Feature: Road building
21 October 2015
With pressure on contractors to complete road projects faster while maintaining or improving quality, there is a lot to be said for researching the latest technology available on the market.
For example in 2013, Weaver-Bailey Contractors won the US$ 20 million project to expand a 9.9 mile (15.9 km) stretch of Route 67 in Arkansas, US, it opted for a Topcon GPS machine control system to complement its GOMACO paver.
The new concrete highway measures 26 ft (7.9 m) – there are two 12 ft (3.7 m) lanes plus shoulders on either side. The project involved laying some 368,838 yd2 (308,000 m2) of cement stabiliser, which was rough graded with a dozer and finish graded with a grader, both equipped with Topcon 3D-MC2 machine control.
“We’ve been using GPS machine control for some time in our dirt work so we’re familiar with its accuracy and production speed, which we’re also seeing on the paving side as well,” said Weaver-Bailey paving superintendent, Roger Weaver.
For the paving work, the company used a four-track GOMACO GHP-2800 slipform paver equipped with a Topcon 3D paving system. The paver features an in-the-pan dowel bar inserter (IDBI), inserting 23 bars across the 7.25 m wide slab at 300 mm spacings.
“The machine’s operating system with stringless technology benefited us greatly in lower costs, higher production, and better results,” said Mr Weaver. “We’ve been using 3D paving for the past two years and like that we get real-time navigation with direct access to the design data from our CAD project model. It accommodates radii and superelevations automatically.”
Topcon’s Millimeter GPS Paver System controls the paver’s lift cylinders independently. The GX-60 control box in the GOMACO paver’s operator compartment features a colour, graphical screen display of machine position on the job, and the receivers being used to control the left and right side of the mold, and current elevation and slope.
Minsk ring road
Meanwhile, another GOMACO GHP-2800 fitted with the company’s IDBI attachment is being used by Belarusian contractor Trest 8 for the Minsk ring road, along with a specially designed T/C-600 texture/cure machine.
Paving passes for the new roadway are 7.48 m wide and 240 mm deep. The independent IDBI attachment on the paver is placing 17 bars across the slab on-the-go for the transverse joint. The bars are placed 440 mm apart at a depth of 120 mm in the new slab.
The GOMACO IDBI attachment is self-contained, self-powered, and inserts transverse joint bars in pavements up to 15.2 meters wide on four-track pavers. It features the GOMACO-exclusive G+® control system, which manages the timing and operation of the IDBI functions. Trest 8 is progressing well on the slipforming of the ring road, averaging 600 m of highway per shift.
Another major new build project is construction of a new motorway in Turkey to link the capital Istanbul and western regions of the country. It includes the Izmit Bay Suspension Bridge, which at 2,682 m long, with a central span of 1,550 m, will be the fourth largest suspension bridge in the world when completed.
Yener Asfalt, the Turkish partner in the international consortium for the scheme is using four Bomag BF 800 C pavers with S 600 screeds on an 8 km section of the motorway. This will be paved with 300,000 tonnes of crushed aggregate and 200,000 tonnes of asphalt, so the BF 800 C’s theoretical output of 800 tonnes per hour is a key ingredient to success.
Yener Asfalt owner Umit Yener said, “It’s not just the machines that do a great job. We are also highly satisfied with Bomag’s service. Bomag provides us with the right solutions for every challenge and we will purchase additional Bomag units as soon as new projects are planned.”
In addition to the pavers, nine other Bomag machines are also in use at Yener Asfalt in Turkey - a BW 120 AD-4 light tandem roller, four BW 161 AD-4 heavy tandem rollers, two BW 24 RH rubber-tyred rollers and two BW 213 D-4 compactor.
Ayrton Senna Highway
In Brazil, the SP-070, also known as the Ayrton Senna Highway, between São Paulo and Campos do Jordão, Vale do Paraíba and Rio de Janeiro, has seen structural repairs carried out on a 35 km section. The stretch in question runs between the 11 and 46 km marks – which extends from São Paulo in an easterly direction.
With 125,000 vehicles using the road every day, the 250 mm cement-bound base course had become damaged. Contractors Ecopistas and Fremix Engenharia e Comércio decided to recycle the existing road material with foamed bitumen, produced in a Wirtgen KMA 220 mobile cold recycling mixing plant.
A restriction was that they could only work during eight-hour overnight shifts, from 9 pm to 5 am to prevent traffic hold-ups. The tight timeframe meant the cooling time for the asphalt was critical.
