# Experimental Study on the Workability and Stability of Steel Slag Self-Compacting Concrete
## 4 Conclusions  
In this paper, the workability of the fresh mixture and the strength of hardened self-compacting concrete with different substitution rate of steel slag sand were studied. By adjusting the water-binder ratio, paste-aggregate ratio, fine-coarse aggregate ratio and the amount of superplasticizer, steel slag self-compacting concrete with ideal workability can be obtained, which can meet the workability design goal. Moreover, the addition of steel slag sand helps to improve the interfacial transition zone in hardened concrete, which is beneficial to the strength of concrete. It can be concluded that it is one of the effective ways to use steel slag sand as fine aggregate to prepare self-compacting concrete. If SSCC is popularized and applied, it will help to realize the resource utilization of a large amount of steel slag, and finally achieve good economic benefits and environmental value. Based on the above test results and discussion, the following conclusions can be drawn as for the workability of SSCC:  
1. The basic workability of SSCC was evaluated by the experimental results of the slump flow test and J-ring flow test. PA (the difference between SF and SF\({}_{\rm J}\)) and \(\Delta\)h (J-ring height difference), were used to characterize the passing ability of fresh steel slag self-compacting concrete. The results show that all the groups of SSCC can meet the workability design goal with the minimum SF, the maximum T500, the maximum PA and the maximum \(\Delta\)h were 655 mm (S\({}_{80}\)SCC), 18.2 s (S\({}_{100}\)SCC), 40 mm (S\({}_{100}\)SCC) and 25 mm (S\({}_{100}\)SCC), respectively. Along with the increase of VPS, the basic workability of SSCC shows little difference when the VPS is less than 60%, but then it changed rapidly. Generally, VPS less than 60% is preferred for SSCC as regards the basic workability.
2. The dynamic stability of SSCC was evaluated by the visual stability index. The evaluation result, according to ASTM C1611/C1611M-18, is highly stable (VSI = 0) for all groups of SSCC which performed ideal segregation resistance.
3. The static stability of SSCC was evaluated by the segregation rate through a sieve analysis test. The SR values of the all groups of SSCC fresh mixtures are far below 15%. The maximum, and the minimum SR values were 8.70 (S\({}_{100}\)SCC), and 5.44 (S\({}_{60}\)SCC), respectively.
4. The comprehensive analysis based on the basic workability, the dynamic stability, and the static stability test results shows that the workability of fresh SSCC will be relatively ideal in all aspects when the substitute ratio of steel slag sand is not more than 60%.
5. It is necessary to pay attention to the expansibility of steel slag and its influence on the volume stability of concrete in the later stage when SSCC is applied to practical projects, and further research is needed.  
[PERSON], [PERSON], [PERSON] and [PERSON] conducted all of the experimental studies, analyzed the test data. [PERSON], [PERSON] conducted the theoretical analysis and wrote the manuscript. [PERSON] advised the theoretical research and experimental work, and revised the manuscript. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (Grant No. 51978002) and the Natural Science Foundation for the Higher Education Institutions in Anhui Province of China (Grant No. KJ2019A0917).  
**Acknowledgments:** The authors gratefully acknowledge the National Natural Science Foundation of China for financial support to this work. The authors would like to express our gratitude to Ma'anshan University and Anhui University of Technology for providing various research conditions to facilitate this work.  
**Conflicts of Interest:** The authors declare no conflict of interest.