**2. Materials and Methods**

#### *2.1. Materials and Mixtures*

The sandy-clay soil used in the experiment was collected from a deposit located in Campos dos Goytacazes, Rio de Janeiro, Brazil, at a depth of 1.0 m on average, after removing the top-soil layer with a high percentage of organic matter. The samples were separated in plastic bags and kept hermetically sealed in order to maintain the humidity of the material. After collection, the soil was divided into different portions for homogeneity of the moisture of the samples. Then, the soil was crushed to reduce its volume, thus standardizing its granulometry. After this step, the soil was sieved, using a sieve with an aperture of 4.75 mm according to [35]. The distribution of the grain sizes of the collected soil samples and mixtures was performed by sieving, according to the procedures by [36]. The consistency limits (Atterberg) of the soil and mixtures were tested, determining the plastic properties of the samples according to [36,37]. Normal Proctor compaction tests were performed for soil and mixtures according to [38,39].

The PET waste used in this research presented particles of virgin material supplied by industries, with physical breakdowns and without contaminants as well as recycled PET treated post-consumer waste, i.e., mixed, with a uniform granulated aspect and white color. As a soil stabilizer, ordinary Portland cement type CPV-ARI was used, which has a high initial strength and is widely used in materials that require rapid hardening [16,27]. By considering that the bricks produced are molded, the use of this type of cement facilitates the transportation of the machine to the curing sites, avoiding its disintegration.

To perform the morphological analysis of the PET incorporated into the bricks, scanning electron microscopy (SEM) model FEG Quanta 250, belonging to the Laboratory of Electron Microscopy (LME) of the Military Institute of Engineering, Rio de Janeiro, Brazil (IME) was used. For this, the PET sample was coated with gold film and analyzed at

60 × magnification. To make the bricks, the mixture used was in the proportion of 1 part cement to 6 parts of soil (1:6). The bricks with 10% addition of PET in relation to the soil, 20% addition of PET in relation to the soil and 30% addition of PET in relation to the soil were analyzed in addition to the reference mixture, which was without any addition of waste (Table 1).

**Table 1.** Compositions (vol.%) of the soil-cement mixtures.


Before manufacturing, the materials used in each mixture were weighed with the aid of a digital scale. After weighing, the mixture (soil, waste and cement) was homogenized with the aid of a mechanical mixer. The addition of water was done with a sprayer in order to distribute the water in the mixture in a controlled and uniform way, thus avoiding the formation of lumps of soil concentrated by the excess of water. The amount of water used was calculated according to the optimum moisture found in the Normal Proctor compaction tests, as shown in studies by [27,33].
