EVALUATION OF THE TECHNOLOGICAL PROPERTIES OF ARTIFICIAL AGGLOMERATED STONES IN EPOXY RESIN AND CASTOR OIL-BASED VEGETABLE POLYURETHANE MATRIX

Objective: The aim of this study was to produce and evaluate the technological properties of artificial agglomerated stone slabs produced using the waste from the stone commercially known as "Preto São Gabriel," using epoxy resin and castor oil-based polyurethane. Theoretical framework: Ornamental stones are widely used in the construction sector and are of great economic importance to the country. During the production stages, a significant amount of waste is generated. The production process generates a substantial amount of waste from the extraction and processing processes that have no economic value, accounting for approximately 40 to 60% of the production during mining, and during the cutting stage, about 30 to 35% is generated. Method: To manufacture the artificial stone slabs, the waste was crushed in a jaw crusher and ceramic plate mill and screened into three particle size ranges. The slabs were produced using the vacuum vibro-compression method. Technological characterization tests were conducted, including bulk density, apparent porosity, water absorption, and three-point strength tests. Results and conclusions: It is concluded that slabs produced with both resins can be applied in locations requiring good flexural strength. For use in areas with water presence, those produced with epoxy resin are recommended, as they exhibited lower porosity and water absorption. Research implications: Utilizing waste from ornamental stones, which amounts to millions of tons and is disposed of in landfills or storage facilities, to manufacture agglomerated stones represents a significant contribution to environmental impact reduction, aligning with the principles of ESG (Environmental, Social, and Corporate Governance). Originality/value: The evaluation of the technological properties of artificial agglomerated stones produced from ornamental stone waste is of fundamental importance for the correct and safe application of these sustainable materials in civil construction.


INTRODUCTION
Brazil is a large producer of natural stones, according to the Federation of Industries of the State of Espírito Santo (FINDES, 2023), Brazil occupies the fourth position in the world, behind only China, India and Turkey.During the first half of 2023, Brazilian exports in this sector reached revenues of approximately US$549.0 million, corresponding to a physical volume of around 915.3 thousand tons (ABIROCHAS, 2023).In addition to natural stones, there is also an increase in the import of artificial stones for the national market.
The production of ornamental stones from extraction to the final product generates a large amount of fine and coarse waste that is sent to landfills.To minimize this impact, companies incur expenses when sending this waste to licensed landfills, as required by Law 12,305, of 2010.This represents a cost that could be avoided, in addition to taking up space that could be used for other purposes.
The objective of this work is the production of artificial agglomerated stones with waste of natural stones, generated during the extraction and unfolding of the stone on a multi-wire diamond loom, from the stone known commercially as Preto São Gabriel with castor oil vegetable polyurethane resin and epoxy resin.In this study, the following technological properties will be evaluated: 3-point flexural strength, apparent porosity, apparent density and water absorption.

