Materials Science Forum Vols. 775-776

Abstract: As one of the world leading producers of natural stones for ornamental purpose, mainly marble and granite, Brazil also generates an increasing amount of corresponding wastes. Several alternatives have locally been proposed for the application of these wastes, including the incorporation into cement matrix concretes. In the present work a granite waste, generated by a sawing system composed of sintered diamond in the form of cylindrical beats attached to a steel wire, was incorporated into a cement matrix to be used as building construction concrete. These cement concretes incorporated with up to 30 wt% of granite waste were evaluated in terms of mechanical and chemical properties as well as their environmental impact. The results indicated that 20 wt% incorporation would be a limit for a concrete with acceptable technical characteristics and safe environmental risks.

Abstract: The practice of sustainability in construction occupies an increasing prominent position in order to preserve the environment. Considering the environmental impacts caused by waste generation, the use of PET bottle flaks and crushed sand in partial substitution of conventional sand used in concretes is proposed. The aim of this work was to formulate concrete compositions with 1:3 and 1:4 mixtures containing varied water/cement factors and 5, 10, 15 and 20% content of PET wastes and gravel powder. The raw materials were characterized by physico-chemical tests. The formulations were subjected to slump tests and the hardened concrete to absorption, void index and simple compressive strength, with curing of 7 and 28 days, tests. The granulometric analysis allowed the calculation of the fineness modulus, which was 1.50, 3.25 and 0.64 for the crushed sand, gravel and PET respectively. The decrease in the strength with the increase in the PET content in the composite was observed, though, in some mixtures the values indicate the possibility of using this concrete in structural elements.

Abstract: Duplex stainless steel is a material that attracts great interest of different branches of engineering and industry because of its combination of good structural and mechanical characteristics and high corrosion resistance. The microstructure of duplex steel presents an example of composite material with approximately equal amounts of austenite and ferrite phases. Physical and mechanical properties of these components are different so their behaviors under loading are different too. Therefore it is important to analyze the distribution of applied stress between ferrite and austenite phases of duplex steel. The analysis of stress distribution was made by X-ray diffraction technique. X-ray diffraction method allows separate measuring of stresses in each phase and determination of others mechanical characteristics as Young ́s modulus, yield stress of ferrite and austenite both in elastic and plastic region. In presented paper the samples of duplex steel after rolling were loaded by calibrated springs; using of Cr-K_α radiation allows carrying out of stress measurements in ferrite and austenite phases of duplex stainless steel.

Abstract: The correlation between the structural network of a diglycidyl ether of the bisphenol-A (DGEBA) epoxy resin, modified by two distinct aliphatic amines (tetraethylenepentamine TEPA and jeffamine D230), and its mechanical properties, was investigated as possible matrix for abrasive composites applications. Both flexural tests, to determine the yield stress and the elastic modulus, as well as impact tests to determine the notch toughness, were performed. The DGEBA/D230 presented the highest stiffness and toughness but lowest yield stress. This epoxy network also displayed a greater plastic deformation during fracture.

Abstract: This study reports the influence of recycled poly (vinyl butyral) (PVB) in dynamic mechanical and mechanical properties of polypropylene (PP)/wood flour composites prepared in a twin screw extruder. After extrusion, the PP/wood flour composites were injection molded to obtain specimens for tensile, flexural, impact and dynamic mechanical (DMA) tests. The morphology of the composites was analyzed by scanning electron microscopy (SEM). The addition 10 wt% of PVB in PP/wood flour composite reduced from 5°C to-10°C the β transition (glass transition) peak temperature of the loss modulus. In a temperature range between 40°C and 100°C the composites containing PVB presented the highest peak in the loss modulus. The most intense tan delta peaks between 50°C and 100°C for composites containing PVB were attributed to the combined effects of PP α transition with the PVB glass transition temperature. The PP/wood flour composites with PVB presented a tendency to increase the absorbed energy by impact.

Abstract: Physical and mechanical properties of a glass-ceramic belonging to the LZS (Li₂O-SiO₂-ZrO₂) system were investigated by dilatometric analysis, differential thermal analysis, X-ray diffraction and measurements of density, hardness, bending strength, modulus of elasticity and fracture toughness. The obtained glass-ceramics showed ZrSiO₄ and Li₂Si₂O₅ as main crystalline phases, relative densities between 84 and 99%, maximum hardness, bending strength, modulus of elasticity and toughness of 8±0.5 GPa, 214±20 MPa, 115±0.42 GPa and 3.65±0.21 MPa.m^1/2, respectively.

Abstract: The blast furnace sludge is a waste generated after the washing step of the blast furnace gas. The reuse of this waste in the steelmaking process itself is quite problematic. This study aims to analyze the possibility of the incorporation of a type of blast furnace sludge, benefited by a process that uses helical separators, into red ceramic. Specimens were prepared by uniaxial pressing at 20 MPa and then fired at 750°C and 950°C. The evaluated technological properties were linear shrinkage, water absorption and flexural rupture strength. The results showed that the benefited blast furnace sludge significantly influences the evaluated properties, by impairing the linear shrinkage and the water absorption but improving the mechanical strength.

Abstract: This study aims at investigating the feasibility of the partial replacement of aggregates of asphaltic concrete by recycled aggregates from construction and demolition waste (CDW). It was adopted as parameter a project design mixture of an asphalt concrete used in the construction of Itaueira-Canto do Buriti state highway (Piaui). Two project mixtures were used: in the first 38% of the natural aggregate were replaced by the recycled aggregate and in the second, 70%. We carried out the characterization of the aggregates through physical, chemical and mechanical testing analyzing them based on specific reference standards of paving. We performed assays related to the asphaltic mixture with CDW determining the apparent specific mass, the volume of voids, the relationship bitumen/voids and mechanical testing of traction resistance by diametric compression and Marshall Stability. The results indicate that the recycled aggregate, in a defined proportion, can partially replace natural aggregate in flexible pavements.

Abstract: The production of urban solid wastes has grown surprisingly in last years, turning into one of biggest challenges for the contemporary society. Among these wastes, the glass waste can be highlighted bearing in mind that, for being totally returned to the productive chain without any loss of mass in the material, it has been receiving several incentives to help on development of alternative and green technologies which aim an adequate destination to this kind of material. Thereby, this research proposes the use of the flat glass waste like a flux, in a partial replacement to the feldspar, in the composition of masses for white ceramics, aiming to obtain products with physical-mechanical similar properties to the industrial products. To do this study, standard specimens were initially prepared, each one with different percentages of glass, to then be burned under temperatures between 1200 and 1250 degree Celsius. Later, the following tests were made: flaring color, linear retraction, apparent porosity and rupture module to flexion in three points, according to the ABNT/NBR 15097/2004 rules. The obtained values were compared with the suggested values for industrial masses, confirming the possibility to apply flat glass waste like a flux in masses to white ceramics, as an alternative to reuse of these materials.

Abstract: The accumulation of garbage in urban centers is, undoubtedly, one of the major environmental problems of today. The high costs of implementation and maintenance of collection systems and garbagess treatment, have often,taken to failure of government attempts to resolve this issue.