Maryangela Geimba de Lima

As indústrias siderúrgicas brasileiras geram, em média, 145 mil toneladas por mês de areia descartada de fundição (ADF) ou resíduos de areia de fundição (RAF), como um subproduto do processo de fundição, impactando meio ambiente, sociedade, as próprias siderurgias e aterros sanitários. Porém, por ser considerado um resíduo não perigoso e muito semelhante aos agregados minerais, seu reuso na construção civil se mostra como uma interessante alternativa, evitando os impactos do descarte, além de beneficiar financeiramente as infraestruturas construídas. Nesse contexto, este artigo objetivou a dedução de uma rota metodológica para contabilizar a economia gerada pelo reuso de ADF/RAF e estimar, em termos de economia financeira e de bens ambientais, os benefícios gerados no Brasil e no município de João Pessoa, estado da Paraíba, como um estudo de caso. Dessa forma, uma equação foi obtida, abrangendo diversos aspectos da cadeia de produção e descarte de ADF/RAF, estimando economias da ordem de 500 milhões de USD anuais, além de redução de emissões de CO2 equivalente ao consumo de mais de 10 mil veículos por ano, pelo reuso da ADF/RAF produzida no Brasil.

Industrial waste reusing, such as Waste Foundry Sand (WFS) is an alternative to reducing mineral aggregates use. This waste is similar to the aggregates; however, it is necessary to prove its technical viability. In this sense, computational models by Finite Element Methods (FEM) complement empirical results, simulating the behavior of this alternative pave. In this paper, a computational model was built using FEM, simulating the behavior of Hot Mix Asphalt (HMA) containing WFS as an aggregate in the Abaqus software environment. This model was validated by comparing response data with empirical results. And then, analyzed for its mechanical behavior and in two case studies. The results obtained were satisfactory when compared to empirical results. Confirming the applicability of FEM in road engineering, particularly in HMA containing WFS.

Steel reinforcement corrosion due to chloride penetration into concrete is one of the main causes of the degradation of marine structures and has been the subject of much research. Among the various factors that influence chloride penetration into concrete are environmental factors such as temperature and exposure conditions. In this context, the present study evaluated chloride penetration for three different exposure conditions (atmospheric, tidal variation and submerged) at temperatures of 15°C, 20°C, 25°C and 30°C over 18 months; samples were collected every 6 months, at depths of 1–5 mm. The environmental conditions were simulated in the laboratory. The results showed a higher concentration of chlorides in the submerged specimens. Moreover, the chloride concentration increased more intensively from 6 to 12 months and temperature was more influential above 20°C. The temperature effects were also found to be higher at advanced ages.

A indústria da construção civil vem apresentando esforços buscando alcançar os avanços tecnológicos necessários para garantir o constante aumento na qualidade das obras e, consequentemente, melhoria na sustentabilidade de seus produtos. Nesse sentido, a tecnologia Building Information Modeling se destaca como uma forma de permitir que diversas equipes e sistemas se comuniquem e utilizem de uma grande quantidade de informações para avaliar indicadores de desempenho importantes de uma edificação. Por outro lado, a Avaliação de Ciclo de Vida é outra ferramenta importante que pode ser utilizada na seleção de materiais, processos e produtos mais sustentáveis. Portanto, a recente busca pela integração dessas duas tecnologias aparece como uma alternativa viável para garantir que engenheiros, arquitetos e construtores tenham acesso a informações importantes durante qualquer fase no desenvolvimento do projeto e possam, assim, tomar decisões corretas, baseadas em dados providos por sistemas computacionais. Visando essa integração, o presente trabalho apresenta uma abordagem que permite a utilização de bancos de composições de custos para o levantamento de materiais e inventários de ciclo de vida de forma conjunta em ambientes BIM, facilitando a utilização de indicadores ambientais em conjunto com custos. A abordagem é então demonstrada em um estudo de caso de seleção de materiais, demonstrando que, quando comparamos blocos de concreto com blocos cerâmicos para sistemas de alvenarias de vedação, a segunda opção apresenta custos relativamente menores, apesar de ter um maior potencial de influenciar no aquecimento global.

RESUMO Neste artigo, resíduos de areias de fundição (RAFs) originários de: escavação em aterro sanitário industrial e diretamente de indústrias siderúrgicas automotivas foram testados como agregado em misturas asfálticas à quente. Estes RAFs, juntamente com o agregado miúdo convencional, foram caracterizados fisicamente obtendo no ensaio de: material pulverulento, teores inferiores a 13%; composição granulométrica, curvas de material passante em função da abertura das malhas equivalentes ao agregado miúdo (segundo a norma de agregados); densidade real, aparente e saturada muito próximas ao agregado mineral; micrografia óptica, imagens ampliadas (de 10 e 40 vezes obtidas em um Estereoscópio óptico) das frações representativas do maior e menor tamanhos de grãos, visualmente uniformes e semelhantes entre si. Em seguida, foram elaboradas formulações de misturas de agregados e RAFs contendo teores de substituição dos resíduos de: 0% (mistura Controle), 50 e 100% em relação ao pó de pedra e moldados corpos de prova cilíndricos pelo método giratório SUPERPAVE com cimento asfáltico do tipo CAP 30/45. Estes CPs foram testados no ensaio de tração por compressão diametral, obtendo valores de resistência a tração (RT) da ordem de: 2,0 MPa, para as misturas contendo 50% de RAF (das duas origens) e da ordem de 1,3 MPa nas misturas contendo 100% de RAF; e ensaio de módulo de resiliência obtendo valores médios da ordem de: 2500 a 6000 MPa. Concluiu-se que o RAF possui viabilidade técnica como agregado em pavimentos flexíveis.

