# Effects of Aging on the Dry Shrinkage Cracking of Lime Soils with Different Proportions
## 4 Discussion
### Effects of pH and Particle Size on the Reasonable Aging Time of the Lime Soil Samples  
The reasonable aging time is an important factor for the restoration of earthen sites. The test results revealed that the lime content, particle size, and aging time of the samples affected the characteristic parameters of the samples, such as volume crack rate, expansion and contraction rate, pH, and particle size distribution. Volume crack rate and expansion shrinkage rate are macro characterization parameters that affect the dry shrinkage cracking of the samples. In addition, the pH and particle size distribution are internal factors affecting lime soil cracking. The analysis of the aforementioned characteristic parameters enabled the determination of the reasonable aging time of the samples with a different lime content and particle size. The volume crack, expansion, and shrinkage rates of the sample after five dry-wet cycles were investigated. The aging time affected the particle size of the lime soil samples containing lime particles with a size range of 0.01-0.5 mm. The results of the analysis of the characteristic parameters of the samples with a different lime content and aging time are shown in Figure 16a-c. The characteristic parameters of the samples with a different lime particle size and aging time are shown in Figure 16b,d,e. Figure 16: Effect of aging time on the characteristic parameters of the samples: (**a**) 10%–0.01–0.074 mm; (**b**) 20%–0.01–0.074 mm; (**c**) 30%–0.01–0.074 mm; (**d**) 20%–0.01–0.074 mm; and (**e**) 20%–0.010.074 mm. With an increase in the aging time, the volume crack and expansion shrinkage rates of the samples with different lime contents decreased, and then stabilized (Figure 16a-c). In addition, the changes in the 10%-0.01-0.074 mm, 20%-0.01-0.074 mm, and 30%-0.01-0.074 mm samples were stable at aging times of 48, 72, and 120 h, respectively. Furthermore, the pH of the samples with different lime contents increased, and then decreased with the increasing aging time. The pH of the 10%-0.01-0.074 mm, 20%-0.01-0.074 mm, and 30%-0.01-0.074 mm samples decreased significantly at 48, 72, and 120 h, respectively, and the corresponding pH decline rates were 0.65, 1.1, and 0.88%, respectively. At this time, the lime soil aging process was over. The stable volume crack and expansion shrinkage rates of the 20%-0.01-0.074 mm, 20%-0.074-0.5 mm, and 20%-0.5-2 mm samples were observed at aging times of 72, 120, and 120 h, respectively (Figure 16b,d,e). At these aging times, the pH of the samples exhibited a notable decline, and the pH decline rates were 1.1, 0.69, and 0.57%, respectively. With an increase in the aging time, the content of the particles with a size of 0.01-0.1 mm decreased, and that of the particles with a size of 0.1-0.5 mm increased (Figure 16a-c). Furthermore, particles with a size of 0.01-0.1 mm were observed in the 10%-0.01-0.074 mm, 20%-0.01-0.074 mm, and 30%-0.01-0.074 mm samples at an aging time of 48, 72, and 120 h, respectively. In addition, there was no significant difference between the decrease and the increase in the content of particles with a size of 0.1-0.5 mm, and the difference was 0-13%. Furthermore, there was a small difference between the decrease in the content of particles with a size of 0.01-0.1 mm and the increase in the content of particles with a size of 0.1-0.5 mm in the 20%-0.01-0.074 mm, 20%-0.074-0.5 mm, and 20%-0.5-2 mm samples at 72, 120, and 120 h, respectively, and the difference was 2-11% (Figure 16b,d,e). These results indicate that the reasonable aging time of the samples increased with increasing lime content. The reasonable aging times of the 10%-0.01-0.074 mm, 20%-0.01-0.074 mm, and 30%-0.01-0.074 mm samples were 48, 72, and 120 h, respectively. This indicates that the reasonable aging time of the samples increased with the increasing lime particle size. The reasonable aging time of the 20%-0.01-0.074 mm, 20%-0.074-0.5 mm, and 20%-0.5-2 mm samples were 72, 120, and 120 h, respectively.