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The production of Portland cement (PC) clinker is responsible for about 6·5% of total carbon dioxide (CO2) emissions worldwide. Therefore, recent studies have focused on alternatives to decrease PC content and thus reduce the carbon footprint of concrete construction. Although guidelines suggest a minimum cement content of approximately 250–300 kg/m3 depending on the type of the structure or structural member, there is currently a lack of information on the impact of the amount of cement on the overall behaviour of concrete. This work evaluates the influence of PC (ASTM C150 Type III) content on the fresh (i.e. rheological behaviour) and hardened (i.e. compressive strength, dynamic and static modulus of elasticity, porosity and permeability) properties of concrete mixtures produced with low to moderate (54, 159 and 260 kg/m3) PC amounts. Results show that it is possible to produce eco-efficient concrete without compromising the fresh and hardened states of the material. However, the durability and long-term properties of low cement content systems should be further appraised.

The effect of time on soil properties, noticeable in many earthworks, is recognized by geotechnicians. For example, secondary compression and aging pre-consolidation are considered in geotechnical design, and strain rate is standardized in geotechnical laboratory and field tests. Elastic-plastic models, from rigid-perfect plastic to Modified Cam Clay, which do not consider the effects of time, solve most geotechnical problems. However, solutions for prolonged settlements, landslides, debris flow and mudflow could profit from a deeper understanding of rheological models. In fact, rheological concepts, despite not always clearly stated, have been used to address some of these problems, and may also be important for using new materials in geotechnical practice (tailings, sludge, soil-polymer mixtures and other materials with water content higher than the liquid limit). This paper introduces basic concepts of rheology for geotechnicians, specially highlighting viscoelasticity under simple shear stress, which explains with reasonable accuracy well known phenomena dependent on time in soils. The objective is to bring geotechnicians to rheology and show another important tool to access geotechnical problems. On the other hand, a brief explanation of geotechnical tests is presented for rheologists not acquainted with geotechnical engineering. Geotechnical tests procedures are discussed in the light of rheology concepts, terminology is clarified, examples of application of rheology in geotechnics are presented, and determination of soil rheological parameters by traditional geotechnical tests as well as by tests on concrete is commented.

Resumo Este trabalho foi realizado com o objetivo de avaliar o impacto do tipo de substrato e do tratamento da superfície na resistência de aderência e na permeabilidade de argamassa de revestimento. Para tanto, uma mesma argamassa foi aplicada sobre blocos cerâmico e de concreto, e substrato-padrão de concreto, nos quais foram realizados tratamentos superficiais com hidrofugante e silicone para alterar os níveis de absorção de água sem mudar a rugosidade superficial. Todas as condições de mistura, aplicação e cura foram mantidas constantes e os resultados indicaram que há considerável diferença no espalhamento e no tempo em aberto das argamassas em função do tipo de substrato ou tratamento superficial; não houve diferença estatística nos resultados de resistência de aderência ou permeabilidade das argamassas aplicadas sobre os blocos cerâmico e de concreto, independente do tratamento da superfície, porém os valores foram menores do que para as argamassas aplicadas sobre o substrato-padrão de concreto; e apesar de o coeficiente de absorção de água dos substratos influenciar diretamente os parâmetros avaliados, para cada tipo de substrato foi observada uma tendência, indicando que a absorção é importante, porém não é a variável de maior interferência na aderência argamassa-substrato. Abstract The main purpose of this study was to evaluate the impact of the substrate type and water absorption on the properties of rendering mortars. A mortar was applied on ceramic and concrete blocks and on standard concrete substrate, which received superficial treatments with water repellent and silicon. This strategy was used to alter the water absorption without changing the roughness. The mixture, application, and cure of the mortars were kept constant, and the results indicated that there are considerable differences in the spreading and open-time of mortars depending on the surface treatment and substrate type; there were no statistical differences in the adhesion or permeability of mortars applied on the ceramic and concrete blocks, regardless of surface treatment, but the values were much lower than those observed on the standard concrete substrate; and even with a direct influence of the coefficient of water absorption on adhesion and permeability, a different tendency was observed for each kind of substrate, indicating that, while absorption is important, it is not the main variable influencing the performance of coatings.

The paper discusses the potential of fillers in CO2 mitigation in the cement industry. A historical overview of the use of fillers is presented as well as the limits of filler use given in cement standards. Globally, limestone filler currently represents only 7% of average worldwide cement composition. The limits of the current route to adding filler in cement by means of intergrinding are discussed. An innovative technology, that compensates binder dilution by a reduction of the water required for good rheological behavior, is presented; this allows clinker replacement rates of up to 70%. The theory that enables the design of such multimodal particle size distributions with high particle packing and low-water demand is presented, and examples of its application in concrete production are given. The efficiency in terms of CO2 mitigation is demonstrated by comparing concrete formulations designed with this innovative approach with a global benchmark of current technology. New filler minerals, as well as the effects of high-filler content on production processes and on durability are also discussed.

