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The standard method of using a caliper to determine aggregate particle dimensions is not sufficient to describe the shape, texture, angularity, and volume of particles, and there is not a r...

This paper compares the use of jaw and impact secondary crushing for producing coarse recycled aggregates from concrete wastes, obtained from road pavement and demolished building materials. The crushing mechanism interferes directly with recycled aggregate properties at different levels: particle size distribution, aggregate shape, generation of micro-fractures, as well as regarding the detachment of porous hardened cement paste from particle surface in order to recover pure, non-porous natural aggregates. However, crusher selection in the recycling industry is mostly carried out by acquisition and maintenance costs, industry and manufacturer traditional habits, low cost associated with second hand equipment. It also does not consider essential parameters such as the final properties of the desired end-product. Representative samples from two recycling plants were collected after primary impact crusher and secondary crushing were performed in a controlled laboratory condition through jaw and impact crushers. The aggregates attained were characterized, demonstrating similar density, porosity, particle size distribution and content of attached cement paste. Minor observed differences do not justify the common belief in the industry that impact crushers provide an improvement in the quality of recycled aggregates due to the higher detachment of cement paste from aggregates. Keywords: Recycled concrete aggregate, Liberation comminution, Recycled aggregate properties, Impact crusher, Jaw crusher

Made available in DSpace on 2022-05-01T03:42:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Calcium aluminate layered double hydroxides (Ca-Al LDHs) constitute a considerable part of cementitious waste fines. Although cementitious waste fines have proven to be recyclable by thermal treatment at moderate temperatures (400–700 °C), understanding how each phase rehydrates and contributes to the binding properties of rehydrated cementitious materials is still necessary. In this study, the dehydration and rehydration of katoite are investigated through in situ techniques, and its applicability as an alternative binder or supplementary cementitious material (SCM) is discussed. The research employed X-ray diffraction, isothermal calorimetry, in situ wide-angle X-ray scattering (WAXS), and rotational/oscillatory rheometry. Katoite synthesized by a mechanochemical process (with contamination of calcite) was dehydrated at 400 °C, producing mainly mayenite. During rehydration, calorimetry presents high heat production in the first minutes. WAXS shows prompt recovery of katoite and increasing formation of monocarboaluminate (Ca-Al LDH) after 30 s of rehydration. The findings confirm the direct association between rapid heat release and phase reformation. Rehydrated pastes present a high yield stress and an increasing storage modulus, indicating rapid binding properties. The consolidation is also correlated with cumulative heat and monocarboaluminate formation. The results indicate the potential of calcined katoite (with presence of calcite) for use as rapid set alternative binder or SCM. Department of Construction Engineering Escola Politécnica University of São Paulo Institute of Chemistry São Paulo State University Department of Metallurgical and Materials Engineering Escola Politécnica University of São Paulo Institute of Chemistry São Paulo State University CNPq: 140054/2020-0 FAPESP: 2014/50948-3 FAPESP: 2019/27284-5 CNPq: 305564/2018-8

The tensile strength of limestone calcined clays (LC3) and Ordinary Portland Cement (OPC) pastes was determined by a point load test (PLT). Testing was carried out on reduced size cubic specimens (10 × 10 × 10 mm), and the results were analysed using the Weibull probabilistic distribution. Mercury intrusion porosimetry (MIP) was also carried out to complement the investigation. Results showed that, despite being slightly more porous, LC3 has higher tensile strength than OPC due to the pore refinement caused by pozzolanic reactions. The data variability was three times lower for LC3 in comparison to OPC, which may be related to the slightly higher fracture energy of the LC3 samples.

Surface roughness of coarse aggregates, regardless of its known influence in the bonding strength with the cement paste in the hardened state and in the viscosity of the composite in the fresh state, it still a barely researched and discussed topic. In addition, little is known about what rock characteristics influences the multiscale roughness of aggregates. This paper aims to evaluate the roughness of distinct types of aggregates in multiscale (macro and micro scale of roughness) using a 3D interferometer and establish a quantitative relation between the granulometry and mineral composition of the rocks and the surface roughness of aggregates. Six types of aggregates, five crushed and one gravel from riverbed, with sizes ranging from 19 to 25 mm were scanned. One sample from each type was chosen for a petrographic analysis. The six types of aggregates analyzed showed statistical differences between them in macro and micro scales of roughness. In the microscale roughness, basalt was considered the smoothest, and surprisingly, the quartzite (gravel), were one of the roughest. In the macro scale roughness, the quartzite (the gravel) was smoother than all the other samples due its rounded shape, while the gneiss was the most irregular particle and had the highest roughness. The quartzite (gravel) is a good example of how an aggregate could be very rough in a microscale (invisible to the naked eye), comparable to crushed aggregates, while being smooth to the touch and rounded. The weathering seems to affect the roughness at micro(nano)scales, independently of the roundness shape observed at millimetric scale. The micro scale roughness appeared to be related to the average size of the grains, the smaller the average grain size, the lower the micro scale roughness is. Rocks with aphanitic textures tends to fracture in smoother surfaces than rocks with phaneritic textures.

Knowledge of the mechanical properties of plain cement pastes, as well as their variability, is important to predict the properties of concretes. Pastes are very susceptible to critical defects that not only reduce the mechanical strength but also increase the variability. The paper proposes a method to evaluate the tensile strength and the elastic modulus of cement pastes, based on the Point Load Test and the Hertz Contact Theory, from experiments on reduced-size cubic samples (~10 mm). Three cement pastes with w/c ratios of 0.30, 0.50 and 0.70 were produced and 40 samples were cast for each paste. A simple method of estimating the chemically combined water and the effective w/c ratio (after bleeding in the stationary stage) of each sample was proposed. Being an expedite method, it allowed obtaining more than 100 valid mechanical results in about 8 h of testing using less than 250 g of cement, with values of tensile strength and elastic modulus that approached the macroscale reference values from the literature. The tensile strength of cement pastes varied considerably, but in the range informed in the literature, whereas the elastic modulus was less variable. Probabilistic functions for the characteristic values of the mechanical properties were provided.

Hydrated cementitious fines can be recycled by thermal treatment (

The article ‘‘Improved method to measure the strength and elastic modulus of single aggregate particles’’, written by ‘‘Natalia V. Silva, Sergio C. Angulo, Aline da Silva Ramos Barboza, David A. Lange, Luis M. Tavares’’, was originally published electronically on the publisher’s Internet portal (currently SpringerLink) on 6 July 2019 without open access.

The standard methods used to determine the mechanical properties of single aggregate particles have shortcomings. Indeed, methods that are commonly used to measure the strength of irregular particles do not provide their elastic modulus and are also only semi-quantitative. The aim of this work is to determine more accurately both the tensile strength and the elastic modulus of single coarse aggregate particles using the point load test fitted with tungsten carbide semi-spheres and coupled with a linear transducer. In the experiment, the poles of the particles are made flat and parallel at the points of contact with the semi-spheres of the apparatus, allowing to estimate the elastic modulus of aggregates in accordance to Hertz contact theory. Glass particles of different shapes (spheres, cubes, and prisms) were used as reference material to validate the experimental method and establish the optimal conditions to conduct the test. These conditions consisted of a deformation rate of 0.2 mm/min, a blunt 4.0-mm diameter cylinder piston for spherical particles, while two 14.0-mm diameter semi-spheres in the case of rectangular particles (cubes/prisms). It is also hereby proposed to measure the tensile strength of irregularly-shaped particles by a modified version of Hiramatsu and Oka’s formula using the equivalent core diameter. The proposed method was then applied to measure the strength and modulus of coarse granite aggregate particles (25.0 to 9.5 mm). It demonstrated that the variability of the elastic modulus and tensile strengths of the individual aggregate particles was quite significant, confirming the importance of using the proposed improved method to qualify materials for structural (high strength) concrete, or to simulate/predict the mechanical behavior of concrete.

