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Materials 2019, 12(14), 2245; https://doi.org/10.3390/ma12142245
2. Calculation Method of the Deteriorated Layer Permeability Coefficient of Soil-Cement
3. Improvement of the Soil-Cement Permeability Testing Apparatus
4. Tests of Soil-Cement
4.2. Preparation and Maintenance of the Soil-Cement Specimen
- The first type of specimen was used for permeability tests. The diameter of the specimen was 75 mm and the height was 30 mm. Specimens were demolded after 24 h of curing. When the soil-cement specimen was cured in saline solution, the surface of the specimen contacted the saline solution directly. Therefore, the corrosion of soil-cement originated from the surface. The internal portion of soil-cement did not experience corrosion until the saline solution penetrated into that region. In this paper, specimens were cured under dry conditions in a curing room environment and under wet conditions in seawater. During immersion in seawater, the internal region of the soil-cement specimen did not experience corrosion from the saltwater and could be regarded as soil-cement in a curing room environment . For the immersion maintenance case, the specimens were first maintained in a curing room for seven days and then in the seawater that was taken from the field. The characteristics of the seawater are shown in Table 3. The temperature of the seawater was kept at 20 ± 2 °C, and during the curing period, the concentration of ions in the seawater was measured every three days and the seawater was renewed to ensure the relative balance of the concentration of ions in seawater.
- The second type of specimen was used for tests of deterioration depth, which was needed for Equation (8). First, the soil-cement was filled into a cutting ring smeared with Vaseline. The cutting ring’s height was 20 mm and its diameter was 61.8 mm. Then, soil-cement specimens were maintained together with the cutting rings in a curing room and in seawater before they were demolded and tested, respectively.
4.3. Tests of Deterioration Depth
4.4. Tests of Permeability
- Remove the soil-cement specimens from different curing conditions and wipe their surface with a wrung-wet cloth. Smear the specimens with grease and place them in the mold with one porous stone installed at the top and one at the bottom. Place the mold in the permeameter and cover the upper surface with filter paper.
- Increase the hydraulic pressure step-by-step. At the beginning of the experiment, the rate of hydraulic growth was 0.02 MPa per step until the hydraulic pressure reached 0.1 MPa, at which time the growth rate changed to 0.1 MPa per step. After applying each pressure level, the pressure should be stabilized for one hour before applying the next level of pressure until the water overflows.
- Record the hydraulic pressure and seepage volume after the fluid level in burette stabilizes. For specimens with large seepage volume, read the scale at an interval of 3–5 min; for specimens with small seepage volume, read the scale at an interval of 30–60 min. Take the average of the three groups of data for each specimen.
- Monitor the seepage process of the specimens during tests. If the water oozes from the lateral surface, the experiment should be stopped, and the specimens should be resealed before proceeding.
5. Test Results and Analyses
5.1. Deterioration Depth
5.2. Permeability Coefficient of Deteriorated Layer
6. Application of the Prediction Model for the Deteriorated Layer Permeability Coefficient
- The growth rate of deterioration depths of soil-cement specimens gradually decreased with an increase in curing age. The deterioration depth increased with an increase in cement content.
- The growth rate of permeability coefficients increased with curing age and cement content. When the curing age was shorter, the permeability coefficient of soil-cement cured in seawater was smaller than that maintained in a curing room, but with increasing age, the permeability coefficient of soil-cement under immersion maintenance was higher than that maintained in a curing room.
- The evolution curve of the permeability coefficient of a deteriorated layer can be formulated as a logistic function.
Conflicts of Interest
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|Specific Gravity of Soil Particle||Natural Moisture Content (%)||Plastic Limit (%)||Liquid Limit (%)|
|Cement Content||ki (×10−8 cm/s)||ku (×10−8 cm/s)||tc (d)||p|
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