The squeeze flow test provides relevant information about the macroscopic rheological behavior of mortars. Nevertheless, the identification and characterization of micro and meso physical phenomena is necessary for a more thorough analysis. This work presents an experimental methodology that combines the squeeze flow test with a pressure mapping system for the rheological evaluation of cement-based mortars. Two compositions were analyzed, with and without viscosity modifying cellulose ether based admixture, and the liquid phase migration was quantified to support the interpretation of the results. The developed pressure mapped squeeze flow (PMSF) method allowed for reliable measurement of the evolution of the pressure distribution on the whole area of the squeezed sample, and the results were compared with theoretical models for different flow types and rheological behaviors. The presence of the cellulose ether admixture resulted in more homogeneous flows, which enabled bigger displacements and generated less fluctuations in the pressure distributions.

Resumo A utilização de incorporadores de ar em argamassas de revestimento é comum no setor construtivo e estudada há muitos anos, seja na academia ou em centros privados de pesquisa. Por isso, uma gama muito ampla de informações obtidas com os inúmeros estudos são reportadas em literatura, na maioria dos casos ilustrando os efeitos da incorporação de ar, trabalhabilidade, espalhamento, módulo de elasticidade, aumento da permeabilidade ao ar, etc. No entanto, poucas informações são obtidas com relação às causas que resultam em tais efeitos, o que pode ser considerada a fonte das incertezas e empirismo durante o processo de desenvolvimento de tais composições cimentícias. Assim, neste trabalho é apresentada uma revisão sobre as variáveis que influenciam na incorporação de ar nos sistemas cimentícios, que aponta para o impacto da utilização do aditivo na água em presença de cimento (pasta) e na argamassa como um todo.

Due to environmental issues, the concrete chain seeks to reduce CO2 emissions. However, growing demand from developing countries causes the increase of CO2 emissions in production to exceed decreases generated by industrial actions, such as improving kilns and clinker replacement. New strategies are important. Changes in the concrete formulation, making it more efficient, can help if these changes produce concrete with the same performance and lower cement consumption. In this regard, the improvement of packing and dispersion of particles increases this efficiency. The better the packing, the lower the volume of voids between particles, thereby requiring lower fluid content (water) to permit flow. The dispersion of the particles also decreases the water content for the same fluidity. The less the water content, the smaller the water/cement (w/c) ratio, and the greater the resistance. Thus, both strategies increase the efficiency by uncoupling obtaining fluidity from the water content. This study investigated the influence of packing and dispersion on the efficiency of cement use in concrete. The increase of packing and the complete dispersion of fine particles has been shown to improve efficiency, as measured by the ratio between binder consumption and compressive strength (the performance parameter used in most practical applications). Resumo Devido a questões ambientais, a cadeia do concreto busca reduzir emissões de CO2. Porém, a demanda crescente de países em desenvolvimento faz com que o aumento da produção supere as diminuições geradas por ações industriais como melhoria de fornos e substituição de clínquer. Novas estratégias são fundamentais. Mudanças na formulação de concretos, tornando-a mais eficiente, podem ajudar caso produzam concretos de mesmo desempenho e menor consumo de cimento. Neste sentido, a melhoria do empacotamento e dispersão das partículas aumentam esta eficiência. Quanto melhor o empacotamento, menor o volume de vazios entre as partículas, demandando menor teor de fluido (água) para permitir fluidez. A dispersão das partículas também diminui o teor de água para a mesma fluidez. Quanto menos água, menor a relação a/c e maior a resistência. Assim, ambas as estratégias aumentam a eficiência ao desatrelar a obtenção de fluidez ao teor de água. Este trabalho estudou a influência do empacotamento e dispersão na eficiência do uso do cimento de concretos. Demonstrou-se que o aumento do empacotamento e a completa dispersão das partículas finas permitem atingir melhor eficiência - medida pela relação entre consumo de ligantes e resistência à compressão (parâmetro de desempenho utilizado na maior parte das aplicações práticas).

Concrete, the major construction material used in the construction industry worldwide, presents a huge environmental impact producing about 7% of the global carbon dioxide. Given the concerns related to global warming, studies have been focusing on distinct approaches aiming to reduce the amount of Portland cement (PC), which is the least sustainable ingredient of the mixture, by adopting alternative mix-design strategies such as the use of particle packing models (PPMs). However, there is currently a lack of data on the efficiency of the use of continuous PPMs to reduce PC while maintaining or improving concrete fresh and/or hardened properties. This work aims to investigate the impact of current and modified versions of continuous PPMs on the fresh (rheological behaviour) and hardened (compressive strength, modulus of elasticity, porosity, and permeability) state of mixtures designed with low and moderate amounts of PC. Results demonstrate that eco-efficient concrete may be produced through current and modified continuous PPMs without compromising the fresh and hardened properties of the material. Nevertheless, further durability and long-term investigations must be performed on systems with reduced PC contents.