The quality control of aggregates for concrete involves determining their water absorption and apparent density, indicators of the material’s porosity. The standard methods were developed for natural aggregates and are less appropriate for construction and demolition waste recycled aggregates (RAs), which have greater porosity and variability. This paper presents a rapid and accurate method to measure water absorption of RAs, combining 0.5 h vacuum saturation with ~2 h microwave oven drying kinetics. The new method anticipates the results by 43.5 h in comparison of standard ASTM C127, making it appealing for quality control operations. Statistical analysis shows new method gives statistically equivalent results for porous recycled aggregates but it over estimates low porosity natural aggregates. Results of the proposed method are different less than 0.5 % of those obtained by standard methods when testing three RAs with absorptions varying between 5 and 19 %. Operator did not influence the results of the new method. Details of the new experimental procedure and equipment developed are given. Suggestions for further improvement of the new method presented.

Concrete waste slurries coming from the washing of concrete mixer trucks in the manufacture of ready-mix concrete generate high costs and environmental impacts. In this work, we examined the consumption of raw materials, water, and generation of wastes for three Brazilian ready-mix concrete plants (that used different waste management strategies). The reuse of concrete slurry fines was also investigated in new concretes considering the waste management scenarios, production and operational costs. The strategy to recover fresh concrete provided the best scenario since it reduced significantly operational costs, despite the inclusion of new production cost, i.e. the hydration stabilizer additive. The replacement of sand with 1 vol.% concrete slurry provided adequate rheological conditions for concretes, when the water content increased up to 6 wt.% or added 0.3 % m.c. of polycarboxylate-based additive. The marginal increase in the production cost can also be compensated by the reduction of the disposal operational costs. The reuse strategy was not enough for the total elimination of concrete fines, requiring market diversification (e.g. pre-cast concrete products); but fines availability can be very limited.

Characterizing the strength and the elastic modulus of single aggregate particles is relevant, in particular for use in high-strength concrete. One problem of methods normally used in this task is the time and effort demanded. The work proposes a rapid and simple test method to measure the probabilistic distributions of those properties for coarse aggregates contained in the range of particle sizes between 9.5 and 25-mm, approximately, applying it to granite and limestone. Water absorption (WA) of a hundred individual particles of each type of coarse aggregate was measured. Afterwards, the Point Load Test method is used to determine the tensile strength of all particles. A Linear Variable Differential Transducer (LVDT) coupled to the mechanical essay measured the displacements, under Hertz contact conditions, between artificially flat-made irregular particles and the testing machine fixture, allowing to determine the elastic moduli. Results were represented using the Weibull probabilistic distribution function. The one hundred individual particles, when stratified on the basis of non-destructive WA measurements, allowed capture the mechanical variability in the data. As such, mechanical tests could be performed only with approximately 20 specially selected particles of each aggregate type. Fundamental inverse exponential functions between the mechanical properties and WA confirmed the possibility of using this artifice. The tensile strengths ranged from 3 to 22 MPa for granite aggregates and from 3 to 16 MPa for limestone aggregates. Elastic moduli of the aggregates were also variable: 18–78 GPa for granite aggregates, and 18–66 GPa for limestone aggregates. Values within these ranges may influence the mechanical performance of high strength concretes.

Waste management solutions and reuse strategies for excavation soils from construction works are needed to increase the circularity of resources in urban areas. In this study, we assessed some reuse strategies for excavated soils, based on a geotechnical-environmental characterization study conducted with samples from an “inert” construction and demolition waste (CDW) landfill in Sao Paulo city. The geotechnical reuse of soil samples should be limited to applications where the material is confined (backfilling trenches, containing walls etc.), because of swelling and loss of bearing capacity after saturation. In addition, CDW-soil mixtures can be used in reinforcement of subgrades and sub-bases of pavements of low-volume roads. Gypsum/cementitious materials in contact with the leakage of sanitary effluents might result in sulfate concentrations that restrict the reuse of CDW due to quality requirements of superficial waters, however, without posing a significant risk to human health. They might also degrade neighboring concrete foundations. A methodological flowchart to support reuse strategies of soils for urban areas was proposed, based on current characterization tests.

The amount of construction waste (CW) at building sites is highly variable, for instance the CW generation index ranges between 50-300 dm3 per square meters of gross floor area. Today there is still a lack of knowledge about variables (building design, construction process, construction technologies, etc.) affecting the CW generation. The objective of this paper is to analyse the influence of multi-storey building design and some construction processes on the CW generation indexes. The CW generation was analysed for two groups of buildings with two different construction processes; one with plumbing and electric services installed inside the masonry element and the other with plumbing and electric services installed onto the masonry element and covered with water-resistant drywall system (reducing the construction waste generation). The gross floor area directly affects the amount of executed construction works in a building site. Since the most important works (concrete, masonry and cladding) for CW generation is related to gross floor area, gross floor of buildings is also directly related to CW generation. For buildings with gross area varying from 20,000 to 80,000 m2, there is a reduction of approximately 18% of construction waste only changing the plumbing and electric services installation system, from embedded in the masonry element to installed onto the masonry element and covered with water-resistant drywall system.

This study aims to investigate the properties of CDW recycled aggregates using silane-based water repellent agent in three different types of treatments: (a) immersion; (b) sprinkling; and (c) dripping; in order to improve the reduces quality of the material due to the high porosity. Wettability and water absorption were determined by apparent contact angle measurements, water absorption after 24h of saturation (standard method) and recording the variation of submerged mass during 24 hs. All treatment allowed reducing the water absorption and its kinetic. The contact angle measurements confirmed the effectiveness of the treatment: the surface resulted always hydrophobic. Comparing the treatments, immersion gave the best result in terms of absolute results and in terms of variability of measurements.

In Brazil, the use of wood in construction is primarily temporary, and it can represent a great percentage of construction waste. It is typically discarded with minimal reuse or recycling. As landfill wood disposal could result in methane emissions and/or leaching of hazardous constituents polluting water or soil, the implementation of temporary wood waste reduction strategies must be a critical issue for local construction companies. To manage and control wood waste generation, including setting some reduction goals, it is necessary to identify the influencing factors and ways to quantitatively predict their relative contributions. This study uses a multiple regression statistical model to estimate the amount of temporary wood waste generated in the construction of high-rise buildings by considering the influencing factors related to the design/construction as well as site and safety installations. The case study includes 22 high-rise residential buildings. The regression model predicted approximately 89% of the factors involved in the generation of wood waste in similar constructions. The dependent variables that had an influence on the amount of wood waste are related to design features ('number of floors'), structural construction system ('in situ moulded concrete volume'), and site and safety installations ('site wood fence' and 'wood use rate'). Ways of minimising wood waste generation and the contributions of each type of temporary wood use were discussed.

Surface treatment techniques may improve the characteristics of recycled aggregates (RAs) for use in cementitious materials, possibly as an alternative to the energy and CO 2 intensive high quality RA production process. In this paper, we investigate the effectiveness of two water repellent treatments (silane solution and paraffin wax) on the characteristics of different RAs in terms of porosity. We explored the relationship between roughness, porosity/surface area, and wettability of RAs on their water absorption (WA) kinetics. The long-term goal of the treatments is to reduce the water demand of concrete/mortar. We proposed a method to measure the roughness of coarse aggregates by optical interferometry. Contrary to popular belief, recycled concrete aggregates are as rough as crushed natural aggregates, and only red ceramic aggregate is less rough than natural aggregates. This technique combined with mercury intrusion porosimetry identified microstructural changes in the treated RAs. Silane was incorporated into smaller pores ( 100 nm), and the wax significantly reduced the total porosity. Paraffin treatment formed a smoother surface and a thicker paraffin layer around the particles. We determined the water absorption kinetics using the standard 24 h WA test with method adaptations in order to improve the accuracy and repeatability of the tests. Treated RA surfaces exhibited hydrophobic behavior but at the cost of efficiency. WA kinetics significantly changed after 2 h.

