# Effects of Aging on the Dry Shrinkage Cracking of Lime Soils with Different Proportions
## 2 Materials and Methods
### Methods  
The effects and mechanism involved in the effect of the aging time, lime content, and particle size on the dry shrinkage cracking of lime soil were analyzed using the dry-wet cycle test, screening test, pH detection test, XRD, and SEM. The test parameters are shown in Table 1. To investigate the effects of various factors on the dry shrinkage cracking of lime soil, samples with different lime particle sizes and contents were prepared, and the analysis was performed at aging times of 6, 12, 24, 48, 72, 120, and 168 h. The samples were named according to the lime content, lime particle size, and aging time. 1. Preparation of bulk sample: Briefly, a soil sample was dried, crushed, and sieved using a 2 mm sieve. Subsequently, a large lime sample was crushed, and sieved using a sieve with different particle sizes. Thereafter, different proportions of the soil samples were mixed with lime, after which an appropriate amount of water was added and the mixture  
Figure 1: Particle grading curve of the site soil. \begin{table}
\begin{tabular}{c c} \hline
**Lime Content (\%)** & **Lime Particle Size (mm)** \\ \hline
10 & \\
20 & 0.01–0.074 \\
30 & \\
20 & 0.074–0.5 \\
20 & 0.5–2 \\ \hline \end{tabular}
\end{table} 
Table 1: Test parameters. Figure 2: Test flow chart. was mixed evenly. Lastly, samples with an initial moisture content of 20% were configured, after which the aging test was performed. 2. Aging test: Briefly, the prepared bulk sample was placed in a standard curing box (temperature: 20 \({}^{\circ}\)C, humidity: 95%) for aging at different times. During aging, 50 g of the aged samples (3 parallel samples) was obtained every 12 h, and dried. Subsequently, the average moisture content of the sample was measured, after which water was added to the sample to maintain the initial moisture content of 20%. 3. Dry-wet cycle test: After the aging test, 2000 g of the aged bulk sample was obtained and placed in a mold with a size of 25 cm \(\times\) 25 cm, after which a Static compaction was performed in a 2 cm steel mold. Subsequently, the sample was placed in a temperature-controlled laboratory at a temperature of 40 \({}^{\circ}\)C for 36 h to dry the sample. Subsequently, water was uniformly sprayed on the surface of the sample using a watering can. The water spraying mass was 800 mL (Figure 3a shows the dry and wet cycle process of the sample). The drying and wetting process was recorded as one cycle, and a total of five dry-wet cycles were performed. During the test, the crack development process was recorded using a camera fixed above the sample. Expansion and shrinkage test: The height of the sample was measured using a vernier caliper with an accuracy of 0.02 mm. To obtain more accurate data, the height of the soil samples was measured at eight different positions using a vernier caliper, after which the average mean value of these eight measured values was considered as the average height of the sample. The expansion and shrinkage test of the samples is shown in Figure 3b. 5. pH detection test: After the aging test, 20 g of the dried samples (three parallel samples) was obtained, and 100 mL distilled water was added to the sample, after which the mixture was mixed. Subsequently, the mixture was left to stand, after which the pH value of the supernatant was measured using a PGS-3C precision pH meter. 6. Screening test: The test took 200 g dried samples (set up 3 parallel samples) and screened the samples with different screen diameters. The screen hole diameters were 2, 1, 0.5, 0.25, 0.1, and 0.075 mm, respectively. 7. X-ray diffraction test: The test instrument adopted the X-ray diffractometer with the model of D8 produced by Brooke Company of Germany, and the scanning incidence angle was 10-70\({}^{\circ}\). After drying and grinding, the samples were tested by X-ray diffraction to explore the changes of aging time on the internal chemical products of the samples. 8. Electron microscope test: The test instrument adopted a S570 scanning electron microscope generated by Hitachi of Japan.