Mixing is one of the mortar processing steps (the others being proportioning, transport and application) that, due to its apparent operational simplicity, has been somewhat undermined. However, the mixing process quality has direct influence on the mortar's rheological behavior and its hardened state properties. In this context, this study's objective is to assess the influence of two mixing parameters (time and water addition rate) on the characteristics of the produced mortar. Both mixing and flow measurements were performed in a rotational rheometer developed at POLI/USP-Brazil. In this equipment, the mixing strain rate is given as a function of torque evolution. Mortar tensile strength, modulus of elasticity and volumetric porosity were evaluated in its hardened state. "Bad mixing" conditions can arise from too short mixing times or too slow water loading. These bad mixing conditions led to mortars with lower mechanical strength and more unfavorable rheology, meaning high thixotropy and flow curve loops with big hysteretic area. When admixture was employed, mixing resulted in a mortar with higher entrained air leading to negative effects on the mechanical properties of the hardened material.

The use of self-compacting concrete in civil construction industry presents various advantages, since the material shows adequate workability during fresh state. When fiber reinforcement is used, there are changes in its behavior that require attention. This study aimed to evaluate the applicability of rheological tests and the correlation between its results and those obtained with regular tests used to control SCCs. In that sense, different mixtures of SCC with different steel fiber contents were produced in order to be analyzed in the experimental program described. Rotational rheology tests and slump flow and L-box tests were performed. The results showed that slump flow test did not present good correlations with rheological parameters. On the other hand, this test was able to point out the risk of segregation of the mixtures with higher fiber contents. A good correlation was obtained between the L-box test results and rheological parameters. The L-box was also able to show loss in the passing ability of SCC related to the rise of plastic viscosity and yield stress. These tests also presented a good correlation with the rheological parameters when lower fiber contents were used. Although the rheometry test was unable to evaluate these problems, this kind of test gave more objective and reliable data on variations in rheological parameters related to the increase of fiber content, and proved to be a more reliable test to this kind of application, especially when applied together with the conventional tests. RESUMO O uso de concreto autoadensável na construção civil apresenta várias vantagens, desde que o material apresente trabalhabilidade adequada no estado fresco. Quando é utilizado o reforço com fibras, há alterações nas propriedades no estado fresco, que nem sempre são detectadas com a utilização de ensaios convencionais normalizados. Este estudo buscou avaliar o potencial de aplicação de ensaios reológicos e a relação com os ensaios comumente utilizados para aceitação de CAAs. Com essa finalidade, foram elaboradas misturas de CAA com fibras de aço em diferentes teores e realizaram-se ensaios de reometria rotacional, espalhamento e Caixa L. Os resultados mostraram que o ensaio de espalhamento não apresentou boa correlação com os parâmetros reológicos medidos, mas permitiu detectar o risco de segregação dos concretos com maior teor de fibras. O ensaio de caixa L obteve boa correlação com os valores obtidos no reômetro, demonstrando perda na habilidade passante em função do aumento da viscosidade plástica e tensão de escoamento, especialmente para baixos teores de fibras, mas apresentou bloqueio entre barras para grandes quantidades de fibras. O ensaio de reometria forneceu dados mais objetivos sobre variação nos parâmetros reológicos, apontando um comportamento pseudoplástico do concreto utilizado no trabalho. Ficou claro o aumento da viscosidade com o aumento do teor de fibras como uso da reometria, fornecendo informações confiáveis mesmo para maiores teores de fibras. Isto comprova que a reometria é um ensaio bastante adequado para este tipo de aplicação.

This study analyses the impact of substituting limestone fillers for cement on the rheological behaviour and drying shrinkage of microconcretes that are used for repair coatings. Three microconcretes were formulated with limestone filler contents of 80%, 60% and 20% by weight in relation of the total fines (cement and limestone filler). The total fines and water contents were kept constant in all of the formulations result in mixtures with similar volume of paste. The rheological behaviours of the mixtures were evaluated using a rheometer with planetary motion. The specimens were then moulded for mechanical characterisation and to measure the drying shrinkage. The porosity of the pastes was also evaluated using the mercury intrusion porosimetry (MIP). Rheological properties such as the yield stress and viscosity were influenced by the amount of cement that was replaced by fillers. Larger volumes of filler in the paste produced lower yield stresses and, consequently, higher slump values were obtained. However, the plastic viscosity increased with the filler content. In the hardened state, greater substitutions of cement by fillers decreased the drying shrinkage. This will cause lower differential shrinkage between the repair material and the existing substrate, generating lower tensile stresses in the repair material (repair coating) and therefore less potential for cracking of this. The experimental shrinkage results were compared to values that were obtained by the ACI 209, CEB-FIP90, B3 and GL2000 shrinkage prediction models. The models were found to overestimate the amount of shrinkage with increased substitution of cement by filler in the paste. Therefore, these models should be calibrated considering other factors such as the quantity of filler used in cement replacement. That consideration could optimize the use of these models in the design stage to verify if the values of expected shrinkage are within usually accepted limits for this application.

