The latest technology continues to improve the quality of concrete paving while contractors are also benefiting from more adaptable equipment - Mike Woof reports
For many concrete paving applications, versatility is required rather than a high production rate. Leading paver manufacturers such asIn addition to offering versatility and mobility, these machines are able to meet tight quality specifications for finish and some units are well-suited to use with the latest GPS and laser-based stringless controls. A very high production rate and a high quality finish have been achieved by a contractor carrying out concrete paving work on a tricky project in St Louis, in the US state of Missouri. The firm has used sophisticated control technology on its paver to meet a tight schedule and has used the equipment to slipform nine tight radii, parking lot islands, in a single day. The contractors used its GOMACO GT-3600 paver and equipped this machine with the latest
The project was in the parking area for the new St Louis City Casino and the company slipformed 610mm wide gutters with a 152mm kerb, in radii as tight as 457mm. Steering of the paver was controlled by the Leica PaveSmart system, which is specified for kerb and gutter applications and uses GPS and 3D components. By using this technology the contractor was able to carry out the work quickly and accurately, while reducing setting out costs by eliminating the need for stringlines for the slipformer to follow. The project has also included kerb and gutter slipformed at specific angles, as well as straight-aways, adding to the complexity of the work.
Meanwhile US contractor, Oklahoma-based Schwarz Paving, is finding its Terex SF2204C HVW concrete paver meets its needs for a versatile machine. The contractor focuses primarily on work for the Oklahoma Department of Transportation, Oklahoma City municipal government and surrounding counties, and private developers. The firm has specialised in concrete production and paving for over 60 years, although it broadened its range when it bought out an asphalt paving firm a few years ago.
Schwarz carries out municipal jobs up to 100km from its base and works on an array of mixed concrete and asphalt intersection paving projects for the most part. A typical job would be to pave a 91.4m section with concrete and finish this with asphalt. The intersections would often require a combination of 4.3m and 3.7m paving widths, so the firm would use two machines set at these widths. As making width changes could take up to four days, it was easier to have its machines set at predetermined widths and the firm had four pavers in all to meet its paving needs. Although this suited projects where no width changes were required, carrying out variable width paving on exit ramps was more complex and the firm found it easiest to sub-contract this work. And where a project required an intersection with a flared fifth turn lane, the paving crew had to carry out an additional pass.
Schwarz realised that by purchasing a new and more versatile paver, it could meet all of its paving needs and the firm opted to buy a Terex SF2204C hydraulic variable width (HVW) model, replacing its four conventional machines. As paver widths can be changed in minutes, the firm can now moves the machine from site to site to handle different jobs and it achieves much higher utilisation than the previous pavers.
The SF2204C HVW has two paving pans mounted in tandem as well as modular guillotine side forms. The machine can be adjusted hydraulically in minutes and offers infinitely variable paving widths, ranging from 2.4-6.1m wide. Each 1.22m long paving pan is constructed as a water storage vessel that adds 1.5tonnes directly over the concrete. In addition, the SF2204C HVW features a novel vibrator mounting system that allows additional units to be fitted (or extra units to be removed) in just 10 minutes. Up 15 individually controlled vibrators can be fitted to help deliver uniform density and high pavement strengths. The machine also has its automatic oscillating float finisher mounted on a telescoping sub-frame to further simplify width changes.
Using this machine Schwarz Paving was able to pave two sites, an access road in Yukon and an intersection in Norman, Oklahoma that was 32km away, within a tight time frame. In Norman, the crews paved a quadrant of the intersection at 4.5m with an integral curb. As soon as the quadrant was paved, the SF2204C HVW was moved to Yukon and set to pave at 3.9m with an integral curb. Using this machine allows the contractor to pave a site with the SF2204C in the morning, load it on the trailer, ship to a site across town and pave in the afternoon. For those intersections that expand to a fifth turn lane, the hydraulic variable width paver delivers a particularly useful time saving for the contractor as this cuts out the need for an extra pass and about two paving days.
Vibration technology advance
Ensuring the concrete density meets specifications is an important component in paving and new technology offers contractors a number of benefits.
In addition the firm has also changed its vibrator speed sensor and this no longer is attached to the back of the motor. Instead, the sensor is in a rubber plug that can fit between hydraulic hoses. This feature allows the user to mount the sensor to the vibrator, without having to disassemble the entire vibrator.
Wacker Neuson says its new concrete vibrators feature an innovative protection system, while the firm is also offering a novel new concrete curing technology. The patented Bodyguard system is said to maximise user and equipment protection and this includes the vibrator heads and power cables.
The integrated safety system can switch off the internal vibrator if any residual current is detected, providing the operator with protection from electric-shocks. The system works through all functions of the device, from the start of the power cable to the vibrator head, situated near the mains plug.
At the same time, this concrete compaction concept offers high productivity. The IRFU operates at an extremely steady speed, offering outstanding compaction performance in comparison with competitor models," explains Martin. The wide input voltage range guarantees stable operation even if the power/generator supply fluctuates significantly or power extension cables are in use. This ensures consistently high levels of productivity. And the integrated display also boosts productivity, using different colors and flash frequencies to indicate the status of the inverter and protection system. This allows the operator to identify any faults immediately, fix them quickly and maximise uptime. Further details such as rounded corners on the inverter casing, preventing them from catching on the reinforcements, complete the sophisticated design.
The company has developed a portable hydronic heater that allows groundwork and concrete curing at temperatures below freezing. The high-performance E700M unit can thaw areas of up to 400m2 and protect them against frost. This provides an inexpensive and efficient means of completing construction projects on time even during cold weather.
According to the firm, the E700M can heat large areas so that construction work and concrete curing can continue as usual, even with extreme frost. The heater runs on diesel and warms a mixture of water and glycol to over 80°C. This warm liquid is then pumped through a 700m hose laid on the area requiring heating. An insulating blanket is placed over the hose to prevent heat loss from the ground.
The firm claims a 94%, compared with just 15% for conventional methods. The firm says that its portable hydronic heater can reach deeper soil layers and thaw large areas faster as a result. The unit takes just three days to prepare an area of 400m2 with a target depth of 1m, compared with 25 days using conventional methods. In addition, the E700M eliminates the need for an enclosure when working with concrete in sub-zero conditions as it directly heats the concrete to an ideal curing temperature of 18- 24°C, accelerating the process and improving results.
Minnich's new monitor will store the data that can be transferred to a USB mass storage device and allow the operator to decide what is stored
Tunnel bound
Concrete paving equipment from
