Concretos leves com agregados reciclados: propriedades físico-mecânicas e térmica
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Data
2021-09-01
Autores
Lucas, Cláudio Nelson Mateus
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O aproveitamento de resíduos de pedra basáltica como agregados para o concreto é relevante, pois diminui a extração de recursos naturais, por exemplo, areia natural. É embrionário o estudo de resíduos de pedra basáltica para produção de concretos leves, entretanto, é uma alternativa, pois a areia é produzida a partir do resíduo de rochas basálticas trituradas, chamada areia de britagem. A partir do exposto, a presente pesquisa estudou as propriedades físico-mecânicas e térmicas de concretos leves estruturais com argila expandida e substituição parcial da areia natural pela areia de britagem. Foram elaborados cinco traços diferentes de concretos leves estruturais. Para avaliação dos traços elaborou-se um programa experimental com caracterização dos materiais, produção dos concretos e realização de diversos ensaios, entre eles, análise das propriedades mecânicas de resistência à tração por compressão diametral, resistência à compressão axial e análise da condutividade térmica. Os valores de massa específica dos concretos produzidos, no estado endurecido, variaram entre 1.490 a 1.602 kg/m3 e são satisfatórios quando comparados com os valores estabelecidos pela ABNT NBR 15220-2:2008, entre 1.000 a 2.400 kg/m3 para concretos leves. Quanto a resistência à tração por compressão diametral observou-se valores acima de 2 MPa, aos 28 dias, valor mínimo estabelecido pela ABNT NBR 7222:2011, demonstrando que a influência da areia britagem incorporada nos traços apresentou-se eficiente. Os valores de resistência à compressão axial variaram entre 17 a 23 MPa, aos 28 dias, resultados superiores aos 17 MPa estabelecido pela NBR NM 35:1995. A avaliação da condutividade térmica foi por meio da placa quente, na qual se observou valores inferiores ao estabelecido pela ABNT NBR 15220-2:2008, demonstrando assim a qualidade deste concreto leve, que apresentou resposta de condutividade térmica entre 0,23 a 0,80 W/(m.k).
The use of basaltic stone residues as aggregates for concrete is relevant, as it reduces the extraction of natural resources, for example, natural sand. The study of basaltic stone residues for the production of light concrete is embryonic, however, it is an alternative, as the sand is produced from the residue of crushed basalt rocks, called crushing sand. From the above, this research studied the physical-mechanical and thermal properties of structural lightweight concretes with expanded clay and partial replacement of natural sand by crushing sand. Five different mixes of structural lightweight concretes were prepared. To evaluate the traits, an experimental program was elaborated with characterization of materials, production of concrete and performance of several tests, including analysis of mechanical properties of tensile strength by diametrical compression, axial compression strength and analysis of thermal conductivity. The specific mass values of the concrete produced, in the hardened state, ranged from 1.490 to 1.602 kg/m3 and are satisfactory when compared with the values established by ABNT NBR 15220-2:2008, between 1.000 to 2.400 kg/m3 for light concrete. As for the tensile strength by diametrical compression, values above 2 MPa were observed, at 28 days, the minimum value established by ABNT NBR 7222:2011, demonstrating that the influence of crushing sand incorporated in the mixes was efficient. The axial compressive strength values ranged from 17 to 23 MPa, at 28 days, results superior to the 17 MPa established by NBR NM 35:1995. The evaluation of thermal conductivity was carried out using the hot plate, in which values lower than those established by ABNT NBR 15220-2:2008 were observed, thus demonstrating the quality of this lightweight concrete, which presented a thermal conductivity response between 0,23 to 0,80 W/(mk).
The use of basaltic stone residues as aggregates for concrete is relevant, as it reduces the extraction of natural resources, for example, natural sand. The study of basaltic stone residues for the production of light concrete is embryonic, however, it is an alternative, as the sand is produced from the residue of crushed basalt rocks, called crushing sand. From the above, this research studied the physical-mechanical and thermal properties of structural lightweight concretes with expanded clay and partial replacement of natural sand by crushing sand. Five different mixes of structural lightweight concretes were prepared. To evaluate the traits, an experimental program was elaborated with characterization of materials, production of concrete and performance of several tests, including analysis of mechanical properties of tensile strength by diametrical compression, axial compression strength and analysis of thermal conductivity. The specific mass values of the concrete produced, in the hardened state, ranged from 1.490 to 1.602 kg/m3 and are satisfactory when compared with the values established by ABNT NBR 15220-2:2008, between 1.000 to 2.400 kg/m3 for light concrete. As for the tensile strength by diametrical compression, values above 2 MPa were observed, at 28 days, the minimum value established by ABNT NBR 7222:2011, demonstrating that the influence of crushing sand incorporated in the mixes was efficient. The axial compressive strength values ranged from 17 to 23 MPa, at 28 days, results superior to the 17 MPa established by NBR NM 35:1995. The evaluation of thermal conductivity was carried out using the hot plate, in which values lower than those established by ABNT NBR 15220-2:2008 were observed, thus demonstrating the quality of this lightweight concrete, which presented a thermal conductivity response between 0,23 to 0,80 W/(mk).
Descrição
Palavras-chave
Concreto leve, Argila expandida, Condutividade térmica, Areia de britagem, Lightweight concrete, Expanded clay, Thermal conductivity, Crushed sand