This work was conducted to evaluate the hardening phenomenon of pastes formulated with Portland cements blended with limestone filler (CPIIF), ground blast furnace slag (CPIIE) or pozzolan (CPIIZ). Vicat test, isothermal conduction calorimetry and oscillatory rheometry were the methods used to monitor this transition. The results of Vicat test indicates the faster setting time of pozzolan cement, but no information before this time was obtained. Using isothermal calorimetry was possible to monitor the related changes to the chemical reactions since the first contact with water, and using rheometry, the rate and force of cement particles agglomeration. The main purpose of this work was not extensively explain the results of these three methods, but show that they are complementary to better explain the transition from fluid-to-solid behavior in function of different kind of mineral addition. Resumo Este trabalho foi realizado para avaliar o fenômeno de endurecimento de pastas formuladas com cimentos Portland compostos: calcário (CPIIF), escória granulada de alto forno (CPIIE) ou pozolana (CPIIZ). Ensaio Vicat, calorimetria de condução isotérmica e reometria oscilatória foram os métodos utilizados para monitorar tal transição. Os resultados do ensaio Vicat indicaram menor tempo de pega na composição com o cimento de pozolana, mas nenhuma informação anterior a esse tempo foi obtida. Usando calorimetria isotérmica foi possível monitorar as alterações relacionadas às reações químicas desde o primeiro contato com a água, e aplicando os conceitos de reometria, obteve-se informações sobre a taxa e força de aglomeração de partículas dos cimentos. O objetivo principal não foi explicar extensivamente os resultados destes três métodos, mas mostrar que são complementares para compreender melhor a transição do comportamento fluido para sólido em função de diferentes tipos de adição mineral. Os resultados obtidos para estes três ligantes, com diferentes SCMs, mostraram que seu desempenho é bastante diferente do ponto de vista da hidratação inicial, e consequentemente, pode ser questionado se podem ser considerados intercambiáveis em misturas de concreto ou argamassas com a mesma finalidade.

Resumo Squeeze flow é uma das principais técnicas para analisar o comportamento reológico de argamassas. Esses materiais podem ser considerados como suspensões concentradas, reativas e heterogêneas com grande extensão granulométrica, nas quais o comportamento reológico é influenciado pelas quantidades e características de seus constituintes. Para avaliar alguns fenômenos de maneira mais detalhada, é interessante reduzir os fatores que influenciam o fluxo. Assim, este trabalho avalia o comportamento reológico de suspensões concentradas de esferas macroscópicas de vidro em fluidos newtonianos de diferentes viscosidades (silicones: 100, 1.000 e 10.000 cSt) e visa analisar a interação entre as fases líquida e sólida e a ocorrência de segregação. As suspensões com 60% e 70% em volume de sólidos foram submetidas a ensaios de squeeze flow com diferentes velocidades. O aumento da quantidade de fluido altera os principais fenômenos relacionados ao fluxo: com baixo volume de líquido o atrito entre as partículas, a capacidade de lubrificação do fluido e a coesão decorrente da formação de meniscos são predominantes na suspensão, enquanto em suspensões com volume de líquido suficiente para afastar as partículas a viscosidade do fluido, a força de arraste e a permeabilidade do sistema granular influenciam no comportamento reológico e na ocorrência de separação de fases. Abstract Squeeze flow is one of the main techniques used to evaluate the rheological behaviour of mortars. This type of material can be considered as a reactive, heterogeneous and concentrated suspension with a wide range of particle sizes, and its rheological behaviour is influenced by the quantity and characteristics of its constituents. In order to evaluate some phenomena in detail, it is interesting to reduce the factors that influence the flow of the material. Thus, this paper assesses the rheological behaviour of concentrated suspensions of macroscopic glass spheres in Newtonian fluids with different viscosities (silicone oils: 100, 1000 e 10000 cSt) aiming to analyse liquid and solid interactions as well as the occurrence of phase separation. Suspensions with 60% and 70%vol of spheres were subjected to squeeze flow tests at different displacement rates (0.01, 0.1 and 1.0 mm/s). The increase in liquid content changed the main phenomena governing the flow: (i) at low liquid volume, friction between particles, liquid lubrication capacity and cohesion generated by meniscus formation have a major effect; while (ii) in suspensions with liquid content enough to separate the particles, the fluid viscosity, drag force and permeability of the granular system determine the rheological behaviour of the suspension and the occurrence of phase separation.

