As cities become more conscientious of the environment, contractors are continuously looking for alternative methods to complete projects. Such efforts often offer several benefits from helping the environment to providing a cost savings. In a recent project completed by Cactus Asphalt, located in Tolleson, AZ, mill and fill was used to reconstruct alleyways located in Chandler, AZ.
Faced with the complications of completing work in tight spaces, Cactus Asphalt’s extensive experience proved invaluable to successfully complete the project. It was especially critical with this project because it called for the use of reclaimed asphalt pavement (RAP) that was laid down with a paver — unlike most alleyways in Southwest that use chip seal. This process has been used for the past five years in Chandler, and it has held up well to the garbage truck traffic.
“This was the city’s way of going green,” says James Gallegos, project manager. “They are reusing all of the millings for their overlays. So, instead of purchasing material at the tax payers’ expense, they are reusing the material in alleyways for dust proofing.” Rex Hartman started this program five years ago and has continued to follow it for the City of Chandler.
Cactus Asphalt was able to complete the project in 4 months. This particular alleyway project consisted of 250,000 square yards of alleyway that was divided into two sections. “The spec called for 14 feet wide and a removal of 4 inches with a mill,” says Jeff Martinez. “We disposed of the milling to a land fill.”
Before the project began, the city of Chandler coordinated with the utility agencies to complete prep work, including trimming trees, to ensure a clear working environment for Cactus Asphalt. “The utility company was key to making sure all of the lines were lowered before worked started,” Martinez says. “If we did hit a line, the utility company was very responsive when it came to repairs.”
The milling work and removal of excess dirt was completed by subcontractor C & S.
“C & S completed the milling operation cutting down between 4 to 6 inches,” Gallegos says. “After that, we came through with a grading operation to get everything prepped, and we put 4 to 6 inches of millings back into the alleyways.”
With a dirt subgrade, Cactus Asphalt prepped the surface by using a process of water trucks and skid loaders to compact the surface.
After the subgrade was prepped, the eight-man Cactus Asphalt crew began laying down the surface. Placing about 50,000 tons of GSA millings, the Cactus Asphalt crew added enough moisture to the material using a water truck and loader at the location of the stock pile.
“A stockpile of asphalt millings that had been crushed was available at another city site,” Martinez says. “The city of Chandler uses an outside crushing company to crush the millings to the Chandler spec of 1¼-inch minus spec. We screened and processed those millings to the specific moisture, and then we trucked them to the jobsite.”
A Volvo/Blawknox 6610 track paver, Volvo DD90 compactor and a Volvo PT125 pneumatic roller were used to complete the project.
One challenge crews faced was timing. “We could only pave as much as the milling machine could go,” Gallegos says. “We had to schedule with the city of Chandler to make sure it didn’t get too close to our paving crew.”
To help bind the material together, asphalt emulsion was applied within one to two days after the millings were laid down and compacted.
The emulsion applied was an SS1-H emulsion that was 50 percent emulsion and 50 percent water at a rate of .10-.15 gallons per square yard with a Bearcat computer-controlled asphalt distributor.
After applying the emulsion, the project was complete. The city can use light grading with a reapplication of emulsion to maintain the surface. This process offers cost savings to cities that must manage dust in low-traffic areas.