Safety and health newsletter for the Oregon construction industry

 

January 15, 2013

Concrete cutting with water

Sawing concrete? Use water.

An article in the September 2012 issue of the Construction Depot, Respirable hazard of the month: silica dust, described the hazards involved in cutting concrete and pointed out that, "When you're cutting concrete, the best safe practice is to cut wet." It turns out there's now some real-world evidence to back up the wisdom.

A new report, Controlling Dust from Concrete Saw Cutting, appears in the February 2013 issue of the Journal of Occupational and Environmental Hygiene (Vol. 10, Issue 2) and was funded by NIOSH through a grant from the Center for Construction Research and Training.

In the study, volunteers from the New England Laborers Training Center used handheld, gasoline-powered saws to cut reinforced concrete pipe while their breathing air was sampled. The research was conducted in settings similar to actual working conditions rather than laboratory conditions, which distinguished it from earlier studies.

The researchers examined dust reductions with water from a hose, and from a sprayer, as a dust control. The volunteers cut reinforced concrete pipe under both "dry" and "wet" control conditions in a series of four tests.

Overall, the mean respirable dust concentration for "dry" cutting was 14.396 mg/m3 (milligrams per cubic meter), which exceeded both types of water-based controls by more than tenfold. Wet cutting reduced the respirable dust concentration by 85 percent compared with dry cutting under different cutting scenarios.

Other findings in the study indicated that the volunteer's experience and whether the cutting was done outdoors or in a partially enclosed setting affected the amounts of respirable dust detected. Experienced journeymen workers generated more than three times the dust than less-experienced apprentices - likely due to the fact that the experienced workers pressed harder during the cut than the apprentices. Wind and ventilation were factors affecting differences in the amount of respirable dust sampled in the outdoor and partially enclosed settings. The level of dust in the partially enclosed setting was nearly four times the level sampled outdoors.

 

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