Navegando por Assunto "Recycled aggregate"

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Acesso aberto (Open Access)
Análise experimental da resistência à punção em lajes lisas com substituição de agregados graúdos naturais por reciclados de concreto
(Universidade Federal do Pará, 2022-05-12) RIBEIRO JUNIOR, Jayron Alves; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485; https://orcid.org/0000-0001-8905-9479
The popularization of the use of recycled concrete aggregates has increased due to socioeconomic aspects, but above all, as sustainability is being pursued and, in this context, some international standards have been published to facilitate and standardize the use of this material. Despite the constant evolution of studies on punching shear, there is a need for national and international regulatory adjustments in relation to the use of recycled concrete aggregates in flat reinforced concrete slabs. Two reasons explain the slight influence of the incorporation of recycled aggregates on the punching shear resistance of concrete slabs: lower mechanical strength and better bond between the cement paste and the recycled concrete aggregate due to the higher cement content, porosity, and roughness, when compared with natural aggregate. Thus, the punching shear strength is influenced by these properties of the aggregates along the shear plane of the cracks, the two effects offset each other, leading to a similar punching shear strength. This research carried out the experimental test of 6 flat slabs of reinforced concrete without shear reinforcement subjected to symmetrical loading, containing variations in the rate of flexural combat reinforcement (0.7% and 1.4%) and replacement rate of natural aggregate by recycled concrete aggregate (0%, 30% and 100%). The study evaluated the influence of these variables on the punching shear resistant capacity and analyzed the upper limits of resistance. The slabs were octagonal with 2500 mm of distance between parallel faces, sides of 1030 mm and thickness of 210 mm, molded with concrete with fck of 25 MPa and supported on columns of 300 mm of side. The standards used as a parameter for estimating resistant capacity were NBR 6118:2014, ACI 318:2019 and Eurocode 2:2004. The experimental results showed that the slabs with ARCO showed a maximum reduction of 6 % in the punching shear resistance when compared to the slabs with conventional coarse aggregates. The reinforcement rate was able to increase the cracking load at the service limit state (ELS) and the recycled concrete aggregate had little influence on the opening of cracks in the slabs with the highest rate of flexural reinforcement.
Acesso aberto (Open Access)
A influência dos agregados reciclados de resíduos da construção civil nas propriedades do concreto permeável: uma revisão sistemática
(Universidade Federal do Pará, 2023-01-27) OLIVEIRA, Thainá Maria da Costa; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
Sustainable development in the civil construction sector has been increasingly promoting the advancement of research on sustainable technologies in order to mitigate the problems caused by this sector. In view of the above, a sustainable measure that aims to reduce the consumption of natural resources and the irregular disposal of waste is the practice of reuse and/or recycling of RCC, and as a solution to flood control, the use of permeable concrete (CPER) is proposed. Due to the lack of standardization and divergence of the procedures determined for the characterization of the CPER with recycled aggregate, it became necessary to analyze the scientific knowledge of this material and demonstrate the feasibility of using RCC in the production of the CPER. In view of the above, this research aims to contribute to the knowledge about the use of recycled aggregates in the production of pervious concrete, through the selection of articles in databases from the last 15 years, in order to evaluate the properties acquired by materials with different types, sizes and contents of recycled aggregates. The present research used the Systematic Literature Review (RSL) as methodology for conducting the study. The articles were collected from the four most prestigious scientific bases for publications on themes related to civil construction. To screen the articles and prepare the RSL, the StArt tool was used, and data extraction from the studies was defined in the research protocol prepared. The results showed that the subject gained more relevance in the year 2016, the Science Direct database presented the highest number of articles, 80% of the works used coarse aggregates in the production of CPER, the percentages of substitution most used among the researches were 100% and 50%. Structural and mixed concrete waste were the most used as recycled aggregates in the production of CPER. It was possible to note great dispersion between the data collected in the surveys and the component materials of the CPER. Moreover, it was found that all types of aggregates met the strength and porosity values determined by the ACI and the permeability met both standards, except for the glass waste. Thus, the application of recycled aggregate in the production of CPER was evaluated as an adequate solution to the problems of irregular waste disposal and shortage of natural aggregates.