Standard procedure: a crushing plant at the side of a highway re-paving project has become standard operating procedure.

The pace of change can be deceptively fast, depending on the circumstances. When a company changes its name and launches a marketing blitz with new signs and corporate colors, that is noticeable.

When the way work is performed changes over the course of a couple of decades, the same splash may not be there, but the changes can be even more profound.

Within the concrete and asphalt crushing sector, the proliferation of on-site crushing at highway repaving projects appears to be an example of that latter type of change. There was no one marketing blitz, but fundamentally, the way work is performed has changed for a lot of people.

FUELISH ENDEAVOR

When highway project requirements allow, it takes little convincing for contractors and subcontractors to plan first to crush old pavement on site as well as to use it on the same job site.

The reason is simple: to cut down on the number of trucks and drivers and the number of miles logged by the truck fleet. "Whether it's a contractor or a sub, they're staring down a huge problem: When you're tipping out a road, what do you do with it and how do you get it out of there?" asks Bill Royce of Eagle Crusher Co. Inc., Galion, Ohio.

Eagle, a maker of portable impact crushers and other equipment for aggregates producers, has found contractors working on such job sites to be a growing market segment. "If you can crush that material on site, you're eliminating a lot of headaches right off the bat," notes Royce.

Techniques to mill and recycle asphalt pavement on site have become firmly entrenched, with entire mobile systems designed to greatly minimize the use of dump trucks and loaders.

AASHTO (American Association of State Highway and Transportation Officials) reports through its Center for Environmental Excellence Web site that "asphalt pavement is the nation's most widely recycled product. The Federal Highway Administration (FHWA) reports that 73 million metric tons of the 91 million metric tons (or 80.3 million of the 100.1 million tons) of asphalt pavement that is removed each year during resurfacing and widening projects is reused as part of new roads, roadbeds, shoulders and embankments, for a recycling rate of 80 percent."

According to AASHTO and FHWA, that means that "twice as much asphalt pavement is recycled as paper, glass, plastic and aluminum combined."

Asphalt recycling practices gained momentum in the 1980s and have solidified into standard operating procedure over the past two decades.

Concrete recycling techniques have followed a similar course, with transportation factors prompting the move toward more on-site crushing and re-use.

The transportation savings that can be obtained with on-site crushing stem from taking fewer loads to the landfill and needing fewer incoming loads of quarried material.

Increasingly, both of these trips can be longer ones than they used to be, as older landfills and quarries near population centers have been dosing, to be replaced by facilities on the outer edges of metropolitan areas. Recently, these longer trips have meant not only more time on the clock, but also higher expenses in an era of rising fuel costs.

When trucking costs are decreased, it is more than just the cost of fuel that must be considered. D.J. Cavaliere of Cavaliere Onsite Crushing, Stamford, Conn., lists several costs that are incurred when a fleet of dump trucks is deployed: "There's fuel, drivers, liability and the possibility of fines and state inspections," he notes.

Cavaliere Onsite Crushing is part of Cavaliere Industries Inc., a 50-year-old excavating and highway contracting company. Cavaliere Industries not only bought its first crushing unit recently, but also became a dealer for the Rubblemaster line of crushers.

"Keeping the material on site--that's the main reason I bought a crusher," says Cavaliere. "I pay for this crusher, but I save if I don't have to haul [material] back in and out," he continues. "When your trucks are off the road, your liability is reduced dramatically."

Eagle Crusher's Royce has helped customers deploy crushing equipment on site at several major highway projects recently. In the Midwest, Eagle customers are currently involved in major interstate highway projects in both Indiana and Illinois.

The project in Indiana involves some 150,000 tons of concrete. According to Royce, that is well above the amount of material needed for on-site crushing to make logistical sense.

Eagle customers working highway projects "have crushed as little as 20,000 tons on site," notes Royce. Provided space can be found for a crusher to operate, the on site option is often sensible.

ON SPEC 

With transportation savings a proven winner, the next factor that needs to be in place for on site crushing to occur is an end use for the material on the job. That has largely been accomplished with the growing approval of crushed concrete as base course for new or re-built highway lanes.

To what extent recycled concrete pavement can be re-used on site varies from state to state. A FHWA 2003 survey revealed that at that time some 38 states were allowing the material to be used as highway base course, and 11 state departments of transportation (DOTs) had specs for the material to be blended into new concrete mixtures.

An ideal situation, and one that would match the recycling capabilities of asphalt pavement, is the use of portions of the recycled concrete stream into new Portland cement concrete mixtures.

On its Center for Environmental Excellence Web site, AASHTO notes that is has issued a "Specification for Recycled Concrete as Aggregate in PCC Pavements."

Notes the group, "The specification covers coarse aggregate derived from reclaimed concrete for use in Portland cement concrete. When aggregate materials are properly processed and manufactured to the requirements of this specification, combined and mixed in accordance with the appropriate requirements, and placed, consolidated, and cured properly, a Portland cement concrete structure of acceptable strength and durability can be produced."

Recycled concrete's most common use on highway job sites remains as a base course, for which AASHTO also has a specification.

The base course market has helped on-site crushing gain its foothold. In major projects that Royce has witnessed, on-site crushing plants are part of a loop churning out product both as fast as old pavement can be torn up and as quickly as new base course is needed.

Clearly, the advantages are many, and whether material is used as base course or back as aggregate, on-site practices are now well established.

"Nine times out of 10, it's more economically feasible to crush it on site and use it," says Royce. "The point is still the same: A lot of positive things happen when you crush on site."

RAP BEFORE IT WAS HIP

On online sidebar on the history of reclaimed asphalt pavement (RAP) is available at www.cdrecycler.com.

The author is editor in chief of C&DR, and can be contacted at [e-mail].