RESUMO Devido ao alto consumo de areia de rio na construção civil e sua extração abusiva, cujos resultados são a geração de diversos impactos ambientais, este estudo analisa a influência da utilização de areia de praia em substituição à areia proveniente de leito de rio na produção de argamassas de revestimento. A partir da areia de rio, foram confeccionadas outras duas variações: a primeira possuía 70% de fração fina (partículas <1,18 mm) e 30% de fração média (partículas <2,36 mm); e a segunda, 60% de fração fina e 40% de fração média. Foram utilizados cimento Portland (CP II-Z) e cal hidratada (tipo CHI) como aglutinantes em proporção constante (em massa) de 1:3 (aglomerante/agregado), com variações de 1:1:6 e 1:2:9 (cimento, cal e agregado). O programa experimental consistiu na análise dos agregados (por meio da granulometria e da massa unitária) e das argamassas no estado fresco e endurecido. No estado fresco foi determinada a relação entre o consumo de água e a consistência e a densidade de massa aparente. No estado endurecido determinou-se o coeficiente de capilaridade, a taxa de variação de massa e a resistência mecânica à compressão e à tração. Os resultados indicaram que a areia de praia e a de rio apresentam comportamentos físicos semelhantes, embora a primeira possua distribuição granulométrica mais uniforme e maior quantidade de finos, refletindo diretamente no desempenho das argamassas.

It is well known that the thermal behaviour of moulds used for thermoplastics processing has an important effect on both the part quality and the process productivity. The present work reports a study on the evaluation of the relative effect of different geometric and operational parameters on the thermal behaviour of injection moulds. It uses a mathematical model developed to simulate the thermal transient exchanged during the entire moulding cycle. The model is based on a 2D Fourier equation, uses an adaptive grid and describes the thermal contact resistance at mould/polymer interface. The cooling time and the interface temperature distribution are calculated from the computed temperature field in the domain under study. Experimental data, obtained with an instrumented tool during typical production conditions, is used to validate the developed model. The evaluation analysis is based on the Taguchi methodology used to rank the relative effect of the parameters on the selected variables (cooling time, temperature distribution and number of cycles to reach the thermal steady state).

Global temperatures have led to an increasing need for air conditioning systems. So, because of this fact, buildings have been improved in terms of their thermal and energy efficiency. Regarding this, the Brazilian standard ABNT NBR 15.575-4/2013 set minimum parameters for the thermal transmittance and thermal capacity of sealing elements, which allow classifying the thermal efficiency of the building. In order to comply with the requirements, the usage and study of lightweight construction materials have been in focus. An example of these materials is vermiculite. The present research reviewed articles about expanded vermiculite. The study involved the examination and comparison of various articles to analyze the properties of vermiculite and the impact of its usage on coating mortars. It was possible to verify that using vermiculite in mortars caused bad workability and a decrease in mechanical strength. However, the porosity and water absorption in mortars increased. Additionally, it reduced the specific weight and the thermal conductivity of the mortars, allowing for a better thermal insulation of the rooms. As an alternative to decreasing the negative effects of vermiculite, it is possible to use chemical admixtures, mineral additions, and mix design with a greater consumption of binder or a combination of particle sizes.