The use of recycled concrete aggregates (RCA) in applications other than road sub-layers is limited by two factors: the high porosity of RCA in comparison with natural aggregates, and the restrictions set forth in standards and building codes. Research efforts aimed at alleviating these restrictions are focused on improving the quality of coarse RCAs by reducing the amount of adhered cement pastes, which is the weakest element in this system and influences the rheological behaviour. This paper presents an analysis of the environmental impacts of the recent mechanical and thermo-mechanical processing techniques which produce high performance RCA by reducing the volume of adhered cement paste. Based on published data, processing scenarios were established. These scenarios permit making rough estimates of energy consumption, CO 2 emissions, fines generation and product quality. Using these data and the available emission factors from several countries, an objective comparison was made between these innovating processes and conventional recycling. The production of fines increases from 40% up to as much as 70% as the volume of adhered cement paste on the RCA is reduced. Fuel fed thermo-mechanical process energy consumption, per tonne of recycled aggregate, varies between 36 and 62 times higher than conventional recycling processes. Mechanical processing, combined with microwave heating, increases energy consumption from 3 to a little more than 4 times conventional recycling. Consequently, CO 2 emissions released by conventional coarse aggregate production go from 1.5 to 4.5 kgCO 2 /t, to around 200 kgCO 2 /t, for that of fossil fuel fed thermo-mechanical treatments. Mechanical and mechanical/microwave treatments appear to have the greatest environmental potential. Notwithstanding, the further development of markets for fines is crucial for reducing environmental loads.

Resíduos de construção e demolição constituem a maior parcela dos resíduos sólidos urbanos. A proibição de sua disposição em aterros, a redução na oferta de agregados naturais somada ao aumento de sua demanda, e a crescente exigência para o desenvolvimento de aplicações sustentáveis para tais resíduos impulsionaram o desenvolvimento de aplicações para este material. Diferentes estratégias foram estabelecidas para melhorar a qualidade dos agregados reciclados (reduzir sua porosidade), no entanto, a liberação das fases presentes é raramente discutida na literatura. Neste trabalho, são apresentados os resultados de um estudo de separabilidade realizado em agregados reciclados provenientes de resíduos de construção e demolição de diferentes origens. Os resultados mostram que a proporção de material mais denso aumenta nas frações mais finas e indicam maior liberação entre as fases presentes, especialmente para as frações abaixo de 12,7 mm. Os produtos obtidos diferem expressivamente entre si, independentes de sua origem, o que pode ser confirmado pelos teores de aglomerantes, perda ao fogo e pela sua composição mineralógica. Tais diferenças refletem diretamente nas propriedades físicas dos agregados reciclados (absorção de água, porosidade e resistência mecânica).

In this paper, we compare different methods for determining the water absorption of recycled aggregates (RAs) and, highlighting advantages and critical points, attempt to suggest alternatives for a better way to measure it. Water absorption (WA) capacity has two purposes: (a) measuring the interconnected porosity, which is useful for mechanical concrete analysis and durability issues, and (b) allowing adjustment of the amount of water used in concrete production. Our analysis shows that vacuum during soaking is recommended for the RAs’ interconnected porosity determination. This approach enables shorter testing time (from ⩾24 h to ⩽1 h) and increases the accuracy of the measurement. The saturated surface dry (SSD) state determination can also be fastened using centrifuge, air flow drum, laser scattering, and microwave drying evaporometry, without significant differences. The use of these techniques is still restricted due to such factors as commercial availability, geometric limitations of the sample containers, and difficulty in controlling the temperature and the relative humidity. For concrete production, WA kinetics during the first 30 min is fundamental. Accuracy of the results is arguable regarding the practical issues, for example, vibration or trapped air bubble. Mathematical artefacts can overcome those problems but need to be calibrated with experimental data determined by standard tests over time. Because the WA kinetics probably changes when RAs are in contact with cement paste, a method to understand and quantify this phenomenon is still a research demand.

Neste trabalho, estimou-se a gerão dos resíduos de construção e demolição por dois métodos de quantificação, um indireto e outro direto, considerando-se a produção advinda dos agentes informais e formais. O método indireto considerou a área construída das edificações (construção) e transformação dos pontos de ligação de água e luz instalados (reforma). O método direto identificou a geração advinda de agentes informais e formais nos pontos de disposição finais em diferentes regiões do município, empregando-se o conceito de balanço de massa. Não é possível quantificar a geração de resíduos de construção e demolição dos agentes informais (reformas) por meio de dados indiretos relacionados Às transformações dos pontos de água no município. Há indícios de que as transformações dos pontos de energia elétrica sejam um indicador indireto mais preciso, podendo evitar a dispendiosa quantificação direta.In this paper, construction and demolition waste generation was estimated by two quantification methods, one direct and other indirect, regarding informal and formal generators. Construction area and transformation of the points of water and energy were applied for indirect quantification method. For the direct one, volume of dumping areas associated with informal and formal generators in different regions of municipality were quantified and the mass balance was applied. Indirect quantification of informal generators by transformation points of water is not precise. There are evidences that transformation points of energy can be more precise, avoiding costly direct construction and demolition waste quantification method.

Os Resíduos de Construção e Demolição (RCDs) representam cerca de 50% dos resíduos sólidos de cidades brasileiras; a reciclagem é, portanto, desejável, tanto do ponto de vista econômico, como ambiental. Nesse trabalho são apresentados resultados de estudos de caracterização química referentes a amostras de duas usinas de reciclagem do Estado de São Paulo. Verificou-se que a classificação corrente do RCD, segundo critérios visuais (tipos cinza e vermelho), não está relacionada à composição química destes, sendo esta influenciada, principalmente, pela granulometria. A composição química dos RCDs varia em função dos conteúdos de pasta de cimento, tipos dos agregados naturais (areia quartzosa ou granito), cerâmica vermelha e argila. Ainda, para a reciclagem dos resíduos como agregados para concretos, são necessários dois estágios de britagem para atendimento às normas ABNT. A fração miúda apresenta um enriquecimento nos teores de sílica, indicando liberação da pasta de cimento para os finos (< 0,15 mm). Os finos têm aplicações potenciais na indústria de cimento. Construction and Demolition Waste (CDW) represents about 50% of the total Brazilian municipal solid waste; thus, recycling represents huge benefits both in environmental and economic perspectives. Herein, the chemical characterization results of three samples from two different recycling plants from the State of Sao Paulo is prevented. The results demonstrated that the visual classification into grey and red is not related to the chemical composition but mostly to the grain size fraction. The chemical composition of the CDW varies according to the content of cement paste, natural aggregates (quartz sand or granite), red ceramic and clay. Furthermore, the production of recycled concrete aggregates requires two crushing stages to meet the technical standards. The sand fraction (below 4.8 mm) presents high grades of SiO2, which indicates the liberation of cement paste to fines (< 0.15 mm). The fines have a great potential to be used in the cement industry.

