## 7 Conclusions
8. The mineralogical composition of RP is complex because of the various mineral phases found in cement-based materials, transitioning between crystalline and amorphous states. 9. As the RP replacement ratio increases, the activity index of the RP decreases. Furthermore, extending the grinding period enhances the fineness and specific surface area of RP, hence enhancing the activity index of RP. In general, the AI of RP fulfills the standard requirement. 10. Thermal activation effectively improves the hydration rate and maximizes the potential activity of RP. In general, an increase in temperature during the thermal treatment of RP results in a noticeable alteration in the size of the particles and on the mineralogy. To achieve a feasible thermal activation, it is recommended to maintain a temperature range of 600-900 \({}^{\circ}\)C. This temperature range will facilitate the generation of active components that can actively engage in the new hydration reaction. Regarding the effect of thermal treatment on the AI of RP, thermal activation increases the SAI up to 800 \({}^{\circ}\)C.
11. The gas-solid and liquid-solid procedures of the direct carbonation method can effectively generate a suitable level of carbonation in RP by enhancing the microstructure of RP, resulting in reduced porosity because of the production of CaCO3 which also enhances the formation of stable CAHC, CAMC, and AFt, hence enhancing the microstructure of the cement matrix. 12. Liquid-solid carbonation was found to be more effective in completing the carbonation process within a shorter timeframe (6 h), when the carbonation time for gas-solid carbonation was 24 h.
13. Direct carbonation has several key benefits, including reduced costs and environmental consequences due to its straightforward nature and decreased use of chemicals compared to indirect carbonation. 14. In general, direct carbonation increases the particle size and SSA of RP due to the particle agglomeration and chemical reaction of hydration products, and the carbonatedRP exhibits a denser and smoother surface topology due to the carbonation of the hydration products which fills the micropores and voids with CaCO\({}_{3}\) and silica gel. * 15. AI demonstrates a substantial enhancement while utilizing carbonated RP and RP treated with biomineralization in comparison to untreated RP. * 16. Biomineralization, chemical activation, TA activation, and the joint application of activation methods have been found to have positive results for different properties. * 17. RP addition decreases the alkalinity of the mixture, while the inclusion of an alkali exciter enhances the effectiveness of the RP. The use of an alkali activator can enhance the development of C-S-H, resulting in a more compact microstructure. * 18. The incorporation of mineral admixtures, and nano materialsis helpful to improve the performance of RP. * 19. The inclusion of the RP leads to a decrease in the peak time of the heat of hydration curves, suggesting that the addition of RP enhances the rate at which the paste hydrates due to its dilution effect. When the percentage of RP is below 30% and the fineness (D50) is below 20 \(\upmu\)m, it enhances the early hydration of cement, leading to an increased rate of heat generation and a shorter induction duration. Similar to mechanical activation, thermal activation and CO\({}_{2}\) activation have also a positive impact on enhancing the rate at which the RP hydrates. * 20. Typically, the microstructure of cementitious matrices including RP is less dense, more porous, and has more cracks compared to the reference mix. Increased looseness, more pores, and cracks can be observed when the RP ratio increases. However, when the RP content is below 30%, it does not have the ability to change the cement matrix. Instead, it forms a dense microstructure that is influenced by physical filling. * 21. The concentration of SiO\({}_{2}\) and CaCO\({}_{3}\) in the cementitious matrices increase, and CH and C-S-H decrease as the rate of RP replacement increases.