## 4 Activation Methods of RP
### Other Activation Methods  
[PERSON] et al. (2013) used tannic acid (TA) for the activation of RCF. TA refers to a plant polyphenol that may dissolve in water. It is considered the third largest category of plant products in the world, following cellulose and lignin (2013). It can be derived from plants, microbes, or the decomposition of organic substances in water (2013; 288). The authors immersed RCF in TA solution for 1 h. Next, the solid particles were separated from the TA solution using filtration and subsequently dried in an electric blast drying oven at a temperature of 80 \({}^{\circ}\)C for a duration of 24 h to eliminate any absorbed water. They observed that the peak intensities of CH are diminished due to a chemical interaction taking place between CH and the TA solution, resulting in the consumption of CH by the TA solution. Nevertheless, the XRD analysis did not reveal any evidence of new mineral formation in the RCF samples treated with 0.5% TA and 1% TA. FTIR analysis revealed that part of the calcite in the RCF samples was depleted during the chemical reaction between the RCF and TA solution and the calcium-TA complex likely formed on the surface of the RCF particles due to the coordination of polyphenol functional groups with calcium ions by chelation. SEM analysis revealed that TA treatment significantly increases the density of the RCF samples, and a considerable quantity of submicron particles are present on the treated RCF particle surfaces of the two samples. [PERSON] and [PERSON] (2018) acid-treated WCP samples using 2 mol/L of HCl. For acid-treated WCP (WCP-HCl), while the proportions of SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) increased, the proportion of CaO decreased significantly. They observed that the crystal structure of the WCP mainly consists of calcite and quartz. Consequently, WCP-HCl underwent a transformation into siliceous particles. [PERSON] et al. (2019) conducted a treatment process involving the addition of NaOH to concrete waste (CW). Following chemical treatment, the CW underwent a structural transformation from inactive to active. The untreated CW was predominantly composed of quartz, calcite, and dolomite. A minor peak associated with CH indicates that cement has been hydrated within the concrete structure. The introduction of NaOH into CW lead to an increase in the production of CH and Mg(OH)\({}_{2}\). Activity Index of CO\({}_{2}\), Biomineralization, and Other Activation Methods on RP  
AI demonstrates a substantial enhancement while utilizing carbonated RP and RP treated with nano materials and chemical activation in comparison to untreated RP as it is presented in Figure 13 (2013; 2014; 2015). [PERSON] et al. (2015) presented the SAI of each mixed sample at a defined age. They reported that the early-age and long-term hydration of cement paste are significantly influenced by the carbonation temperature of RCF, and eventually the early-age strength development of the blended cement material can be facilitated by the high-temperature carbonated RCF (60 \({}^{\circ}\)C, 100 \({}^{\circ}\)C, and 140 \({}^{\circ}\)C). This is primarily due to the nucleation effect and the acceleration of cement hydration that are caused by the reaction of CaCO\({}_{3}\) in the carbonated RCF (CRCF) with C\({}_{3}\)A of cement clinker. They stated that the nucleation effect of carbonation products in CRCF on cement hydration becomes less apparent as time progresses. [PERSON] et al. (2015) calculated the SAI as per ASTM C311/C311M-18 (2015), by utilizing 20% of WCP to replace cement. They reported that the reaction between C3A and CaCO\({}_{3}\) in carbonated WCP led to the creation of calcium carboaluminate hydrate, which was accountable for the initial increase in strength. The carbonated WCP mortar exhibited a SAI value exceeding 75 at both 7 and 28 d, indicating its suitability as a potential SCM in cement concrete, in accordance with the ASTM standard (2015). [PERSON] et al. [169] tested the AI of RHCP according to JG/T573-2020 [292].