# Uniaxial Testing of Soil-Cement Composites to Obtain Correlations to Be Used in Numerical Modeling
## 4 Laboratory Test Results and Discussion of the Obtained Results
### Testing of Laboratory Made Samples  
Reference samples for testing the uniaxial compressive strength of cement-soils were made in four variants. These variants were differentiated by the type of soil used and the density of the cement slurry. Basic information about the combinations (compositions) of soil-cement composites that were prepared as references in the lab is given below:  
* Type I--soil taken from a depth of 1-3 m + cement grout (1500 kg/m\({}^{3}\)). * Type II--soil taken from a depth of 3-6 m + cement grout (1500 kg/m\({}^{3}\)). * Type III--soil taken from a depth of 1-3 m + cement grout (1400 kg/m\({}^{3}\)). * Type IV--soil taken from a depth of 1-3 m + cement grout (1400 kg/m\({}^{3}\)). As the target amount of cement in 1.0 m\({}^{3}\) of the composite in all testing procedures was fixed at 250 kg, the proposed receipt just meant 330 L and 405 L of cement's slurry to be pumped for each 1 m\({}^{3}\) of the composite, for a target 1500/1400 kg of every 1.0 m\({}^{3}\) of grout, respectively. In addition, tests for reference samples were performed depending on the time of their preparation, i.e., after 3, 7, 14, 28, and 56 days. The averaged results of the reference tests of Type I are given in Table 2 below. Every result juxtaposed in the table above is an average of four results from four tested samples. The results are not surprising because one could expect a reduction in density (due to drying), an increase in compressive strength and elastic modulus, and a probable decrease in the critical deformation (which usually corresponds to increasing stiffness). Generally, these results prove the former authors' experiences [30; 32] and the information provided in the literature [13; 17; 24]. This preliminary part of the research program also  
Figure 8: Chart that embodies uniaxial compressive test performed on soil–cement composite sample. confirmed that in the case of non-standard soil-cement, the time of testing may be a crucial factor in the proper evaluation of the long-term parameters of the tested material [29; 31]. Simply referring to codes designed for concrete composites and limiting the curing time to last 28 days may lead to highly inaccurate conclusions (despite proper results). Referring again to the previous authors' experiences, it is important to check the dependency between the elastic modulus and the compressive strength of the material (see Figure 9). This information is crucial for the numerical modeling of soil-cement composites in the absence of proper stiffness testing (which is unfortunately a common practice in the construction industry). From the results given in Figure 8, we may derive the simplest linear function describing this relationship:  
\[\text{E}=68\times\text{R}_{\text{c}}+4.53\text{ [MPa]}, \tag{1}\]  
For the proceeding types (Type II, Type III, and Type IV), the results are given in Tables 3-5, respectively, together with the stiffness-strength relationships given in Formulas (2)-(4). \[\text{E}=135\times\text{R}_{\text{c}}\text{ i 22.02 [MPa]}, \tag{2}\]  
For the proceeding types (Type II, Type III, and Type IV), the results are given in Tables 3-5, respectively, together with the stiffness-strength relationships given in Formulas (2)-(4). \[\text{E}=135\times\text{R}_{\text{c}}\text{ i 22.02 [MPa]}, \tag{3}\] \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Time of Curing Days** & **Density g/cm\({}^{3}\)** & **Compressive Strength kPa** & **Critical Deformation \%** & **Elastic Modulus MPa** \\ \hline
3 & 1.740 & 335.52 & 2.8 & 7.721 \\
7 & 1.724 & 516.66 & 2.0 & 52.886 \\
14 & 1.775 & 674.20 & 2.1 & 58.131 \\
28 & 1.683 & 825.67 & 2.3 & 68.926 \\
56 & 1.510 & 1249.45 & 1.9 & 79.153 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Averaged values of Type I reference tests.