## 4 Conclusions  
The conclusions extracted from this research work are as follows: (1) Blended cements made with natural pozzolan, P, siliceous coal fly ash, V, silica fume, D, and blast-furnace slag, S were found to be effective in alleviating ASR expansion in mortar bars; (2) The more reactivity of the aggregate is, the higher ASR mitigation level was found in blended cements; (3) The best additions with regard to the ASR inhibition are the silica fume and the siliceous fly ash; (4) The higher addition contents provide improved ASR inhibition performances, however, mechanical properties are negatively affected at the same time. Regarding the compressive strength evolution, coal fly ash and natural pozzolan additions in blended cements do not affect positively in any case. Nevertheless, ground granulated blast-furnace slag has a positive effect in mortars made with reactive aggregates. This seems to be a synergic effect between the ASR products and the blast-furnace slag. Finally, low silica fume contents (3-10%) enhance the mechanical strength at early ages, whereas higher levels have a negative influence in this characteristic. The traditional way of explaining the compressive strength evolution via open porosity measurements no longer serve in cement-based materials made with reactive aggregates because the microstructure has changed in these cases not only by the effect of the additive, but also by the influence of the ASR reaction.  
The best mix design to mitigate the ASR reaction should consider both the ASR inhibition and the mechanical performance. Accordingly, two main groups can be distinguished: (i) mixtures providing a large ASR reduction but also a significant compressive strength reduction and (ii) mixes with a moderate ASR inhibition and a compressive strength results broadly similar to those of the reference sample. The results of this work package have been taken into careful consideration in the development of the following proposal. The blended cements recommended to be used to mitigate the ASR reaction should contain high amounts of siliceous coal fly ash, natural pozzolan, silica fume, or blast-furnace slag. In this study, V was the most effective in suppressing ASR followed by D, P and S, respectively. It is believed that this depends partly on the different amount of alumina and silica present in these pozzolanic materials and their reactivity. In addition, the more cement replaced with pozzolanic materials, the higher the drawdown in expansion due to ASR.  
Finally, it is suggested that decreasing the Ca/Si ratio, the ASR expansion is reduced as there is less dissolution of silica. This is due to the lower availability of calcium to enhance the dissolution of silica and to the higher amount of aluminum available to hinder mentioned dissolution.  
**Author Contributions:** Conceptualization, E.M., R.G.-R. and M.A.S.; methodology, E.M., R.G.-R. and M.A.S.; validation, H.R., E.M., R.G.-R., M.A.S. and C.A.; investigation, H.R., E.M., R.G.-R., M.A.S. and C.A.; resources, E.M.; data curation, E.M., R.G.-R., M.A.S. and C.A.; writing--original draft preparation, M.A.S.; writing--review and editing, E.M., H.R., R.G.-R., M.A.S. and C.A. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the CSIC (_Intramurales Projects PIE 201660E054 y PIE 202060E176_).  
**Acknowledgments:** Authors gratefully acknowledge the valuable contributions of [PERSON] and [PERSON].  
**Conflicts of Interest:** The authors declare no conflict of interest.