Abstract The present paper evaluated the potential application of the functionally graded material (FGM) concept to develop more durable concrete to carbonation, one of the main degradation mechanisms of reinforced concrete structures. Accelerated carbonation tests with controlled temperature (27 ( 2°C), CO2 concentration (3 ( 0.5%) and humidity (65 ( 5%) were carried out in homogeneous concretes and with functional gradation in which the porosity of the material was varied across the slices. For the manufacture of graded concrete specimens, concretes with water/cement ratios equal to 0.35, 0.45, and 0.55 were produced, with lower porosity (w/c = 0.35) close to the surface of the specimen. The advance of the carbonation front was evaluated after 8, 9, 10, 14, and 24 weeks of accelerated exposure, using the chemical indicator phenolphthalein. The results show that the functionally graded concrete had a carbonation coefficient (K) slightly higher than that of the concrete with a w/c ratio equal to 0.35 (1.71 and 1.54 mm.week-0.5, respectively) and much lower than concrete with water-cement ratio equal to 0.45 (2.31 mm.week-0.5) and 0.55 (3.78 mm.week-0.5). This demonstrates that functional grading can be an efficient method to increase the durability of concrete elements subject to carbonation.

Resumo O presente artigo avalia o potencial de aplicação do conceito de material com gradação funcional (MGF) ao desenvolvimento de concretos mais duráveis frente à carbonatação, um dos principais mecanismos de degradação das estruturas de concreto armado. Ensaios acelerados de carbonatação com temperatura (27 ( 2 °C), concentração de CO 2 (3 ( 0,5%) e umidade (65 ( 5%) controladas foram realizados em concretos homogêneos e com gradação funcional em que a porosidade do material foi variada ao longo dos corpos de prova. Para a confecção dos corpos de prova de concreto com gradação funcional foram utilizados concretos com relações água/cimento iguais a 0,35, 0,45 e 0,55 de forma que tivéssemos uma redução de porosidade à medida que nos aproximássemos da superfície da peça. O avanço da frente de carbonatação foi avaliado após 8, 9, 10, 14 e 24 semanas de exposição acelerada, empregando-se o indicador químico fenolftaleína. A partir dos resultados obtidos observou-se que os concretos com gradação funcional apresentaram coeficiente de carbonatação (K) ligeiramente superior ao do concreto com relação a/c igual a 0,35 (1,71 e 1,54 mm.semana -0,5 , respectivamente) e bastante inferior aos concretos com relação água cimento iguais a 0,45 (2,31 mm.semana -0,5 ) e 0,55 (3,78 mm.semana -0,5 ), evidenciando que a gradação funcional pode ser um método eficiente para proporcionar o aumento da durabilidade de elementos de concreto sujeitos à carbonatação.

Abstract Sisal (Agave sisalana) is a plant exploited in semi-arid regions of Brazil for fiber production, but the floral scape of sisal (peduncle) is collected and often burned, causing environmental problems, even through irregular disposal. To circumvent this scenario, the objective of this work was to produce reconstituted panels using the sisal arrow and castor-based polyurethane resin. The panels were obtained using 175 g of crushed sisal arrow core with dimensions smaller than 2 mm and adopting 10% castor-based polyurethane resin and The samples were pressed under tension of 2 MPa. The properties of reconstituted panel were evaluated through NBR 14810-1 (ABNT, 2013) and NBR 14810-2 (ABNT, 2018), the physical properties were investigated: moisture, density, thickness swelling and absorption; as well as mechanical properties: MOR, MOE, internal bond and parallel compression. The found results show that the panel is classified as low density (419.8 kg/m³), and with physical and mechanical properties similars to other panels of the same classification in the literature. For average values of MOR and MOE it was found 5.24 MPa and 147.49 MPa, respectively. For internal bonding it was found 0.14 MPa and for parallel compression properties it was found 1.14 MPa.

