Navegando por Assunto "Cement composites"

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Acesso aberto (Open Access)
Compósitos cimentícios reforçados com fibras do epicarpo do coco babaçu para aplicação em placas cimentícias.
(Universidade Federal do Pará, 2022-08-25) ARAÚJO, Myrela Vieira de; SANTANA, Audirene Amorim; http://lattes.cnpq.br/7431678688628387; PICANÇO, Marcelo de Souza; http://lattes.cnpq.br/4535052395600357
The search for new materials for civil construction based on renewable sources has contributed to sustainable development. Lignocellulosic fibers are possibilities for strengthening cementitious mortars, since they are low cost, easy to reach, and renewable, unlike artificial fibers. However, when added to the cement matrix, they reach low durability and undergo degradation. Thus, the present research aimed to analyze the physical, mechanical, morphological and mineralogical properties of cement composites reinforced with fibers from the epicarp of the babassu coconut of the species Attalea Speciosa Mart. Ex Spreng in 0natura and impregnated in silica fume paste. The composites trace was established through a pilot study, using the trace 1:3:0.62 and addition of 1% of fibers with length ≤ 25 mm. Three families of mortar were molded, the first without the addition of fibers (REF), the second with the addition of in natura fibers (AFST) and the third with the addition of treated fibers (AFCT). The babassu coconut epicarp fibers had a specific mass of 1.398 g/cm³, a moisture content of 6.93% and an average tensile strength of 141.9 MPa. After 28 days of wet curing, the properties of the composites were analyzed, reaching an increase of 46.68% for theflexural tensile strength after the addition of in natura fibers and for composites with treated fibers a decrease of 14.16%. For the apparent density, both AFST and AFCT conditions, there was a decrease in the property and in the water absorption, there was an increase of 8.20% and 11.49%, respectively. In the permeability test, there was no formation of droplets in all samples and the thermometry analysis showed fiber compatibility with the cement. Through the micrographs of the mortars, it was observed in the AFST samples the presence of waxes that offer protection against water penetration, while in the AFCT samples there was a loss of waxes. From the diffractograms, it was verified that the impregnation of the fibers in silica paste caused the loss of calcite and portlandite, producing samples with greater porosity. Thus, the addition of fibers in natura provided improvements in the properties of the composites, but the treatment in silica fume paste caused a decrease in properties, not being suitable for use.
Acesso aberto (Open Access)
Influência do uso de resíduos industriais nas propriedades mecânicas e reológicas de argamassas utilizadas na indústria da construção civil
(Universidade Federal do Pará, 2019-03-21) CARDOSO, Dilson Nazareno Pereira; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/1711061955509303
The general objective of this work was to develop alternative and usable materials within the construction industry, addressing a logic of recovery and reuse of solid waste, generated from construction and demolition construction sites, as well as the reuse of waste generated from the construction industry mining industry and mineral processing. Were used in the work the residue of construction (RCC), residue of sulfide copper ore (RMCS) and the waste of circulating fluidized bed boilers from the combustion of coal to fly ash (CV). The samples of these materials showed appropriate characteristics, such as recycled fine aggregate within the NBR 7211 standard. The materials were subjected to physical and chemical characterization through laser particle size analysis, x-ray fluorescence (FRX), diffraction and x-ray (DRX).). The mortars produced were studied in the free state, that is, without additives and also within the insertion of polymeric organic additive polyvinyl acetate (PVA) and Styrene Butadiene (SBR). The obtained mortars were physically characterized through the analysis of apparent porosity, water absorption, apparent specific mass and resistance to axial compression. Thermal analyzes of (TG and DTG) and scanning electron microscopy - SEM were also performed. In the fluid state rheological tests were performed to evaluate its behavior according to time (thixotropy), workability and the most representative rheological model for its flow. The developed materials presented technical properties approved by the ABNT standards, making them suitable for certain types of applications, in terms of laying and covering of walls, floors and ceramic tiles, respecting the technical characteristics of these materials.