Carbonation Resistance of Surface Protective Materials Modified with Hybrid NanoSiO2

To date, reinforcement concrete is the main construction material worldwide. As the concentration of atmospheric CO2 is steadily increasing, carbonation of the reinforcement concrete becomes a pressing concern. In this study, novel surface protective materials (SPMs) modified with hybrid nanoSiO(2) (HNS), fly ash, and slag were developed to reduce CO2 emissions and extend the service life of the reinforcement concrete. The carbonation depths were measured by phenolphthalein to reflect the carbonation resistance. X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) were conducted to analyze the chemical components of the samples after carbonation. In addition, MIP was carried out to examine the microstructures of the samples prior to carbonation. Thermodynamic modeling was employed to calculate the changes in the phase assemblages of each blends in an ideal situation. The experimental results showed that the carbonation depth and CaCO3 content of the SPM modified with HNS decreased by 79.0% and 64.6% compared with the reference, respectively. The TGA results showed that after carbonation, the CaCO3 contents were 4.40% and 12.42% in the HNS modified samples and reference samples, respectively. MIP analysis demonstrated that the incorporation of HNS in SPM led to a 48.3% and 58.5% decrease in big pores and capillary pores, respectively. Overall, the SPMs modified with HNS in this study possessed better carbonation resistance and refined pore structures.