# CBR Predictive Models for Granular Bases Using Physical and Structural Properties
## 2 Materials and Methods  
### Characteristics of Tested Materials  
Material 1 was obtained from a quarry in the city of Queretaro, while materials 2, 3, and 4 were obtained from the city of Mexicali. Samples from both cities were extracted according to the recommendations reported in the ASTM D75 Norm [13], and also, the process documented in the norm ASTM C702/C702M-11 was followed [14]. The location and geological characteristics of the above-mentioned materials are summarized in Table 1.  
In the condition received from the quarry, Table 2 presents some of the main characteristics of the materials studied in this research. The CBR values corresponded to samples compacted at the optimum water content, resulting from the Modified Proctor compaction tests. Besides, for their classification, the following 6 tests were performed: (1) consistency limits according to standard ASTM D4318-05 [15], (2) dry loose volumetric mass according to standard M-MMP-1-08/03 [16], (3) relative density of solids according to standard ASTM C127-12 [17], (4) modified Proctor compaction test according to standard ASTM D1557-09 [18], (5) CBR test according to standard ASTM D1883-07 [19], and (6) water content according to standard ASTM D2216-10 [20]. For the thirty-six different samples, their grain size distribution was obtained. Also, the main volumetric and gravimetric parameters for these samples were obtained, as well as the results of the CBR test. Seven different samples were tested from quarry 1 (samples 1 to 7). These samples were prepared with different grain sizes distributions and water contents. In this way, sample 1 showed the original grain size distribution of the quarry. The grain size distribution for samples 2, 3, and 4 was modified to produce samples with 50% gravel and 50% sand. Samples 5, 6, and 7 only contained sand. Samples with different characteristics were prepared from quarries 2, 3, and 4:10 for quarry 2, 9 for quarry 3, and 10 for quarry 4 (samples 8 to 36). Samples from the same quarry presented similar grain size distributions. Figure 1 shows the grain size distribution for the different samples according to standard ASTM C136-06 [15]. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Location**} & \multirow{2}{*}{**Quarry**} & \multicolumn{3}{c}{**Coordinates UTM (m)**} & \multirow{2}{*}{**Origin of Rock**} & \multirow{2}{*}{**Type of Material**} & \multirow{2}{*}{**Treatment**} & \multirow{2}{*}{**Classification**} \\  & & & **North** & **East** & & & & & **USCS** \\ \hline Querétaro & 1 & 2281062.80 & 363855.13 & \begin{tabular}{c} Igneous basic \\ extrusive \\ \end{tabular} & Basalt & \begin{tabular}{c} Total crushing \\ and sieving \\ \end{tabular} & GW-GM y SM \\ \hline \multirow{4}{*}{Mexicali} & 2 & 3603070.10 & 629274.95 & Sedimentary & Clastic & \begin{tabular}{c} Partial crushing \\ and sieving \\ \end{tabular} & SP \\ \cline{2-7}  & 3 & 3573429.00 & 657540.00 & Sedimentary & Clastic & \
\begin{tabular}{c} Partial crushing \\ and sieving \\ \end{tabular} & GW \\ \cline{1-1} \cline{2-7}  & 4 & 3568274.44 & 657006.26 & Sedimentary & Clastic &
\begin{tabular}{c} Partial crushing \\ and sieving \\ \end{tabular} & GP \\ \hline \hline \multicolumn{7}{c}{USCS: unified soil classification system; GW: well-graded gravel; GM: silty gravel; SM: silty sand; SP: poorly graded} \\ \multicolumn{7}{c}{sand; GP: poorly-graded gravel; GW-GM: well-graded gravel with silt.} \\ \end{tabular}
\end{table} 
Table 1: Location and geological characteristics of the rocks, treatment, and classification of the soils.