Durability performance of concrete made with fine recycled concrete aggregates

Fine recycled aggregates are seen as the last choice in recycling for concrete production. Many references quote their detrimental influence on the most important characteristics of concrete: compressive and tensile strength; modulus of elasticity; water absorption; shrinkage: carbonation and chloride penetration. These two last characteristics are fundamental in terms of the long-term durability of reinforced or prestressed concrete. In the experimental research carried out at IST, part of which has already been published, different concrete mixes (with increasing rates of substitution of fine natural aggregates sand - with fine recycled aggregates from crushed concrete) were prepared and tested. The results were then compared with those for a reference concrete with exactly the same composition and grading curve, but with no recycled aggregates. This paper presents the main results of this research for water absorption by immersion and capillarity, chloride penetration (by means of the chloride migration coefficient), and carbonation resistance, drawing some conclusions on the feasibility of using this type of aggregate in structural concrete, while taking into account any ensuing obvious positive environmental impact

Environmental life cycle assessment of concrete made with fine recycled concrete aggregates

The majority of worldwide structures use concrete as its main material. This happens because concrete is economically feasible, due to its undemanding production technology and case Of use. However, it is widely recognized that concrete production has a strong environmental impact in the planet. Natural aggregates use is one of the most important problems of concrete production nowadays, since they are obtained from limited, and in some countries scarce, resources. In Portugal, although there are enough stone quarries to cover coarse aggregates needs for several more years, Supplies of fine aggregates are becoming scarcer, especially in the northern part of the country. On the other hand, as concrete structures' life cycle comes to an end, an urgent need emerges to establish technically and economically viable solutions for demolition debris, other than for use as road base and quarry fill. This paper presents a partial life cycle assessment (LCA) of concrete made with fine recycled concrete aggregates performed with EcoConcrete tool. EcoConcrete is a tailor-made, interactive, learning and communications tool promoted by the Joint Project Group (JPG) on the LCA of concrete, to qualify and quantify the overall environment impact of concrete products. It consists of an interactive Excel-spreadsheet in which several environmental inputs (material quantities, distances from origin to production Site, production processes) and outputs (material, energy, emissions to air, water, soil or waste) are collected in a life cycle inventory, and are then processed to determine the environmental impact (assessment) of the analysed concrete, in terms of ozone layer depletion, smog or "greenhouse" effect

Using graphene oxide as means of improvement of concrete: a brief review

Este trabalho foi financiado pelo Concurso Anual para Projetos de Investigação, Desenvolvimento, Inovação e Criação Artística (IDI&CA) 2018 do Instituto Politécnico de Lisboa. Código de referência IPL/2018/Nanomortar_ISELThe use of nanomaterials (NM) to improve the performance of cement and concrete matrixes nowadays appears as a potential alternative to the exclusive use of Portland cement (PC). Similarly, there is currently no doubt in the construction industry (CI) about the pressing need to reduce consumption of PC. The CI represents the world's third-largest industrial energy consumer, and the component related to the production of PC alone represents 7% of the carbon dioxide (CO2) emissions globally (OECD, 2018). PC is undoubtedly the most used material in construction in terms of its relative volume. Raw materials for PC production are generally plentiful and are available throughout the world. It is possible to state that there is, at this moment, no other material, with the same availability as the PC, that is able to fulfil the construction’s technical requirements as the concrete’s main component. In this sense, it is imperative that the cement industry obtains viable technical solutions that allow the reduction of PC consumption. That reduction can be achieved either by its direct replacement with another material (as for example with the use of fly ash), or by improving the cement and concrete matrix performance with the addition of new materials such as NM. This second option is quite interesting since it allows, for example, to maintain the cement and concrete matrix properties/characteristics, reducing PC consumption by adding a tiny amount of a NM.info:eu-repo/semantics/publishedVersio

The influence of curing conditions on the mechanical performance of concrete made with recycled concrete waste

Research on the use of Construction and Demolition Waste (CDW) as recycled aggregate (in particular crushed concrete) for the production of new concrete has by now established the feasibility of this environmentally-friendly use of otherwise harmful waste. However, contrary to conventional concrete (CC), no large applications of concrete made with recycled concrete have been made and there is still a lack of knowledge in some areas of production and performance of recycled aggregate concrete (RAC). One issue concerns curing conditions: these greatly affect the performance of concrete made on site and some potential users of RAC wonder how RAC is affected by far-from-ideal curing conditions. This paper shows the main results of experiments to determine the influence of different curing conditions on the mechanical performance of concrete made with coarse recycled aggregate from crushed concrete. The properties analyzed include compressive strength, splitting tensile strength, modulus of elasticity, and abrasion resistance. The general conclusion in terms of mechanical performance is that RAC is affected by curing conditions roughly in the same way as CC. (C) 2011 Elsevier Ltd. All rights reserved

Juca Kfouri - jornalista, advogado ou simplesmente torcedor: analise de discurso da coluna do jornal on-line lancenet

Analisa os textos que compõem a coluna do jornalista Juca Kfuri no jornal esportivo eletrônico Lancenet e que foram publicados entre os dias 10 de agosto e 30 de setembro de 2004. Observa a estrutura da coluna, tipo de discurso, interdiscurso, intertextos presentes na fala, marcas discursivas, propriedades discursivas, lugar de fala e personagens-paradigmas. Pode se perceber que a coluna esportiva goza de uma liberdade tanto no âmbito da opinião quanto no discurso adotado pelo jornalista. Além disso, percebe-se que o colunista realiza a função de gatekeeper ao eleger os personagensparadigmas. Utiliza-se metodologia baseada em pesquisa bibliográfica e análise de discurso

