Carbon Nanotubes Enhances Cement Based Materials

One of the potential uses of the exceptional tensile strength of carbon nanotubes (CNT) is in cement based materials. The addition of CNT to concrete can significantly enhance some mechanical as well as physical properties of the material. However, due to the lack of toxicological data many countries take precautionary measures and handle CNT fibers as asbestos.  Lawrence Technological University has in collaboration with the National Research Center for the Working Environment (Denmark) initiated a small-scale feasibility study for production of CNT-reinforced mortars by assessing the nanoparticle release during production, physical failure and demolition.

The laboratory scale production and testing of the CNT reinforced mortar is shown in Figure 1 through 4 under the photos tab within this section. Dispersing the CNT in a designed liquid before mixing was developed as it results in a low CNT exposure risk during the production. Owing to dustiness of dry CNT and their potential toxicity, the research team concluded that the traditional dry-mixing method was not practicable for implementing CNT's in the cement industry. CNT powder can stay suspended in air as dust particles.

The wet-mixing production method for the CNT concrete resulted in at least similarly improved early age and long-term strengths as compared to literature data on CNT-doped concrete produced from the dry-mixing method. The exposure risk during destruction of concrete containing CNT is also investigated based on failure-testing the CNT reinforced mortar cubes in a closed particle sampling and monitoring chamber.

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Figure 1 - 4. Top left: 55-kip axial load frame for beam, cylinder and cube testing. Top right: Close-up of strain measurements on 2" by 2" inch cube with low vol% carbon nanotubes. MTS FlexTest multistation controller and particle sampling chamber shown in the photo on the left. Bottom left: 2.2 lb of industrial grade multi-wall carbon nanotubes sealed in a 1 gallon bag (BSG: 2.1, UW ~ 40 lb/ft3). Bottom right: 10 gram of carbon nanotubes dispersed in 0.75 lb of liquid.