# Soil Stabilization Using Waste Paper Fly Ash: Precautions for Its Correct Use
## 2 Materials and Methods
### Experimental Methods: Specimen Preparation and Testing
#### 2.2.3 Expansion in Stabilized Soil  
The procedure of swelling in soils is explained in the European standard EN 13286-49 [25]. The test measures the volumetric expansion in cylindric samples. The test is done by making samples and submerging them into a water bath. After immersing, the samples are measured using a caliper. Generally, the soils analyzed with this method are clayey and provide a good cohesive sample. Applying this method to granular soils causes desegregation of the samples, and it is not useful.  
Additionally, as mentioned in EN 13286-49 [25], the measurement by caliper makes it impossible to measure expansion correctly over time. Therefore, a homemade experiment was proposed to measure the expansion in soil samples.  
The test measures the height change of a confined specimen (soil with WPFA or cement) placed vertically in a mold. The displacement is related to the reactions of cementitious material in the soil samples.  
The test contained a circular plastic (PVC) mold with a diameter of 10 cm, a height of 15 cm, and a thickness of 0.5 cm to withstand the lateral forces. The mold had a perforated PVC base attached to the mold with eight screws, in order to make a uniform mold. A paper filter was added to the bottom of the mold to avoid any material loss. Then, a sample soil was ground and sieved through a 16 mm sieve, since the diameter of the mold was 10 cm. The soil is mixed with WPFA and water, and then poured into the mold and compacted in 2 layers with a vibratory rammer (the goal is to reach the density obtained from the modified proctor test). The time of the compaction and water ratio depends on the density obtained from the proctor. After compacting the material, another filter was added to the top layer of the soil. Then, 125 g of small glass spheres with a diameter of 3 mm were added to the mold to have a uniform surface. To simplify the measurement, a metallic mold with a thickness of 0.5 cm was added. To measure the expansion in the mixture, a precise displacement measurement device with six sensors and an accuracy of 0.1 um is used. The measurement device used was an Ametek solartron model DS/50/G (United Kingdom).  
Three of the six sensors were placed on the PVC mold and used as the reference point, and the other three sensors were placed inside the mold, on the metallic plate, to measure the displacement of the material. Figure 1 shows the expansion apparatus used in this study.  
The test was carried out under seven conditions to measure the expansion in WPFA, as listed in Table 1. In order to compare the effect of water on expansion in stabilized soil, the study tested different water ratios and different delay times. [PERSON] [4] applied a 25 min delay time when fabricating mortars, leading to a better workability; however, in this study, different delay times according to shaking results were used. It should be mentioned that the expansion test was also carried out with soil-cement samples to have a reference. In soil-cement samples, no delay time was applied. After mixing the water with the mixture, it was poured into the mold and compacted.  
Figure 1: Expansion apparatus.