PSI - Issue 67

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Dan Huang et al. / Procedia Structural Integrity 67 (2025) 61–79 Huang, D., Velay-Lizancos, M., Olek, J./ Structural Integrity Procedia 00 (2024) 000–000

The addition of nano-silica not only reduced the total volume of porosity but also increased the formation factor, while nano-TiO 2 addition reduced the porosity, though its impact on the formation factor is not significant. These observations suggest that both types of nanoparticles decrease the overall quantity of permeable pores by accelerating the hydration process. Additionally, nano-silica appears to be particularly effective in reducing pore connectivity. Furthermore, as depicted in Fig. 7(b), the simultaneous addition of both types of nano-silica led to a more substantial increase in the formation factor compared to adding only one type. Once more, this underscores the synergistic impact of employing both varieties of nano-silica to enhance concrete quality. Moreover, the decrease in total pore volume of concrete resulting from the addition of nano-silica is more pronounced when cured at low temperatures as opposed to room temperature. 4.4. The effect of the addition of nano-TiO 2 and nano-silica on the water absorption of OPC concretes The effects of nanoparticles (both nano-TiO 2 and nano-silica) on the water absorption of OPC concrete cured at the temperature of 23°C are presented in Fig. 8. It was found that both the initial and secondary absorptions of concrete were reduced due to the addition of nanoparticles, regardless of the type of nanoparticles.

Fig. 8. The water absorption test results for OPC concrete with and without the addition of (a) nano-TiO 2 and (b) nano-silica cured for 28 days at the temperature of 23°C (adapted from (Dan Huang, 2022)).

Fig. 9 presents the water absorption data for the same type of samples but cured at 4°C. While these graphs also show the reduction in the water absorption values upon the addition of nanoparticles, in the case of OPC concrete with nano-silica (Fig. 9(b)), the absorption curves exhibit greater differentiation compared to those associated with concrete containing nano-TiO 2 (Fig. 9(a)). This might be related to the fact that the low curing temperature significantly slows down the hydration process. This slowed pace of hydration may provide more opportunities for different types of nano-silica to exert their effects, thereby impacting water absorption to varying degrees.

Fig. 9. The water absorption test results for OPC concrete with and without the addition of (a) nano-TiO 2 and (b) nano-silica cured for 28 days at the temperature of 4°C. (adapted from (Dan Huang, 2022))