# Reutilization of Recycled CDW Sand in Mortars, Paving Blocks, and Structural Concrete
## 3 Results and Discussion
### Properties of Aggregates
#### 3.1.3. Physico-Mechanical Properties of Aggregates  
Table 6 summarizes the physico-mechanical properties of both the NA and CDW aggregates. The CDW particles exhibited lower specific weight than the NA sand, which indicates higher porosity and water absorption for the recycled sand versus the NA calcareous particles. This difference is attributed to the presence of ceramic particles in the CDW recycled sand. [PERSON] et al. [52] observed significant variation in water absorption values among different types of ceramic materials. They report water absorption values of 0.69%, 6.28%, and 15.76% for the fine ceramic sand obtained from ceramic sanitaryware, ceramic tiles, and red clay bricks, respectively. [PERSON] et al. [25] also report water absorption values ranging from 2.0% to 17.2% for fine recycled aggregates derived from different types of ceramic tiles, which they used in concrete.  
The natural sand meets the maximum water absorption requirement outlined in the Spanish Structural Concrete Code for NAs used in structural concrete (5% for both fine and coarse aggregates, as per Article 30.6). According to Article 30.8.3.1. Physical-mechanical conditions of recycled aggregates, the water absorption of the recycled coarse aggregate must not exceed 7%, while that of the natural coarse aggregates to be mixed with should remain below 4.5%. Although the Spanish Structural Code does not contemplate recycled sand use, the CDW RA would meet the requirements established for coarse RAs in structural concrete.  
As shown in Table 6, the CDW recycled aggregate exhibited slightly better wear resistance compared to natural limestone, as indicated by the lower mass loss after the Micro-Deval test. These results were due to the presence of ceramic particles in the CDW, which may be harder than calcareous aggregates. A study by [PERSON] et al. [25] also indicates greater resistance to fragmentation, measured by the \"Los Angeles\" test, in RAs obtained from ceramic sanitaryware compared to NAs.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **NA** & **CDW** \\ \hline Specific weight, kg/m\({}^{3}\) & 2808.9 & 2441.2 \\ Water absorption, wt.\% & 2.01 & 5.62 \\ Resistance to wear, wt.\% & 29.2 & 23.9 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Physico-mechanical properties of the NA and CDW aggregates.  
The results indicate that the properties of the analyzed CDW aggregate are comparable to those of the NA limestone and suggest its suitability for use in structural concrete exposed to environmental classes X0 (no carbonation risk) and XC (carbonation-induced corrosion). However, the current structural code permits RA use in structural concrete only if sourced from concrete, with a maximum replacement of natural coarse aggregates limited to 20% by weight. Removing sulfates at the source before CDW disposal could facilitate the production of aggregates with larger particle sizes. Nevertheless, these aggregates would still remain ineligible for concrete applications under current regulations, which restrict the use of RAs to those derived from concrete. While RAs from non-concrete sources are currently excluded from structural concrete, further research is essential to assess their potential and to extend their reuse opportunities. Additionally, this CDW recycled aggregate could be considered for non-structural applications, such as mortars or paving blocks.