## 3 Test Results
### Fresh Properties of RPC
#### 3.1.2 Penetration Resistance and Setting Time  
The setting time of the RPC mixture was determined using ASTM C403/C403M-16, which is the time required for the penetration resistance (PR) of each mixture to reach 3.44 MPa for the initial set and 27.6 MPa for the final set. Figure 3 presents the PR characteristics of six key RPC mixtures. Similar to the relative flowability results, the SF content and WB influence the PR of the RPC mixture. As the amount of SF in the RPC mixture increases and the WB decreases, the PR increases. For example, Figure 3a shows the effect of SF on the PR. While the PR value of the mixture 0.22 WB-25 SF containing 25% SF was approximately 6.9 MPa at 350 min, the mixture 0.22 WB-15 SF with 15% SF had approximately 3.8 MPa at the same elapsed time. Again, the plain concrete mixture 0.22 WB-0 SF due to a low dosage of SP had a higher PR value than the RPC mixtures. Moreover, the influence of WB on the PR for the mixture containing 20% SF is presented in Figure 3b. It clearly shows that the PR increases as WB decreases from 0.26 to 0.18. For instance, the PR values of the mixtures with WB = 0.26, 0.22, and 0.18 at 450 minutes was 6.14 MPa, 31.99 MPa, and 33.65 MPa, respectively.  
Figure 3: _Cont._  
Figure 2: Relative flowability of six key mixtures.  
As observed from Figure 4a, both the initial and final setting times increased with the increase in WB. While the initial increase of WB from 0.18 to 0.22 has little effect on both the initial and final set time, a further increase of WB from 0.22 to 0.26 produced significant influences on both setting times. It seems that a higher WB plays a more critical role in controlling setting time in RPC mixtures.  
Figure 4b shows the effect of SF on setting time. At a high SF content, the addition of SF to a binary cement system exhibits the increase in setting time. [PERSON] and [PERSON] [33] reported that the delay in setting time of concrete containing a high amount of SF was attributed to the combined effect of lower cement content and the relatively high dosage of superplasticizers that is needed for the high amount of silica future that is added to concrete.  
On the other hand, Figure 4b also shows that changing the SF content has no significant effect on both the initial and final set times, although increasing the SF content slightly decreases the setting time. This result matches with previous findings [34]. Generally speaking, if the optimum amount of SF is used, the addition of SF reduces the setting time, because the pozzolanic reaction of SF is very active at the early hours of hydration [35]. However, at a higher SF content (more than 15%), the setting time is not influenced by the SF. This could be related to the higher specific surface area of SF. If the RPC needs to achieve the same flowability, it requires an increase in water demand. This water increment is not much different when the SF content is beyond 15% [34; 36].  
Figure 4: \(Cont\).  
Figure 3: Penetration resistance: (**a**) effect of SF on penetration resistance (PR) for the mixtures with WB = 0.22; (**b**) effect of WB on PR for mixtures containing 20% SF.