# Advances in the Study of the Behavior of Full-Depth Reclamation (FDR) with Cement
## 3 Results and Discussion
### Estimation of Flexural Strength at Long-Term Using the UCS and ITS Values  
An additional equation for estimating the flexural strength at long-term of the FDR with cement was developed as a function of the unconfined compressive strength and the indirect tensile strength by means of a multiple linear regression, as shown in Equation (4).  
\[FS_{LT-2}=0.074\ UCS_{LT}+0.826\ ITS_{LT} \tag{4}\]  
where \(FS_{LT-2}\) is the flexural strength at long-term by means of \(UCS_{LT}\) and \(ITS_{LT}\) simultaneously, and \(UCS_{LT}\) and \(STS_{LT}\) are as defined in Equations (1) and (2), respectively.  
Equation (4) has a coefficient of determination (\(R^{2}\)) of 0.684. Including an intercept in Equation (4) made the coefficients of the intercept and UCS not significant. Without the intercept, both coefficients are different from 0, with a significance level over 99% (\(p\)-value of the Student's \(t\)-test \(>\)0.99).  
Figure 8 shows the obtained values of FS and the values estimated by Equations (1), (2), and (4).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Materials** & \(UCS_{LT}\)/\(ITS_{LT}\) \\ \hline Soil-cement, cement-bound granular material, & \\ compacted concrete & 8–10 \\ FDR pavement with cement & 10.20 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of the relationship between unconfined compressive strength and indirect tensile strength at long-term for soil-cement, cement-bound granular material, and obtained values for the FDR with cement of the study.  
Figure 7: Relationship between ITS and UCS at long-term.  
As seen in Figure 8, Equation (4) is suitable for calculating FS at long-term, especially with regard to the average values of the material, despite the disperse values obtained for some specimens of the recycled material. For the extreme values, the proposed model does not fit so accurately. For specimens with the lowest values in FS, higher values are predicted with all the developed equations. On the other hand, for the highest values of FS, lower values are predicted. This fact can be attributed to the heterogeneity of the material or flawed specimen preparation or testing.  
From the point of view of sustainability, the advantages of FDR when compared with soil-cement and cement-bound granular mixture are considerable. When manufacturing FDR, it is avoided to transport -emove material to landfills; there is no need to use quarries and the quantity of material that must be transported is lower and, hence, CO\({}_{2}\) emissions are reduced. Moreover, the roads that are used for transporting the material are not so damaged.  
With regard to the (expected) behavior, it can be said that the average UCS and ITS value at long-term are similar to soil-cement. In the case of the FS at long-term, the value is lower than usual for soil-cement. The fact that the FS values are lower could be regarded as a disadvantage, and perhaps the expected life of the pavement structure would not be as long as with soil-cement. However, if we compare the expected life of the new higher quality base that we are designing with the previous pavement structure, which was composed of unbound aggregates, an improvement is observed. The quality is not as high as with soil-cement, but it must be taken into account that there is a big increase in the quality of the new base compared to the previous one. With this technique, a material that is near to a standardized material is designed, which is cheaper and more sustainable. Consequently, the advantages overcome the disadvantages.