The properties of recycled aggregate produced from mixed (masonry and concrete) construction and demolition (C&D) waste are highly variable, and this restricts the use of such aggregate in structural concrete production. The development of classification techniques capable of reducing this variability is instrumental for quality control purposes and the production of high quality C&D aggregate. This paper investigates how the classification of C&D mixed coarse aggregate according to porosity influences the mechanical performance of concrete. Concretes using a variety of C&D aggregate porosity classes and different water/cement ratios were produced and the mechanical properties measured. For concretes produced with constant volume fractions of water, cement, natural sand and coarse aggregate from recycled mixed C&D waste, the compressive strength and Young modulus are direct exponential functions of the aggregate porosity. Sink and float technique is a simple laboratory density separation tool that facilitates the separation of cement particles with lower porosity, a difficult task when done only by visual sorting. For this experiment, separation using a 2.2 kg/dm³ suspension produced recycled aggregate (porosity less than 17%) which yielded good performance in concrete production. Industrial gravity separators may lead to the production of high quality recycled aggregate from mixed C&D waste for structural concrete applications.

Entre os desafios para a expansão de mercado da reciclagem, encontra-se o de viabilizar o emprego dos agregados de resíduos de construção e demolição (RCD) reciclados em concretos. No entanto as normas que regulamentam tal emprego não são facilmente aplicáveis nas usinas de reciclagem, existindo pouca informação sistemática de como as diferentes características dos agregados de RCD reciclados influenciam no desempenho do concreto. O objetivo desta tese é identificar as características dos agregados de RCD reciclados que exerçam influência relevante no comportamento mecânico dos concretos. As seguintes etapas experimentais são desenvolvidas: a) caracterização química e mineralógica das frações granulométricas de três amostras representativas de agregados, b) caracterização das propriedades físicas de agregados graúdos separados por densidade, assim como da composição química, mineralógica e por fases, c) influência das características dos agregados graúdos separados por densidade no comportamento mecânico dos concretos. Na caracterização dos agregados foram utilizados os seguintes métodos: análise granulométrica, análise química por FRX, análise mineralógica por DRX, determinação da fração solúvel por ataque com solução de HCl 33%, e análise termogravimétrica, separação por densidade empregando líquidos densos e equipamento “Sink and Float", catação das fases, determinação da massa específica aparente e absorção de água dos agregados, dosagem e avaliação do comportamento mecânico de concretos produzidos com esses agregados. Os resultados permitem concluir que a porosidade (ou massa específica aparente) dos agregados de RCD reciclados controla o comportamento mecânico dos concretos produzidos com relação água e cimento constante, assim como a soma dos teores de aglomerantes e de cerâmica vermelha – frações mais porosas. A separação por densidade é uma técnica eficiente para separar esses agregados em subgrupos de diferentes porosidades, gerando concretos com comportamento mecânico e absorção de água similares. O estudo realizado aponta para uma densidade de corte em torno de 2,2 a 2,3 g/cm³. Os agregados contidos no intervalo “d> 2,2" possuem teores elevados de rochas e teores baixos de cerâmica vermelha, resultando em concretos com comportamento mecânico semelhante ao dos agregados naturais analisados. A avaliação da distribuição de densidade pode ser um método simples e rápido para a classificação de lotes desses agregados e controle do comportamento mecânico dos concretos produzidos. Na fração graúda e miúda, os teores de rochas e cerâmicas são superiores a 50% da massa, e o comportamento dos principais óxidos da composição química é semelhante. Esse comportamento muda significativamente na fração fina, em que predominam os aglomerantes e argilominerais (teores superiores a 77%). A origem (Itaquera e Vinhedo) e a cominuição influenciaram, de forma representativa, a distribuição de massa dos agregados graúdos de RCD reciclados separados por densidade. O agregado de Itaquera apresentou mais de 70% da massa no intervalo de densidade superior a 2,2 g/cm³. Construction and demolition waste (CDW) recycled aggregates are not largely used in concrete due to CDW composition heterogeneity and CDW recycled aggregate physical property variability from visual classification and hand sorting of proposed standards that provide insufficient relation between the aggregate characteristics and concrete performance. This thesis aims to identify CDW recycled aggregate characteristics that influence the concrete mechanical performance. The experimental design was divided in three stages: a) detailed chemical and mineralogical characterization of three representative CDW recycled aggregate samples, b) characterization of the physical properties of the coarse CDW recycled aggregates separated by heavy media as well as the composition in terms of chemical, mineralogical, and visual phases, and c) the influence of the coarse CDW recycled aggregate separated by heavy media on concrete mechanical performance. The following methods were used: particle size distribution, chemical analysis by XRF, mineralogical analysis by XRD, soluble fraction in chloride acid leaching assay, thermal analysis, sequential heavy media and gravity separation, hand sorting, bulk specific gravity and water absorption, concrete mix design and its compressive strength and elastic modulus using the CDW recycled aggregates. In conclusion, CDW recycled aggregate porosity controls concrete mechanical performance formulated with constant cement and water relation. The concrete mechanical performance is related to bulk specific gravity of CDW recycled aggregates separated by density, including to the sum of binder and red ceramic content. Heavy media and gravity separation is efficient to separate CDW recycled aggregates in bulk specific gravity groups, producing concrete with similar concrete mechanical behavior and water absorption. Cutting density in 2.2-2.3 g/cm³ seems to be efficient since the aggregates with the upper density have high rock content resulting concrete mechanical performance similar to that produced using natural aggregates. Mass distribution in density separation could be a simple and fast method to classify CDW recycled aggregate and to control concrete mechanical performance. The coarse and sand fraction of CDW recycled aggregates had more than 50% in mass of rocks and ceramics, with quite similar main oxide contents in chemical composition. However, the contents changed in fine fraction (lower than 0.15 mm) whose binder content and clay minerals are in majority (upper to 77% in mass). The origin of CDW recycled aggregate and comminution influenced in mass distribution of sequential density separation. In Itaquera (São Paulo), the mass distribution upper to 2,2 g/cm³ was around 70%.

O concreto leve pode ser obtido pela substituição do agregado convencional por agregado de menor densidade, como a argila expandida, a qual apresenta também alta porosidade e absorção de água elevada. Essas propriedades se assemelham às dos agregados reciclados de resíduos de construção, o que os torna aptos para a obtenção de um concreto leve. Porém, os agregados reciclados diferem quanto a composição variável, menor resistência a esforços e à abrasão, e formato mais irregular. Assim, o artigo analisa como algumas propriedades dos agregados reciclados influenciam no comportamento do concreto leve nos estados fresco e endurecido. O estudo utilizou dois tipos de agregados reciclados, um oriundo de blocos vazados de concreto com EPS (ARBCE) e outro de blocos cerâmicos (ARBC), com o propósito de entender a variabilidade dos materiais caracterizando as composições desses agregados e verificar a viabilidade de aplicação deles na obtenção de concretos leves. Os agregados reciclados foram britados por dois diferentes equipamentos (moinho argamassadeira para o ARBC e britador de martelo para o ARBCE). Os agregados reciclados obtidos desses processos distintos apresentaram distribuição granulométrica e forma diferentes. Com ambos os agregados reciclados foi possível produzir concretos leves, ou seja, com massa específica abaixo de 2,00 g/cm³. As resistências à compressão aos 28 dias entre 9,0 e 13,0 MPa indicam uso em elementos sem função estrutural, mas aplicáveis em componentes construtivos de resistência moderada (p.ex. painéis e blocos). Lightweight concrete can be obtained by replacing conventional aggregates by a lower density aggregate, such as expanded clay, which also present high porosity and high water absorption. These properties resemble those of recycled aggregates from construction waste, contributing to the achievement of a lightweight concrete. However, recycled aggregates have characteristics that make them very different: variable composition, low resistance to abrasion, more irregular shapes. This article analyses some properties of recycled coarse aggregates and their influence on the behaviour of lightweight concrete in fresh and hardened state. The study used two types of recycled coarse aggregates, one originating from concrete blocks with EPS (ARBCE) and another one from ceramic blocks (ARBC), with the purpose of understanding the variability of the materials characterising the composition of these aggregates in order to verify the feasibility of application of these aggregates in lightweight concrete. The aggregates were crushed by two different equipments (mortar mixer mill and hammer mill). The recycled aggregates obtained through these different crushing processes presented different size distribution and shapes. In spite of that, it was possible to produce the two recycled lightweight concretes using both aggregate types. The compressive strength at 28 days was between 9.0 and 13.0 MPa, pointing to their use in elements without any structural function, but applicable in building components of moderate strength (e.g. panels and blocks).

