applications.

For ease of operation, the SF-2404 has one-touch track positioning and simple steering controls, as well as a telescoping frame that facilitates width adjustments.

All three machines – the Power Curber 7700 and the two new Power Pavers – are stringless ready, meaning that they can be used with 3D and GPS control systems from Leica, Topcon and Trimble.

Economies of scale

Precision is of particular importance in large-scale projects where the millimetres really add up. Detroit Metropolitan Wayne County Airport (DTW) recently decided to reconstruct its 4L/22R runway, which encompassed 10.5 km of 1-m-thick airfield pavement in total.

Lois Kay Contracting was made responsible for milling the runway and associated taxiways. With a fleet of five Roadtec RX-900e cold planers, two Roadtec RX-700e milling machines and a variable-width Roadtec RX-400e milling machine, they removed just under 200,000 tonnes of material.

3D profile milling was performed over an area of almost 300,000 m², using four RX-900e planers, all of which were equipped with 3D machine control systems that automatically guided the milling drums. Over-cutting was minimised by the use of 3D design models and total stations.

The project as a whole was awarded the Envision Silver Award from the Institute of Sustainable Infrastructure (ISI).

The original runway had been quick to deteriorate due to an alkali-silica reaction (ASR) that caused the concrete to expand and contract in response to moisture over time. Although the problem in this case was integral to the concrete, so reconstruction was necessary, there are instances when premature failure can be avoided.

GSSI (Geophysical Survey Systems Inc) has created a new tool designed to detect early signs of weakness in asphalt that can lead to road ravelling, cracking and deterioration along joints.

Their PaveScan RDM assesses asphalt density by measuring dielectric values in real time. This offers a non-intrusive method of locating areas of poor uniformity and significant variations in density. Unlike other options, such as nuclear density gauges or radioactive alternatives, PaveScan does not result in site hazards or require the closing of work areas.

Due to its modular design, the PaveScan is available either as a small, portable, single-sensor cart-based system or as a three-sensor configuration on an extended cart.

Another large project that is currently underway is the building of a highway in Panama. The contractor Bagatrac SA is transforming 36 km of deteriorating roads – including 17 bridges – into a modern, 6 m-wide highway.

Bagatrac has been using a Terex Bid-Well 2450 automatic roller paver that can be configured for a variety of paving widths, from 2.4 m to 17 m.

The machine has four paving functions: dual strike-off augers trim excess concrete; paving rollers finish the surface; the dry pan system seals and textures the deck; and the Rota-Vibe system consolidates the top 6.9 cm of concrete. All of these functions are carried out simultaneously by the paving carriage, thereby reducing labour requirements.

Javier Caballero, project superintendent for Bagatrac, said, “The machine effectively cut our labour needs for deck paving in half.”

At its standard width of just over 8 m, the paver weighs 2.75 tonnes, so it puts minimal pressure on bridges as it works on them.

To date, over half of the bridges have been completed using the Terex Bid-Well 2450.

Terex has also been busy developing new innovations for its pavers. At World of Concrete 2017, they unveiled three new remote control options that are available on their Terex Bid-Well 2450, 3600 and 4800 pavers.

Two tethered control boxes can be attached to any part of the paver’s frame and offer entry-level keypad control or local control with a touchscreen display.

Operators are also free to move 360 degrees around the machine at ground level while modifying its performance mid-action by using a radio remote control panel. Various functions can be adjusted, such as speed, engine throttle and paving width.

Mixing it up

As the desire for greater flexibility grows, companies such as Ammann are working to provide solutions from beginning to end of the roadbuilding process.

Their CBT 60 SL Elba is a mobile concrete mixing plant. It is currently being used in Russia for the construction of the M11 – a high-speed motorway between Moscow and Saint Petersburg.

The Moscow-based transportation construction firm TSM has been working on the stretch of road from km 58 to 149. In order to meet the 2018 deadline, they required a ready-mixed concrete plant that could be relocated to supply materials promptly.

