# Influence of Partial and Total Replacement of Used Foundry Sand in Self-Compacting Concrete
## 3 Results and Discussion  
### Fresh State Properties  
The results of the fresh state properties tests can be seen in Table 5. The replacement of natural sands by UFS resulted in an improvement in the slump flow, as can be seen in Figure 3. The SCC-C (a) presented a slump flow of 500 mm, the SCC-UFS-50 (b) a slump flow of 730 mm, while SCC-UFS-100 (c) resulted in a slump flow of 750 mm, improving the fluidity by 46% and 50%, respectively, both corresponding to a SF2 category according to EN-206-1 [39]. This is because LS and SS have more fines than UFS, resulting in a higher absorption of water, thus decreasing the SF value. [PERSON] and [PERSON] [28] also reported an increase in the slump flow when up to 15% replacement of UFS was used. Regarding viscosity, Figure 4 shows that the t\({}_{500}\) test of SCC-C obtained a time of 5 s to reach the 500 mm mark, which classifies it as in class VS2 according to EN-206-1. It is observed that the incorporation of UFS decreased the time in which the SCC reached the 500 mm mark; SCC-UFS-50 achieved a time reduction of 80% (1 s), while SCC-UFS-100 reduced the time by 60% (2 s). These two SCC are catalogued in class VS1 according to EN-206-1. It is observed that there may be a relationship between the analyzed parameters, so a \begin{table}
\begin{tabular}{c c c} \hline \hline
**Test** & **EN Guidelines** & **EFNARC Guidelines** \\ \hline Slump flow (mm) & 550–850 & 650–800 \\ t\({}_{500}\) (s) & \textless{}2–\textgreater{}2 & 2–5 \\ L-box (dimensionless) & \textgreater{}0.8 & 0.8–1 \\ Japanese ring (mm) & \textless{}10 & 0–10 \\ V-funnel (s) & \textless{}9–9 to 25 & 6–12 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: EN and EFNARC guidelines. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Material** & **SF (mm)** & **t\({}_{500}\) (s)** & **V-Funnel (s)** & **J-Ring (mm)** & **L-Box** \\ \hline SCC-C & 500 & 5 & 10 & 10 & 0.13 \\ SCC-UFS-50 & 730 & 1 & 5 & 14 & 0.80 \\ SCC-UFS-100 & 750 & 2 & 3 & 16 & 0.80 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Fresh state properties of the self-compacting concretes. fitting formula between the t\({}_{500}\) and the v-funnel is performed. The equation analyzing the correlation between the v-funnel test and t\({}_{500}\) shows an R\({}^{2}\) result of 0.99, thus concluding a relationship between these parameters. The variation between the V-funnel time and the t\({}_{500}\) is higher with respect to the lower percentage of replacement. This is more evident in the SCC-C, which has the longest throughput times. The improvement in the t\({}_{500}\) test result can be attributed to the fact that UFS does not have as many fines as LS and SS, resulting in a less viscous paste. Figure 4 also shows the results of the V-funnel test. It can be observed that partial and total replacement of UFS results in a decrease in the passing times. A reduction of 70% and 50% was found, respectively. The reduction in V-funnel passage times and t\({}_{500}\) is due to the improved fresh state properties of UFS concretes, which is reflected in the slump diameter. This is because this by-product has less fines than natural sands, leading to a higher flowability of the paste. This is more evident in the SCC-UFS-50, where the V-funnel times and t\({}_{500}\) decrease significantly compared to the SCC-C. From Figure 4, it can also  
Figure 4: Time reduction of t\({}_{500}\) test and V-funnel test. Figure 3: Appearance of the slump flow of the three self-compacting mixes; SCC-C (**a**), SCC-UFS-50 (**b**) and SCC-UFS-100 (**c**). be observed that there is a relationship between the V-funnel test and the t500 test, which means that from the result of the t500 test, the V-funnel results can be predicted. According to the research presented by [PERSON] et al. [43] where UFS from the automotive industry was used, this is because UFS has sub-angular-to-round-shaped particles, which improves the fluidity of the SCC. [PERSON] and [PERSON] [28] also reported a decrease in V-funnel time of 10% with the incorporation of up to 15% of UFS.