The 100 mm asphalt surface and 250 mm underlying cement stabilised layer, both requiring rehabilitation, were milled out separately and conveyed onto trucks using W 1900 and the
W 2000 Wirtgen milling machines
The reclaimed material was transported by truck to a mixing location set up close to the site. Here it was crushed using a Kleemann MC 110 Z EVO track-mounted jaw crusher to ensure that the grain size did not exceed 20 mm.
Two Wirtgen KMA 220 cold recycling mixing plants were then used to make the foamed bitumen mix. The hot bitumen is mixed in the expansion chamber of the KMA 220 with air and water. This produces foamed bitumen which has 20 times the volume of the original product. The foamed bitumen is then combined with hydrated lime and the reclaimed material to produce a homogeneous mix.
This was then paved in two layers. The 200 mm thick first layer was compacted by both a 14 tonne Hamm 3414 compactor and a 9 tonne Hamm HD 90 tandem roller, and then the HD 90 completed the compaction of the 130 mm thick second layer on its own. A Vögele Super 1300-3 tracked paver was used to apply an unusually thin 20 mm surface course. A Hamm GRW 280 rubber wheeled roller took care of the final compaction of the asphalt mix.
Safety barrier installation
In another rehabilitation project McCarthy Improvement Company of Davenport, Iowa, US is engaged in removing and reconstructing the interchange of the busy I-57/70 in Effingham, Illinois. The ultimate goal of the ongoing project is to upgrade the Interstate from four to six lanes, with completion targeted for July next year.
To keep workers safe, McCarthy Improvement separated traffic from the work zone with a stretch of temporary concrete barriers. This totalled some 36,000 ft (11 km) of wall to pin in place.
The company turned to Minnich Manufacturing, which designed and built a unique barrier-mounted machine.
Built to ride along the top of the area wall and drill all three holes simultaneously, the self-propelled machine runs on compressed air, while a tethered controller allows the operator to move the machine to its desired location, make adjustments and operate the drills to nail down the temporary concrete barriers. The process eliminates the need for multiple workers drilling holes by hand, therefore freeing them up to manage other jobs.
“The temporary concrete barrier mounted machine has substantially helped get the job done and the manpower and safety of the crew greatly increased because of this drill,” said Ryan Birney, product manager at McCarthy Improvement. “Without the drill, workers would have needed to drill thousands and thousands of holes by hand, but now we are able to let the machine do all the work. It’s a pure cost savings as opposed to drilling all the holes manually with standard impact drills.”
In a rehabilitation project of a different kind, runway 16L/34R at Rome Fiumicino airport in Italy is being replaced, which involves the milling and repaving of the 3.9 km long, 60 m wide surface by contractor Pavimental.
Before full paving production began on the project, Pavimental wanted to test whether a Roadtec SB-2500e Shuttle Buggy material transfer vehicle (MTV) could reduce thermal segregation in the hot-mix asphalt (HMA) and ensure a higher-quality finished mat.
The Roadtec SB-2500e/ex Shuttle Buggy is designed to store and transfer HMA from a truck to a paver for continuous paving. A patented anti-segregation auger remixes materials just before they are delivered to the asphalt paver. The 25 ton (22.7 tonne) surge capacity of the Shuttle Buggy allows trucks to unload material immediately and return to the asphalt plant.
The Fiumicino 16L/34R runway project was less than five minutes away from the asphalt plant so Pavimental was initially doubtful that material transfer vehicles (MTVs) like the Shuttle Buggy could offer benefits. However, using Moba infrared scanning equipment to look at thermal segregation, it found less than an 8° C temperature difference throughout the material, compared to more than 20° C when the HMA was loaded straight into the paver.
At an 8° C temperature difference, there is no segregation of the asphalt material. In addition, the Roadtec Shuttle Buggy helps keep the paving process continuous by acting as a buffer for materials and keeping a stock of asphalt on hand for
Meanwhile in Africa, XCMG supplied a variety of equipment to the US$ 70 million World Bank-financed project to upgrade a 74 km section of the Kombolcha-Bati-Mille highway in Ethiopia. The road in the Northeast of the country provides a link to the port of Djibouti.
Among the fleet was an XS223J roller, XS262 roller, GR180 motor grader, RP952 asphalt paver and XTF120 chip spreader. All had to work in the harsh African conditions, with daytime temperatures reaching 46° C.
The XS262 is a 26 tonne duty single drum vibratory roller. It is one of a new generation of machines from XCMG offering enhanced performance, increased cooling capacity and improved reliability. The controls, display and buttons are arranged on the adjustable control panel in an ergonomic manner with the forward and reverse gears on the right to facilitate easy