The use of red mud from Bayer process in association with Portland cement has been shown to be promising because of its good performance on the hardened state. However, the physicochemical interactions during the cement reaction have not been explored in depth in the literature. As the red mud is rich in iron, aluminates, silicate and, mainly, sodium components, the interaction with Portland cement is rather complex. Additionally, the large amount of finer particles can introduce another variable in the development of hydrated compounds. This work was aimed at evaluating the impact from partial substitution of Portland cement for different contents of red mud collected in an alumina production plant in the northeast of Brazil. The hydration reaction was monitored by isothermal conduction calorimetry and the setting time of cement by the Vicat test. The results indicate that the residue of bauxite ore affects the chemical reaction of cement, due to nucleation effects, packing and dilution, and the high amount of sodium and soluble aluminates from the red mud causes the formation of sodium silicoaluminate hydrate (NASH) and a greater amount of hydrated calcium aluminate, which had no effect on the setting time.

The current compressive strength test for cement classification is performed under a fixed water to cement ratio according to the Brazilian and European standards, regardless the consistency obtained. However, under practical conditions the amount of water required is related to the rheological need to obtain and maintain a desired workability. Intrinsic cement characteristics influence the water demand such as the cement particle’s granulometry, specific surface area, density, the presence or not of water reducing admixtures, chemical and mineralogical nature of raw materials, etc., influence particles agglomeration state. Because water demand influences the mechanical properties of cement based products, the compressive strength class under a fixed water to solids ratio specified by the standards may not be representative for the user. The present work investigates the influence of mixing conditions on mini-slump spread results, a test that has been used for many years but never standardized. Cement paste samples were produced with varied mixing conditions (time and rotation speed) using a conventional stirrer and subjected to mini-slump spread test immediately after mixing and at fixed hydration times. Results show that mixing and hydration time do influence on mini-slump spread. At lower rotation speeds, results variability increases. Under fixed time after first contact with water, increasing rotation speed leads in a reduction of results variability and increase the test’s repeatability on cement pastes. Resumo O ensaio de resistência do cimento, segundo às normas brasileiras e europeia atuais, é realizado com uma relação água/cimento fixa em massa, independente da consistência obtida. No entanto em condições normais de uso, a quantidade de água é uma variável definida com a finalidade de manutenção da consistência dos materiais cimentícios para obter trabalhabilidade adequada. Características intrínsecas dos ligantes, como distribuição de tamanho de partículas, área superficial especifica, densidade e natureza química ou mineralógica, ou extrínsecas, como presença de aditivos, temperatura ambiente e da água, tempo e energia de processamento, etc., podem afetar de forma distinta o estado de aglomeração e, consequentemente, a necessidade de líquido para a mistura. Como a demanda de água influencia a resistência mecânica dos produtos, a utilização da relação água/cimento fixa torna, em termos práticos, a classificação do cimento pela resistência pouco significativa para o usuário. Neste trabalho foi investigada a influência das condições de mistura na repetibilidade do ensaio de mini-slump, bastante usado para avaliação da quantidade de água nas composições, mas não normatizado. Pastas de uma mesma amostra de cimento foram misturadas por diferentes tempos e/ou rotações, usando um agitador mecânico convencional, e submetidas ao ensaio de mini-slump imediatamente após o ensaio ou após o mesmo tempo de contato com a água. Observou-se influência significativa nos resultados: quanto maior a rotação ou a manutenção do tempo de mistura, menor a variabilidade do espalhamento mini-slump sendo que a influência é mais sensível para diferenças de rotação.

