*3.2. Physical Indices*

Table 2 presents the physical indices (apparent density, water absorption, and apparent porosity) results found after testing 18 specimens of both ENS-15 and ENS-20.


**Table 2.** Physical properties of apparent density, water absorption, and apparent porosity of ENS-15 and ENS-20.

As can be seen in Table 2, by modifying the amount of resin, a difference in the physical indices was observed. ENS-20 had density values lower than ENS-15, which is due to the fact that the resin content increased, hence a decrease in the amount of waste. The rise in water absorption and porosity values observed in ENS-20 is explained by the resin binding action that brings the particles together. More resin means fewer waste particles in the mixture, forming more empty spaces, called voids, increasing both apparent porosity and water absorption.

Lee et al. [14] developed engineered stone based on glass and granite wastes under different conditions of pressure, temperature, and vacuum. In their work, the results ranged between 2.03 and 2.45 g/cm<sup>3</sup> for density and from 0.01 to 0.20% for water absorption. By observing Table 2, one can notice that the density and water absorption values found for both ENS-15 and ENS-20RAVQ 20% are within the range found by Lee et al.

A commercial stone named Stellar™, also produced by EcologicStone, the same company that supplied the quartz dust for this work, was characterized in the work of Carvalho et al. [15], presenting 2.38 g/m<sup>3</sup> density, 0.18% water absorption, and 0.44% apparent porosity. Both ENS-15 and ENS-20 are relatively lower than the commercial stone, with similar porosity and water absorption, indicating that the produced rock can be an alternative to replace the commercial Stellar™ stone, not only reusing the wastes but also with structure and logistic savings because of the lower density.

According to Chiodi and Rodrigues [30], lining or facing civil construction materials classified as high quality must have porosity below 0.5%. As can be seen in Table 2, the porosity values found for both ENS-15 and ENS-20 are below this value, evidencing the high quality of both engineered stones produced for coating applications.

As ENS-15 showed better physical indices, it was chosen to be tested for its mechanical and thermal properties.