Resumo O sisal (Agave sisalana) é uma planta explorada nas regiões semiáridas do Brasil para produção de fibras, mas o escapo floral do sisal (flecha) é coletado e frequentemente queimado causando problemas ambientais, até mesmo pelo descarte irregular. Para contornar este cenário, o objetivo deste trabalho foi produzir painéis reconstituídos usando a flecha do sisal e resina poliuretana à base de mamona. Os painéis foram obtidos empregando 175 g do miolo da flecha de sisal triturada com dimensões inferiores a 2 mm e adotando 10% de resina poliuretana à base de mamona e as amostras foram prensadas com tensão de 2 MPa. Avaliou-se no painel reconstituído, através da NBR 14810-1 (ABNT, 2013) e NBR 14810-2 (ABNT, 2018) as propriedades físicas: umidade, densidade, inchamento e absorção; bem como as propriedades mecânicas: MOR, MOE, força de ligação e compressão paralela. Os resultados encontrados mostram que o painel é classificado como de baixa densidade (419,8 kg/m³), e de propriedades físicas e mecânicas semelhantes a outros painéis de mesma classificação da literatura. Para MOR e MOE foram encontrados 5,24 MPa e 147,49 MPa de média, respectivamente. Já os ensaios de tração perpendicular e compressão paralela obtiveram resultados de 0,14 MPa e 1,14 MPa, respectivamente.

This paper evaluates the effect of adding glycerol to the electrodeposition bath on the deposition efficiency and characteristics of Ni-Mo coating in concentrations ranging from 0.07 to 0.82 mol.L-1. Evaluation of the corrosion resistance was performed by means of weight loss tests in four different periods of immersion. Electrochemical techniques, such as obtaining polarization curves, linear polarization resistance, corrosion current density, corrosion potential, and electrochemical impedance spectroscopy were applied. Corrosion measurements were obtained in 0.5 mol.L-1 NaCl acid solution and 0.5 mol.L-1 NaOH alkaline solution. The morphology and microstructures of electrodeposited were analyzed using Scanning Electron Microscopy and Spectrometry X-Ray Diffraction. The effect of glycerol on Ni-Mo hardness was evaluated by Vickers microhardness measurements. The presence of glycerol in the electrodeposition bath increased the grain size and decreased the hardness of the coating. However, it promoted the formation of a more compact and less porous coating, increasing the corrosion resistance of the coating. Moreover, the addition of 0.82 mol.L-1 glycerol increases current efficiency, thereby reducing the amount of energy consumed during electroplating.

Resumo A corrosão é um dos principais fenômenos que geram manifestações patológicas nas estruturas de concreto armado em ambientes agressivos, sendo o íon cloro o maior responsável por sua ocorrência. Desta forma, entender os mecanismos de transporte deste íon através da microestrutura do concreto é de fundamental importância para impedir ou retardar a penetração destes agentes agressivos, visando garantir uma estrutura durável. Na literatura são vastos os estudos referentes à difusão de cloretos em concreto e a influência das adições pozolânicas neste mecanismo, entretanto, poucos correlacionam os diferentes métodos de análise. Assim, este trabalho visa determinar os coeficientes de difusão do íon cloro em concretos contendo diversos teores de adição de sílica ativa (5%, 10% e 15%) ou com variação do teor de argamassa (54%, 80% e 100%), comparando os resultados obtidos por meio dos ensaios de migração iônica e de coluna. Observou-se que, apesar das técnicas utilizadas serem bastante distintas, os valores de coeficientes de difusão obtidos foram semelhantes, colaborando para a validação de ambas as técnicas. Além disso, a variação no teor de argamassa acarreta uma redução na zona de transição interfacial agregado graúdo/argamassas e um aumento no teor de aluminatos, o que promove efeito semelhante ao uso de sílica ativa.

Abstract Corrosion is one of the main phenomena that lead to pathological manifestations in reinforced concrete structures under aggressive environments. with the chloride ion being the most responsible for its occurrence. In this way, understanding the transport mechanisms of this ion through the microstructure of the concrete is of fundamental importance to prevent or delay the penetration of these aggressive agents to guarantee a durable structure. In the literature, there are extensive studies concerning the diffusion of chlorides in concrete and the influence of pozzolanic additions in this mechanism. However, only a few correlate the different methods of analysis. This work aims to determine the chloride ion diffusion coefficients in concrete containing various levels of silica fume (5%, 10%, and 15%) or varying the mortar content (54%, 80%, and 100%), and compares the results obtained through column tests and chloride migration tests. It was observed that, although the techniques used were quite distinct, the diffusion values obtained were similar, contributing to the validation of both techniques. Furthermore, the variation in the mortar ratio causes a reduction in the interfacial transition zone of coarse aggregate/mortars and an increase in the content of aluminates, which promotes a similar effect to the use of silica fume.