Due to the environmental impact of construction and demolition waste (CDW), recycling is mandatory. It is also important that recycled concrete aggregates (RCA) are used in concrete to meet market demands. In the literature, the influence of RCAs on concrete has been investigated, but very limited studies have been conducted on how the origin of concrete waste and comminution processes influence RCA characteristics. This paper aims to investigate the influence of three different comminution and sizing processes (simple screening, crushing and grinding) on the composition, shape and porosity characteristics of RCA obtained from concrete block waste. Crushing and grinding implies a reduction of RCA porosity. However, due to the presence of coarse quartz rounded river pebbles in the original concrete block mixtures, the shape characteristics deteriorated. A large amount of powder (

A remoção de resíduos de cerâmica vermelha dos agregados mistos procedentes de resíduos de construção e demolição (RCD) deve ser priorizada para este material possa ser utilizado para a confecção de concreto. Isso pode ser realizado por meio de diferentes técnicas de processamento mineral, com princípios de separação, eficiência, custos e impactos ambientais distintos. A principal vantagem da separação óptica é o uso reduzido de água ou energia quando comparado com outros processos industriais. Este artigo tem por objetivo analisar os produtos obtidos por separação óptica de RCD mistos, com foco na remoção da cerâmica vermelha e conseguinte redução da porosidade dos agregados reciclados para uso em concreto. A remoção da cerâmica vermelha viabiliza a obtenção de um agregado reciclado essencialmente composto de concreto, com menor porosidade e cuja absorção de água varia entre 4% e 7%. No Brasil, teores de até 5% de cerâmica vermelha são esperados no produto (agregado triado), e a produção de concretos de 20 a 30 MPa torna-se viável com esse material. The removal of red ceramic residues from mixed construction and demolition waste (CDW) is a priority if that waste is to be used as recycled aggregates in concrete. There are many processing techniques that fit this purpose, with different separation principles, efficiency levels, costs and environmental impacts. The main advantage of optical sorting is lower use of water or energy when compared with other processing techniques. The aim of this paper is to analyze the products obtained by automatic optical sorting, focusing on the removal of red ceramic from mixed CDW recycled coarse aggregates and the expected porosity reduction for their use in concrete. The product obtained is mainly composed of recycled concrete aggregates (RCA), with water absorption levels from 4 to 7%. In Brazil, contents of about 5% of red ceramic in the product (sorted aggregates) can be expected, and the production of 20-30 MPa concrete with this material is feasible.

Existing construction waste recycling technologies and standards have long been applied in construction and demolition waste recycling. However, they have been essentially focused on the production and use of coarse recycled aggregates. This paper presents a technology that permits the production of high quality recycled sand. The selective removal with a vertical impact crusher of the cement paste attached to recycled aggregates and the potential improvements in the quality of the recycled sand that is produced were investigated. The results showed that the proposed method permitted the production of low-porosity sand from construction and demolition waste and may contributes to changing the construction recycling model.

As an outcome of recycling the mineral part of construction and demolition waste significant quantities of the fine fraction, particle size below 4 mm in Europe, are generated. A common feature of the produced fine recycled aggregates is the high content of cement paste that could impair its quality. With the recent advances on the processing technologies improvement on the characteristics of the fine fraction of C&DW can be envisaged and new perspectives to their application arise.

The quality of recycled aggregates from construction and demolition waste (CDW) is strictly related to the content of porous and low strength phases, and specifically to the patches of cement that remain attached to the surface of natural aggregates. This phase increases water absorption and compromises the consistency and strength of concrete made from recycled aggregates. Mineral processing has been applied to CDW recycling to remove the patches of adhered cement paste on coarse recycled aggregates. The recycled fine fraction is usually disregarded due to its high content of porous phases despite representing around 50% of the total waste. This paper focus on laboratory mineral separability studies for removing particles with a high content of cement paste from natural fine aggregate particles (quartz/feldspars). The procedure achieved processing of CDW by tertiary impact crushing to produce sand, followed by sieving and density and magnetic separability studies. The attained results confirmed that both methods were effective in reducing cement paste content and producing significant mass recovery (80% for density concentration and 60% for magnetic separation). The production of recycled sand contributes to the sustainability of the construction environment by reducing both the consumption of raw materials and disposal of CDW, particularly in large Brazilian centers with a low quantity of sand and increasing costs of this material due to long transportation distances.

Neste trabalho, estimou-se a gerão dos resíduos de construção e demolição por dois métodos de quantificação, um indireto e outro direto, considerando-se a produção advinda dos agentes informais e formais. O método indireto considerou a área construída das edificações (construção) e transformação dos pontos de ligação de água e luz instalados (reforma). O método direto identificou a geração advinda de agentes informais e formais nos pontos de disposição finais em diferentes regiões do município, empregando-se o conceito de balanço de massa. Não é possível quantificar a geração de resíduos de construção e demolição dos agentes informais (reformas) por meio de dados indiretos relacionados Às transformações dos pontos de água no município. Há indícios de que as transformações dos pontos de energia elétrica sejam um indicador indireto mais preciso, podendo evitar a dispendiosa quantificação direta.

Resumo A presença de cal nas argamassas mistas é responsável pelo aumento na demanda de água de amassamento para uma dada consistência. A água adicional, que não é consumida na hidratação do cimento, permanece livre no sistema e, ao evaporar, dá origem a porosidade elevada da argamassa endurecida. Este trabalho apresenta o método do cálculo de volumes como uma ferramenta para estimar a porosidade de argamassas mistas a partir de seus constituintes, inclusive a cal, bem como sua correlação com propriedades relevantes no estado endurecido. O método apresentado mostrou-se favorável para a previsão de propriedades que definem o comportamento dos revestimentos de argamassa. Os dados apresentados sugerem continuidade e aprofundamento desta linha de estudo envolvendo aspectos não considerados no cálculo teórico de volume, tais como a influência da retração e da carbonatação nas argamassas. Abstract The presence of lime in mixed mortars is responsible for the increase in the demand for mixing water for a given consistency. The additional water, which is not consumed in the cement hydration, remains free in the system and when evaporating it leads to high porosity in the hardened mortar. This paper presents the method of volume calculation as a tool for estimating the porosity of mixed mortars through their constituents, including lime, as well as its correlation with relevant properties in the hardened state. The method presented proved to be adequate for predicting the properties that define the behavior of the rendering. The data suggest that this approach needs further research, involving issues not considered in the theoretical volume calculation, such as the influence of shrinkage and carbonation.

