Avoiding a dust up

Dust generated in the act of crushing and recycling concrete and asphalt is unwelcome for a variety of reasons pertaining to human health, traffic safety and its ability to lead to complaints and inquiries from nearby property owners.

Operators of concrete crushing units have no shortage of dust suppression options to deploy when putting a crusher to work, whether at a fixed site or as part of an on-site highway or demolition project.

Manufacturers of dust suppression units might debate vigorously about the merits of their own technology compared with those of their competitors, but they tend to agree regarding the problems that must be addressed.

Health and safety

Birmingham, Alabama-based Vulcan Materials Co. is among the largest producers of crushed, recycled concrete in the United States and, as such, has produced a seven-page safety data sheet on the material.

Vulcan describes crushed concrete as containing “a naturally occurring mineral complex with varying quantities of quartz (crystalline silica).”

The firm continues, “Recycled crushed concrete may be subjected to various natural or mechanical forces that produce small particles (dust), which may contain respirable crystalline silica (particles less than 10 micrometers in aerodynamic diameter). Repeated inhalation of respirable crystalline silica (RCS, or quartz) may cause lung cancer.”

Vulcan cites the France-based International Agency for Research on Cancer; the Durham, North Carolina-based National Toxicology Program of the Washington-based National Institute of Environmental Health Sciences; and the Cincinnati-based American Conference of Governmental Industrial Hygienists as sources that have identified RCS as “a suspected cause of cancer.”

Keeping concrete slabs and rubble out of the landfill, however, entails crushing. That leaves mitigating dust as a necessary step, and spraying water droplets that “capture” most of the dust and let it fall to the ground—rather than being inhaled—has proven to be an effective and cost-efficient way to address the problem.

And people are on the lookout for the problem, according to dust suppression equipment providers, with the federal Occupational Safety and Health Administration (OSHA) among the agencies involved.

Hugh Gordon of Ohio-based Company Wrench/C.W. Machine Worx Ltd. says, “OSHA air quality monitoring or fugitive dust leaving the site” are critical reasons why contractors seek out his company to provide dust suppression units.

Gordon Santry, director of sales/USA for Natick, Massachusetts-based HKD Blue Eco-Protection, says concrete being crushed into smaller aggregate sizes tends to increase dust control requirements.

“In my experience, the smaller the product, the dustier the stacking process is. So, if you are crushing to a fine product and are stacking the material into a stockpile, that is often the largest source of dust,” he says.

Operating a crusher, whether because of dust or noise generated, will tend to get noticed.

Like a good neighbor

Pasadena, California, is best known as the home of the Rose Bowl parade and football game on New Year’s Day. In 2017 and 2018, however, the Los Angeles suburb made news of interest to concrete recyclers because of complaints stemming from an Interstate-210 highway project that entailed the use of a crusher.

A late December 2017 online news report from KABC-TV of Los Angeles referred to the crushing plant as being “a stone’s throw” from the upcoming Rose Bowl parade route. Civic officials in Pasadena raised concerns with Caltrans (the state’s department of transportation) about noise and dust arising from the crushing operations.

The TV station quotes Tim Weisberg of Caltrans as saying the crushing operation “is a short-term disruption for a long-term gain.” However, he also acknowledged the city of Pasadena had spent time over the course of the prior 12 months to “share [its] concerns regarding the operations and the impact on our residents” of the crusher.

The same article also says California’s South Coast Air Quality Management District had confirmed the existence of prior dust violations, which had been resolved by late December.

The combination of reasons means vendors like Company Wrench and HKD Blue Eco-Protection interact regularly with customers who seek their advice. “The [paving] contractor, or crushing contractor, usually reaches out to us to determine what size unit may work for their particular application,” Gordon says.

Determining how many dust control units to place on-site, which models and at which settings are decisions better off made ahead of time. Having a dust control strategy in place can help avoid unsafe and unhealthy conditions as well as the types of complaints tied to the I-210 project that have the potential to distract a contractor that is trying to maintain a tight schedule.

Deployed and ready

In terms of creating a workable plan, Santry says awareness to one’s access to water—the key element in dust control—is a good place to start.

“First, the vendor should communicate with the contractor to determine what resources on-site could be used for dust suppression (i.e., a natural water source, such as a pond or river) versus municipal hydrants,” he says.

How to supply power to the dust control units provides another on-site consideration. The options on that front include plugging into an available electrical outlet (which is not always an option) or using a diesel-fuel powered model.

Also worth considering, Santry says, are opportunities when a contractor “can connect an electric dust suppression unit to the existing power plant for an electric crusher.”

In terms of budgeting dust control operating costs, Gordon says C.W. Machine Worx Dust Destroyer units will entail “diesel fuel costs [or] generators to power electric fans.”

C.W. Machine Worx describes the HAWC 300-100-D model it offers as “the only self-contained, multipatented, diesel-powered dust suppression unit on the market.”

Santry points to diesel fuel (unless connecting to an existing power plant for an electric crusher is an option) and municipal water charges as unavoidable expenses. If one is fortunate to have access to water from a nearby river or well, that water may not be entirely “free,” he adds, because additional pumps likely will need to be brought on-site.

HKD Blue markets its V-400GT model cannon as “offering reduced power consumption, water requirements and weight—all done to increase efficiency and reduce the overall cost of ownership.”

How many units to deploy, where to place them and how to direct them varies with the unique nature of each job site. On a highway project, the units almost certainly will need to be moved around.

Peoria, Illinois-based BossTek introduced its new DustBoss Atom in 2021 by saying the device had been “engineered to provide an unmatched level of mobility and performance.”

“After more than 15 years of designing purpose-built dust suppression equipment in a variety of sizes and styles, we found that some companies expressed a desire for a smaller, more maneuverable unit, with a lower price point,” BossTek Vice President of Sales Mike Lewis said when the Atom was introduced.

Lewis added, “This machine is well-suited to demolition projects, recycling operations, transfer stations, bulk material processing, ports/shipping applications, quarrying/crushing, biomass handling, concrete curing and even indoor operations where significant air movement may be undesirable.”

Buffalo Turbine, Springville, New York, says its Dust Controller offers positional flexibility via its turbine-driven Gyratory Atomizing Nozzle. This oscillation feature allows the spray nozzle to rotate up to 270 degrees on a vertical plane, the company says.

The available combination of technology is helping ensure concrete crushing plant operators can stay within health and safety parameters relative to the dust being generated by their recycling activities.

The author is senior editor with the Recycling Today Media Group and can be contacted at btaylor@gie.net.