An amine-modified SiO₂ aerogel (AMSA) was prepared using the sol–gel method and supercritical drying technology. CO₂ adsorption tests were conducted under different conditions. High adsorption capacities were achieved in the presence of water vapor, with the highest CO₂ adsorption capacity of 6.97 mmol/g-sorbent at 25 °C. A novel adsorption mechanism associated with the CO₂ sorption process is proposed. The test results indicate that AMSA is a promising CO₂ adsorbent.

The impact of nano-SiO₂ on the early hydration properties of alite-sulphoaluminate (AC$A) cement was investigated with a fixed water to solid ratio (w/s) of one. Nano-SiO₂ was used in partial substitution of AC$A cement at zero, one and three wt %. Calorimetry, X-ray diffraction (XRD), thermogravimetric/derivative thermogravimetric (TG/DTG), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) analyses were used to characterize the hydration and hydrates of the blended cement. The hydration of the AC$A cement was significantly promoted, resulting in an increase of the heat released with the addition of nano-SiO₂. Phase development composition analysis showed that nano-SiO₂ had no effect on the type of crystalline hydration products of the AC$A cement. Moreover, nano-SiO₂ showed significant positive effects on pore refinement where the total porosity decreased by 54.09% at three days with the inclusion of 3% nano-SiO₂. Finally, from the SEM observations, nano-SiO₂ was conducive to producing a denser microstructure than that of the control sample.