Performance improvement of cement paste loaded with MWCNT–magnetite nanocomposite

The outstanding properties of carbon nanotubes (CNTs) mean they can be considered as potential components of high-performance cementitious composites. However, the major challenges of using CNTs in cement are their agglomeration, poor dispersion and weak interaction with the cement matrix, which can nullify the potential benefits of CNT addition. A method for increasing the interaction between the CNT surface and cement matrix using magnetite (Fe₃O₄) nanoparticles, which increases the roughness and dispersibility of CNTs, was investigated. Nanocomposites of multi-walled CNTs (MWCNTs) and magnetite were prepared by electrostatic attraction and added to the cement matrix to produce a novel cementitious composite. Fourier transform infrared spectroscopy and transmission electron microscopy analyses revealed the successful preparation of the MWCNT–magnetite hybrid structure. The mechanical, electrical and microstructural features of nanocomposite-reinforced cements were tested. The results revealed that increasing the weight fraction of the nanocomposite reinforcement improved the mechanical properties of the cement paste. Compared with the control, the compressive, flexural and tensile strengths of cement loaded with 0.3 wt% MWCNTs and 0.3 wt% magnetite at 28 days increased by 83%, 104% and 98%, respectively; the porosity and electrical resistivity were reduced by 31% and 48%, respectively. Microstructural studies of the fracture surfaces were also conducted to elucidate the mechanical behaviour of the samples.