# Preparation of a Low-Cement-Content Silty Soil Stabilizer Using Industrial Solid Wastes
## 3 Results and Discussion  
### Compressive Strength  
Figure 3 shows the solidified soil's compressive strength for different curing ages and dosages. It can be seen that the compressive strength increased with stabilizer dosage. And, as expected, the longer the curing time, the higher the strength. Moreover, the 7-day strength was over 65% of the strength at 28 days for all mixes. After 7 days, the growth rate of the compressive strength decreased gradually. Under the same stabilizer dosage, stabilizer B had a higher strength than stabilizer A. This could be attributed to the fact that stabilizer B had a higher cement content. On the other hand, as shown in Figure 4, a high value of the coefficient of determination (R\({}^{2}\)) indicated that a strong linear relationship existed between stabilizer dosage and compressive strength for both stabilizers.  
Figure 4: The linear relationship between stabilizer dosage and compressive strength. (**a**) Stabilizer A; (**b**) stabilizer B.  
Figure 3: Development of compressive strength with curing age. (**a**) Stabilizer A; (**b**) stabilizer B.  
Figure 5 shows the influence of the delay period on the 7- and 28-day compressive strengths with various stabilizer dosages. Both the 7- and 28-day strengths declined with the prolonged delay period. This could be explained by the fact that a time delay could increase the density of macropores in the soil samples [28], which decrease the strength [29]. Strong linear relationships were found between compressive strength and delay time, with R\({}^{2}\) values ranging between 0.9631 and 0.9984.  
The influence of stabilizer proportion and delay time on compressive strength is shown in Figure 6. As regulated in JTG D50-2017, the 7-day strength of stabilized soil should be greater than 0.8 MPa when used for bases and subbases [30]. Figure 6 shows that both stabilizers A and B could satisfy the standard even after 8 h of delaying, which offered sufficient time for the operation at the construction site.  
Figure 6b shows the 28-day compressive strength of A and B with a stabilizer dosage of 10%. When the delay time was shorter than 2 h, the decrease in strength in stabilizer A is slightly more than that of stabilizer B. This was probably because the cement in the stabilizer was in the initial setting state during that period. Static compaction destroyed the newly formed bond structures between soil particles and hydration products [31]. Stabilizer B had more cement in the stabilizer; therefore, the decrease in strength is more notable. When the delay time was longer than 2 h, the decrease in strength in stabilizer A is smaller than that of stabilizer B. This could be due to the fact that stabilizer A contained  
Figure 5: Effect of stabilizer dosage and delay period on compressive strength. (**a**) 7–day strength of stabilizer A; (**b**) 28–day strength of stabilizer A; (**c**) 7–day strength of stabilizer B; (**d**) 28–day strength of stabilizer B.  
more FGD gypsum. According to [PERSON] et al. [32], sulphate could slow down the pozzolanic reaction. Thus, the strength development of stabilizer A was delayed, and correspondingly, the strength of stabilizer A was less disturbed by the delay period. Furthermore, according to [PERSON] et al. [33], the pozzolanic reaction contributed to strength development at a later stage than cement hydration. It could, therefore, be inferred that stabilizers with a higher solid waste supplementary content could compromise the adverse effect of delay periods on strength, especially when the delay period was longer than 2 h.