Mechanical fracture behavior of cement pastes incorporated with carbon nanotubes and nanofibers synthesized in-situ in Portland cement clinker

Reference Presenter Authors
(Institution)
Abstract
04-062 Francisco Aristides Santos Neto Santos Neto, F.A.(Federal Center for Technological Education of Minas Gerais); Ludvig, P.(Federal Center of Technological Education of Minas Gerais); Calixto, J.F.(Federal University of Minas Gerais); Souza, T.C.(CTNano - Nanomaterials Technology Center); Morato, L.T.(Federal Center of Technological Education of Minas Gerais); Coelho, I.D.(Federal Center of Technological Education of Minas Gerais); Souza, V.C.(CTNano - Nanomaterials Technology Center); Cement materials are commonly characterized as quasi-brittle materials with low energy absorption, deformation and tensile strength. These characteristics impose limitations on structural designs and affect the long-term durability of structures. The use of macro- and microfibers is used to overcome these shortcomings. However, the cementitious materials show failures in nanometric scales in which this traditional reinforcement is not effective. The addition of carbon nanotubes and nanofibers (CNTs/CNFs) to the cementitious matrices allows the reinforcement and modification of their behavior at the nanoscale, because CNTs/CNFs have remarkable mechanical properties and it could inhibit the growth and propagation of cracks in the early ages of cement materials. In this experimental work, nanostructured clinker was used to produce Portland cement pastes to investigate the influence of CNTs/CNFs on the mechanical fracture behavior of cementitious materials at 7 days of age. The notched specimens had 40x40x160 cm³ and were produced with four types of admixtures, which are cement pastes containing CNTs/CNFs at amounts of 0.10 wt.%, 0.20 wt.% and 0.30 wt.% by weight of cement, and a paste without addition of nanomaterials for comparison. The three-point bending test and the Digital Image Correlation (DIC) method were used to obtain the data for treatment and analysis. The results showed that the nanocomposites pastes showed higher fracture energy, fracture toughness and flexural tensile strength than the reference paste during the beginning of the hydration process. They also presented that cement pastes with a lower addition of nanomaterials showed better performance than the other two nanocomposites cement pastes.
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