## 7 Conclusions  
The utilization of RP as a partial substitute for cement introduces a novel range of possibilities for repurposing WC, thereby making a substantial contribution to the recycling of one of the primary CDW streams. Moreover, using RP in real-world scenarios could potentially offer an alternative and additional resource to tackle the current issue of limited access to local sources, high levels of energy consumption, and substantial pollution. This paper provides an overview of the application of RP in cementitious matrices. A comprehensive analysis has been provided on the characteristics, benefits, and constraints of using RP, specifically focusing on fundamental and micro-properties. RP possesses an uneven microstructure, fine particle size, and large specific surface area, with RP particles in paste enveloped by C-S-H gel, hence enhancing its filler efficacy. RP comprises a mass of siliceous oxide and calcareous oxide, along with certain hydrated components and unhydrated cement particles. Eventually, the mineral composition of RP closely resembles that of FA, therefore allowing for the partial substitution of RP for cement in cement-based material production. The characteristics and mineral composition of RP in the literature are inconsistent due to the multitude of sources of concrete waste. The blended RP reduces the quantity of cement and its resultant CH and C-S-H gel in novel cement-based products. Consequently, the blended RP results in a reduction in hydration products and negatively impacts the pore structure of cement-based materials. Replacing fine RP with cement reduces the fluidity of the resulting cement-based products. The viscosity of the paste increases with an increase in RP particle size at a constant RP replacement ratio. The setup time is extended with the substitution of RP. When the RP type and replacement ratio are identical, the setting time is extended as the particle size of RP increases. The review provided above allows for the following inferences to be made. Figure 36: Fresh density (kg/m\({}^{3}\)) versus RP percentage (%) [72; 210]. When utilizing RP as an SCM, it is advisable to ensure it has a high reactivity and has a small particle size, comparable to or smaller than cement. 2. RP reactivity has been shown to increase with higher SSA and fineness, grinding time, and grinding type. Enhancing the RP's fineness can elevate the SSA of the RP, transform the stable SiO2 into amorphous SiO2, and therefore enhance the RP's activity. 3. Mechanical grinding can decrease the particle diameter and enhance the SSA of RP. However, the process of grinding to achieve fine RP requires a significant amount of energy, resulting in adverse environmental impacts and increased costs for RP. Furthermore, excessive grinding duration leads to an agglomeration of the material and reduces the strength of the specimen. Based on the analysis, 20 to 30 min is an appropriate duration for dry-grinding, whereas 60 to 80 min is ideal for wet grinding and the smallest RP particle sizes were produced by wet grinding. 4. RP is a dry powder which has an off-white, grey color, and its look is comparable to that of cement, FA, SF, and LP. On the other hand, RP particles exhibit non-uniform shapes and uneven edges with sharp angles unlike cement, FA, SF, and LP particles. 5. The primary chemical constituents of the RP are SiO2, CaO, Al2O3, and Fe2O3, whose contents vary according to waste origin. These chemical constituents closely resemble the composition of regular cement, FA, and GGBS which indicates an optimal distribution of oxides and an efficient source to be utilized as SCM in cement-based materials. 6. SiO2 and Al2O3 are produced from sand and residues of coarse aggregate. CaO is formed through the hydration of cement particles, as well as from unhydrated cement particles and CaCO3. 7. RP fulfills the necessary criteria to be classified as a pozzolanic material, with a composition of Fe2O3+Al2O3+SiO2 above 70%. On the other hand, the maximum LOI requirement, 6%, is not met for most of the cases.