THEORETICAL FRAMEWORK
Ornamental stone is defined as "natural stone material, subjected to different degrees or types of processing or refinement (raw, dressed, peaked, flamed, carved or polished), used to perform an aesthetic function", according to ABNT NBR 15012 (2013).Natural stone material, subjected to different degrees or types of processing, is used to perform an aesthetic function, being used to finish surfaces, especially floors, walls and facades.
In the manufacture of sheets of these materials for sale, from extraction to the polishing and cutting phases, significant waste is generated.These wastes represent a considerable proportion, ranging from around 40% to 60% of total production.In the specific cutting stage, waste generation is around 30% to 35% (GOMES et al., 2019).Per year, ornamental stone mining in Brazil generates around 240,000 tons of waste (SANTOS, 2016).
In this way, part of this material becomes waste, which, as it does not have economic value for the market, often does not receive proper disposal.As a result, this waste is deposited in landfills, taking up space, causing various environmental impacts.Currently, many studies are focused on more sustainable actions, supported by precepts such as the circular economy, which brings the concept of production that makes the most of possible resources before discarding them (GOROKHOVA et al., 2023, ALBORNOZ et al., 2023).
Several studies are carried out to transform this waste into raw materials, mainly in construction.Therefore, we seek to use these wastes in materials that can neutralize them and give them an environmentally correct purpose, demonstrating that their use does not present environmental risks.Studies are carried out to incorporate these materials into red ceramics, mortar, concrete, glass, cement matrix artifacts, agglomerated stones, among others (SANT'ANA et al., 2019, DELUNARDI, 2019, GOMES et al., 2020, SENA et al., 2020, MOFATI et al., 2021, LIMA et al., 2021, GADIOLI et al., 2022, AGUIAR et al., 2022, VALE JÚNIOR, 2022, AMORIM et al., 2022, GADIOLI et al., 2023).
One of the viable and sustainable alternatives is the production of artificial agglomerated stones from these stone wastes, proving to be an effective strategy to minimize environmental impacts and offer an economically advantageous and sustainable solution.In this way, artificial agglomerated stones have advantages in reducing the amount of waste discarded in nature, transforming an undesirable material into a source of added value.
According to standard EN 14618 (ASSOCIACIÓN ESPANÕLA DE NORMALIZACIÓN Y CERTIFICACIÓN, 2011), agglomerated stone is defined as a product manufactured through an industrial process that involves the combination of aggregates, generally quartz with a variety of particle sizes, additives and binding agents, the which may consist of resin, hydraulic cement or a combination of both.Agglomerated stone can also be called artificial stone, artificial stone, manufactured stone or composite stone.
In the period 2011 to 2020, Brazilian imports of artificial agglomerated stones grew by more than 120%.(ABIROCHAS, 2021).Artificial agglomerated stones are increasing their market growth and are of great importance in reducing environmental impact, making it increasingly important to evaluate their physical properties in order to improve the quality of the final product (ALMEIDA et al., 2022).

MATERIALS AND METHODS
In this research, waste from the processing of ornamental stone, commercially known as "Preto São Gabriel" (Figure 1) was used, consisting of 50% Plagioclase; 15% Biotite; 10% Clinopyroxene; 10% Orthopyroxene; 5% Quartz, 5% Orthoclase and 5% Opaque Minerals.These materials were extracted in the city of Colatina, Espírito Santo, and processed in Cachoeiro de Itapemirim in the state of Espírito Santo by the company MARBRASA.To make the artificial stone slabs, vegetable polyurethane resin from castor oil and epoxy resin were used.Castor oil do not have a composition of volatile minerals (solvents), they are biodegradable (FERNANDES et al., 2020).Epoxy resin is used to preserve works and the construction materials used, which is applied in some stages of the ornamental stone process, which suggests preserving it from anthropogenic actions (VIDAL et al., 2014).Initially, the wastes were crushed in the jaw crusher and in the ceramic plate mill and then sieved into coarse and medium particle sizes (Figure 2).The fine wastes were obtained from the cutting process in the quarry known as fines from the processing of ornamental stones (FIBRO).These wastes were dried in an oven at a temperature of 100º C and then passed through a porcelain mortar and pestle (Figure 3), for better particle separation.6 These wastes were classified into three ranges particle size: large, medium and fine (Table 1), for its use in the production of artificial agglomerated stone slab.The Preto São Gabriel artificial stone slabs were made at CETEM -Mineral Technology Center in the Regional Center of Espírito Santo.The amount of each waste used is presented in Table 2. To make the artificial stone slabs, 90% waste and 10% resin were used, that is, 110 g of mixture (resin + catalyst).The amount of vegetable polyurethane resin (PUV) was 50 g and 60 g catalyst.The amount of epoxy resin was 73.33 g of resin and 36.67 g of catalyst.Figure 4 represents this weighing of the epoxy resin.7 To make the artificial stone slabs, the waste was mixed in a mixer together with the resin until a mass was formed and placed in a mold measuring 200x200x100mm, covered with Vaseline and baking paper to facilitate the demolding process (Figure 5).The mold with the dough was subjected to a hydraulic press (Figure 6) heated to a temperature of 90ºC and a compaction pressure of 3.67 MPa.This system is connected to a 600 mmHg vacuum system and 60 Hz vibration.To make the slabs with castor resin, the slabs remained in the press for 40 minutes and with the epoxy resin for 20 minutes.8 The slabs were removed from the mold and went through a post-curing process.The slabs produced with vegetable polyurethane resin were stored in an oven at 60ºC for 72 hours and 24 hours at 80ºC.The boards produced with epoxy resin were cured at room temperature for 7 days.After this process, the boards were sanded on a manual sander with sandpaper with grain sizes of 50, 100 and 200 mesh and cut to the appropriate dimensions for technological characterization tests.
To carry out the apparent density, apparent porosity and water absorption tests, the UNE-EN 14617-1 (2013) standard was used.6 specimens of each material were used with dimensions 100 x 100 x 10 mm (Figure 7).