This study presents a methodology for the characterization of construction and demolition (C&D) waste recycled aggregates based on a combination of analytical techniques (X-ray fluorescence (XRF), soluble ions, semi-quantitative X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTG) and hydrochloric acid (HCl) selective dissolution). These combined analytical techniques allow for the estimation of the amount of cement paste, its most important hydrated and carbonated phases, as well as the amount of clay and micas. Details of the methodology are presented here and the results of three representative C&D samples taken from the Sao Paulo region in Brazil are discussed. Chemical compositions of mixed C&D aggregate samples have mostly been influenced by particle size rather than the visual classification of C&D into red or grey and geographical origin. The amount of measured soluble salts in C&D aggregates (0.15-25.4mm) is lower than the usual limits for mortar and concrete production. The content of porous cement paste in the C&D aggregates is around 19.3% (w/w). However, this content is significantly lower than the 43% detected for the C&D powders (

Estruturas de aço não apresentam bom comportamento em situação de incêndio quando não protegidos devido à elevada condutividade térmica do material e à esbeltez de seus componentes, promovendo, dessa maneira, um rápido aquecimento do elemento estrutural e uma acelerada degradação de suas propriedades mecânicas. Uma das formas de melhorar a resistência ao fogo de elementos metálicos consiste em revesti-los com concreto, o qual funciona como um material isolante térmico protegendo os perfis de aço contra a ação do fogo. Tendo em vista o apelo ambiental, buscou-se estudar a influência do tipo concreto produzido com agregado reciclado no comportamento à flexão de vigas mistas parcialmente revestidas em situação de incêndio. Inicialmente, os agregados reciclados foram caracterizados e, em seguida, aplicou-se a técnica de empacotamento de partículas, Modelo de Alfred, para produção dos concretos. Os resultados indicaram que esses agregados são mais porosos, absorvem mais água e apresentam menor massa específica quando comparados com os agregados naturais. Diante disso, foram produzidas sete misturas de concreto: uma de referência (uso apenas de agregados naturais) com o emprego da dosagem tradicional, e outras seis, utilizando diferentes agregados reciclados a partir do empacotamento de partículas. Essa metodologia promoveu uma redução do consumo de cimento da mistura de referência e possibilitou a substituição integral da fração de agregados naturais por reciclados, gerando concretos com resistência à compressão superior a 20 MPa, ou seja, adequados para serem utilizados em estruturas. Posteriormente analisou-se o comportamento dessas sete misturas enquanto barreira térmica de perfis de aço. Notou-se que os concretos com agregados reciclados apresentaram grande potencial de isolamento térmico, tendo em vista que os elementos de aço revestidos com esse material, com exceção daqueles que sofreram spalling, tiveram temperaturas próximas ou inferiores quando comparados ao elemento revestido com concreto convencional. Com base nesses experimentos, modelos numéricos térmicos foram propostos usando o código computacional ABAQUS, cujos resultados foram consistentes quando adotadas propriedades térmicas adequadas. No que se refere aos elementos estruturais, quatro vigas de aço foram revestidas com diferentes concretos (um convencional e os demais com agregados reciclados). Elas foram sujeitas a ensaios de flexão em temperatura ambiente, em situação de incêndio (tempo de aquecimento igual a 35 min) e pós-fogo. Em termos de capacidade resistente, notou-se que o tipo de concreto não impactou de forma significativa a resistência mecânica do elemento estrutural em temperatura ambiente. No que diz respeito aos ensaios em incêndio, a viga constituída por 100% de brita reciclada apresentou as temperaturas mais elevadas e os maiores deslocamentos no meio do vão ao final do aquecimento. Em contrapartida, as vigas mistas com 100% de areia reciclada ou com 100% de agregados totais reciclados exibiram comportamento mais satisfatório que a viga mista de referência, por conta dos menores deslocamentos centrais e temperaturas para o mesmo tempo de aquecimento. Essa tendência também foi identificada nos ensaios de flexão pós-fogo e de propriedades mecânicas residuais dos concretos. Logo, verificou-se que o uso de agregados reciclados é uma estratégia promissora para a produção de concretos de revestimento de vigas de aço, por conta do desempenho adequado do sistema misto em situação de incêndio. Steel structures do not show a good behavior under fire situation when not protected due to the high thermal conductivity of the material and because of the slenderness of their components. This leads to the quick heating of the structural elements and to an accelerated degradation of their mechanical properties. One of the ways to improve the fire resistance of steel elements consists of encasing it with concrete to protect them from the fire, since concrete is a good thermal insulator material. Considering the environmental concerns, this work aimed to study the influence of the concrete encasing produced with recycled aggregate on the flexural behavior of partially encased composite beams in a fire situation. Initially, the recycled aggregates were characterized and then the particle packing technique, Alfred&#x27s Model, was applied to produce the concrete. The results of this step indicated that these aggregates present higher porosity, higher water absorption and lower specific mass when compared to natural aggregates. Then, seven different concrete mixtures were produced: the reference one made with natural aggregates and using a traditional design and another six mixtures using different recycled aggregates employing the particle packing. This methodology promoted a reduction in cement consumption of the reference mixture and entire substitution of the part of natural aggregates for recycled ones, generating concrete with compressive strength greater than 20 MPa, thus being suitable for structural usage. The next step consisted in analysing the efficiency of those seven mixtures as a thermal insulator to the steel profiles. The experiments revealed that those recycled aggregates concretes have good thermal insulation properties once the steel elements encased with these concretes presented equal or even low temperatures compared to the element encased with conventional concrete, except those that presented spalling. Based on these experiments, numerical thermal models were proposed using the ABAQUS computational code, whose results were consistent when adopting correct thermal properties. Regarding the structural elements, four steel beams were partially encased with different concretes (one conventional and others with recycled aggregates). They were subjected to bending tests at room temperature, in fire situation (heating time equal to 35 minutes) and post-fire. In terms of resistance, the tests showed that the concrete type does not significantly influence the structure resistance at room temperature. When evaluating the performance in fire, the beam made of 100% recycled coarse aggregate presented the highest temperatures and half-span displacements at the end of the heating process. However, the composite beams with 100% recycled sand or 100% total recycled aggregates showed better performance compared to the composite beam used as reference, due to the smaller central displacements and temperatures for the same heating time. This tendency was also identified in the post-fire bending and residual mechanical properties concrete tests. Therefore, it was found that the usage of recycled aggregates is a promising strategy for the production of concrete for encasing steel beams due to the good behaviour of composite structures in a fire situation.

A rugosidade dos agregados influencia o desempenho do concreto no estado fresco e no endurecido. Agregados com elevadas rugosidades melhoram as propriedades na interface pasta-agregado, mas aumentam a viscosidade do concreto, devido ao aumento do atrito entre as partículas. Apesar da importância da rugosidade, não há estudos que realizem uma análise multiescala (macro e micro), impedindo uma melhor compreensão dos seus efeitos no concreto. Diante disto, esse trabalho propõe um estudo multiescala da rugosidade de diferentes agregados. Para tanto, a rugosidade dos agregados foi medida através da interferometria óptica, que fornece dados quantitativos em 3D. Seistipos de agregados foram analisados e apresentaram rugosidades distintas entre si, em ambas escalas (macro e micro). As análises petrográficas mostraram que a rugosidade pode estar relacionada com o tamanho e quantidade dos grãos da microestrutura da rocha. O escaneamento 3D foi utilizado para caracterizar o formato das partículas e complementar os dados de rugosidade considerando o volume, permitindo a determinação da área superficial volumétrica (ASV) dos agregados, na microescala de observação. A medida física da área superficial (AS) obtida pela técnica de adsorção de azul de metileno obteve indícios de boa correlação com a AS obtida pelo interferômetro. The roughness of aggregates influences the performance of the concrete in the fresh and hardened state. Aggregates with high roughness improve the properties at the pasteaggregate interface but increase the viscosity of the concrete due to the increased friction between the particles. Despite the importance of roughness there are no studies that perform a multiscale analysis (macro and micro), preventing a better understanding of its effects on concrete. Therefore, this work proposes a multiscale study of the roughness of different aggregates. For this purpose, the roughness of the aggregates was measured through optical interferometry, which provides quantitative data in 3D. Six types of aggregates were analyzed and presented different roughness in both scales (macro and micro). Petrographic analyses showed that the roughness may be related to the size and quantity of the grains in the microstructure of the rock. The 3D scanning was used to characterize the particle shape and complement the roughness data with the volume, allowing the determination of the volumetric surface area (VSA) of the aggregates at the microscale of observation. The physical measurement of the specific surface area (SSA) obtained by the methylene blue adsorption technique obtained evidence of good correlation with the interferometer SSA.