Resumo A etapa de mistura influencia as condições de execução do revestimento de argamassa, visto que desde o primeiro contato dos materiais sólidos com água uma série de eventos de aglomeração e desaglomeração no sistema é verificada. Acontece que durante o processamento das argamassas em obra a utilização de equipamentos com distintos mecanismos de mistura pode modificar o desempenho do sistema de revestimento. Este trabalho foi realizado com o objetivo de avaliar a influência da condição de mistura durante o processamento de argamassas aditivadas com incorporador de ar e formuladas com diferentes tipos de cimento. As misturas foram realizadas em um reômetro rotacional variando-se a velocidade de rotação, porém mantendo-se o tempo total de batimento. Reometria de mistura, ciclo de cisalhamento e teor de ar incorporado foram as propriedades avaliadas no estado fresco, enquanto porosidade, resistência mecânica, módulo de elasticidade e permeabilidade ao ar foram utilizados para avaliação do estado endurecido. Com base nos resultados obtidos pôde-se afirmar que a variação da velocidade de rotação e o tipo de cimento utilizado impactaram as propriedades das composições nos estados fresco e endurecido. Abstract The mixing stage is one of the most important step for the execution of the rendering mortar, since from the first contact of the solid materials with water a series of agglomeration and deagglomeration events in the system is verified. However, during the mortar processing in the buildings the use of different equipments, with distinct mixing concepts, makes this stage very uncontrolled. The main purpose of this work was to evaluate the influence of mixing condition during the processing of mortars with addition of air-entraining agent and formulated with different kind of Portland cement. The mixing was performed on a rotational rheometer in different rotational speed, but maintaining the total time of shear. Mixing and shear rheometry, and air-incorporation were the properties evaluated in the fresh state, while porosity, mechanical strength, dynamic elasticity modulus and air-permeability were used to evaluate the hardened state. Based on the obtained results, it could be stated that the variation of the rotational speed and the type of cement used impacted the properties of the compositions in the fresh and hardened states, mainly due to changes in the air-volume incorporated and, consequently, in the total porosity generated in the mortars.

RESUMO Grandes quantidades de materiais finos (na forma de pó) são coletados e armazenados nas pedreiras, constituindo um sério problema ambiental, pela falta de destinação específica para esse resíduo. No entanto, esses materiais poderiam ser utilizados como um fíler em concreto autoadensável (CAA), o qual necessita de um grande volume de finos na sua constituição. Desta forma, neste trabalho, foram investigados os efeitos do fíler calcário (empregado como referência), fíler diabásico e gnáissico, nas propriedades de CAAs. A influência da mineralogia, forma e tamanho das partículas foram avaliadas por meio de ensaios no estado fresco (monopontos e reométricos) e ensaios no estado endurecido de CAAs. Os resultados mostraram que concretos contendo fíler gnáissico ou diabásico podem apresentar propriedades reológicas similares aos concretos contendo fíler calcário, quando apresentam distribuição granulométrica e tamanho de partícula similar ao fíler calcário usualmente utilizado (d50 entre 30 e 40 µm). Além disso, CAAs contendo fíler diabásico apresentaram resistência à compressão superior aos concretos dosados com os demais fílers. Diante dos resultados, pode-se concluir que os fílers de diabásio e gnaisse apresentam potencial para serem utilizados como materiais alternativos ao fíler calcário em CAA, embora possam demandar maior quantidade de aditivo superplastificante para atingir propriedades comparáveis no estado fresco. ABSTRACT Large amounts of powders have been collected in quarries and storage of these by-product dusts is a serious environmental concern. However, these materials may be used as a filler in self-compacting concrete (SCC), which requires a large amount of fines in its composition. Thus, in this paper, the effects of limestone filler, diabase, and gneiss quarry powder on the properties of self-compacting concrete were investigated. The influence of the mineralogy, shape and particle size distribution were evaluated by rheometry, and by fresh and hardened concrete properties. SCC containing gneissic or diabasic powder can show rheological parameters values very similar to those of SCC containing limestone filler when the material has the same particle size to that of an usual limestone filer (d50 between 30 e 40 um). SCC containing diabasic powder showed higher compressive strength than that of SCC containing limestone filler or gneiss powder. It was found that diabasic and gneissic quarry powders could be used successfully for producing SCC, although a higher superplasticizer content was required than that of SCC containing limestone filler.

Resumo A substituição parcial de cimento Portland por resíduo de bauxita (RB) resulta em produtos com, no mínimo, propriedades similares às dos produtos fabricados com o ligante puro. No entanto, as interações físico-químicas entre os diferentes tipos de cimento e o RB durante a reação de hidratação ainda é pouco explorada em literatura. A elevada quantidade de sódio e a presença de Al2O3, SiO2 e Fe2O3 são fatores que afetam a formação dos produtos hidratados e dependem do tipo de cimento utilizado na mistura. Sendo assim, este trabalho foi realizado com o objetivo de avaliar o impacto da presença do resíduo de bauxita em associação ao cimento Portland simples nas primeiras idades de hidratação. Calorimetria de condução isotérmica, difração de raios X, análise termogravimétrica e espectroscopia de infravermelho foram as técnicas escolhidas para o monitoramento. Os resultados ilustraram que a presença do resíduo coletado na planta da Alcoa (Poços de Caldas) aumenta o tempo de indução, o consumo de portlandita, e as quantidades de etringita e monossulfoaluminato formadas. Ao mesmo tempo, houve formação de silicoaluminato de sódio e bicarbonato de sódio, devido às reações com silicatos, aluminatos e com o carbonato do cimento. Abstract The partial substitution of Portland cement by bauxite residue (BR) results in products with, at least, properties similar of products with pure binder. However, the physicochemical interactions between Portland cement and BR during the chemical hydration reaction is still poorly explored in literature. The high amount of sodium and presence of Al2O3, SiO2 and Fe2O3 are factors that affect the formation of hydrated products and depends on the type of Portland cement used. The main purpose of this work was to evaluate the impact of use bauxite residue in substitution of part of cement on the early age of hydration. Isothermal conduction calorimetry, X-ray diffraction, thermogravimetry and FTIR were the methods to this monitoring. The results show that the presence of BR, from Alcoa (Poços de Caldas, Brazil), increases the induction period, the portlandite consumption and the amount of ettringite and monosulfoaluminate produced. At the same time, there are the formation of sodium silicoaluminate hydrate and sodium bicarbonate, due to the reactions with silicates, aluminates and with carbonate from cement.

