# Experimental Study on the Workability and Stability of Steel Slag Self-Compacting Concrete
## Materials and Methods
### Test Methods  
The stability of SCC, including dynamic stability and static stability, is an important index of its workability [30; 31; 32]. Static stability refers to the ability of the coarse aggregate to stably suspend in the mortar from the completion of concrete pouring to the initial setting. Dynamic stability refers to the ability of the coarse aggregate to keep the synchronous flow with the mortar in the transportation, pouring, pumping and other engineering operations of the fresh self-compacting concrete. There are many experimental instruments and methods for measuring and evaluating the workability of SCC. The slump flow test, J-ring test, sieve analysis and visual stability index were selected after comprehensive consideration to evaluate the workability of SCC with different substitute rate of steel slag as fine aggregates. So these methods can be divided into three categories: basic workability, static stability and dynamic stability. The selected test methods and evaluating indexes are shown in Table 10. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Method Types** & **Evaluating Method** & **Evaluating Indicator** & **Workability** \\ \hline \multirow{3}{*}{Basic workability} & Slump flow test & Slump flow diameter (SF) & Filling ability \\ \cline{2-4}  & T500 test & Slump flow time (T500) & Filling ability \\ \cline{2-4}  & J-ring test & J-ring spread diameter (SF\({}_{\text{J}}\)) & \multirow{2}{*}{Passing ability} \\  & J-ring height difference (\(\Delta\)H) & & \\ \hline Dynamic stability & Visual stability & Visual stability index (VSI) & Segregation resistance \\ \hline Static stability & Sieve analysis & Segregation rate (SR) & Segregation resistance \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Test and evaluation method of workability for SCC. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Group** & **W/B** & **Water** & **Cement** & **Fly Ash** & **Gravel** & **Natural Sand** & **Steel Slag** & **Superplasticizer** \\ \hline S\({}_{0}\)SCC & 0.40 & 192 & 312 & 168 & 836 & 656.0 & 0.0 & 4.80 \\ S\({}_{20}\)SCC & 0.40 & 192 & 312 & 168 & 836 & 525.0 & 131.0 & 4.80 \\ S\({}_{40}\)SCC & 0.40 & 206 & 334.5 & 180.5 & 807 & 380.6 & 253.6 & 6.18 \\ S\({}_{60}\)SCC & 0.40 & 215 & 349.4 & 188.1 & 807 & 235.7 & 380.5 & 8.06 \\ S\({}_{80}\)SCC & 0.40 & 220 & 357.5 & 192.5 & 807 & 126.8 & 507.4 & 8.25 \\ S\({}_{100}\)SCC & 0.42 & 231 & 357.5 & 192.5 & 739 & 0.0 & 580.0 & 8.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Mix proportion of steel slag self-compaction concrete (SSCC, /kg/m\({}^{3}\)). As is known, the slump flow test is one of the earliest test methods evaluating the workability fresh SCC mixture, which evolved from the slump test for concrete fluidity. The slump flow method is a relatively simple and effective method to evaluate the filling performance of fresh SCC from three parameters of SF, filling velocity and T500. Soon after the J-ring test used to evaluate the performance of SCC appeared, it became a common method of scholars all over the world. The J-ring test can fully reflect the viscosity of fresh SCC and its ability to pass through a narrow space, so which can better reflect the passing ability of SCC. Two parameters, J-ring spread diameter (SF\({}_{\rm J}\)) and J-ring height difference (\(\Delta\)h), were used to characterize the passing ability of fresh SCC. According to the Chinese Standard JGJ/T 283-2012 [33], the difference between SF\({}_{\rm J}\) and SF is used as evaluation indicator of passing ability (PA) and can be divided into two grades: PA1 (25 mm \(<\) PA \(\leq\) 50 mm) and PA2 (0 \(\leq\) PA \(\leq\) 25 mm). PA1 is applicable to structures with reinforcement spacing between 80 mm and 100 mm. PA2 is applicable to structures with reinforcement spacing between 60 mm and 80 mm  
The visual stability index, as the only standard test method at present, was incorporated into the American Society for Testing and Materials (ASTM) Standard in 2009 and accepted by the American concrete field [34].