RESULTS AND DISCUSSION
Figure 9 shows the artificial stone slab, using waste from the material commercially known as Preto São Gabriel and with 10% epoxy resin (RAEP-10%).Figure 10 shows the artificial stone slab, using waste from the material commercially known as Preto São Gabriel and with 10% castor oil polyurethane resin (RAM-10%).

Physical Indices
Table 3 shows the results of the apparent density, apparent porosity and water absorption tests.The density found by the stone produced with vegetable polyurethane resin is lower than that of epoxy resin according to the results in Table 3.Studies carried out on artificial stones by Lee et al. (2008), indicated values of 2.03 to 2.45 g/cm³ for density, varying compaction pressure, vibration and vacuum pressure.The density found for both stones in this study is within the values found by the author.RAPV stone is a lighter material compared to RAE, thus reducing transportation costs and ease of handling.
A coating with low absorption according to Chiodi Filho and Rodriguez ( 2020) should have values between 0.1 -0.4% and medium absorption between 0.4 -1.0%.The water absorption results show that RAE (0.32%) had low water absorption and RAPV (0.89%) had medium water absorption.
The apparent porosity of the RAE was 0.78% and the RAPV was 2.00 %.According to Chiodi Filho and Rodriguez (2020), coating materials between 0.5 -1.0% have low porosity and between 1.0 -3.0 medium porosity.These values indicate that RAE has low porosity and RAPV has medium porosity.

Flexural strength test by three-point
Table 4 shows the 3-point strength test, which determines the maximum rupture stress of the stone subjected to bending efforts.The ABNT NBR 15844 (2015) standard establishes that a stone to be used in environments that may undergo bending (such as kitchen countertops), performing the 3-point strength test, must reach at least 10 MPa.In this way, both materials can be used in these environments, as both obtained results above 10 MPa, that is, twice the value stipulated by the standard.The epoxy resin showed greater resistance due to a lower concentration of pores in its structure, as proven by the apparent porosity result.

CONCLUSION
With this study it was possible to conclude that RAPV stone (2.24 g/cm 3 ) is a lighter material compared to RAE (2.44 g/cm 3 ) thus facilitating handling during civil construction and a decrease in calculation of material freight.
The water absorption results show that RAE (0.31%) had low water absorption and RAPV (0.89%) had medium water absorption.Regarding porosity, the values indicate that RAE (0.78%) has low porosity and RAPV (2.0%) has medium porosity.These results indicate that the stone produced with epoxy resin would be more suitable for use in humid environments, thus avoiding future pathologies by stains.
In relation to flexion, the results were satisfactory for both materials, considering that these stones obtained twice the resistance compared to that required by the ABNT NBR 15844/2015 standard.RAPV is considered a stone of high strength (20.6 MPa) and RAEP (23.79 MPa) of very high strength.These results corroborate the low porosity obtained by RAPV and explained by the greater degree of cross-linking and crystallinity of the epoxy resin in relation to castor oil vegetable polyurethane.These stones can be safely applied to benches and in civil construction, where bending efforts are required.
Given the results presented, it is possible to conclude that it was technically feasible to produce eco-efficient materials with ornamental stone waste and apply them in civil construction, thus contributing to an adequate disposal of waste that would be discarded in the environment.

Figure 3 .
Figure 3. Waste in Grall It is Pistil Source: Prepared by the authors (2023).
The flexural strength test by three-point loading was carried out in accordance with the UNE-EN 14617-2 (2008) standard.The equipment used was the EMIC model DL10000 universal testing machine (Figure8).Six specimens were used in dry condition with dimensions 200 x 50 x 10 mm.

Table 2 .
Sieve particle sizes and their percentages used.

Table 3 .
Physical indices of artificial stone

Table 4 .
Flexural strength test by three-point