## 2 Experimental Programme
### Fresh-State Concrete Properties  
In this investigation, it was intended that all concrete mixes had a similar slump, in the range of 125 \(\pm\) 25 mm, in order to belong to the S3 consistency class. Therefore, prior to the first phase of the experimental campaign, several concrete mixes were produced with the objective of assessing the effective water/cement (w/c) ratio to be used. It should be clarified that the effective w/c ratio only considers the amount of water available for the hydration of cement at the time of mixing of the materials. In other words, when calculating the effective w/c ratio, contrary to what happens with the total w/c ratio, the water that will be absorbed by the aggregates during the concrete production is not considered. Figure 1 depicts all the values of slump obtained from the Abrams cone test, allowing us to conclude that the workability of the various mixes remained within the range of the S3 consistency class (100 mm to 150 mm). This is considered essential for a valid comparative analysis of all the remaining properties of the mixes. Figure 1: Slump measured using the Abrams cone. Abbreviations: RA, recycled aggregates; CRA, coarse recycled aggregates; FRA, fine recycled aggregates. Table 7 shows the values of the effective w/c ratio used in the production of the various concrete mixes. For two types of RA (from Valnor and from Ambilei), it was not necessary to increase the effective w/c ratio as the ratio of aggregates replacement increased. However, the significant increase in the effective w/c ratio with the increase of fine RA from Vimajas should be highlighted. This is due to the high content of clay of these RA [23]. These fine particles adsorb a high amount of water, resulting in the need of a higher effective w/c ratio in the mixes made with these RA, to maintain the target workability. The variation of the effective w/c ratio was not identical for all families of RA. Hence, in addition to the differences caused by the composition of the RA, the workability of the various mixes may have also been influenced by the different shape of the RA, as shown by the results of the shape index test. As reported by [PERSON] and [PERSON] [38], the rougher shape of the RA, compared to that of the NA, may contribute to the variability of the workability observed. In Table 8, the fresh-state density values determined for the different concrete mixes are shown, as well as the variation of this property in each concrete mix when compared to that of the NAC mix. It is found that, with the use of 100% coarse RA and 100% fine RA, maximum decreases of 7.1% and 6.1% are obtained, respectively. Figure 2 compares the results obtained in this investigation with those established by other authors. The results obtained here are within the scatter of results yielded by the literature. One other test performed on fresh-state concrete was the determination of its air content, whose percentage should be limited in order to not affect the mechanical strength of concrete. According to the recommendations of ACI (specifications for structural concrete) [39], concrete with a maximum aggregate dimension of 22.4 mm, after compaction, must not have an air content above 4.7% (47 L/m\({}^{3}\)). Table 9 shows that the air content of the concrete mixes produced with RA reached a maximum of 26.5 L/m\({}^{3}\). On the other hand, for NAC an air content of 15 L/m\({}^{3}\) was obtained. It is recalled that when the design concrete composition was determined, an air content of 17.4 L/m\({}^{3}\) was predicted. According to [PERSON] et al. [40], a 4% to 5% decrease in the compressive strength of concrete may be expected for each percent (10 L/m\({}^{3}\)) of air content.