# Preparation of a Low-Cement-Content Silty Soil Stabilizer Using Industrial Solid Wastes
## 2 Experiment
### Experimental Design and Test Methods  
Two soil stabilizers were designed. Their mixture proportions are given in Table 2. For soil stabilization, the stabilizer dosage was set at 4%, 6%, 8%, and 10%. Figure 1: Relationship between dry density and water content of the silt. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Component** & **CaO (\%)** & **SiO (\%)** & **Al\({}_{2}\)O\({}_{3}\) (\%)** & **MgO (\%)** & **Fe\({}_{2}\)O\({}_{3}\) (\%)** & **SO\({}_{3}\) (\%)** & **TiO (\%)** & **K\({}_{2}\)O (\%)** & **MnO (\%)** \\ \hline Cement & 63.21 & 18.48 & 6.74 & 3.24 & 3.45 & 3.16 & 0.35 & — & — \\ Ground & 44.71 & 29.29 & 14.85 & 7.33 & 0.39 & 1.28 & 0.68 & 0.41 & 0.42 \\ GBFS & 3.44 & 49.93 & 36.17 & 0.79 & 5.8 & 1.12 & 1.1 & 1.17 & — \\ FGD gypsum & 45.35 & 1.56 & 0.8 & 0.35 & 0.12 & 50.63 & 0.02 & 0.41 & — \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of the cement and solid wastes. Figure 2: Particle size distribution of particles. The ground GBFS, fly ash, and FGD gypsum in the stabilizer were first mixed with the dried soil. Afterwards, a portion of water was added and mixed for 90 s [25]. At this stage, the moisture content of the mixture was 1-2% less than the OMC. Then, it was placed in sealed plastic bags for 6-8 h for uniform moisture distribution. Finally, cement and another part of water were added 1 h before static compaction [26], and the samples were mixed again to reach the OMC. The static compaction method was used to ensure that the specimens had a compaction degree of 98%. For compressive strength measurement, the samples were compacted into cylindrical specimens of 50 mm in diameter and 50 mm in height [26; 27]. The specimens were cured at a temperature of 20 \({}^{\circ}\)C \(\pm\) 2 \({}^{\circ}\)C, with the relative humidity higher than 95%. Curing ages were 7, 28, 90, and 180 days, respectively. The loading speed was 1 mm/min. Six specimens in parallel for each group of specimens were used to test the compressive strength values. In practice, a certain delay period exists between mixing the stabilizer with soil to on-site operation. The influence of this delay period on the development of compressive strength was investigated. Delay periods of 0, 2, 4, 6, and 8 h were selected. The operating steps were as follows: the soil-stabilizer mixture was thoroughly mixed after adding the second part of water. The mixtures thus prepared were placed in sealed plastic bags and kept in moisture-controlled desiccators during the time delay period. After the desired duration of time delay (0, 2, 4, 6, and 8 h), the mixtures were compacted statically to achieve the corresponding maximum dry unit weights. Eventually, their 7- and 28-day strengths were tested. The California Bearing Ratio (CBR) test was conducted according to JTG 3430-2020 [24]. Firstly, the soil sample with 4% dosage stabilizer was cast in 3 layers and compacted into specimens under OMC. Three specimens were made for each mixture, and then they were soaked in water for 96 h. Finally, a strength tester for pavement materials with an experimenting rod was employed for loading. The penetration speed of the experimenting rod was 1-1.25 mm per minute, and the stress was recorded when the rod's penetration depth reached 2.5 mm. The temperature shrinkage test was performed following JTG E51-2009 [26], and the specimen size was 50 mm \(\times\) 50 mm \(\times\) 200 mm. Three specimens were tested for each mixture, and the curing age was 7 days. An environmental chamber was employed to control the temperature, and the dial indicator was used to measure the specimens' length. The specimens were first soaked in water for one day prior to the test. Afterwards, they were dried in an oven, and their initial lengths were measured. The temperature setting range was between \(-\)10 \({}^{\circ}\)C and 40 \({}^{\circ}\)C. Every specimen was equipped with two dial indicators to ensure the reliability of the measurements.