*3.1. Materials Characterization*

The SEM-EDS results of the molasses shows this is mainly an organic compound, see Table 1, with oxygen and carbon with concentrations of 46.67% and 41.23% respectively. It also has potassium, calcium, and chlorine in concentrations of 6.86%, 2.1%, and 2.08% respectively; and magnesium, and sulfur in lower concentrations of 0.64% and 0.41% respectively.

Table 2 summarizes the kaolin´s index properties. According the USCS, the soil is a lean clay with sand (CL). Table 3 presents the experimental design for the formulations prepared. The fibers and molasses contents were estimated in a high precision balance. The soil was mixed with 35% of water, which is three percentage points up from the optimum moisture content to facilitate soil extraction without fracturing the samples (Table 2).



**Table 3.** Soil mixtures.

Figure 3a shows the particle-size distribution of the kaolin soil, with grain sizes from 0.2 µm to 4.5 mm, and the thickest particles corresponding to parental rock with less degree of weathering. Figure 3b represents the polymer fibers diameter fitted in a normal probability distribution. Fibers showed a diameter from 10 to 40 µm, with an average of 22.4 µm. Figure 3c shows the rubber grain size in a normal probability distribution. These residual grains showed a diameter from 15 to 105 µm, with an average of 46.03 µm. When comparing these two size distributions for nylon diameters and rubber particles with the sieve analysis for the clay, it is clear that almost all particles are very fine, with very sharp distributions below 100 µm, suggesting a very particular mixture of materials in the microscale.

**Figure 3.** Grain/fiber diameter size distribution, (**a**) shows the particle-size distribution for the kaolin soil used, (**b**) shows the polymer fibers diameter distributions, (**c**) shows the residual rubber grain size distribution.