A pasta de cimento hidratada é um material frágil e, portanto, o desempenho mecânico é governado por defeitos pré-existentes na microestrutura. Durante a produção e moldagem, defeitos críticos (poros largos, trincas e fissuras) podem ser introduzidos causando drástica redução da resistência mecânica. Tais defeitos ocorrem e se distribuem aleatoriamente, o que intensifica a dispersão das propriedades mecânicas. Conhecer a variabilidade é importante para determinar valores característicos, que acabam por definir a confiabilidade estrutural do concreto. Neste contexto, o presente trabalho avalia a variabilidade da resistência à tração e do módulo de elasticidade de pastas de cimento, correlacionando-a à ocorrência de defeitos críticos. Dentre as variáveis investigadas estão a relação água/sólidos, o teor de fíler calcário (em substituição e em adição ao cimento) e o teor de superplastificante. Para cada composição, pelo menos 40 pequenas amostras cúbicas (~10 mm) foram moldadas para garantir representatividade estatística. As propriedades mecânicas foram determinadas através de um ensaio simples, baseado no ensaio de carga pontual e na teoria de contato elástico de Hertz. O comportamento da resistência à tração e do módulo elástico foi avaliado a partir de análises probabilísticas utilizando as distribuições de Weibull e lognormal, respectivamente. Ensaios de Porosimetria por Intrusão de Mercúrio (MIP) e Microtomografia de Raios-X foram realizados para correlacionar a dispersão dos resultados mecânicos com a microestrutura das amostras. O fíler calcário aumenta a porosidade aberta quando usado em substituição ao cimento (a/s constante); por outro lado, em adição ao cimento (a/c constante), a porosidade diminui. A magnitude do módulo elástico só foi afetada pela porosidade total, de maneira inversa, e a variabilidade das observações é pequena, independente da composição da pasta. A variabilidade da resistência à tração é relativamente alta devido à distribuição aleatória dos defeitos críticos; entretanto, pode ser substancialmente reduzida com a inclusão de fíler calcário e com o aumento da porosidade, devido ao mecanismo de tenacificação na zona de propagação da fratura. A ocorrência de exsudação/segregação após a moldagem das amostras aumentou significativamente a variabilidade dos resultados mecânicos. O diâmetro crítico determinado pela MIP apresentou correlação negativa com a resistência mecânica, e a relação a/c parece ser o principal fator que afeta sua dimensão. Hydrated cement pastes are brittle materials and therefore their mechanical performance is governed by pre-existing defects in the microstructure. During production and molding, critical defects (large pores and cracks) may be introduced causing a drastic reduction of the mechanical strength. The occurrence and distribution of such defects are random, which intensify the dispersion of the mechanical properties. Knowing the variability is important to determine reliable characteristic values; nonetheless, little attention is given to the subject. In this context, the present work evaluates the variability of the tensile strength and elastic modulus of cement pastes, correlating it to the microstructure and occurrence of critical defects. Among the variables investigated are the water/solids ratio, the content of limestone filler (in replacement and addition to cement) and the content of superplasticizer. For each composition, at least 40 small cubic samples (~10 mm) were cast to ensure statistical representativeness. The mechanical properties were determined through a simple and practical test, based on the Point Load Test and the Hertz elastic contact theory. The behavior of tensile strength and elastic modulus were evaluated through probabilistic analyses using the Weibull and lognormal distributions, respectively. Mercury Intrusion Porosimetry (MIP) and X-ray Microtomography tests were performed to correlate the dispersion of the mechanical results with the microstructure of the samples. The results showed that the effect of limestone filler on the open porosity depends on the strategy used: in replacement to cement (constant w/s), the porosity increases; on the other hand, in addition to cement (constant w/c), the porosity decreases. The magnitude of the elastic modulus was only affected by the total porosity, in a negative way, and the data variability was low regardless of the composition of the paste. The increase in total porosity also tends to reduce the magnitude of the tensile strength; however, the presence of limestone filler can compensate this effect and improve the mechanical performance thanks to toughening mechanisms during fracture. Tensile strength variability is relatively high due to the random distribution of critical defects; however, it can be substantially reduced with the inclusion of limestone filler and with the increase of porosity, which is also due to the increase in toughness. The occurrence of bleeding/segregation after casting the samples significantly increased the variability of the mechanical results. The critical diameter determined by the MIP had a strong negative correlation with the mechanical strength, and the w/c ratio seems to be the main factor affecting its dimension.

A indústria da construção é responsável pelo consumo de mais de 50% de todos os recursos extraídos globalmente, exercendo uma pressão ambiental significativa. Manter ou aumentar os níveis de produção e, ao mesmo tempo, reduzir a pressão ambiental é um dos desafios da atualidade e está igualmente previsto nas metas dos Objetivos do Desenvolvimento Sustentável. Por outro lado, apesar da indústria da construção evidenciar oportunidades para promover o descolamento entre o crescimento econômico e os aspetos ou impactos ambientais, estas oportunidades muitas vezes não são atendidas, em especial nos países em desenvolvimento onde, nos próximos anos, devem liderar a demanda por recursos naturais. Para promover o descolamento e a sustentabilidade na indústria da construção é necessário o uso de indicadores que permitam quantificar o desempenho ambiental de produtos, estabelecer metas e monitorar o progresso. Este estudo tem como objetivo desenvolver um conjunto de indicadores para quantificar o uso de recursos de forma simples e acessível a pequenas e médias empresas, auxiliando os vários profissionais e gestores a promoverem estratégias para aumentar a eficiência no uso de recursos e o potencial de desmaterialização. O método de pesquisa inicia-se por uma análise setorial identificando aqueles que são foreground ou background definidos em função da participação de mercado, em termos de massa e energia, dentro da indústria da construção. Os setores foreground são aqueles controlados ou influenciados pela indústria da construção; enquanto os setores background pela baixa participação são menos sensíveis a inventariar dados e a colaborar com diretrizes ou políticas públicas da indústria. Dentro dos vários setores, destacam-se os materiais a base de cimento, com uma participação superior a 60% (em massa). Para este setor foi conduzido uma Análise de Fluxo de Materiais (MFA) para quantificar as principais etapas e atividades que mais afetam a eficiência de recursos, bem como o potencial da industrialização para promover a desmaterialização do setor. Por fim, utilizado os conceitos de MFA e considerando uma perspectiva de ciclo de vida, foi desenvolvido um conjunto de indicadores - intensidade de material e eficiência, circularidade, e taxa de geração de resíduos - voltados para indústria da construção para contabilizar o consumo de materiais. Estes indicadores podem ser utilizados em diferentes etapas (projeto, produto ou construção) e diferentes escalas (local, regional, nacional). Os indicadores foram desenvolvidos para serem fáceis de aplicar e de entender pela indústria de forma a permitir a comparabilidade setorial identificando as melhores práticas. The construction industry is responsible for consuming more than 50% of all resources extracted worldwide, exerting a significant environmental pressure. Maintaining or increasing production levels and while reducing environmental pressure is a challenge and is also foreseen by the Sustainable Development Goals. Although construction industry has opportunities to decouple growth and environmental impacts, these opportunities are often missed, especially in developing countries which are expected to take the lead of natural resources consumption. To promote decoupling and sustainability in the construction industry, it is necessary indicators that allow quantifying the environmental performance of products, establishing goals and monitoring progress. This study aims to develop a set of indicators to quantify the use of resources in a simple and accessible way for small and medium-sized companies, helping professionals and managers to engage in strategies to increase resource efficiency and dematerialization. The research method starts evaluating the economic sectors and classified them as belonging to the foreground or background system from the perspective of construction industry. Foreground sectors are those controlled or influenced by the construction industry and are defined based on the production share consumed by the construction value chain; while the background sectors are those that has a low market-share and less sensitive to inventory data and to collaborate with industry procedures or even public policies. Within the several sectors, cement-based materials are stand out since as a market-share above 60% (by mass). For this sector, a Material Flow Analysis (MFA) was conducted to quantify the main activities that influence the resource efficiency and the dematerialization potential between industry and on-site mix production. Finally, using the concepts of MFA and considering a life cycle perspective, a set of indicators was developed - material intensity and efficiency, circularity, and waste generation rate - to quantify the use of materials. These indicators can be used in different scales (construction designers, material producers, builders, developers) and for several industrial sectors. Since they are simple to understand and easy to measure, it allows developing of benchmarking and ranking designs, facilities, and firms according to the best practices.

