## 5 Micro-Properties of the Cemertitious Materials with RP
### Pore Structure
They observed that the volume of harmful and more harmful pores in the paste containing 30% RCP-800C is lower compared to the paste containing 30% RCP-20C. Additionally, the paste including 30% RCP-800C has the smallest pore size among all of the groups. They explained this result by stating that RCP-800C contains a greater number of active components compared to RCP-20C. [PERSON] et al. [101] reported that the addition of 50% WCP significantly increases the size of the paste's pore structure, with the increase in average pore diameter being more pronounced than the increase in porosity. But when the replacement level of WCP is maintained at 50%, the paste that contains heat-modified WCPC exhibits a finer pore structure compared to the paste that contains untreated WCP. They also stated that the proportions of harmful and more harmful pores decrease when the temperature of WCP is increased, and the most significant reduction in the percentages of harmful and more harmful pores is observed in the 50% WCP-800T blended paste. Figure 22: Pore volume fraction (%) versus pore sizes (nm) for thermally activated RP utilized in cement-based materials [101; 256]. [PERSON] et al. [219] observed that the pore width and pore volume decreased significantly after carbonation. This phenomenon occurs because of the aggregation of calcite crystal particles, which effectively occupy the pores during the process of carbonation [219; 261; 305]. [PERSON] et al. [80] reported that the introduction of carbonation in RCF promoted the development of CaCO crystals and nano-silica, resulting in a faster cement hydration process and a more refined pore structure in mortars containing RCF. Figure 23: Average pore diameter (nm) of CO\({}_{2}\) activated RP utilized in cement-based materials [91; 130]. Figure 16:0 Porosity variation (%) in CO\({}_{2}\) activated RP utilized in cement-based materials [262]. [PERSON] et al. [263] stated that CRCF reacts with CH in cement paste and improves the pore structure of cured cement paste. Nevertheless, the inclusion of CRCF leads to an augmentation in the proportion of large pores in the cement paste. [PERSON] et al. [180] reported that, as a method for utilizing CO\({}_{2}\), it entails the interactions between CO\({}_{2}\) and either unhydrated clinker particles or hydrated products, primarily C-S-H gel and CH. These reactions facilitate the formation of a stable CaCO\({}_{3}\), which enhances the material's pore structure. [PERSON] et al. [130] reported that increasing the CRCF replacement ratio leads to the production of smaller pores in the CRCF-OPC pastes. [PERSON] et al. [221] reported that the carbonated RCFs had a significant particle size effect on their pore structure. RCF015 (particle size smaller than 0.15 mm) saw the development of many gel holes due to the synthesis of silica gel, leading to a significant 70% increase in the total pore volume. When comparing RCF118 (particle size between 0.6-1.18 mm) and RCF236 (particle size between 1.18-2.36 mm), it was observed that the pore volume decreased by up to 31%, suggesting that the structure became denser. Regarding the nano-activation, [PERSON] [213] reported that NS enhances the hardening performance of cement pastes with WCP. Consequently, the NS enhances the pore structure, leading to enhancements in the compressive strength. The total pore volume or porosity was reduced. Consequently, the level of harmlessness was significantly elevated. [PERSON] et al. [100] observed that the inclusion of nano-SiO\({}_{2}\) in the mixture enhanced the secondary hydration reaction and improved the pore diameter of the paste containing WCP. Specifically, the proportion of harmful pores and the proportion of more harmful pores in WCP paste decrease as the NS concentration increases. Figures 25 and 26 present the effect of nano activation on porosity variation and pore volume fraction. Regarding the TA treatment method, [PERSON] et al. [103] observed that the TA treatment has substantially decreased the pore size and overall porosity of the RCF.