VOL 21 ISSUE #1

The Roadtec SB-2500e/ex Shuttle Buggy proved to be the superior method to produce a high-quality mat for the Rome airport refurbish project.

Rome’s airport Fiumicino or the Leonardo da Vinci Airport of Rome, is Europe’s sixth busiest airport. It lies 16 mi (26 km) southwest of Rome, about a 30-minute train ride away.

The airport features three terminals: domestic flights depart from passenger station Terminal A, some domestic and international flights depart from Terminal B, and transatlantic flights leave from Terminal C.

Rome airport Fiumicino officially opened on January 15, 1961, with two runways replacing the small Rome Ciampino Airport, which remains in service for domestic and charter operations. During the decade, Alitalia, the national airline of Italy, invested heavily in the new airport, building hangars and maintenance centers, and during the period, a third runway was planned.

A number of changes occurred in the early 1970s when the two existing runways were lengthened and the construction of a third runway began.

In 2007, the combined traffic in Rome airports, Fiumicino and Ciampino, hit about 38 million passengers traveling to/from 150 destinations worldwide, which were operated by the 160 airlines in the two airports.

Recently, Fiumicino 16L/34R runway required total rehab. The runway measuring 12,801 ft x 197 ft (3,902 m x 60 m) required both milling and repaving. Pavimental SpA, Rome, Italy, won the contract to refurbish the runway and is considered the leader in asphalt production in Italy.

Detecting thermal segregation on the paved test layers.
Pavimental used MOBA Mobile Automation AG and its PAVE-IR Scan to detect the thermal segregation on the paved test layers.
Roadtec Shuttle Buggy’s maximum thermal segregation detected was 47 degrees F (8 degrees C).
The collected data showed that the Roadtec Shuttle Buggy’s maximum thermal segregation detected was 47 degrees F (8 degrees C), indicating NULL segregation.

Thermal Segregation

Before full paving production began on the project, Pavimental wanted to test whether a Roadtec SB-2500e/ex Shuttle Buggy® material transfer vehicle (MTV) could reduce thermal segregation in the hot-mix asphalt (HMA) and ensure a higher-quality finished mat. They also wished to test another manufacturer’s MTV.

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 (23 tonnes) 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 making Pavimental doubtful initially that MTVs could offer benefits.

For the three tests conducted, Pavimental used MOBA Mobile Automation AG, Limburg, Germany, as an independent quality controller. MOBA used its PAVE-IR Scan to detect the thermal segregation on the paved test layers. The PAVE-IR Scan is a quality-control system that offers the ability to record the asphalt temperature while paving and is designed to depict a temperature profile. Temperature differences that lead to thermal segregation of the material and to premature wear and tear of the road can be determined during paving.

Pavimental used the PAVE-IR Scan system to show the overall quality achieved by each paving method: (1) paving with the help of the Roadtec SB-2500e/ex Shuttle Buggy MTV, (2) paving with the help of another manufacturer’s MTV, and (3) paving with HMA trucked directly from the production plant and loaded right into the paver.

The Test

The determining factor in the research test was to measure the level of thermal segregation occurring in the asphalt mat after each paving method used. In the recent past, extensive testing resulted in Stroup-Gardiner and Brown establishing in 2000 a classification of thermal segregation and its related consequences. In the classification system, when temperature differences are below 50 degrees F (10 degrees C) segregation, it is considered nonexistent or NULL, between 50 degrees F (10 degrees C) and 61 degrees F (16 degrees C) it is LOW, between 63 degrees F (17 degrees C) and 70 degrees F (21 degrees C) it’s MEDIUM, and it is considered HIGH when over 72 degrees F (22 degrees C). Therefore, the higher the measured temperature the more likely the paved surface will experience fatigue and be less durable. What all the tests clearly point out is that temperature deviations will make pavement less durable and will consequently increase maintenance costs.

For the Rome international airport test, a lift was laid by each method. The testing occurred over a six-day period with three test mats laid by each method.

MOBA used infrared scanning to examine the level of thermal segregation. The data results concluded that the finished pavement quality from each paving method showed:

  • < 47 degrees F (8 degrees C) when using the Roadtec Shuttle Buggy MTV
  • between 59 degrees F (15 degrees C) and 72 degrees F (22 degrees C) with the other manufacturer’s MTV
  • between 68 degrees F (20 degrees C) and 77 degrees F (25 degrees C) when trucked HMA is loaded directly into the paver
Testing occurred over a six-day period at the Rome international airport.
The testing occurred over a six-day period at the Rome international airport with three test mats laid by each method; infrared scanning was used to examine the level of thermal segregation.
The Roadtec SB-2500e/ex Shuttle Buggy® remixing materials with its anti-segregation auger just before delivery to the asphalt paver.
The Roadtec SB-2500e/ex Shuttle Buggy® with its anti-segregation auger remixing materials just before delivery to the asphalt paver proved through the MOBA tests to be the superior method.

The Conclusion

The collected data shows that when the Roadtec Shuttle Buggy is used, the maximum thermal segregation detected is 47 degrees F (8 degrees C), so the results indicate NULL segregation. When the other manufacturer’s MTV or direct truck-to-paver methods are used, the temperature differentials can be more than 68 degrees F (20 degrees C) at any given time. Thus, these methods will have durability that is expected to be about half of what can be achieved using the Roadtec Shuttle Buggy, which remixes the HMA and provides continuous paving.

Pavimental found the results to be quite telling. The initial thinking was that with the HMA production source so close to the jobsite—five minutes away—that there would be no need for a material transfer vehicle. Clearly, the Roadtec SB-2500e/ex Shuttle Buggy with its anti-segregation auger remixing materials just before delivery to the asphalt paver proved through the MOBA tests to be the superior method.

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