Passing the Tests

Merano, in northern Italy, is a city filled with tradition and history. Its residents have included artists, intellectuals and scientists of acclaim.

The favourable climate of the mountain town attracts both residents and visitors, as does the culture. The rich history, while appreciated by the public, also means areas of the town were created centuries ago. The streets in this city are often narrow and winding.

While picturesque, they are a challenge when it's time to pave. That was the case when Italian paving contractor Varesco Ltd. put a Cat® AP500E Asphalt Paver to work on a project on via E. Toti.

Varesco chose the AP500E because the wheeled paver is a perfect fit for a confined site with an abundance of manholes. The company also wanted to test the paver's performance, and evaluate whether it could be of use in other challenging jobs.

A Cat AP500E Asphalt Paver

Confined Space

The job was paving an access road leading to a residential area in Merano, with a population of 38,000. The road was bound by a pathway on one side and a wall on the other.

Varesco first was responsible for rebuilding the sub-base (20 cm handled by the AP500E), then placing an 8 cm binder course. A 3 cm surface course was added in the spring.

This road was 100 m long and only 4m wide. The paver's ability to accommodate paving widths as narrow as 2.55 m made it ideal for the narrow road. The ample ground clearance was beneficial as well, allowing the paver to pass over manhole covers without interference.

The asphalt plant was located in Bolzano, about 25 km away. Three-axle trucks transported the mix, which arrived at a temperature of about 180° C. The trailers were covered to keep the mix warm as it traveled through the thin mountain air. Supervisors calculated the distance, type of job, speed of paver and other factors when determining the number of trucks needed for each day of work.

The asphalt was placed at a temperature of about 170° C. The crew had no problems with the temperature of the mix, which was important because the job had other challenges in addition to the tight working area.

Adjustable operator stations helped the crew work close to the curb and wall. Each station could be positioned in different locations to maximise visibility. The stations also can extend out beyond the machine frame when even greater side visibility is required.

The frequent starts and stops caused by manholes presented additional challenges. Creating an even, smooth mat despite the lack of continuous movement required precise delivery of mix from the hopper through the screed. Adding to this precision were the paver's tight ratio control and independent auger drive. These components enabled the proper distribution and allocation of mix when paving resumed.

Also key to a smooth restart was the wheeled paver's ability to grab the surface and effortlessly pull the paver and its full load of asphalt. This capability, combined with a screed counterbalance system that manages and neutralises screed weight and movement during the start and stop transitions, helps to prevent defects on the surface of the mat.

The paver proved quite productive. It was able to average about 5 m per minute despite the challenges created by the manholes and other obstructions.

In addition, manoeuvrability of the paver and quick adjustment of the Cat AS4252C Screed proved important on the narrow street. "The paver has a great screed, with optimum steering," said Mr. Heinz Serra, operator of the paver. The inside turning radius in the "maoeuvre" operating mode is very short, enabling the machine to move easily, even make a complete U-turn, in confined spaces without complex manoeuvring. Because of this, the paver easily and immediately repositioned where necessary.

The screed's central display helped ensure an even flow of materials. It also enabled other improvements.

"The new central display on the screed makes all the key data easily accessible in one place," said Mr. Serra. "It enables the operator to check the temperatures of the four sections of the screed, the number of strokes of the tamper bar, which number is modified according to the thickness of the mat, the frequency of the vibrating screed, and the barometric adjustment of the screed assist."

Compaction

A 4-ton roller handled breakdown compaction immediately behind the paver. The compactor, in vibratory mode, made as many passes as necessary to achieve compaction.

The breakdown roller stayed between 5 m and 20 m behind the paver. The temperature of the mat was about 130º C during the breakdown process. A finish roller completed the process.

Assessing the performance

Mr. Serra reflected on the paver's performance after the Merano project, as well as a test at another jobsite in the mountains surrounding Merano. On that project, Varesco tested the AP500E on a road with a slope so steep the transport truck trailers were covered to prevent material from spilling out the back. The results of both tests led Varesco to purchase the paver.

"The machine is quite easy to move according to your needs in any working environment, from small jobsites like residential street works to industrial yards, from local and regional streets to narrow mountain roads that represent the majority of our jobs," he said. "I appreciate the electronically controlled traction, the recovering of fumes, the perfect operation of the electric screed and the easy access to all major service points for daily maintenance."

A Cat AP500E Asphalt Paver