The ongoing process of industrialization of construction sites encourages the use of new building systems that conflict with traditional techniques associated with the risks of incompatibilities and continuance of control fixed ideas with a significant variability. A practical example is the cement mortar for plastering, commonly used as a corrective factor for facade flatness failures caused by the inaccuracy of the plumb line, rudimentary method used in geometric control of concrete structures and facade of mapping during the execution of the work, favoring the accumulation of errors that reflect the mortar thickness, increasing consumption, losses and defects. Alternatively for improvement, this study analyzed through a case study, the innovative application of 3D laser scanning technology consolidated on the facade of a building to map the surface flatness of the façade and, in an unprecedented manner, to quantify the volume of mortar. The results showed the feasibility of the technique as a solution to accurately identify the critical areas of the facade on the peripheral concrete structure and masonry and calculate, based on the volumes, the financial impact associated with mortar overthicknesses in critical areas compared with the reductions thickness after treatment of these areas. O processo contínuo de industrialização dos canteiros de obra estimula o uso de novos sistemas construtivos que conflitam com técnicas tradicionais associada aos riscos de incompatibilidades e permanência de controles executivos com significativa variabilidade. Um exemplo prático é a argamassa cimentícia para reboco, comumente utilizada como fator corretivo de falhas na planicidade das fachadas causadas pela imprecisão do fio de prumo, método rudimentar usado no controle geométrico das estruturas de concreto e no mapeamento da fachada durante a execução da obra, favorecendo o acúmulo de erros que refletem nas espessuras de argamassa, potencializando consumo, perdas e defeitos. Como alternativa para melhoria, este trabalho analisou através de um estudo de caso, a aplicação inovadora da tecnologia consolidada de escaneamento 3D laser na fachada de um edifício para mapear a planicidade superficial da fachada e, de forma inédita, para quantificar o volume de argamassa. Os resultados mostraram a viabilidade da técnica como solução para identificar com precisão as áreas críticas da fachada sobre a estrutura de concreto periférica e alvenaria e, a partir da volumetria, calcular o impacto financeiro associado às sobrespessuras de argamassa nas áreas críticas comparada com as reduções de espessura após tratamento dessas áreas.

Producing cementitious materials with low CO2 emissions is a key challenge for sustainability, considering the increasing demand for cement and the inefficacy of current industrial solutions. Improving the efficiency of binder use is mandatory, so that binder replacement by inert fillers with lower environmental loads is an alternative, which demands careful control of the rheological behaviour to decrease the water demand of pastes. Dispersion and packing models are well known, but other less explored parameters of raw materials (surface area, density, roughness) and paste (water content, distance between particles) determine the interaction among particles, affecting the paste's rheological behaviour. The aim of this paper is to assess the influence of inert fillers on the rheological behaviour of cementitious pastes. A range of 12 inert fillers with varied aspects was evaluated. The results indicated a good agreement between the Casson viscosity and the interference parameter calculated using the interference model.

This paper reports an experimental investigation regarding the influence of the squeeze velocity, during positioning of the parallel-plate gap, on the rotational shear flow behaviour of a cement paste. The descent of the upper plate was performed using diverse speeds while the normal force generated due to the compression of the paste was recorded. The slower the plate speed, the higher the resulting normal force. This behaviour was caused by liquid–solid separation, which is more likely to occur at slow squeeze velocities. Phase separation was confirmed by assessing, via microwave drying, the water contents of the trimmed portion of the paste sample and of the portion actually subjected to rotational shear cycles. Owing to the variation of water/cement ratio induced by liquid radial migration, paste's Bingham yield stress and plastic viscosity were significantly affected by squeeze speed, and both rheological parameters presented an inversely proportional relationship with this experimental variable.

