Flexible films of a conductive polymer nanocomposite-based castor oil polyurethane (PUR), filled with different concentrations of carbon black (CB) nanoparticles or multiwall carbon nanotubes (MWCNTs), were obtained by a casting method. The piezoresistive, electrical, and dielectric properties of the PUR/MWCNT and PUR/CB composites were compared. The dc electrical conductivity of both PUR/MWCNT and PUR/CB nanocomposites exhibited strong dependences on the concentration of conducting nanofillers. Their percolation thresholds were 1.56 and 1.5 mass%, respectively. Above the threshold percolation level, the electrical conductivity value increased from 1.65 × 10⁻¹² for the matrix PUR to 2.3 × 10⁻³ and 1.24 × 10⁻⁵ S/m for PUR/MWCNT and PUR/CB samples, respectively. Due to the better CB dispersion in the PUR matrix, the PUR/CB nanocomposite exhibited a lower percolation threshold value, corroborated by scanning electron microscopy images. The real part of the alternating conductivity of the nanocomposites was in accordance with Jonscher’s law, indicating that conduction occurred by hopping between states in the conducting nanofillers. The piezoresistive properties were investigated under tensile cycles. The nanocomposites exhibited piezoresistive responses and, thus, could be used as piezoresistive sensors.

Currently, cement manufacturing accounts for approximately 8% of global carbon emissions, and the continuously increasing demand driven by population growth makes it impossible to halt production. At the same time, nature offers abundant renewable resources that can be reused to mitigate this environmental challenge. This study presents a systematic review of experimental investigations evaluating the partial replacement of Portland cement with biochar in mortar production. The review compiles and analyzes the tests and findings reported by several authors, focusing on key parameters such as aggregate granulometry, feedstock type used for biochar production, replacement ratios, water absorption, compressive and tensile strength, permeability, and microstructural behavior assessed through X-ray diffraction (XRD) and thermogravimetric and analysis (TGA). The results were compared with the limits established by current construction standards, emphasizing the types of biochar that demonstrated the most favorable performance in mechanical and durability properties.

Boilers are widely used by industries and thermoelectric plants to generate renewable energy. However, when biomass is consumed, residues are generated, which for the most part cannot be discarded appropriately. This study investigated the reuse of eucalyptus wood waste with the goal of transforming the residue into resistant and durable briquettes for reuse in furnaces and boilers. The physico-chemical properties of the residue were studied in terms of chemical composition by X-ray fluorescence, and its crystalline structure was evaluated by X-ray diffraction. Both thermogravimetric analysis and differential thermogravimetric analysis were used to characterize the thermal decomposition of the wood waste residue. The residue was compacted in a universal press with sufficient humidity to fabricate briquettes under different conditions of mechanical pressure. Apparent density, durability, and burning tests were carried out on the briquettes. The maximum temperature reached during burning is dependent on the fabrication compaction pressure. The briquettes proved suitable for burning in boilers and furnaces, and their durability is advantageous for handling, reuse, and transportation.

Incorrect tire disposal has a major impact on the environment, making it necessary to search for technologies. Thus, this study evaluated the effect of adding silica fume on the mechanical, microstructural and thermal properties of lightweight concrete using waste tire rubber (RB) for the production of lightweight cementitious composite compared to the cementitious composite with expanded polystyrene (EPS). A reduction in density was observed in 9% of the samples with 10% replacement of the cement with silica. The results showed low compressive strength to be applied as a structural material, however the value proved to be effective for several other functions, a gain in tensile strength was observed compared to the composite with EPS, the RB showed a better tenacity. The microstructure analysis revealed regions that do not produce good contact between the different phases present. Rubber concrete showed greater impermeability with the addition of silica fume, indicating greater resistance to chemical attacks. Thus, the results showed that large percentages of rubber in the cementitious composite can bring benefits even if there is a certain reduction in mechanical properties.

Este artigo apresenta a verificação da influência da variação da temperatura e do tempo de tratamento térmico nas propriedades mecânicas do bambu maciço (Dendrocalamus strictus) e da ação de insetos na sua durabilidade. Os corpos de prova foram submetidos a temperaturas de 160 ºC, 180 ºC e 200 ºC, durante 1 hora, 1h30 horas e 2 horas, em uma estufa convencional. Posteriormente foram determinadas as resistências mecânicas à tração e em compressão e o teor de umidade das amostras. O teste de ataques biológicos do bambu foi realizado por meio da exposição das amostras ao caruncho do bambu (Dinoderus minutus) por 21 dias. Foram estudados os efeitos do tratamento térmico em 3 faixas de temperatura e 3 durações de exposição, obtendo-se, em média, tensões de ruptura à compressão e de tração paralela as fibras, iguais a 68,83 MPa e de 123,53, respectivamente. Os dados obtidos demostraram que as faixas de temperatura e duração adotadas nesta pesquisa, não alteraram os resultados das propriedades mecânicas e nos testes de ataques biológicos foi constatado que o tratamento térmico reduziu a deterioração das amostras, prolongando sua durabilidade.

With the increase in floods in urban areas, the use of permeable pavement has become increasingly advantageous. In this context, the objective of this study was to evaluate the influence of the addition of concrete floor polishing waste (CFPW) on the physical, mechanical, and microstructural behavior of permeable concrete. Three different mixtures were evaluated: a reference sample determined based on the literature review and dosed with natural aggregates and two other samples with the addition of 2% CFPW and 4% CFPW, respectively, in relation to cement mass. When comparing the dosages of 2% CFPW and 4% CFPW to the reference sample, there was an increase in the average compressive strength of 57.45% and 33.78% for three days of curing, and 45.41% and 37.20% for seven days of curing. Furthermore, the flexural strength of 2% and 4% CFPW samples exhibited a superior performance of 55.70% and 58.75%, respectively, compared to the control after three days. At 28 days of age, the 4% CFPW composition showcased a 16.3% increase relative to the control and an 11% improvement compared to the 2% CFPW composition. For the permeability tests, no significant variations were observed. For the 2% CFPW and 4% CFPW samples, respectively, a reduction in the void ratio was observed to 25.08% and 12.44%. A good correlation between compressive and flexural strengths was determined.