## 4 Conclusions  
In this study, a new concrete based on the use of concrete waste has been tested. The concrete waste used incorporates a by-product of the steelmaking industry (EAFS), thus waste production and natural aggregate consumption are reduced. The physical, mechanical and durability properties of the new material have been characterized and compared with the results of a reference conventional concrete with the same mix design of the recycled aggregate concrete tested. Moreover, experiments from other authors on the properties of concrete with recycled aggregates from other sources were also compared with those of this experiment. The following conclusions were drawn:  
* The use of RCA with a water absorption twice that of NA requires compensation water, but the rounded shape of the RCA produced from concrete with EAFS (shape index 20% lower than NAC) makes it possible to use slightly lower effective w/c ratio to obtain the same workability;  
Figure 11: Mean drying shrinkage over time for all mixes.  
* The replacement level affects the physical properties of RAC. Bulk density increased by 7%, unlike in current RAC (typically density decreases), due to the iron present in this recycled aggregate. Both porosity and capillarity slightly increase (18% and 9% for full replacement respectively) as replacement increases due to the porosity of the source concrete mortar;
* Compressive strength is not affected by the replacement level for ages over 28 days due to the hydration of the unhydrated cement grains of the source concrete and to a good bond strength between RCA and the new mortar. This good bond, favoured by the cavernous form of EAFS in the source concrete, allows tensile strength to be very similar to that of NAC. On the other hand, the modulus of elasticity is the property most affected by the replacement of RCA, showing losses that can reach 17% with respect to NAC. Typical decreases of the modulus of elasticity caused by full recycled aggregate incorporation are higher than this value;
* Durability properties are negatively but slightly affected. Carbonation depths and chlorides diffusion coefficients are 15% and 25% higher respectively for full replacement at 91 days. Both properties are linked to the porosity of RAC and hence with the quality of the RCA used, which is reflected in a low w/c ratio and a good bond between aggregate and paste;
* Drying shrinkage values 13% higher for total replacements have been obtained at 91 days, consistent with the modulus of elasticity obtained;
* The mechanical and durability tests results obtained are satisfactory, usually near the lower limit of the interval of change found in the literature and sometimes showing a behaviour very similar to that of the reference NAC;
* Concrete designed by recycling an EAFS-based concrete has potential applications as a structural material and can also be used in applications where its self-weight is important, as in bridge counterweights, seawalls or radiation-proof structures.  
Data curation, J.d.B.; Formal analysis, P.T., J.P., C.T. and J.d.B.; Funding acquisition, C.T. and J.R.; Investigation, P.T., J.P. and C.T.; Methodology, C.T.; Project administration, C.T.; Resources, J.R.; Writing-original draft, P.T. and J.P.; Writing-review & editing, C.T. and J.d.B. All authors have read and agreed to the published version of the manuscript.  
This research was co-financed by the European Regional Development Fund (ERDF) and the Ministry of Economy, Industry and Competitiveness (MINECO) within the framework of the project RTC-2016-5637-3 and in collaboration with the company INGECID and the department LADICIM (University of Cantabria).  
The authors gratefully acknowledge the support of the CERIS Research Unit, IST, University of Lisbon and of FCT.  
The authors declare no conflict of interest.