Resumo Segundo estudos anteriores, materiais finos provenientes de um agregado reativo podem agir como mitigadores da reação álcali-agregado (RAA), contudo, a efetividade da ação desses finos depende do seu grau de reatividade, finura e teor adicionado. Assim, o presente trabalho visa estudar se finos de rochas graníticas reativas (FRG), passante na peneira #200, podem mitigar ou reduzir a RAA e como a finura do material influencia na sua capacidade de mitigação. Para isso, foram utilizados FRG provenientes de 2 diferentes jazidas, obtidos após moagem. Cada adição foi utilizada em três finuras diferentes e adicionadas à argamassa nos teores de 10% e 20%, em relação à massa de cimento. Observou-se que a presença dos FRG não prejudicou as propriedades físico-mecânicas da argamassa, e ainda possibilitou redução da RAA, sendo mais acentuada à medida que se aumentou a superfície específica do material.

Abstract According to previous studies, fine materials originated from reactive aggregates can act as a Alkali-Aggregate Reaction mitigator, having its effectiveness dependent on their reactivity, fineness and added content. Thus, the present work aims to study if reactive granitic rock fines can mitigate or reduce the AAR and how the fineness of the material influences its mitigation capacity. For this purpose, granitic rock fines (GRF) from 2 different deposits and Pyrex glass fines (PGF) were tested as concrete addition. Each one of these fines were used in two different finesses and added to the concrete in the contents of 20% by mass of cement. It was observed that the addition of GRF did not affect the physical-mechanical properties of concrete and allowed the reduction in the AAR, being more accentuated with the increase of its specific surface.

Abstract This study investigates the effect of hydrothermal aging on the properties of glass fiber reinforced polymer (GFRP) rebars manufactured with isophthalic polyester or vinylester resin and glass fiber type E. The GFRP rebars were immersed in an alkaline solution (pH 12.6) for 1000 h at different temperatures (23 and 60 ºC), and their deterioration was evaluated based on microstructural and chemical changes (using SEM, DSC, XRF, and FTIR techniques), moisture absorption, and variation in mechanical properties. The results indicated an increase in the presence of voids and water absorption of the rebars with accelerated aging, with a reduction in the glass transition temperature of the resin and alteration of the chemical composition of the glass fiber. The comparison between the experimental results indicates that the rebars with matrix in vinylester resin present greater chemical resistance than the rebars with a polyester matrix. The degradation of the rebar also resulted in a reduction of approximately 6% in the tensile strength of the rebar and 2% in the modulus of elasticity. Using the damage model, it was possible to identify that the reduction in mechanical strength was associated with the simultaneous degradation of the resin and glass fiber due to the alkaline attack.

Resumo Intensificaram-se os esforços para a redução das emissões de gases do efeito estufa no contexto do desenvolvimento sustentável, com o desenvolvimento de pesquisas, visando a produção de novos materiais e ligantes para a construção. Esse artigo analisa a influência da geometria dos pellets, na produção de clínqueres, com a incorporação de resíduo da construção civil (RCC). Foram adotados procedimentos adaptados da metodologia proposta pela ABCP e adotada em estudos de clínqueres laboratoriais, na tentativa de simular etapas do processo industrial. Pellets foram preparados com a mesma formulação, porém, com quarto diferentes geometrias: esféricos, com diâmetros de 1 cm, de 2 cm e de 3 cm, com modelagem manual, e semi-esféricos, com diâmetro de 2 cm, empregando-se moldes de PLA (ácido polilático) impressos em impressora 3D, que facilitaram a moldagem dos clínqueres de forma padronizada. Os clínqueres foram caracterizados mineralogicamente por difração de raios x (DRX) e o método de Rietveld foi empregado na quantificação das fases. Observaram-se variações nas quantidades das fases alita e belita em função da geometria dos pellets, embora tenham sido utilizadas as mesmas condições de calcinação, provavelmente devido à variação da área superficial (área de exposição) e a gradientes da taxa de resfriamento.

