Leonardo Gonçalves Pedroti

Experimental Evaluation of the Influence of Mortar’s Mechanical Properties on the Behavior of Clay Masonry

This study aims to evaluate the influence of mortar’s mechanical properties on the behavior of clay masonry. Experimental studies were performed using prisms of clay blocks under axial compression. The clay units were produced with a clay from Tres Rios, Rio de Janeiro, Brazil and had compressive strength of 4.9 MPa. Two mortar compositions were used, which had compressive strength of 94.7 and 50.4% of the clay blocks’ net area compressive strength. It was noticed a slight increase on the prism’s compressive strength with the increase of the mortars’ compressive strength and stiffness. Prisms made with flexible mortars had a ductile failure and collapsed under lower compressive stresses, while prisms made with stiff mortars resisted higher compressive stresses, but had a brittle failure, crushing the blocks. A very strong mortar is not recommended. Using more flexible mortars does not compromise the strength and stiffness of the masonry and prevents an excessively brittle failure of the structure.

Influence of the Blocks and Mortar’s Compressive Strength on the Flexural Bond Strength of Concrete Masonry

This work presents an experimental investigation of the influence of concrete blocks and mortar’s compressive strength on the flexural bond strength, normal to the bed joints, of concrete structural masonry. Third-point beam tests were performed on concrete prisms, considering two different kinds of concrete blocks (compressive strength of 5.9 and 8.2 MPa) and six different cement-lime mortar compositions (compressive strength around 30, 70, and 120% of the blocks’ net area compressive strength). Units’ absorption and mortar’s initial flow and water retentivity were not varied, but remained within the suitable range for use in structural masonry. For both types of concrete blocks, it was observed an increase on the prism’s flexural bond strength with the increase of the mortars’ compressive strength. A lower mortar’s water-cement ratio led to higher bond strength. When fixing the ratio between mortar’s and concrete block’s compressive strength, it was noticed that the increase on the blocks’ strength contributed to a slight increase on the masonry’s flexural bond strength, except when using high strength mortar, in which the increase was significantly greater.

Comparison of Performance Between Granite Waste Pigments Based Paints and Soils Pigments Based Paints

This work aims to produce paints using granite waste, as a pigment, and compare their performance to soil pigments based paints, in terms of hiding power and abrasion resistance. Initially, the residue and soils were physically, mineralogically and morphologically characterized. For the production of the paint samples, an experimental model was defined, based on the variation of the proportions of pigment and resin. The proportion of water varied in each sample, in order to maintain the viscosity within a range considered ideal for application. Sequentially, tests were done to determine the hiding power and abrasion resistance of inks. It was found that, in comparison to soil paints, the granite residue paints presented greater hiding power. This result can be explained by the characteristics of the granite residue, which allowed a high nonvolatile content in the mixtures. With respect to abrasion resistance, granite residue paints showed less resistance than soil paints, possibly due to the granulometry of the residue that resulted in a greater roughness of film. In addition, none ink sample satisfied the minimum specifications prescribed in the Brazilian standards for hiding power and abrasion resistance, at the same time. This means that these inks, when used, will require more repair and repainting over time than conventional paints.

Addition of Dregs in Mixed Mortar: Evaluation of Physical and Mechanical Properties

The dregs is a waste from the cellulose production, and its reuse is an effective way to reduce environmental impacts. Researches have already been done to incorporate it into building materials. The present work aimed at incorporating dregs in the production of mortar to replace hydrated lime. The methodology adopted was the Simplex network with ten sampling points, varying the amount of cement, sand, and dregs. Each mix was submitted to flexural strength, compressive strength, apparent mass density and water absorption by capillarity tests. The results were analyzed by the software Minitab, obtaining the influence of each component in the mixture. The best results were observed in mixes with a higher proportion of cement and less of residue when it was analyzed the flexural and compressive strengths. Larger rates of apparent mass density and water absorption were noticed with a greater amount of dregs. The experimental design also allowed the obtainment of mixture ratios from predetermined values of the tested properties and indicated that the addition of dregs in mortar could be an alternative to civil construction.

The Use of Network Simplex Method for Planning the Incorporation of Recycled Paper Mill Sludge in Manufacturing of Ceramic Bodies

The final disposal of sludge from recycled paper mill effluent treatment plants is costly and demands large areas for landfilling. Environmentally sound alternative uses of the sludge, enabling economic valoration of this material appear to be advantageous to industry and to the environment. This paper evaluates the feasibility of the incorporation of paper mill sludge in manufacturing of ceramic bodies. The combination of different proportions of weak clay, strong clay and sludge from recycled paper effluent treatment plant for the production of ceramic bodies was determined by using the Network Simplex method planning of mixtures. Samples were prepared and burnt in oven at temperatures of 750, 850 and 950 °C. Physical, mechanical and environmental tests were carried out, in addition to chemical, microscopic and thermic analysis. The results demonstrated that the flexion resistance increased with the increase in temperature, while the absorption decreased at higher temperatures. The mixture design is efficient combining sludge addition at small fractions with large amount of clay, which demonstrate the viability of sludge incorporation for ceramic bodies manufacture, since the desired characteristics are observed.

