## 6 Fresh-State Properties in Cementitious Matrices with RP
### Workability
[71] reported that the fluidity of the samples decreased significantly as the content of RCPs increased, in comparison to the control sample. Blending samples with composite RCPs does, however, reduce the fluidity difference. Particularly at the maximum FA dosage (FS22), the fluidity reaches a maximum comparable to the control group. FA particles serve as a \"ball bearing\" by lowering the frictional forces between themselves and other particles; this, in turn, reduces the likelihood of floc agglomeration and breaking, which in turn releases any trapped water [71; 137; 297]. Regarding the effect of chemical activation on workability, [PERSON] et al. [201] worked with an alkali-activated slag system. The mortar exhibited an initial increase in fluidity, followed by a subsequent decrease, as the RCP content increased. This is primarily because passivated RCP particles have a ball effect and are more spherical than slag particles. The fluidity of the mortar begins to decrease when RCP surpasses 30%. This suggests that the  
Figure 27: Spreading diameter (mm) versus mechanically grinded RP percentage (%) [35; 61; 62; 71; 82; 84; 98; 152; 201]. increased water demand caused by an excess of RCP has a substantial influence on the mortar's fluidity. Regarding the effect of thermal activation on workability, [PERSON] et al. [8] stated that the fluidity of paste reduces as the temperature of WCP increases up to 900 \({}^{\circ}\)C, because the newly generated CaO, C\({}_{2}\)S, or C\({}_{3}\)S in the thermally modified WCP consumes the free water. Furthermore, when the rate of WCP increases, the impact of the thermal modification temperature of WCP on the fluidity of the freshly prepared paste becomes more pronounced. [PERSON] et al. [247] stated that both the untreated and thermally treated RCFs exhibit a greater water need compared to cement. To achieve a comparable spread to the reference mortar, the samples were treated with a superplasticizer when 20% and 30% of the OPC was substituted with RCF. The 10% replacement samples exhibited satisfactory flowability even in the absence of superplasticizer. Figure 28 presents the effect of the thermal activation on spreading diameter. Regarding the carbonation effect on workability, the carbonation of RP might improve the mixture's workability by forming calcite and reducing the porosity of the RP microstructure [61; 97; 130; 263; 270; 130] as presented in Figure 29.  
[PERSON] et al. [91] stated that when applying CRCF at 100 \({}^{\circ}\)C, the pastes' flowability was reduced. An increase in the specific surface area of CRFC leads to an increase in the wetting surface area and the water demand, which are directly proportional to one another. [PERSON] et al. [263] reported that the flowability of fresh cement paste marginally reduces as the CRCF increases. Nevertheless, the impact is negligible if the dosage of CRCF is below 15%. [PERSON] et al. [270] observed that despite having a bigger particle size and smaller surface area, the CRP-cement paste exhibited greater flowability compared to the RP-cement paste. The strong affinity between H\({}_{2}\)O and the silica gel on the surface of CRP is the reason for this. [PERSON] et al. [130] reported that as the proportion of CRCF replacement increases, the flowability of the paste diminishes because there is less available water during the initial mixing step. They also stated that the inclusion of CRCF has a positive impact on enhancing the structural integrity of the OPC paste. The addition of nano-SiO\({}_{2}\), nano-CaCO\({}_{3}\), and nano-TiO\({}_{2}\) can enhance the pore structure of cementitious materials, but it also leads to a decrease in the fluidity of the mixture [100]. Figure 28: Spreading diameter (mm) versus temperature (\({}^{\circ}\)C) for thermally activated RP [8; 179; 245; 255].