Thermally induced cracking patterns of the MWCNTs modified cement paste

This paper investigates the influence of the multi-wall carbon nanotubes (MWCNTs) on the structure of cracking patterns (CPs), which is the main novelty, of cement pastes subjected to thermal loading up to 600 °C. The compressive and tensile strength, ultrasonic pulse velocity and weight loss during the thermal loading were investigated. The CPs structure was analyzed using a proprietary digital image segmentation procedure with the use of machine learning algorithms. The total crack area, crack density, fractal dimension and lacunarity of the CPs were determined. In addition, cross sections of cement paste samples were analyzed to determine the average crack depth. The results indicated that the most beneficial MWCNTs content is 0.05 % by weight of cement, for which the increase in the compressive strength was equal 7.8 %. In terms of CPs development, the total crack area and crack density decreased by as much as 41 % at temperatures above 500 °C. At temperatures below 400 °C, MWCNTs increased the crack depth by up to 47.2 %, while at higher temperatures the crack depth decreased to a difference of 1.5 %, compared to the reference cement paste.Funder: Polish National Agency for Academic Exchange (PPN/BEK/2020/1/00014/U/DRAFT/00001);License full text: CC BY