# Effect of Micro-Silica Addition into Electric Arc Furnace Steel Slag Eco-Efficient Concrete
## 4 Conclusions  
This study investigated the compressive and flexural behaviour of EAFS with micros-silica additive in concrete. From the above discussion, the following conclusions can be drawn:  
1. Examining the results of samples C25 and F25, it can be concluded that under the same conditions, water absorption of EAFS fine aggregates is greater than that of EAFS coarse aggregates, which may be due to the low density of EAFS fine-grained compared to coarse aggregates, which has a direct effect on workability and the slump has concrete.
2. In CF25 sample, with the addition of EFAS coarse aggregates to the mixture containing fine aggregates, it can be seen that adding only 25% of EAFS coarse aggregates can greatly help workability and improve slump, which is due to more porosity in coarse aggregates and shows that if EAFS coarse aggregates is used, the amount of water used in the mixing plan should be reconsidered.
3. By adding micro-silica, 6% wt. of cement in a mixing design in the CF25M6 sample, workability can be largely increased and slump concrete, which is very important in the production of high resistance concrete.
4. Comparing the CF25M8 design with the D design, it can be seen that the density of these two designs is close to each other, and this shows that by optimizing the percentage of use of EAFS aggregates to the compressive strength obtained, it can be used in the production of structural concrete. It is important to use this.
5. The results show that the replacement of more than 75 coarse and 50 fine aggregates EAFS, except for increasing the density, does not have a significant effect on gaining more compressive strength.
6. Addition of micro-silica up to 8% significantly increases the strength in concrete with EAFS aggregates, but by increasing its amount, the process of gaining strength decreases to the point that by adding 10% micro-silica, this trend is reversed, and the compressive strength decreases to CF25 concrete compressive strength.  
Figure 15: Encounter of cement and EAFS aggregate in the interfacial transition zone.  
In terms of compressive strength, there is not much difference between the samples containing 6% CF25M6 micro-silica and 8% CF25M8 micro-silica, but the workability of the first sample is much higher than that of the second sample.
* Increasing the percentage of EAFS fine aggregates does not have a significant effect on the acquisition of flexural strength, but increasing more than 50% of EAFS coarse aggregates, the flexural strength increases at once.
* Consumption of micro-silica up to 6% has no effect on flexural strength, so that the flexural strength of CF25 and CF25m6 samples is almost the same, which means that EAFS fine aggregates in the process of obtaining strength have a good density and continuity.  
Conceptualization, A.A. and C.T.; methodology, A.A. and C.T., validation, K.B. and A.A.; formal analysis, A.A., C.T. and K.B.; investigation, A.A.; data curation, A.A.; writing--original draft preparation, A.A. and C.T.; writing--review and editing C.T., K.B. and A.A.; visualization, A.A.; supervision, C.T. and K.B.; project administration, C.T. and K.B. All authors have read and agreed to the published version of the manuscript.  
Not applicable.  
The data presented in this study are openly available.  
The authors of this research would like to thank Isfahan University of Technology (IUT) for help with performing the required tests, Bonyad Beton for providing a laboratory environment for making concrete samples and Esfahan Steel Company for the EAFS aggregates.  
The authors declare no conflict of interest.