Development of a Controlled Sawing Apparatus for Characterizing Aerosols Generated from Cutting Concrete Composed of Different Formulations

Details

• Personal Author:
  Afshari A ; Antonini JM ; Bunker K ; Casuccio G ; Erdely AD ; Gill R ; Kodali VK ; Lee E ; Lersch T ; McKinney W ; Rickabaugh K
• Description:
  Background and Purpose: Concrete, a widely used and cost-effective construction material, often undergoes maintenance and alterations, including cutting, drilling, or grinding. These operations release airborne particles that have been observed to cause respiratory illnesses in construction workers. Additionally, concrete is a material constantly subject to examination for a range of applications adapting to changing environmental conditions and is continually refined through advancing technology. Recently, multi-walled carbon nanotubes (MWCNT) have been incorporated into concrete to enhance its compressive strength, abrasion resistance, reduced water and chloride penetration, and general increased durability. The aerosolization of MWCNT has been linked to lung inflammation, cancer, and other serious health risks potentially exacerbating respiratory hazards when added to concrete. This paper introduces a computer-controlled concrete aerosolization system designed for operation within a controlled laboratory environment to study the aerosols generated by cutting concrete that can contain additives such as engineered nanomaterials. The system can control saw travel speed, chamber air change rate, depth of cut, and time between cuts. This system represents the initial phase of a comprehensive study on the potential respiratory effects of aerosols generated during cutting using acellular, in vitro, and in vivo models. Methods: The current system integrates an industrial saw with a computer-controlled concrete feeding mechanism, enclosed within a mobile metallic chamber with a sealable door. The system is equipped with multiple ports facilitating the transfer of concrete particles to real-time particle measuring instruments and various offline sampling devices tailored to different applications. Standardized concrete specimens, with a 4" diameter and 8" length, commonly used in mechanical testing, were consistently employed in the experiments. The specimens to be cut were prepared with varying percentages of MWCNT: 0, low, and high wt %. Results: To maintain consistency, each concrete specimen was cut for approximately 54 seconds with multiple cuts averaged, ensuring a representative cross-section while collecting samples and preventing sampler and equipment overload. Results indicated a singular main mode with a peak particle size of approximately 0.72 µm as determined by using a Micro Orifice Uniform Deposit Impactor to measure particle sizes generated across all concrete specimens, regardless of the presence of MWCNT. No observable shift in particle size distribution occurred when comparing the aerosols generated from the sawing of all three concrete samples. Moreover, the mass median aerodynamic diameter fell within the respirable size range (< 6 µm) and remained similar for all specimens. Scanning and transmission electron microscopic analysis did not detect any free MWCNT in the collected aerosolized particles. Conclusions: A computer-controlled, laboratory-based concrete cutting aerosolization system was constructed that produces consistent respirable aerosols. It was determined that addition of MWCNT to concrete does not shift the particle size range or release free MWCNT by the methods of determination during cutting of the concrete. The developed system holds the potential to function as a standard concrete or other masonry material aerosolization system for studying various additive formulations in the future. [Description provided by NIOSH]
• Subjects:
  Aerosols Construction Industry Construction Materials Laboratories Occupational Health Safety
• Keywords:
  Concretes Construction Materials Cutting Tools Laboratory Testing Multi-walled Carbon Nanotubes MWCNT Nanomaterials
• ISSN:
  1096-6080
• Document Type:
  Text
• Genre:
  Abstract or Summary
• Place as Subject:
  OSHA Region 3 ; Pennsylvania ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  HELD - Health Effects Laboratory Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  198
• NIOSHTIC Number:
  nn:20069347
• Citation:
  Toxicologist 2024 Mar; 198(S1):417
• CAS Registry Number:
  Carbon nanotubes (CAS RN 308068-56-6)
• Federal Fiscal Year:
  2024
• NORA Priority Area:
  Construction
• Peer Reviewed:
  False
• Source Full Name:
  The Toxicologist. Society of Toxicology 63rd Annual Meeting & ToxExpo, March 10-14, 2024, Salt Lake City, Utah
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:a65170fc2dfd5ff141997063de0bf3580ea3f5ca623af9b34f34263678e11d7f9738c7f2c8e245cd10f0da143c2281a8f33591427c0b0b0c73646b5f19949c22
• Download URL:
  https://stacks.cdc.gov/view/cdc/207845/cdc_207845_DS1.pdf
• File Type:
  [PDF - 540.34 KB ]