Recycling

This study aimed to evaluate the technical and environmental feasibility of producing concrete paver blocks and pervious concrete paver blocks by incorporating marble waste to evaluate its filler effect within the cementitious matrix. The methodology included the characterization of marble waste, the production of test specimens with the control (0%), 10%, 20%, and 30% of cement replacement, and the execution of performance tests, supplemented by statistical analyses. The results indicated that marble waste replacement significantly impacted the properties. In terms of pervious concrete paver block permeability, the highest rates were observed in the control and 30% treatments. For water absorption, concrete paver blocks showed higher values at a maximum of 20%, while pervious concrete paver blocks maintained statistically analogous values for 10% and 20%. Regarding compressive strength, the concrete paver block formulation with 10% marble waste was statistically compatible with the control. It is concluded that the incorporation of marble waste into concrete and pervious concrete paver blocks is environmentally advantageous as it valorizes an industrial waste. However, mix design optimization is essential, given that excessive replacement (above 10%) resulted in a reduction in compressive strength.

Mechanochemical regeneration aims to selectively cleave the crosslinked network of vulcanized rubber. In this study, a tire-grade styrene–butadiene rubber (SBR) compound was vulcanized and then subjected to mechanochemical regeneration using a zinc (II) dithiocarbamate complex (ZNIBU) at 6, 8, and 10 phr. The regenerated materials were subsequently revulcanized, and their properties were assessed before and after both processing steps. The regenerated (non-revulcanized) samples exhibited reduced crosslink density and increased swelling, indicating effective network cleavage by the regenerator. After revulcanization, the compounds presented higher hardness (23%) but lower tensile strength (75%) and tear strength (25%) compared to the virgin vulcanizate. Overall, ZNIBU proved highly effective for the mechanochemical regeneration of SBR, with optimum performance observed at 8 phr.

This study investigated the chemical recycling of poly(ethylene terephthalate) (PET) fiber residues from two sources—high-molar mass mooring ropes and low-molar mass textile-grade fibers—to produce functional oligomers. Glycolysis was carried out using polyethylene glycol (PEG400) as the depolymerizing agent, and two catalysts were assessed, zinc acetate and lithium octoate, with the latter reported on for the first time in this application. Reactions were performed for 180 min under mechanical stirring, inert atmosphere, reflux, and controlled heating. The resulting oligomers were characterized by Fourier-transform infrared spectroscopy (FTIR), hydroxyl and acidity indices, and thermogravimetric analysis (TGA). Both PET feedstocks showed high reactivity toward glycolysis. Monitoring the reactions by acidity index indicated that conversion reached equilibrium at approximately 120 min. ATR-FTIR confirmed the formation of ester and hydroxyl groups, consistent with oligomer structures. Glycolysis of PET derived from mooring ropes produced oligoesters with hydroxyl values of 228 and 242 mgKOH/g for zinc acetate and lithium octoate, respectively, and molar masses of 1296 and 1338 g/mol for zinc acetate and lithium octoate, respectively. These values are suitable for subsequent syntheses such as polyester polyol production.