# Effects of Cement Treatment on Mechanical Properties and Microstructure of a Granite Residual Soil
## 3 Results and Analysis
### Mineralogy and Microstructure  
Cementitious products include the C-(A)-S-H and CH (calcium hydroxide). The C-A-S-H and C-A-H are unidentifiable due to the negligible C\({}_{3}\)A in the cement used in this study. XRD patterns of the saturated untreated and cement-treated GRSs cured to 28 d are shown in Figure 12. The crystalline minerals include the Kaolinite and Quartz from the original soil and the non-hydratable Calcite from the cement (see Figure 12a). For the treated specimens cured to 28 d, C-S-H was identified at 20 = 29.0\({}^{\circ}\), 29.2\({}^{\circ}\), 29.5\({}^{\circ}\), and 32.1\({}^{\circ}\) (see Figure 12b) [38; 39; 40]. Figure 11: Compressibility and vertical yielding pressure of saturated untreated and cement-treated GRSs depending on cement content and curing time. (**a**) Compressibility; (**b**) Vertical yielding pressure. Figure 12: _Cont._SEM images of the saturated untreated and cement-treated GRSs are shown in Figure 13. The untreated specimen consists of clay lamella and quasicrystals (see Figure 13a). By convention, the pores within the quasicrystals are deemed to be micro-pores, and those between the quasicrystals are referred to as macro-pores. For the treated specimens, their microscopic morphology and the types of C-S-H [41] were observed to depend on the cement content. The C-S-H is fibrous (C-S-H of type I) in the case of \(C_{\text{vi}}=1\)-2% (see Figure 13b,c); the long C-S-H fibers were observed to fill the macro-pores (see Figure 13b), whereas the short ones attached to the surfaces of the clay lamellae (see Figure 13c). The C-S-H became reticular (C-S-H of type II) in the case of \(C_{\text{vi}}=3\)-5%; the quasicrystals were assembled by the C-S-H and aggregates (stacks of quasicrystals) of larger size and more rounded geometry were observed to form (see Figure 13d-f). CH of a hexagonal tabular shape can be observed in the inter-aggregate pores as the volumetric cement content increased to 5% (see Figure 13f). The changes in the pore structure due to cement treatment can be assessed based on the MIP results. The pore size distribution and cumulative curves of the saturated untreated and cement-treated GRSs cured to 28 d are shown in Figure 14. The PSD curves were derived from the differential intrusion volume of the mercury (per unit mass, \(V_{\text{in}}\)) multiplied by the equivalent grain density (i.e., \(\text{de}_{\text{in}}/\text{dlog}D=\text{d}V_{\text{in}}/\text{dlog}D\times \rho_{\text{s}}\)) (see Figure 14a). The sudden increase of intrusion at a pore size of 5.4 um is an artifact due to the transfer of the samples from the low-pressure chamber to the high-pressure chamber during MIP tests. The untreated specimen is of single-porosity, characterized by a single peak at a pore diameter of about 0.4 um in the PSD curve; this single pore family represents both the pores within and between the quasicrystals. The treated specimens are of dual-porosity with two peaks in the PSD curve representing two distinguishable pore families; the first pore family represents the pores within the aggregates, whereas the second represents the pores between the aggregates. The first peak was observed to decrease with the cement content in the case of \(C_{\text{vi}}\leq 2\%\), and this tendency reversed as the cement content further  
Figure 12: XRD profiles of saturated untreated and cement-treated GRSs cured to 28 d. (**a**) Identification of crystalline minerals; (**b**) Identification of C–S–H. increased. The pore diameter corresponding to the first peak decreased successively as the cement content increased. The second peak is not distinct in the case of \(C_{\text{vi}}\leq 2\%\) and becomes notable as the cement content further increases. Contrary to the first peak, the second peak and its corresponding pore diameter increased sequentially as the cement content increased.