| Every year millions of construction workers are exposed to dust in levels that create a hazard to them (Fundukian, 2011). Their environment is contaminated by activities such as cutting, chipping, grinding and sanding building materials. The Occupational Safety and Health Administration (OSHA) refers to this general collection of building materials debris and fine particulates as nuisance dust. Some of the particles in nuisance dust possess properties that make them especially hazardous, such as their shape or specific gravity. It has been found by the Center for Disease Control (CDC) that inhalation of quantities of silica dust above the permissible exposure limit (15.0 mg/m3) causes a deterioration of the outside lining of the lung. This research seeks to limit this exposure by a pretreatment process using acid application and then absorbed moisture content that reduces airborne particulate during the removal of cement stucco surfacing materials. Successful pretreatment would allow removal of CSSM from substrates such that the release of airborne particulates does not exceed the permissible exposure limits (PEL) found in the 29 CFR-Table Z-3 for mining applications (15-mg/m3).;Concrete blocks were prepared with 5/8-inch stucco, cured for at least 28 days, and were exposed to nine different conditions, which were the result of the application of sulfuric acid solutions for 0-hours, 2-hours, and 72-hours. These acid treated blocks then had the moisture content adjusted by adding water or drying the blocks in an oven to produce three moisture ranges (e.g. =5%WME, 15%WME, and =30%WME) for each acid treatment level. Moisture content were measured using a Tramex moisture meter. Blocks were placed in a 1-m 3 environmental chamber, and stucco was removed using an air-powered chipping hammer. The dust generated during the removal process was measured using a particulate meter (PDR-1000). Post-processing statistical analysis was accomplished using Excel and analytical software Matlab and included producing graphs of the data as well analysis of statistical measurers of the samples such as mean, median, deviation, variance, and error.;It was found that moisture played the dominate role in the generation of airborne particulate. During acid treatments of 0, 2, 72-hours at stucco moisture contents of 5% and 15%, median particulate levels were substantially greater than OSHA's PEL of 15.0 mg/m3, and statistical similarities to each other were observed. However, stucco with 30% WME was found to be statistically different than all the 5% and 15% WME treated samples, and stucco with 30% WME that received 0-hours of acid treatment only generated a maximum median particulate value of 15.4 mg/m3, which is nearly at the PEL. These findings indicate that absorbed moisture at 30%WME or greater can provide significant reduction in particulate generation. This implies that adding moisture to the surface can be a feasible method of pretreatment of cement stucco surfacing material that will reduce the workers' exposure to nuisance dust. |
