# Comparison of Field and Laboratory Tests for Soil Suitability Assessment in Raw Earth Construction
## 2 Experimental Program
### Testing Methodology
#### 2.2.2 Laboratory Tests  
The following laboratory tests were selected: wet sieving for the particle size distribution above 63 um; sedimentation by densimeter for the distribution of the fine fraction (particles < 0.063 mm); the pycnometer test to measure the absolute density; the Atterberg limits to determine the plasticity domain; the MBV test to study the activity of clays; and the calcination test for the measurement of OM content. Each laboratory test was conducted according to standardized procedures to guarantee the reproducibility and reliability of results. For the analysis of particle size distribution, the soils underwent wet sieving in accordance with ISO 17892-4 [51]. In cases involving clay-rich soil, this technique is essential, as it assists in disintegrating clay aggregates, thereby preventing their influence on the size measurements of larger grains. Prior to testing, the soils were soaked in water for a minimum of 24 h, allowing the clay aggregates to break down. After soaking the soil, it was gradually poured through sieves ranging from 40 mm to 0.063 mm and shaken vigorously to facilitate particle settling. If clay lumps formed, additional water was added as needed. The residue remaining on each sieve was collected in a container and placed in an oven at 105 \({}^{\circ}\)C. Once fully dried, the mass of the residue was weighed to determine the soil's particle size distribution. For testing the fine fraction, sedimentation testing was performed using a calibrated hydrometer under controlled temperature conditions [51]. The Atterberg limits were determined following the ASTM protocol [52]. The liquid limit was established through multiple measurements at different moisture contents using the Casagrande apparatus, ensuring consistent drop height and rate. The plastic limit was determined using the standardized thread-rolling method, with each test carried out in triplicate to ensure the statistical reliability of the results. Consistency was verified through repeated testing when variations exceeded standard tolerances. The MBV test was performed in accordance with the standard [53], using a precisely prepared methylene blue solution (10 g/L). The procedure commenced with the preparation of a soil suspension in deionized water under controlled temperature conditions. The methylene blue solution was added incrementally, with spot tests conducted on filter paper at one-minute intervals. The endpoint was identified by the appearance of a light blue halo surrounding the central spot, which indicated complete saturation of the clay minerals. Multiple tests were conducted to verify the consistency of the results. The OM content was determined through calcination, following the XP P94-047 standard [54]. The soil was first dried at 105 \({}^{\circ}\)C until it reached a constant mass and then heated in a muffle furnace at 450 \({}^{\circ}\)C for 3 h. The OM content was calculated based on the mass loss between 105 \({}^{\circ}\)C and 450 \({}^{\circ}\)C, expressed as a percentage of the dry mass. Testing was performed in duplicate to ensure reliability. Density measurements were conducted using the pycrometer method as per ISO 17892-3 [55]. The pycrometer was calibrated with distilled water at controlled temperatures. Soils were dried, ground to pass through a 2 mm sieve, and carefully placed in the pycrometer. After adding distilled water and removing any entrapped air through gentle heating and vacuum application, the mass was determined. The particle density was calculated from the measured masses and calibration data, with necessary temperature corrections applied. Table 1 groups the different field and laboratory tests carried out in this study. Note that for the field tests, the soil was sieved at 5 mm and for the tests carried out in the plastic state, the soil was prepared 24 h in advance. The field test for the OM content involves a simple smell test, as described in [45; 56].