INFLUÊNCIA DA TEMPERATURA NAS PROPRIEDADES FÍSICAS E MECÂNICAS DE CERÂMICA PRODUZIDA COM ADIÇÃO DE CHAMOTE

Resumo O chamote é um resíduo proveniente da indústria cerâmica, classificado como material não-plástico. Tal rejeito pode ser retornado ao processo de produção de cerâmicas, substituindo parte da matéria-prima convencional. O objetivo deste trabalho foi avaliar a incorporação de chamote nas propriedades físicas e mecânicas de peças cerâmicas sob três temperaturas de queima distintas: 850°C, 950°C e 1050°C. As matérias-primas utilizadas na pesquisa foram caracterizadas quanto à granulometria, limites de consistência e composição química por meio de EDX. Foram propostas três misturas, contendo 0%, 13,33% e 40% do resíduo. Corpos de prova prismáticos foram produzidos por prensagem e, após, realizou-se os ensaios de determinação da retração na queima, índice de absorção de água e resistência à flexão. Os resultados revelam que, quanto maior a temperatura, maior a retração linear na queima e a resistência à flexão em todas as misturas. Em relação à absorção, foram observados menores valores a 1050°C, devido ao processo de vitrificação. Verificou-se que a adição de chamote reduz a retração; no entanto, reduz também a resistência mecânica. Dentre as misturas com resíduo, a composição com 13,33% apresentou melhores resultados, sobretudo sob a temperatura de 1050°C. Palavras-chave: Chamote; Cerâmica; Propriedades; Temperatura.

AVALIAÇÃO DO DESEMPENHO DE TINTAS PARA CONSTRUÇÃO CIVIL À BASE DE RESÍDUO DE GRANITO

Resumo Este trabalho busca avaliar a utilização do resíduo de granito, como pigmento, em tintas para construção civil, que atendam aos requisitos de uma tecnologia social. Inicialmente, caracterizou-se o resíduo, para determinar a potencialidade de uso desse material em tintas. Para a produção das amostras de tintas, definiu-se um modelo experimental, baseado na variação das proporções dos componentes da mistura. Nesse modelo, as proporções de pigmento e resina foram definidas de acordo com a faixa de variação de PVC (Pigment Volume Concentration) esperada para uma tinta fosca. Já a proporção de água variou, de modo a se manter a viscosidade dentro de uma faixa que permitisse a boa aplicação da tinta. Em seguida, foram realizados ensaios de determinação do poder de cobertura e resistência à abrasão para cada uma das amostras. Verificou-se que, o resíduo de granito apresenta características que o habilitam a ser utilizado, como pigmento, em tintas. Notou-se ainda que foi possível produzir misturas com elevados teores de sólidos e que o PVC exerceu grande influência sobre o desempenho das tintas. Entretanto, os resultados dos ensaios de determinação de desempenho indicaram que em nenhuma das misturas produzidas foi possível atender simultaneamente aos requisitos estabelecidos pela ABNT NBR 15079:2011. Palavras-chave:Resíduo de granito; Tintas; Tecnologia social; Desenvolvimento sustentável.

Evaluation of Physico-Chemical Properties When Adding Boiler Ashes to Mortar

Over the past few years, environmental concern is on focus, it is the case of the continuous reuse of residues from several areas. This work aimed to reuse ashes from a boiler, which temperature reaches 600°C, from a textile factory fueled by wood splinter. It is notorious the amount of generated residue, around 15 tons a month. The material was chemically analyzed with high contents of CaO, this element is ordinarily found in the main binders used in this research. In order to reuse the residue in the mortar mix, several experiments were made, such as SEM, EDX, XRD, pozzolan content, bending and compression trials, adherence and consistency, to characterize the material. The samples analyzed showed progress regarding resistance characteristics, revealing that the residue can be a viable alternative when it comes to contributing to the reduction of Environmental Issues in textile industries.

Evaluation of Incorporation of Dregs in Mortar Production in Replacement of Hydrated Lime

The dregs is a residue from the cellulose production, and finding new ways to use it would be interesting to reduce environmental impacts. This study aimed at incorporating it into mortar mixture ratios to replace the hydrated lime. Different proportions of cement, sand and dregs were evaluated using the Simplex-Lattice method of experimental design, and it was analyzed water absorption coefficient, compressive strength and flexural strength. The model adjustment was made with seven points plus three axial points and in terms of pseudo-components. A linear model was adjusted for the first characteristic, and a quadratic model for the second and third characteristics. Larger rates of capillary suction and smaller resistance values were noticed with a larger amount of dregs. This experimental design proved feasible, allowing the obtainment of mixture ratios from pre-determined values of water absorption coefficient and resistance, and making more objective the addition of dregs to mortar mixtures.

Granite Waste from Diamond Wire Sawing Addition into Concrete for Civil Construction

The ornamental stone industry in Brazil is a major world producer of marble and granite with a significant amount being destined to foreign countries export. A considerable amount of waste is generated at the several stages of stone processing specially the sawing with the so called diamond wire technique. In the present work a granite waste from a diamond wire sawing was added into conventional mixture of cement, gravel and sand to fabricate concrete used in civil construction. The waste was chemically and mineralogically characterized by X-ray and its pozzolanic activity was evaluated. Concretes with 0, 10 and 20 wt% of waste were tested for the water absorption and mechanical strength as well as environmental behavior. The results indicated that up to 20 wt% addition, the granite waste does not change the concrete performance and attends its environmental requirements.