Featured Application: The use of construction and demolition waste (CDW) in the development of building materials has been done constantly. The CDW from Passo Fundo region of Rio Grande do Sul/Brazil can be used in development of foamed concrete fully replacing the natural sand. Abstract:The main objective of this study was to evaluate the use of construction and demolition waste (CDW) from the Passo Fundo region of Rio Grande do Sul (RS), Brazil, in the development of aerated foamed concrete. This waste had not yet been characterized or even reused. CDW was processed (sieved only), characterized, and used as an aggregate, completely substituting natural sand. The influence of CDW granulometry and the amount of foam upon compressive strength, wet and dry bulk density, water absorption, and the air voids of concrete blocks were determined. Results showed that CDW has regular characteristics for the development of aerated foamed concrete. Compressive strength and density decreased as the amount of foam increased, while water absorption and air voids also increased. Also, CDW that was classified as coarse showed higher compressive strength. On average, CDW medium-sized particles had a higher air void content, while water absorption showed little variation with respect to granulometry. CDW residue from the region of study can be used as aggregate for the development of aerated foamed concrete. However, it must characterized before being used to guarantee the quality of the final product.

Abstract:The main aim of this work was to evaluate the influence and optimize the factors of the TIG-MIG/MAG hybrid welding process on the geometry of the weld bead. An experimental design using the Taguchi methodology (robust design method) was used to conduct the experiments. The experiments were carried out according to an orthogonal matrix with 27 experiments, with three replicates each, totaling 81 test specimens. The factors (MIG/MAG shielding gas type, MIG/MAG voltage, MIG/MAG wire feed, gas flow rate of TIG, electric current intensity of TIG and welding speed) were varied with three levels each. Penetration, heat-affected zone (HAZ), bead width and bead height were the response variables analyzed. The results showed that the penetration was significantly influenced by the MIG/MAG wire feed, MIG/MAG shielding gas type, MIG/MAG voltage and welding speed. The HAZ has been influenced by MIG/MAG voltage, MIG/MAG shielding gas type, welding speed and electric current intensity of TIG. All factors had effects on the width, except the MIG/MAG wire feed. The bead height was significantly influenced by the MIG/MAG wire feed and by the electric current intensity of TIG. Optimizing the process was performed, so that for each output variable, the values of the factors that should be used were indicated, and the optimization was confirmed by welding test specimens.

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Abstract:The use of solid waste for the development of new building materials has been an alternative to reduce environmental impacts through the preservation of natural resources. In this context, this paper evaluates the possibility of using agate gemstone waste, called rolled powder, which basically consists of silica (SiO 2 ), in the manufacture of aerated foamed concrete blocks completely replacing the natural sand. Preformed foam was used as the air entrained by mechanical stirring with a mixture of natural foaming agents derived from coconut. To produce test specimens, the water/cement ratio and foam concentrations were varied, with three and four levels, respectively. The specimens were left for 28 days at room temperature to be cured, and then underwent analysis to determine their compressive strength, density, and the distribution of air-voids. The experiments demonstrated that the best water/cement ratio was 1.28 for 18% (of total solid mass) addition of foam, which generated a sample with a density of 430 kg/m 3 , and a compressive strength of 1.07 MPa. The result for compressive strength is 11% smaller than the requirements of the Brazilian standard (NBR 13438) for autoclaved aerated concrete blocks, but the results are promising.

(green, red, blue, and black) and with organic dyes (green, red, pink, and purple ResumoO Rio Grande do Sul é um dos principais produtores de geodos de ágatas do mundo. As ágatas da região de Salto do Jacuí permitem a introdução de alguns corantes em seus poros, tornando-as coloridas. O objetivo do presente trabalho foi estudar a perda de cor de ágatas tingidas artificialmente, considerando diferentes ambientes de exposição. Estudaram-se ágatas coloridas pelos procedimentos clássicos (verde, vermelho, azul e preto) e coloridas com corantes orgânicos (verde, vermelho, rosa e roxo). O procedimento experimental consistiu em expor as chapas de ágatas em três ambientes com luminosidades distintas: escuro, doméstico e ao ar livre. A evolução da cor foi avaliada pela técnica de colorimetria diferencial, usando o sistema colorimétrico CIE L*a*b*. Os resultados obtidos demonstram que os métodos clássicos de tingimento proporcionam cores permanentes, enquanto que os corantes orgânicos promovem cores instáveis. Dependendo do grau de luminosidade e tempo de exposição, a perda de cor pode ser praticamente total.Palavras-chave: Ágatas, tingimento, cor, fotodegradação.

Acid mine drainage (AMD) in the coal mining industry is recognized as one of the major sources of environmental damage. The active treatment of AMD involves adding alkaline reagents to wastewater so as to raise pH and to precipitate dissolved metals in the form of oxides/hydroxides. Studies have shown that yellow pigment (goethite) can be produced from the iron present in AMD. However, the presence of other metals can prevent the formation of pigment. Therefore, this paper seeks to evaluate several processes for purifying iron sludge so as to obtain raw material that can be recovered from AMD and thereby obtain a good quality of yellow pigment. The experiments were carried out by causing precipitation with strong and weak bases and removing other metals from the sludge by washing and filtering the sludge or by centrifugation. The results show that the color, type and morphology of the compounds changed, depending on the number of contaminants, and that these factors are strongly dependent on the type of reagent and less dependent on the separation process and the repetition of washes.

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