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Circular Economy
3. Results and conclusions
An analysis of variance and a regression analysis were realised to each pair of variables to correlate with the aim, to demonstrate whether it is possible or not, to obtain a correlation between each physical-mechanical property of RA and its composition.
As a result of the variance analysis, it has been evidenced that there is a significant influence between the composition of the RA and the six physical-mechanical properties studied. In every analysis, the p-value of the F-Test were less than 0.05, with a confidence level of 95%.
Moreover, the results of the six regression analyses realised showed that four of the physical- mechanical properties studied have significant correlation with the composition of aggregates: rd, SSD, WA and ACV. In all of them, the determination coefficient (R2) was greater than 0.8 using multiple linear regression.
The following equations show the best fit obtained from each multiple linear correlation between the different physical-mechanical properties studied and the independent variables.
𝑟𝑑 = 1813.9641 − 1.0892 Rb + 4.6918 Rc1 + 2.7025 Rc2 + 5.8361 Ru 𝑆𝑆𝐷 = 2073.2551 − 0.4959 Rb + 3.4583 Rc1 + 2.1597 Rc2 + 4.2775 Ru WA = 13.0670 + 0.0446 Rb − 0.0712 Rc1 − 0.0430 Rc2 − 0.0900 Ru ACV = −79.6951 + 1.1746 Rb + 1.2219 Rc1 + 1.2785 Rc2 + 0.9550 Ru
(p-value= 7.8e-15; R2=0.904)
(p-value= 5.5e-14; R2=0.891)
(p-value= 2.5e-14; R2=0.896)
(p-value= 1.1e-8; R2=0.860)
Therefore, it is deduced from this study that there is an influence of the RA composition in the following physical-mechanical properties: oven-dried particle density, saturated and surface dried particle density, water absorption and ACV. In addition, this relation can be expressed with a multiple linear correlation with a very high significance (R2>0.8). These results will allow to predict the physical-mechanical properties of recycled aggregates from their composition.
4. Acknowledgment
Pilar Muñoz-Moreno would like to thank the Spanish Government (MECD- FPU16/04253) for its funding support.
5. References
Tam, V. W. Y., Soomro, M., Catarina, A., & Evangelista, J. (2018). A review of recycled aggregate in concrete applications (2000-2017). Construction and Building Materials, 172, 272-292.
Silva, R. V., De Brito, J., & Dhir, R. K. (2014). Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production. Construction and Building Materials, 65, 201-217.
Barbudo, A., Agrela, F., Ayuso, J., Jiménez, J. R., & Poon, C. S. (2012). Statistical analysis of recycled aggregates derived from different sources for sub-base applications. Construction and Building Materials, 28, 129-138.
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