Abstract Efforts to reduce greenhouse gas emissions in the context of sustainable development have intensified, with the development of research aimed at the production of new materials and binders for construction. This article analyzes the influence of pellet geometry in the production of clinkers, with the incorporation of construction waste (CCW). Procedures adapted from the method proposed by Brazilian Portland Cement Association were adopted in studies of laboratory clinkers, in an attempt to simulate the stages of the industrial process. Pellets were prepared with the same formulation, however, with four different geometries: spherical, with diameters of 1 cm, 2 cm and 3 cm, with manual molding, and semi-spherical, with a diameter of 2 cm, using molds of PLA (polylactic acid) printed on a 3D printer to facilitate the molding of the clinkers in a standardized way. Clinkers were characterized mineralogically by x-ray diffraction (XRD) and the Rietveld method was used to quantify the phases. Variations in the quantities of the alite and belite phases were observed depending on the geometry of the pellets, although the same calcination conditions were used. This is probably due to the variation in the surface area (exposure area) and the gradients of the cooling rate.

Resumo O presente estudo avalia a utilização de finos de rocha granítica (FRG) em argamassas autoadensáveis, visando obter características reológicas adequadas sem incorporar aditivos modificadores de viscosidade. Para isso, realizaram-se ensaios de mini funil-V e mini-slump test e ensaios de caracterização físico-mecânica em argamassas de referência (sem FRG) e com teores de substituição de FRG iguais a 5%, 15% e 25% em relação ao volume de cimento. Avaliou-se a hidratação das pastas que compõem essas argamassas, por meio da técnica de calorimetria isotérmica. Posteriormente, foi analisada a porosidade teórica das pastas, por meio do ensaio de compacidade, visando obter o espaçamento entre partículas (IPS) das pastas. Ao incorporar FRG, a viscosidade da argamassa foi ajustada, com o aumento do tempo de escoamento em até 4,3 s, reduzindo-se o consumo de cimento em até 12% e, consequentemente, a liberação de calor durante a hidratação. Ademais, concluiu-se que a incorporação de FRG reduz a porosidade das argamassas em até 17,63% e aumenta a resistência à compressão em cerca de 11% como consequência da adição de 15% de FRG. No entanto, pelo fato de reduzir a distância entre as partículas da pasta, aumentou-se o consumo de teor de aditivo superplastificante para alcançar o espalhamento ideal.

Abstract The present study evaluates the use of granite rock fines (GRF) in self-compacting mortars, aiming to obtain adequate rheological characteristics without incorporating viscosity modifying additives. For this, mini Funnel-V, mini Slump Test and physical-mechanical characterization tests were carried out on reference mortars (without GRF) and with GRF substitution levels equal to 5%, 15% and 25%, to cement’s volume. The hydration of the pastes of these mortars was also evaluated using the isothermal calorimetry technique. Subsequently, the theoretical porosity of the pastes was analyzed through the compactness test, in order to obtain the interparticle spacing (IPS) of these pastes. When incorporating GRF, the viscosity of the mortar was adjusted, increasing the flow time by up to 4.3 sec, reducing cement consumption by up to 12% and, consequently, the release of heat during hydration. Furthermore, it was concluded that the incorporation of GRF reduces the porosity of mortars by up to 17.63% and increases the compressive strength by about 11% as a result of the addition of 15% FRG. However, due to the fact that the distance between the particles of the paste is reduced, the consumption of superplasticizer additive content has been increased to achieve the ideal spreading.

Abstract Materials such as magnesium phosphate cement (MPC) have attracted significant attention of researchers, therefore, understanding the effects of dosage parameters, such as water content and MgO/NH4H2PO4 ratio on phase formation is essential for obtaining cementitious matrices with improved performance. In the present work MgO was sintered at 900 °C and 1110 °C in a conventional oven, and the effect of water concentration and MgO/NH4H2PO4 (or ADP) ratio on the properties of MPC was evaluated in terms of phase formation by X-ray diffraction, pore size distribution, mechanical properties, and microstructure. For less-reactive MgO (calcined at 1100 °C) with a high MgO/ADP ratio, increased water content did not cause additional solubilization of ADP or formation of more hydrated phases, although the cement porosity increased. Compositions with more reactive MgO (calcined up to 900 °C) formed dittmarite (NH4MgPO4.H2O) independent of water content. Higher water content and MgO calcination temperature were associated with increased MPC setting time and decreased mechanical strength due to higher porosity.

