## 2 Materials and Methods
At a certain moisture variation, the soils go through different physical states (solid, semi-solid, plastic, fluid), being possible to determine the moisture content range at which they behave plastically (SR EN ISO 14688-1). In the case of soils, the property of being plastic can be summarized by five indicators, namely:  
* the contraction limit (s), which represents the moisture content below which the decrease of the soil volume does not take place;
* the lower limit of plasticity (p), also called the kneading limit, which indicates the moisture content from which the soil becomes plastic;
* the upper limit of plasticity (f), also called flow limit, which represents the moisture content at which the soil becomes fluid;
* plasticity index (fp), represented by the interval between the upper limit of plasticity (Wc) and the lower limit of plasticity (Wp), calculated with the Equation (8). \[\rm I_{P}=W_{c}-W_{p}\ [\%] \tag{8}\]
* the consistency index (lc), which quantitatively expresses the physical state of cohesive soils and depends on the water content, and can be calculated with the relation (9), where W represents the soil moisture in its natural state. Figure 2:0  
Soils with a plasticity index of less than 10% have very low plasticity, while those with a plasticity index of more than 50% have high plasticity. The determination of plasticity limits is performed in the laboratory in accordance with the provisions of STAS 1913/4-86, which establishes its own methods of determination. Determination of lower plasticity limits. The procedure is applied to soils made up of particles less than 2 mm in size and containing organic matter up to 5% by weight, in the dry state, by the soil cylinder method. This method consists in determining the minimum moisture content at which a soil can be shaped into cylinders. From the soil under analysis, a quantity of approximately 100 g is taken, which is sifted, homogenized, and then kneaded. If the sample under analysis does not have sufficient moisture, it can add water until a thick paste is obtained. From the resulting paste, it takes a quantity from which a cylinder with a diameter of 3-4 mm and a length of 30-50 mm is rolled on a sheet of glass. Examine the surface of the earth cylinder, and if no cracks appear on its surface or the cylinder does not break into pieces, the sample is mixed again (to lose water) and rolled until the first cracks appear on the surface of the cylinder or can no longer be made, due to the low humidity that leads to its rupture. This is the moment when, according to STAS 1913/1-82 [22], the moisture in the sample corresponds to the lower limit of plasticity, and the sample can be introduced into the oven to determine the moisture. Determining the upper limits of plasticity. The procedure applied to soils composed of particles less than 2 mm in size and containing organic matter up to 5% by mass, in the dry state. The cup method and the one-point method consist in determining the moisture content at which a slit made in a paste of soil from the cup of the Casagrande apparatus, closes on a length of 12 mm after 25 falls of the cup from a height of 10 mm. In the case of the cup method, a quantity of 200 g is taken from the soil under analysis and passed through a grater, water is added and is homogenized until a homogeneous paste results. In the case of soils where fractions larger than 0.5 mm predominate, a quantity of approximately 200 g is taken from the soil under analysis and dried in an oven, after which it is ground and passed through a 0.5 mm sieve. Then 2/3 of the Casagrande apparatus (Utest, Ankara, Turkey) cup was filled to determine the plasticity of the soils, its surface is leveled, a deep slit was drawn in the middle of the cup to the bottom of the cup.