Effect of amine functionalized nanosilica on the cement hydration and on the physical-mechanical properties of Portland cement pastes

In recent years, due to the rapid development of nanotechnology and the desire for breakthroughs in cementitious materials, there has been a strong research focus on the application of nanoparticles as supplementary cementitious materials (SCM) such as nanosilica (NS). This paper investigates the effect of functionalized nanosilica (NSF) with amino groups on Portland cement pastes. Fourier transform infrared (FTIR) spectroscopy, 29Si nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) assays were performed to characterize the NSF and confirm the grafting of the amine organic groups on the nanosilica surface (NS). Samples of cement masses were prepared containing NSF or NS with varying content of 0.3, 0.9 and 2.7% by weight, a reference sample of cement mass was also prepared without any addition. For the characterization of cement pastes, induction calorimetry, mercury intrusion porosimetry, and compressive strength tests were performed. The results showed that NSF samples led to reduced superplasticizer use and decreased hydration rate and that the 0.9% NSF sample achieved compressive strength at 28 days greater than 50 MPa.