Magnesium phosphate cements (MPCs) are formed when an aqueous solution of ammonium dihydrogen phosphate (ADP, NH4H2PO4) and magnesium oxide (MgO) react in the presence of other aggregates for filling or reinforcement (e.g., fibers, waste, and sand). Therefore, understanding how the MgO/ADP ratio influences phase formation to produce cementitious matrices with better performance is essential. MgO dissolved in an acid solution undergoes numerous transformations because of which different opinions exist regarding the mechanisms by which the setting reactions and formation of hydrated phases occurs in MPCs. In this study, the effect of different MgO/ADP ratios on the properties of MPCs was evaluated regarding phase formation using X-ray diffraction, setting time, and pore size distribution. Increased ADP concentration was found to increase the concentration of hydrated phases, however, this increases the pore content while decreasing the apparent density of MPCs. Compared with compositions with lower MgO/ADP ratios, the composition with the highest MgO/ADP ratio required higher setting time due to the lower concentration of hydrated phases.

Resumo O reaproveitamento de resíduos industriais para o setor da construção civil tem se mostrado uma alternativa ambiental e economicamente atrativa, principalmente para a indústria do cimento, que por muito tempo tem procurado procedimentos que efetivamente reduzam a alta energia e emissões de CO2 gerados durante a produção de clínquer. Nesse sentido, destaca-se a necessidade de utilização de materiais alternativos na produção de clínquer como substitutos parciais às matérias-primas. Dessa forma, o objetivo da presente pesquisa é avaliar a produção de clínquer Portland com baixa emissão de dióxido de carbono a partir da incorporação de minério não reagido (MNR), resíduo gerado durante a produção de dióxido de titânio (TiO2). As emissões de dióxido de carbono geradas durante a produção desse material foram verificadas através de análises térmicas (TG/DTG), e a influência do resíduo na formação de fases dos clínqueres foi verificada por análise mineralógica (DRX), por microscopia óptica (MO) e por microscopia eletrônica de varredura (MEV). A partir dos resultados obtidos, determinou-se o teor de incorporação ideal de TiO2 para produção de clínquer, sendo constatado que o MNR, até um teor limite de incorporação, atua como mineralizante, sendo, assim, benéfico para a formação de alita.

Abstract The reuse of industrial waste in the construction industry has proven to be an environmentally and economically attractive alternative, especially for the cement industry, which has long sought after procedures that effectively reduce the high use of energy and CO2 emissions generated during clinker production. In this sense, it is necessary to use alternative materials as partial substitutes for raw materials in clinker production. Thus, the objective of this research study is to produce Portland clinker with low carbon dioxide emissions from the incorporation of unreacted ore (UOW), a waste generated during the production of titanium dioxide (TiO2). The carbon dioxide emissions generated during the production of this material were verified by thermal analysis (TG/DTG), and the influence of the waste on the formation of clinker phases was verified by mineralogical analysis (XRD), optical microscopy (MO) and scanning electron microscopy (SEM). The results obtained led to the determination of the ideal incorporation content of TiO2 for clinker production, and they also showed that the UOW - up to a limit content of incorporation - acts like a mineraliser and is, therefore, beneficial for the formation of alite.

Zinc electrodeposition is an economical process of Zn coating compared to conventional galvanic process. The galvanizing process is used in various industrial sectors to protect ferrous alloys during the corrosion process. In buildings, the galvanizing process is widely used to coat mortar protective screens. The electrodeposition of zinc has a relatively low cost compared to other coating materials for the same purpose; however, its corrosion resistance is lower than that of most protective deposits. This study evaluated the effect of adding glycerol to the electrodeposition bath on the corrosion resistance, deposition efficiency, morphology and microstructure of the zinc electrodeposit in concentrations ranging from 0.03 to 0.82 M. The electrodeposition was performed on carbon steel AISI 1020 with a current density of 10 mA.cm-2. The electroplating solution composition was 0.10 M ZnCl2, 2.80 M KCl and 0.32 M H3BO3. Electrodeposition time was 17.56 min, 5 µm thick coating, equivalent to the mass of 7.166E-3 g of zinc on the steel surface. Evaluation of the corrosion resistance was performed by means of the electrochemical tests of Anodic Voltammetry, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) as well as Weight Loss tests in NaCl 0.5 M in 4 (four) different period of immersion. The morphology and microstructures of electrodeposited were analyzed using the techniques of Scanning Electron Microscopy (SEM) and Spectrometry X-Ray Diffraction (XRD). The presence of glycerol in the electrodeposition bath decreased the deposition efficiency; however, it increased corrosion resistance and promoted the formation of more compact and refined electrodeposited coatings. Moreover, the results showed that the corrosion rate does not vary linearly with the addition of glycerol.