Resumo A redução do consumo de cimento na composição de argamassas de revestimento é uma alternativa para a diminuição do impacto ambiental provocado na cadeia de produção do ligante. A utilização de materiais cimentícios suplementares (supplementary cementitious materials - SCM) e a dosagem com base nos conceitos de empacotamento e mobilidade de partículas são estratégias que podem resultar nas propriedades projetadas tanto no estado fresco quanto endurecido. O objetivo deste trabalho foi ilustrar a influência da alteração no consumo de ligante nas propriedades no estado fresco e endurecido de argamassas de revestimento mantendo-se constante a distribuição de tamanho de partículas, o que resultou em porosidade de empacotamento com insignificante variação. O consumo de cimento variou de 8% a 16% em massa, com adição de filler calcário como SCM, sendo que a consistência foi a mesma devido à alteração dos teores de água nas argamassas. Os resultados indicaram que a redução no consumo de cimento afeta negativamente as propriedades no estado endurecido, mas ainda assim atendem às exigências estabelecidas para esse tipo de revestimento. Abstract The reduction of cement consumption in rendering mortar composition is an alternative to reduce the environmental impact in the binder production chain. The use of supplementary cementitious materials (SCM) and the dosage based on the concepts of particle packing and mobility are strategies that can result in designed properties both fresh as hardened state. The objective of this study was to illustrate the influence of the change in binder consumption in the properties of formulated rendering mortars keeping constant the particle size distribution, resulting in negligible variation in packing porosity. The cement consumption was ranged from 8 to 16% by mass, with the addition of limestone filler as SCM, with the consistency has being the same due to the alteration of the water content of the mortars. The results indicated that the reduction in cement consumption adversely affect the properties of the mortar in the hardened state, but still quite comply with the requirements for this type of rendering.

The mixing process of fiber-containing cementitious suspensions is a crucial factor to obtaining a good dispersion of fibers and guarantee adequate mechanical performance of the hardened products. The addition of fibers into the suspension causes reduction of the fluidity of the system due to factors inherent to the fibers, the matrix and their interaction. During mixing, these interactions make dispersion and homogenization processes more difficult due to the formation of fibers - particles agglomerates. Conventional techniques to assess workability of mortars are inadequate to evaluate the rheological behavior of fiber-reinforced systems, in which parameters like viscosity and yield stress are not completely taken into account. Therefore, this work employs rotational rheometry to evaluate the influence of fiber and water addition sequences on mixing and rheological behavior of mortars containing Polyvinyl Alcohol (PVA) fibers. Constant test parameters were: mixing time of 317s; impeller velocity 126.5 rpm; water flow 128g/s. A constant mix design was used with a water content of 16%wt, and a 0.2%vol of fibers were added to the reference composition. Four mixing sequences were studied: S1 and S2 are based on the addition of fibers at different stages of the mixing process; while in S3 and S4 not only the fibers are added at different stages, but also the water addition is performed in two steps (25% first and 75% latter).Results showed that it is possible to optimize the mixing step of fiber-containing systems by changing the moment of fiber addition into the mixture. The introduction of fibers after mixing the dry mortar with water, when it already had achieved its fluidity point, demanded a lower mixing effort and produced a more flowable material. RESUMO O processo de mistura de suspensões cimentícias contendo fibras é uma etapa crucial para que se obtenha uma boa distribuição das fibras, garantindo os benefícios que as mesmas podem trazer ao desempenho mecânico. A introdução das fibras na suspensão tende a provocar redução na fluidez. Isso ocorre devido a uma série de fatores inerentes às fibras, à matriz e, à interação entre elas. Durante a mistura, essas interações tornam a dispersão e homogeneização mais difícil devido à formação de aglomerados de partículas e fibras. Técnicas convencionais de avaliação da trabalhabilidade são insuficientes para avaliar o comportamento reológico de sistemas reforçados com fibras porque parâmetros como viscosidade e tensão de escoamento não são considerados em sua totalidade. Assim, este trabalho propõe utilizar técnicas de reometria rotacional, para avaliar a influência da sequência de adição da fibra e da água na mistura e no comportamento reológico de argamassas. O tempo de mistura é mantido fixo em 317s, a velocidade do equipamento é 126,5rpm e a taxa de adição de água 128g/s para todas as sequências. Uma mesma composição granulométrica foi usada fixando o teor de água em 16% e o de fibra em 0,2%. Quatro sequências de mistura foram estudadas: S1 e S2 são baseadas na adição das fibras em diferentes estágios do processo de mistura, enquanto na S3 e S4, não só as fibras são adicionadas em diferentes estágios, mas também a água é adicionada em duas etapas (primeiro 25% e depois 75%). Os resultados indicaram que é possível otimizar o preparo de sistemas com fibras de PVA modificando etapas simples do processo como o momento de introduzir as fibras. Entre as sequências avaliadas concluiu-se que introduzir as fibras após a homogeneização prévia dos materiais, no ponto de fluidez, tende a produzir sistemas mais fluidos e com menor esforço para mistura.