Physical-chemical and mineralogical characterization of fine aggregates from construction and demolition waste recycling plants

Construction and demolition waste (CDW) represents around 31% of all waste produced in the European Union. It is today acknowledged that the consumption of raw materials in the construction industry is a non-sustainable activity. It is thus necessary to reduce this consumption, and the volume of CDW dumped, by using this waste as a source of raw materials for the production of recycled aggregates. One potential use of these aggregates is their incorporation in reinforced concrete as a replacement of natural aggregates. A concrete that incorporates these aggregates and still performs well requires them to be fully characterized so that their behaviour within the concrete can be predicted. Coarse recycled aggregates have been studied quite thoroughly, because they are simpler to reintroduce in the market as a by-product, and so has the performance of concrete made with them. This paper describes the main results of research designed to characterize the physical and chemical properties of fine recycled aggregates for concrete production and their relationship with mineralogical composition and preprocessing. The constraints of the incorporation of fine aggregates in reinforced concrete are discussed. It is shown that, unless a developed processing diagram is used, this application is not feasible. (C) 2013 Elsevier Ltd. All rights reserved

Comportamento de betões com agregados finos reciclados

A presente comunicação tem como objetivo apresentar o trabalho experimental a desenvolver acerca do desempenho de betões com agregados finos provenientes da reciclagem de betão. Presentemente, os documentos normativos relativos à utilização de agregados reciclados em betões prevê a utilização da sua fração grossa, com diferentes taxas de incorporação, dependendo do fim a que o betão final se destina, mas apontam para a não inclusão da fração fina dos mesmos. Genericamente, apontam-se como principais problemas para a inclusão destes materiais a sua elevada porosidade, que conduz a uma estrutura do betão menos compacta, com consequentes reduções de desempenho. No entanto, alguns trabalhos anteriormente desenvolvidos apontam para que a inclusão da fração fina dos agregados reciclados possa não ser tão prejudicial como se julga, podendo ser um substituto eficaz dos agregados naturais, em especial se se tiver em atenção as condicionantes ambientais inerentes ao processo extrativo. O trabalho pretende obter mais informação sobre o desempenho de betões com agregados finos reciclados de betão, comparando-os com betões convencionais, executados exclusivamente com agregados naturais pétreos.info:eu-repo/semantics/publishedVersio

Liderazgo auténtico y compromiso organizacional en la municipalidad distrital de Huaura, 2021

Objetivo: Demostrar la relación entre el liderazgo auténtico con el compromiso organizacional en la Municipalidad Distrital de Huaura, 2021. Métodos: la población de estudio fueron 155 trabajadores de la entidad edil, seleccionados mediante una fórmula estadística para muestra. Considerándose como dimensiones el liderazgo auténtico y compromiso organizacional. Se usaron los instrumentos Authentic leadership questionnaire ALQ traducido al español, adaptado por María Elena Magallanes (2016) y el cuestionario para la percepción del compromiso organizacional de Meyer y Allen, adaptado por María Elena Magallanes (2016). Resultados: Los resultados muestran que el 66.0% de los trabajadores ediles reconocen el liderazgo del gerente municipal en sus dimensiones transparencia en las relaciones, moral interiorizada y el procesamiento balanceado, respecto al compromiso organizacional, los trabajadores señalan su compromiso afectivo (64.8%), de permanencia (60.8%) y el normativo (72.5%). Conclusión: Los resultados demuestran que existe relación positiva significativa entre el liderazgo auténtico y el compromiso organizaciona

Implementación de un sistema de costo basado en el tiempo invertido por actividad para mejorar la productividad en Fabricaciones CJL SAC

El objetivo general del presente estudio es mejorar la productividad de la empresa Fabricantes CJL SAC mediante la implementación de un sistema de costos basados en el tiempo invertido por actividad. Se demuestra que mediante el método de asignación de costos indirectos aplicando el tiempo como inductor único de la actividad. También se calculó los costos indirectos empleando un sistema de costeo ABC para compararlo con los resultados obtenidos del costeo basado en el tiempo invertido por actividad. Resultados obtenidos sobre la aplicación en la actividad de inspección de pieza de espuma del proceso productivo de asientos para buses. Las conclusiones obtenidas son: Diagnóstico del proceso de fabricación de espuma para asientos y sus respectivos tiempos estándares, diseño y aplicación de un sistema de costeo basado en el tiempo invertido por actividad con su capacidad de costo por minuto y tiempo de proceso en minutos es económico de obtener por su simple formulación, comparación con el sistema de costeo basado en la actividad, se consiguió una evaluación del método de costeo por actividad con el otro método de costeo basado en el tiempo invertido por actividad utilizando como indicador de desempeño la productividad resultando un 15% de incremento en el método propuesto

Comportamento em flexão de vigas de betão armado produzidas com agregados finos reciclados

Apesar de em Portugal existir legislação que permite, mesmo que a pequena escala, a utili-zação de agregados reciclados para a produção de betão, a prática mostra que são raros os casos em que esta solução é implementada, ao contrário de um vasto conjunto de países europeus. No entanto, em Portugal, a utilização da fracção fina dos agregados reciclados (AFR) é restringida ou mesmo proibida. Estudos mais recentes mostram, contudo, que a uti-lização de AFR é possível e que os desempenhos mecânicos obtidos são perfeitamente aceitáveis. Nesta comunicação, são apresentados os ensaios de flexão realizados em vigas de betão armado produzidas com substituição de agregados finos naturais por reciclados, comparando os resultados obtidos em termos de carga e deformação de ruptura, ductilidade, capacidade resistente e fendilhação com os resultados de vigas de referência, em betão convencional.info:eu-repo/semantics/publishedVersio