Reinforced concrete is the main structural material used in the world in the construction of bridges, roads and commercial and residential buildings. One effective method for preventing corrosion of steel reinforcement is the application of galvanic coatings to the reinforcement itself. The present study evaluated the performance of three groups of reinforcing steel bars (black steel, used as a reference and rebars electroplated with Zinc and Zinc-Nickel alloys) to corrosion and adherence to the concrete matrix. For the analysis of corrosion, the specimens were subjected to two different accelerated corrosion tests: salt spray exposure and wet and dry semi-cycles. The corrosion potential was measured for the qualitative monitoring of the corrosion process and the corrosion rate was estimated. In order to evaluate the steel-concrete adherence, the pullout test was used, in accordance with RILEM-CEB-FIP. The results showed that Zinc and Zinc-Nickel coatings increased the durability of the reinforcing bars and the accelerated corrosion test of wetting and drying cycles proved to be more aggressive compared to the salt spray method to evaluate the corrosion process in the reinforced concrete specimens. Additionally, galvanized reinforcement reduced adherence to the concrete matrix.

Resumo De acordo com o Balanço Energético Nacional (ano-base 2013), o consumo nacional de lenha foi de 79,29 milhões de toneladas. Estima-se uma geração de cinza na ordem de 3% durante esse processo, o que ocasiona problemas de armazenamento e de descarte. Sendo assim, a potencial transformação desses resíduos em matéria-prima para elementos construtivos apresenta-se como uma oportunidade para a preservação do meio ambiente e para a redução do custo de materiais da construção civil. O presente trabalho objetiva, portanto, avaliar a viabilidade desse reaproveitamento por meio da análise das propriedades das argamassas no estado fresco, incluindo a reologia, além da reatividade potencial (RAA), utilizando cinza proveniente da queima de cavacos de eucalipto com teores de 10%, 20% e 30% de substituição, em massa, ao cimento Portland. Através dos ensaios realizados verificou-se que a utilização da cinza de eucalipto como substituição parcial ao cimento não altera significativamente as propriedades de argamassas no estado fresco e não apresenta reatividade significativa, apresentando-se como uma alternativa de uso tecnicamente viável.

Abstract According to the National Energy Balance (base year 2013), the national wood consumption was 79.29 million tons. It is estimated an ash generation in the order of 3% during this process, causing storage and disposal problems. Thus, the potential transformation of such waste into a source of raw material for construction elements is presented as an opportunity for the preservation of the environment and to reduce the cost of construction materials. The paper aims, therefore, to evaluate the feasibility of this reuse, through analyses of the properties of mortars in the fresh state, including rheology, using eucalyptus ash levels with 10%, 20% and 30% replacement, in weight, to Portland cement. Through the performed experiments it was found that the use of eucalyptus ash as partial replacement of cement does not significantly alter the properties of fresh mortars, presenting itself as a possible alternative.

Rotary-vacuum-filter mud (RVFM) is waste generated during the manufacturing process of titanium dioxide. In this work, RVFM and ceramic bricks containing different ratios of this waste are investigated. The mud samples were characterized using thermal analysis (TG/DTG). The aim of the present work was to determine the effect of adding RVFM on the ceramic properties of clay, such as apparent porosity, water absorption, linear shrinkage and flexural strength, used to produce red ceramics (bricks and roofing tiles). Samples were dried out at 110°C and fired at 800°C, 950°C and 1100°C. The addition of RVFM tends to increase the apparent porosity and water absorption and to decrease the flexural strength of the ceramic specimens. Based on the results, ceramic specimens with 20% RVFM content that are burned at 800ºC can not be used as bricks, and ceramic specimens with 20% RVFM content that are fired at 800ºC and 950°C can not used as roofing tiles, according to Brazilian standards.