Waste foundry sand (WFS) are industrial by-products from the foundry process which represent challenges for environmental departments with respect to the proper disposal in landfills due to their high production. The road infrastructure such as asphalt paving is a major consumer of mineral aggregates originating from the mining activity of exhaustible natural resources. Thus, the WFS reuse for the construction of roads is an alternative to discarding of waste and a reduction in the use of mineral aggregates. In this article hot mix bituminous (HMB) mixtures were produced containing WFS (by weight) substitution contents in relation to manufactured sand of 25%, 50%, 75% and 100% from two origins: industrial landfill and the steel industry; after mechanical and gyratory compaction, these cylindrical specimens were subjected to mechanical tests of splitting tensile strength and resilient modulus obtaining very similar performances as that of the control mixture (which did not contain WFS). These mechanical results as well as the microstructural characterisation of this HMB containing residue led to the conclusion that the reuse of WFS in the asphalt pavement is technically viable, creating an alternative to by-product disposal and reduction of the financial-environmental costs of highways.

In this study, representative samples of waste foundry sand (WFS) from an industrial landfill and steel industries were characterised according to mineral aggregate criteria; these same residues were also characterised microstructurally using optical microscopy (OM) and scanning electron microscopy (SEM). The results showed that the WFS have very similar physical characteristics compared to conventionally manufactured sand used in asphalt paving. These residues additionally showed similar petrographic characteristics and less risks of potential alkali-reactivity. The elemental composition revealed a predominance of silica (46–52%), ferrous oxides (3–30%) and carbonaceous materials (2–15%), i.e. elements that would not act as pathogenic agents to the pavement asphaltic matrix if the residues were incorporated into it as aggregates materials. Important benefits generated from this practice include cost reduction in asphalt paving projects, reduction in the use of mineral resources and in the discard of waste, increase in the lifespan of landfills and reduction of environmental contamination.

Adequate compacting is an important stage contributing for the durability and final quality of concrete structures. The two main ways of compacting concrete are: manual and mechanical (immersion vibrator). This paper has the goal of verifying the influence of those two compacting methods on the compressive strength of concrete from long term data. In order to do that, cylindrical test specimens of a same concrete were molded with different compacting methods and the compressive strength was investigated at 1, 3 , 7, 14, 21, 28, 63, 91, 180, 365 and 730 days. Concrete used was casted in plant. Manual compacting was performed using a metallic and cylindrical rod. Mechanical compacting was performed using a rigid immersion vibrator driven by an electric motor. This study confirmed greater compressive strength in test specimens compacted with immersion vibrator, when compared with results in manually compacted test specimens. However, the novelty of this article is that variance analysis test demonstrated that only from 63 days the difference between compressive strengths is significant. Long term data also made it possible to generate a trend equation with good coefficient of determination for estimating the difference between compressive strengths for the two compacting methods investigated over time.

This paper discusses the influence of different curing conditions on the compressive strength of concrete test specimens monitored for 365 days. Five cures were analyzed. Statistical tests were applied (variance analysis and Fisher's) in order to evaluate the data. According to results, different curing conditions influence the compressive strength of concrete. The main novelty of this article is that the curing conditions affect the concrete compressive strength significantly only for ages over 28 days. Furthermore, this study shows that concrete specimens saturated with water have superior strength to concrete cured in a standard environment (moist chamber). The compressive strength of concrete decreases, respectively, with the following types of curing investigated: water tank, moist chamber, tank with water and lime, laboratory internal environment and external environment. The compressive strength gain over time also varies for each condition. The lower values found for the external environment confirm the greater difficulty of controlling the water loss on this environment, resulting in decrease of compressive strength.

This paper studies the influence of the corrosion degree calculated by the mass loss and by the smaller diameters on the yield strength, ultimate strength and final elongation. Reinforcements buried and naturally corroded for 60 years were studied. The mechanical properties of the protruding reinforcing steel were compared to reference bars, which also remained buried for 60 years, but without going through the corrosion process. Micrographs, besides the chemical composition and the characterization of the aggressiveness of the soil were realized. The micrographs and the chemical composition show the presence of pits in the reinforcements and sulfur contents for steel above the prescriptions of the time when the foundations were initially implement, respectively. The results also show that the effects of pitting corrosion on the mechanical properties of the naturally corroded bars may not be adequately expressed by the mass loss. This type of corrosion (pits) produces geometric variations in the cross sections along the length of the test specimens, generating stress gradients between successive sections. This has a noticeable impact on the mechanical properties of the reinforcements. In general, the effects of corrosion are more pronounced on the ductility of the reinforcement. Regarding the aggressiveness of the soil, high corrosion rates were identified in the reinforcement, even with the soil being classified as essentially non-corrosive.