Newton, MA, highway officials are hoping for smoother-riding streets as they turn their focus to paving more residential areas, thanks to a new asphalt paver, a promising new pavement preservation treatment, and the work of its own paving crew.
"This would allow us to pay more attention to our residential streets," said David Turocy, deputy commissioner of the Newton Department of Public Works, as he and Stephen Tocci, director of the Highway Department, closely watched the department's in-house paving crew recently install a thin-lift asphalt mix overlay for the first time on a Newton street.
A suburb of Boston with a population of about 84,000, Newton is one of the few municipalities in the Bay State that pave local streets using their own crews. "We've always had a paving machine, but in recent years we've had to cut back on doing residential streets ourselves because the paver was down for repairs more times than it was up and running," said Turocy. He said the new LeeBoy asphalt paver, used in conjunction with the new pavement preservation treatment, could enable the city to "get more paving footage" for the money available. And thereby get to more public roads with the same paving budget.
Stretching pavement maintenance dollars is a main concern of the highway department for this densely populated city, which has 1,500 streets, many of them in residential areas saturated with cars. Half of the city's 36,000 housing units are single-family homes with two cars — in 2000 three-quarters of all households had two or more cars — and a substantial number of these households are located on narrow streets such as the one that recently underwent Newton's first thin-lift asphalt overlay.
The highway department's paving crew, a team of seven headed by working foreman Adam Szetela, employed the 8-1/2-ton paver to install a 1-inch-thick asphalt overlay on about 600 feet of Clarendon Street, with a 10-ton Dresser static steel roller providing compaction. Showing evidence of substantial surface crack sealing but otherwise structurally sound, the pavement of this 24-foot-wide local road was a suitable candidate for the treatment's debut, Turocy said.
Supplied by the Saugus, MA, plant of Aggregate Industries, the asphalt overlay material was a dense-graded, warm-mix formulation modified with latex polymers, and contained a significant percentage of recycled asphalt product (RAP). Aggregate Industries markets the thin-lift asphalt overlay as an alternative to current roadway maintenance products, saying it has a service life of up to 10 years, and that its thin profile preserves curb reveal and often precludes having to raise catch basins and manhole covers.
There are at least 12 different proprietary warm-mix technologies being used in the U.S., all of which enable producers to make, and contractors to install, hot mix asphalt designs at lower than normal HMA temperatures. This yields a number of benefits to sustainable or "green" development such as reducing plant fuel consumption and greenhouse gas emissions.
However, Aggregate Industries manufactures its thin-lift asphalt overlay product at normal HMA temperatures,incorporating Sasobit warm-mix technology to take advantage of another important benefit: Warm-mix formulation makes asphalt pavement mix workable and compactable over a longer period than is possible with regular HMA. This is critical when installing lifts of 1 inch or less thickness, because they cool down quickly.
Furthermore, the performance of the Aggregate Industries thin-lift asphalt mix receives a significant boost by the injection at the plant of styrene butadiene rubber (SBR) latex polymers, which are manufactured by BASF Corporation. Sold directly to emulsified asphalt manufacturers for surface treatment application binders, or supplied to HMA producers by BASF distributor Rub-R-Road, SBR latex substantially improves the bond between the asphalt binder and mineral aggregate, and expands the effective temperature range of the mix, according to Chris Lubbers, senior technical service engineer for BASF Corporation's construction polymers business.
"The latex polymers strengthen the mix and improve its resistance to oxidation, raveling and rutting. And it makes the mix more flexible in winter to resist cracking, and stiffer in summer to prevent shoving," Lubbers noted.
Fred Mello, consultant for Rub-R-Road, supports the Saugus plant from his home office in Barrington, RI. The Rub-R-Road facility is located in Ohio.
Newton officials decided to try the thin-lift overlay after reading an article in New England Construction magazine about an application in Wellesley, MA, ("Thin-Lift Warm-Mix Protects Road," NEC Dec. 24, 2007, p. 6), Turocy pointed out.
As he watched the crew placing the thin layer of asphalt, he noted that the material was easy to work with, produced a very smooth surface, and was less costly to install than having the road "milled and filled." He was referring to the process in which milling machines cold plane normally 1-inch to 3-inches of the top pavement, then haul trucks move the small, milled pieces of asphalt pavement to a RAP stockpile. Following street sweeping of the milled paving surface and the raising of any utility structures, conventional asphalt paving replaces the removed material with new asphalt mix. He said that using their in-house paving crew in conjunction with their new paver would make thin-lift overlay especially economical for maintaining pavements of the city's numerous residential streets.
Tocci agreed with this assessment and added that the paver, purchased in September from distributor Woods CRW Corp. of New Hampshire, was seeing its first extended use with the Clarendon Street application.
He said the LeeBoy 8515 paver has a paving width of 8 to 15 feet and an electric screed, and is large enough to push an asphalt mix-filled truck yet small enough to be transported on a tag-along trailer.
For the paver's full-scale debut on the Newton project, Woods CRW of New Hampshire's president, Jeff Lothrop, was on hand to provide operating tips and answer any questions the crew might have about the new machine.
Turocy and Tocci both feel the Clarendon Street project bodes well for the future of thin-lift pavement preservation in Newton.
"We have a good first impression of the product, and we'll see how it performs over winter," said Turocy.
Tocci, who as highway director is sensitive to residents' complaints about lengthy, disruptive construction under way on their streets, is happy about the speed of installation and residents' reactions to the appearance of the pavement preservation treatment.
"We've had no negative response from the neighbors as the work went on, and they're all excited that their road is being paved."