“We acquired the CBT 60 SL Elba because it has several advantages, including its ability to be quickly assembled,” said Dmitry Popov, technical department chief of TSM.

Thanks to its folding mechanisms and compact design, the plant needed just two open-top containers for relocation.

What’s more, it has provided the necessary productivity, with a potential output capacity of 58 m³ per hour. The plant achieves this short cycle time by directly weighing inert material on the belt conveyor and feeding directly into the skip, according to Dmitry Popov.

In North America, Ammann recently began sales of its asphalt mixing plants.

The ABA Unibatch, for example, helps to cut down a project’s carbon footprint by using a high percentage of recycled asphalt (RAP). It also has energy-saving software that works in combination with the fumes extraction system to minimise emissions, and the plant’s noise reduction system counters sound pollution.

Rolling out innovations

Towards the other end of the roadbuilding process, Ammann has introduced two innovations for compactors.

Ammann Intelligent Compaction systems, ACE^force and ACE^pro, are available on many of its rollers, including the ARP 95 K Tier 4i Pivot-Steer Roller and the ARX 90 Tier 4f Articulated Tandem Roller. By identifying uncompacted spots, these systems can help to eliminate unnecessary passes and therefore reduce costs.

Another innovation for compactors has come from Caterpillar, with the introduction of an oscillatory vibrator system on its new 10-tonne CB10 asphalt compactor.

The design combines Caterpillar’s vertical vibration – available in two amplitude, five amplitude or Versa-Vibe systems – on the front drum with new oscillation technology on the rear drum. While the front drum provides the initial compaction, the rear optimises smoothness and density.

This makes for an adaptable compactor that can be put to effective use equally in large expressway projects and small urban work. The front drum is good for thicker lifts and tough mix designs, while the rear drum lends itself to thin lifts and surfaces close to sensitive structures, such as building foundations and tunnels.

The oscillatory system, which uses pod-style eccentric weight technology developed by Caterpillar, has a 2,000-hour service interval to maximise uptime and keep maintenance costs to a minimum.

A unique belt-drive system is used in the power transmission to deliver two times the load capacity of timing belt systems.

Compactness of design is of particular importance for jobs being carried out in urban settings. With this in mind, Dynapac has launched its new CC950D roller.

The small tandem roller, which has an operating weight of 1.45 tonnes, is geared towards small-scale jobs, such as bicycle paths, narrow roads and small parking areas.

Measuring 97 cm wide, the front drum vibrates at 70 Hz while the rear drum is static.

The CC950D runs on a 15 kW, water-cooled, 3-cylinder, 4-stroke Kubota D722-E4B-KEA-2 diesel engine that is Tier 4 Final compliant.

High clearance along the edges of the drums facilitates compaction close to elevated structures, such as curbs, and the 227 L water tank allows operators to work for long periods of time without interruption.

Case has also introduced two new double drum vibratory asphalt rollers.

Their DV209D and DV210D both run on Tier 4 Final 75 kW Deutz engines that meet emission regulations for Department of Transport (DOT) projects. Compared with previous models, fuel consumption has been cut by up to 15% thanks to a combination of EGR (Exhaust Gas Recirculation), DOC (Diesel Oxidation Catalyst) and SCR (Selective Catalytic Reduction) after-treatment technologies, as well as an updated cooling system and automatic idle control.

The balanced drum design and automatic vibration control help to avoid surface damage and deliver a smooth finish. A high frequency option – of up to 67 Hz – also offers better control of the compaction process, and the articulated roller joint helps to maintain drum-to-ground contact.

Both models include crab steer for precision work, and can be fitted with rear pneumatic tyres to give surfaces a smooth finish.

An optional compaction meter can be added for monitoring densities in real time and therefore avoid over-compacting. Those densities can even be mapped across large jobsites using GPS.

With operating weights of just over 9.5 tonnes for the DV209D and 10.4 tonnes for the DV210D, these rollers can be used on a range of scales, from municipal roads and parking lots to highways and airports.