Optimum solution: Cold recycling in-plant
Both Ecopistas and Fremix Engenharia e Comércio Ltda., the company contracted to rehabilitate the road surface, decided to use the technology that would deliver the best results in the fastest construction time: recycled material with foamed bitumen, produced in Wirtgen's mobile cold recycling mixing plant KMA 220.
When selecting the optimum rehabilitation method, the contractors also needed to meet one strict condition: on working days, the construction work on this vital transport route was restricted to an overnight 8-hour window from 9 p.m. to 5 a.m., since even the most minor closures for roadworks can cause massive traffic hold-ups. The tight timeframe meant that a thick asphalt pavement was out of the question. While the thicker asphalt layers produced in conventional rehabilitation processes need to cool for about four days – and for concrete pavements, setting takes even longer – Wirtgen's cold recycling technology allowed the pavement to be repaired section by section before being immediately reopened to traffic.
"During the daytime, no lanes can be closed between the São Paulo city limits and the airport, due to the high volume of traffic. That's why the work was carried out at night during the week or at weekends," explains Elio Cepollina Junior, Commercial Manager at Fremix. Further advantages of using this process include rapid completion of the works, a minimal number of transport journeys and the complete recycling of the reclaimed material. All in all, this adds up to a very cost-effective and eco-friendly process.
Wirtgen cold milling machines and Kleemann jaw crushers clear the way
The approximately 10-cm asphalt surface course and the underlying 25-cm cement stabilization layer, both requiring rehabilitation, were milled out separately and conveyed onto trucks. For this task Fremix used two of Wirtgen's large milling machines, the W 1900 and the W 200.
The reclaimed material was transported by truck to a mixing location set up in close proximity to the site. Here it was crushed using a state-of-the-art Kleemann MC 110 Z EVO track-mounted jaw crusher to ensure that the grain size did not exceed 20 mm and that the material had an optimal granulometric composition. The mobile crusher can be used for a variety of applications, including the preparation of both natural stone and asphalt and materials that have been quarried or mined.
Wirtgen KMA 220 recycles reclaimed material on site
Using two Wirtgen mobile cold recycling mixing plants KMA 220, the reclaimed material was then recycled into a top quality mix with foamed bitumen (BSM). The KMA 220 is easy to transport and can be quickly set up on site. As a result, the two plants were quickly installed next to the motorway, greatly reducing the number of material transfers.
Juliano Gewehr, Product Specialist at Ciber Equipamentos Rodoviários, explains: "The cold recycling mixing plant allows us to re-use the reclaimed material. We optimize it by adding binders and supplementary materials in order to deliver a pavement with a very long service life and optimum material properties."
The key to success: Precision metering of binders
Loudon International and its engineers were in charge of the mix design and quality monitoring. Working with the technicians from JBA Engineering and Consulting Ltda., they provided support for the preliminary investigations and project execution. Using the results of preliminary tests carried out with the Wirtgen laboratory scale foamed bitumen plant WLB 10 S, the quality of the foamed bitumen and the optimum composition of the mix – obtained in combination with the Wirtgen laboratory-scale twin-shaft compulsory mixer WLM 30 – could be precisely identified before construction work commenced. The formula finally selected comprised 1% hydrated lime and 2% bitumen.
The hot bitumen is foamed in the expansion chamber of the KMA 220 by adding air and water. This produces foamed bitumen which is 20 times the volume of the original product. The foamed bitumen is combined with the hydrated lime and the reclaimed material to produce a homogeneous mix. The recycled reclaimed material was paved in two layers: The 20 cm-thick first layer was compacted by both a 14-t Hamm 3414 compactor and a 9-t Hamm HD 90 tandem roller, and then the HD 90 completed the compaction of the 13 cm-thick second layer on its own. The Vögele SUPER 1300-3 tracked paver was used to apply an unusually thin 2-cm surface course. A Hamm GRW 280 rubber wheeled roller took care of the final compaction of the asphalt mix.
Wirtgen Group machines for an excellent result every time
Valmir Bonfim is very happy with the result. Cold recycling technology enjoys a reputation for excellence worldwide – and now the Technical Manager at Fremix can see why. Indeed, he now sees further great potential for cold recycling in Brazil: "There is no doubt that this project will set a precedent for future roadworks in Brazil."
Ten different Wirtgen Group machines were involved in this challenging project. They had been deliberately selected by Valmir Bonfim: "On a construction site of this size, where the rehabilitation of the various sections has to be completed within one day, we couldn't afford to take any risks. That's why we decided to use the Wirtgen Group's reliable machines and its state-of-the-art technologies and application processes." Ongoing assistance from Wirtgen Group experts and service technicians provided additional security.
Alvaro Rodrigo Pinheiro, Engineering Manager at Ecopistas, the concessionaire, is impressed by Wirtgen's cold recycling technology and sees it as an excellent, eco-friendly solution for the structural repair of the Brazilian road network. Based on the excellent results obtained, Ecopistas is planning to make further investments in this technology in the coming years.