## 4 Conclusions  
The crushing of wind-turbine blades to produce raw-crushed wind-turbine blade (RCWTB) and its addition to self-compacting concrete (SCC) is a possible way to re-cycle these wind-turbine components. This contributes to the circular economy in the wind sector and to the revaluation of material that currently has no added value. This paper has presented a first approach for the use of RCWTB as a raw material in SCC production following a conventional design. These conclusions can be drawn from all the aspects discussed:  
* RCWTB decreased the flowability of the SCC under free-flow conditions, reducing slump flow and increasing \(t_{500}\) time. This behavior was independent of the presence (16-bar J-ring test) or not (slump-flow test) of obstacles simulating concrete reinforcement. An amount of 1.5% RCWTB content yielded SCC with proper fresh behavior under free flow, while an amount of 3.0% RCWTB was excessive to obtain SCC with proper flowability in the 16-bar J-ring test. * The passing ability of SCC was affected differently by RCWTB depending on the type of flow imposed. Thus, this property was not affected under free-flow conditions (16-bar J-ring test). However, any RCWTB content led to a very noticeable decrease of the blocking ratio when flow was imposed in a specific direction (3-bar L-box test). It is thought that the fibers of glass fiber-reinforced polymer (GFRP) present in this waste may have been retained by the bars simulating concrete reinforcement in this test, hindering the passage of SCC. * Obtaining the Bingham parameters based on the results of the slump-flow test by computational fluid dynamics (CFD) simulations showed that RCWTB did not affect the yield stress of SCC, but it did significantly increase the plastic viscosity. Thus, SCC started to flow freely under the same shear stress regardless of the waste content, but RCWTB did slow down the flow, especially in the long term. * The CFD simulation based on the Bingham model was valid for free flow, both with and without obstacles simulating concrete reinforcement, obtaining valid differences with the experimental results. This simulation was more suitable for long-term flow, since slump flow was always simulated more accurately than \(t_{500}\) time. * CFD tools did not allow accurate modeling of the passing ability of SCC, although the plastic viscosity obtained did exhibit a good relationship with the 3-bar L-box blocking ratio. Modeling the effect of the GFRP fibers on SCC flow could improve the accuracy of the simulation. * The addition of RCWTB worsened all mechanical properties due to the presence of polymer and balsa-wood particles and to the increase of the water/cement ratio with increasing contents of this waste. Moreover, these aspects offset the beneficial effect of stitching the GFRP fibers, which was only relevant in terms of Poisson's coefficient, which remained constant for all RCWTB content. The mix with 3.0% RCWTB did not exhibit adequate mechanical properties for use in structural elements. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Property** & **Age (Days)** & _p-Value_ & **Pearson’s Correlation** & **Spearman’s Correlation** \\ \hline \multirow{4}{*}{Compressive strength} & 7 & 0.0030 & \(-\)0.92 & \(-\)0.95 \\  & 28 & 0.0005 & \(-\)0.95 & \(-\)0.95 \\  & 90 & 0.0000 & \(-\)0.97 & \(-\)0.95 \\ \multirow{4}{*}{Modulus of elasticity} & 28 & 0.0000 & \(-\)0.96 & \(-\)0.95 \\  & 90 & 0.0000 & \(-\)0.94 & \(-\)0.95 \\ \multirow{4}{*}{Poisson’s coefficient} & 28 & 0.0865 & \(+\)0.05 & \(+\)0.05 \\  & 90 & 0.6696 & \(-\)0.34 & \(-\)0.51 \\ \multirow{4}{*}{Splitting tensile strength} & 28 & 0.0404 & \(-\)0.77 & \(-\)0.74 \\ \cline{1-1}  & 28 & 0.0009 & \(-\)0.95 & \(-\)0.95 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: _p_-Values for the one-way ANOVA and correlations of the mechanical properties.