https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39251 2) which can be used as supplementary cementitious material (SCM) to replace part of Portland cement. Existing studies mainly focus on the impact of solid waste on tricalcium silicate (C₃S) hydration. Since tricalcium aluminate (C₃A) is the most reactive component of the Portland cement, it is of great interest t to investigate the effect of solid waste containing SiO₂ on the hydration process of C₃A. In this study, different amounts of nano-silica (nano-SiO₂) were mixed with C₃A and the hydration products after 72 h of hydration were analyzed by means of X-ray diffraction (XRD), Fourier Transform Infrared analyzer (FT-IR), Environment Scanning Electronic Microscope - Energy Dispersive Spectrometer (ESEM-EDS), X-ray Photoelectron Spectroscopy (XPS) and Solid-state Nuclear Magnetic Resonance (NMR). The results showed that nano-SiO₂ can promote the hydration of C₃A and stabilize the hydration products of C₃A in the form of crystalline hydrogarnet (C₃AH₆). The formation of Si-O-Al bonds was also found in the hydration products. ESEM results revealed that the surface of the crystalline hydration products (C₃AH₆ particles) was covered by gel-like products. The results from the XPS and NMR analyses further confirmed that the negatively charged nano-SiO₂ and the silicate anions can literally interact with C₃A to produce calcium silicoaluminate hydrate (C-A-S-H) gel, whereas the formation of C-A-S-H is attributed to the substitution reaction of Al in the Si-O-Si network occurring on the surface of C₃A. In addition to the reactive silica-aluminum component reacting with Ca(OH)₂ to form additional calcium silicate hydrate (C-S-H) and C-A-S-H gels, the reactive silicon in solid waste can also undergo pozzolanic reaction with C₃A to form C-A-S-H gel.]]> Tue 09 Aug 2022 14:10:52 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39233 3A) is the most reactive component of the Portland cement and its hydration has an important impact on the workability and early strength of concrete. Recently, nanomaterials such as nano-silica (nano-SiO₂) have attracted much attention in cement-based materials because of its pozzolanic reactivity and the pore-filling effect. However, its influence on the hydration of C₃A needs to be well understood. In this study, the hydration kinetics of C₃A mixed with different percentages of nano-SiO₂ were studied and compared with pure C₃A. The hydration products were examined by different characterization techniques including XRD, XPS, and NMR spectroscopy and isothermal calorimetry analyses. The XRD results showed that the addition of nano-SiO₂ promoted the conversion of the intermediate product C₄AH₁₃. The isothermal calorimetry results showed that the addition of nano-SiO₂ significantly reduced the hydration exotherm rate of C₃A from 0.34 to less than 0.1 mW/g. With the presence of nano-SiO₂, the peaks for Q¹ were observed in ²⁹Si MAS-NMR measurements, and the content of Q¹ increased from 6.74% to 30.6% when the nano-SiO₂ content increased from 2 wt.% to 8 wt.%, whereas the proportion of Q⁴ gradually decreased from 89.1% to 63.6%. These results indicated a pozzolanic reaction provoked by the nano-SiO₂ combined with aluminate structures generating C-A-S-H gel.]]> Thu 28 Jul 2022 09:20:43 AEST ]]>