# Influence of Recycled Precast Concrete Aggregate on Durability of Concrete's Physical Processes
## 4 Conclusions  
Once the results obtained in this study had been analyzed, it could be concluded that:  
* The results obtained, when analyzing the physical and chemical properties of RA, are within the limits of the current Spanish Specification EHE-08. Therefore, it can be said that the properties of RAs are adequate for the manufacture of a new concrete resulting in a good material with good strength, resistance, uniformity and little contamination.
* As expected, the densities of hardened SCCs are decreased as the percentage of RA present in the mixture increases.  
\begin{table}
\begin{tabular}{l c c c} Type-SCC & In(a) Starting & In(a) Findings & A Weight(c) \\ \hline HR-30 0\% & 2433.0 & 2438.0 & +0.21 \\ HR-30 20\% & 2325.0 & 2329.0 & +0.17 \\ HR-30 50\% & 2399.5 & 2401.8 & +0.10 \\ HR-30 100\% & 2323.9 & 2338.2 & +0.61 \\ HR-45-0\% & 2427.0 & 2433.0 & +0.25 \\ HR-45-20\% & 2390.0 & 2395.0 & +0.21 \\ HR-45-50\% & 2404.6 & 2409.9 & +0.22 \\ HR-45-100\% & 2372.3 & 2378.8 & +0.27 \\ \hline \end{tabular}
\end{table}
Table 7: Accelerated ageing by thermal shock: Pn mass variation.  
Figure 11: Comparison of compressive strength results after thermal shock cycles (**blue**) with the reference (**red**) specimens as a function of their effective _w_/_c_ ratio.  
* The incorporation of RAs produces an increase in the shrinkage of SCCs. The greatest variation occurs for a 100% substitution, while for 20% and 50%, the variations with respect to control concrete are smaller.
* The shrinkage values obtained show that during the first 90 days the variation is more pronounced regardless of the percentage of RA.
* The results obtained show a decrease in shrinkage as the compressive strength increases. For a ratio of 100% a more marked increase in shrinkage is observed, which shows the influence of the recycled aggregate on the concrete paste.
* The use of RAs has little influence on physical actions such as thermal shock or abrasion, since the values are similar to those of the control concrete. In addition, in the case of the abrasion test, the results are below the maximums required by Spanish regulations.
* The behavior of concrete under freeze-thaw cycles was more favorable for concrete with a lower _w/c_ ratio, even achieving resistance values significantly higher than those of control concrete and reference specimens. For higher _w/c_ ratios, in general, the results reflect a trend towards poorer behavior, as also occurs and as we increase the degree of substitution.  
The results obtained in this study show a favorable response of recycled SCC to physical actions that affect durability. Ultimately, we can conclude that it is feasible to manufacture a concrete with high strength and performance with aggregates recycled from precast elements, obtaining satisfactory results even with a 100% replacement.  
Conceptualization: F.F., C.T., [PERSON]; Data curation: [PERSON], [PERSON]; Formal analysis: [PERSON], C.T., [PERSON]; Funding acquisition: [PERSON], [PERSON]; Project administration: [PERSON], [PERSON]; Resources: [PERSON], [PERSON]; Supervision: [PERSON], [PERSON]. Validation: [PERSON], I.L.; Visualization: [PERSON], C.T., [PERSON]; Writing--original draft: [PERSON], I.L.; Writing--review & editing F.F., C.T., [PERSON]. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Junta de Castilla y Leon (Regional Government) for funding UIC-231 through project BU119P17; MINECO for funding through project BIA2014-55576-C2-1-R; FEDER (European Regional Development Funds) and LADICIM.  
We are grateful to the precast concrete company Artepref for having collaborated with the present research work.  
The authors declare no conflict of interest.