Dustiness Testing and Particle Characterization of CNT-enhanced Concretes

Abstract: The introduction of fibers into concrete is a common way of reinforcing the mechanical properties and preventing cracking. The fibers act as bridges between the composite components and help reduce the porosity. Today, micrometer-sized fibers are widely used, but there is an increased interest in using smaller fibers e.g. carbon nanotubes (CNTs), as they are able to stop smaller cracks and the initiation of cracks. These CNTs share structural similarities to asbestos fibers and they have been shown to cause increased risks of pulmonary diseases when inhaled. Therefore, the introduction of CNTs into any material requires life-cycle risk assessments. In this project, focus has been on characterizing the number and mass concentrations and size distributions of airborne emissions of crushed concrete in order to assess the dustiness. A continuous drop-method (according to EN 15051-3 standard) was setup in a controlled laboratory setting where three different crushed concrete-types were tested and the number and mass concentrations and size distributions were measured with both online instruments and filter sampling. Each concrete type was tested both without CNTs and with two different weight concentrations of CNTs in three replicates. The results show that the method is reproducible and that the CNTs could affect different concrete types differently, depending on both the concrete type and the CNT concentration. The concrete type with the lowest density and highest porosity (cellular lightweight concrete) resulted in the highest dustiness levels.