Functionalization of multi-walled carbon nanotubes with 3-aminopropyl-triethoxysilane for application in cementitious matrix

Carbon nanotubes (CNT) usually have low interfacial interaction with the cementitious matrix, which can compromise the good mechanical performance of the composite. To overcome this issue, CNT's covalent functionalization can be conducted. This work investigated the functionalization of CNT with 3-aminopropyltriethoxysilane (APTES) for application in cementitious nanocomposites. Energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR) results revealed that APTES effectively functionalized the CNT. Thermogravimetric analysis (TGA) indicated a content of approximately 2.0% of silicon in the CNT's surface after the functionalization. Zeta potential and particle size distribution measured through dynamic light scattering (DLS) indicated CNT hydrophilicity decrease promoted by the silane functionalization. When added in cementitious matrix, 0.10 wt% incorporation of APTES-functionalized CNTs increased the 1-day composite strength by 16% and 7- and 28-day compressive strength by 13% compared with the control sample. This is associated with reductions in the volume of permeable voids (by 2.2%), total pore volume (by 14.0%), and average pore diameter (by 6.1%). Overall, the potential of CNT silanization for improving the mechanical performance of cementitious composites was confirmed.