## 5 Conclusions  
The findings of this research are summarised below:  
* The application of a secondary thermal treatment to non-ferrous slags from the lead and copper industries can significantly reduce the amounts of heavy metals in the slags and enable their use in cementitious materials.  
Such slags are primarily composed of iron silicates. Despite the differences in the source and compositions of the slags, while granulation results in a substantial increase in their amorphous content, they are only moderately reactive according to R3 and calorimetry findings.
* Replacement of cement with such slags were found in all cases to result in an increase in the clinker degree of reaction in all ages, which is potentially due to the increase in the availability of water to cement grains.
* TGA results also indicate an acceleration in hydration reactions when cement is partially replaced by the studied slags. However, the portlandite and bound water contents of slag-blended mixtures in the early ages found to be lower than those of mixtures containing quartz powder. This is in agreement with the calorimetry results and indicates a slight retarding effect of such slags compared to quartz.
* While a notable increase in the porosity as well as coarsening of the pore size structure of cement paste mixtures was observed up to the age of 28 days as a result of cement substitution, a considerable refinement of the pore structure was detected at later ages. No such later-age refinement was observed for the pastes incorporating quartz powder.
* Despite the existence of sufficient evidence for the pozzolanic reactivity of the studied slags, the compressive strength of mortars prepared by such slags were found to be similar to that of mixtures containing quartz powder at different ages. This was attributed to the lower mechanical strength and filler effect of the slag grains compared to quartz powder.
* All three slags were found to satisfy the minimum strength activity and maximum leaching requirements and are thus suitable for use in concrete.
* While the slags were found to satisfy the minimum technical and environmental requirements for being used in concrete, it appears that mere granulation of such slags is not sufficient for promoting their pozzolanic activity. Addition of other oxides such as calcium or aluminium oxide to boost the reactivity is recommended.  
Conceptualisation, L.H., A.G.V. and R.S.; methodology, A.G.V., L.H., R.S., J.M. and B.F.; software, A.G.V. and P.T.; validation, L.H., R.S., A.P. and J.M.; formal analysis, A.G.V., P.T. and R.S.; investigation, A.G.V., L.H. and R.S.; resources, J.M., K.K., L.H. and R.S.; data curation, A.G.V., P.T., R.S. and J.M.; writing--original draft preparation, A.G.V., R.S., L.H. and A.P.; writing--review and editing, A.G.V., R.S., L.H., A.P., J.M. and K.K.; visualisation, A.G.V. and P.T.; supervision, R.S. and L.H.; project administration, L.H.; funding acquisition, L.H. and B.F. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the European Institute of Innovation and Technology (EIT) RawMaterials (grant number 17181).  
Not applicable.  
The SlagVal project is a KIC Added Value Activity (KavA) funded by the European Institute of Innovation and Technology (EIT) RawMaterials (Project No. 17181). The EIT is a body of the European Union and receives support from the European Union's Horizon 2020 Research and Innovation Programme.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.