A indústria cimenteira é responsável por emitir grandes quantidades de gases do efeito estufa para a atmosfera durante a produção do clínquer. Para reduzir o impacto ambiental, novos materiais cimentícios suplementares (SCMs) têm substituído parcialmente o teor de clínquer Portland. Os SCMs são, na grande maioria, resíduos industriais ou subprodutos com grande volume de geração. A escória de alto-forno e a cinza volante já são comumente utilizadas em substituição ao clínquer na produção do cimento, mas novos materiais têm sido empregados, como as escórias siderúrgicas. Apesar dos SCMs já serem consumidos pelas plantas cimenteiras para produção do cimento, suas características não são bem compreendidas no desempenho do estado fresco e endurecido, principalmente quando se trata de diferentes escórias, como a de manganês. Tais propriedades influenciam diretamente o desenvolvimento da microestrutura e, consequentemente, a resistência e a durabilidade. Além das propriedades físico-químicas, outros critérios são considerados para atender o consumo industrial: volume de produção e proximidade à planta. Portanto, o objetivo desse trabalho é analisar a influência das características físico-químicas das escórias de alto-forno, aciaria e manganês associadas ao cimento Portland, quanto a reatividade nas primeiras horas até 120 dias de hidratação. As escórias foram previamente moídas para atingir três áreas superficial específica (ASE). Todas as matérias-primas foram fisicamente e quimicamente caracterizadas. Os sistemas tiveram 50% (em massa) de substituição do cimento pelas escórias. A evolução da hidratação foi acompanhada por calorimetria de condução isotérmica e análise termogravimétrica. O estudo em argamassa analisou o ar incorporado, a porosidade, a resistência à compressão e o módulo de elasticidade. Os cimentos com escórias com maior área superficial específica proporcionaram menor porosidade e, consequentemente, maior resistência à compressão, pois desempenham efeito fíler no sistema. O alto teor de manganês característico da escória de manganês retarda a reação de hidratação do cimento, e sua viabilidade é possível apenas para soluções regionais. A composição com escória de alto-forno, além do efeito físico, interagiu quimicamente na reação de hidratação e foi o ligante mais eficiente. The cement industry is responsible for the emission of large quantities of greenhouse gases into the atmosphere during the clinker production. To reduce the environmental impact, new supplementary cementitious materials (SCMs) have partially replaced the content of Portland clinker. SCMs are, in the vast majority, industrial waste or by-products with a high volume generated. Blast furnace slag and fly ash are already commonly used to replace clinker in cement production, but new materials have been employed, such as slags from the steel industry. Even though SCMs are already applied by cement plants industry, their characteristics are not well known in the performance of the fresh and hardened properties, especially when it comes to different slags, such as manganese. Such properties directly affect the microstructural development, and consequently the strength and durability. In addition to the physical and chemical properties, other criteria are considered to meet cement industry consumption: production volume and plant proximity. The objective of this work is to analyze the influence of the physicochemical characteristics of blast furnace slag, steelmaking slag and manganese slag associated with Portland cement, regarding the reactivity in the first hours up to 120 days of hydration. The slags were previously ground to reach three specific surface areas (SSA). All raw materials were physically and chemically characterized. The systems had 50% (weight) replacement of cement by slag. The evolution of hydration analyzed through isothermal conduction calorimetry and thermogravimetric analysis. The mortar study evaluated the incorporated air, the porosity, the compressive strength and the Young\'s modulus. Cements with slag with a greater specific surface area provided better results of porosity and compressive strength, as they have a filler effect on the system. The high manganese content, characteristic of manganese slag, slows down the cement hydration reaction, and its viability is only possible for regional solutions. The composition with blast furnace slag, in addition to the physical effect, interacted chemically in the hydration reaction and was the most efficient binder.

Water is the most used substance in the world, followed by concrete. Water scarcity is nowadays more common due to concentrated population growth and climate change. Concrete demand is ~15 billion m3 per year fulfilling the need for more and better housing and infrastructure for a growing and wealthier population. Since no other material could fulfil this demand, concrete needs to be produced in a sustainable way, minimizing environmental loads such as water consumption. The water footprint is a tool that measures water use over a products\' life cycle and estimates its potential environmental impacts. Despite the growing concern on water, the existing water footprint methodologies are too complex and require large amounts of data. This study develops a streamlined water footprint methodology for concrete production, simple enough to be useful to the industry and robust enough to be environmentally meaningful. An extensive study on existing water footprint methodologies have been conducted. Then a streamlined methodology was proposed focused on the water flows that are more relevant in concrete production including water quantity and quality letting to meaningful results with less data. Typical water inventory includes the batch water (150-200 H kg/m3), dust control (500-1500 H kg/day), truck washing (13-500 H kg/m3), cement production (0.185-1.333 H kg/kg) and aggregates production (0.116-2.0 H kg/kg). Regarding water quality, the most critical flows - Zinc, Lead, Nitrate, Nitrogen oxides and Sulfur dioxide- were identified based on the contribution of these flows to the potential environmental impacts, the control or influence that the concrete producer has on the activities were these flows appear and the feasibility to measure these flows on site. Concrete water footprint varies due to mix design, technological routes, location and choice of impact assessment method. The results are of interest to the research community as well as to the stakeholders of the cement and concrete industries and a contribution to sustainable construction since study of water footprint is fundamental to improve water efficiency. A água é a substância mais utilizada no mundo, seguida pelo concreto. A escassez de água é hoje em dia mais comum devido ao crescimento populacional concentrado e às mudanças climáticas. A demanda de concreto é ~15 billion m3 por ano que atende a demanda de mais e melhor moradia e infraestrutura para uma população crescente e mais prospera. Uma vez que nenhum outro material pode satisfazer essa demanda, o concreto precisa ser produzido de forma sustentável, minimizando as cargas ambientais, como o consumo de água. A pegada hídrica é uma ferramenta que mede o uso da água ao longo do ciclo de vida de um produto e estima seus potenciais impactos ambientais. Apesar da crescente preocupação com a água, as metodologias existentes de pegada hídrica são muito complexas e exigem grandes quantidades de dados. Este estudo desenvolve uma metodologia optimizada de pegada hídrica para produção de concreto, simples o suficiente para ser útil para a indústria e robusta o suficiente para ser ambientalmente significativa. Um estudo extensivo em metodologias existentes da pegada da água foi conduzido. Em seguida, uma metodologia optimizada foi proposta focada nos fluxos de água que são mais relevantes na produção de concreto, incluindo quantidade e qualidade, permitindo resultados significativos com menos dados. O inventário de água típica inclui a água de mistura (150-200 H kg/m3), controle de poeira (500-1500 H kg/dia), lavagem de caminhões (13-500 H kg/m3), produção de cimento (0.185-1.333 H kg/kg ) e produção de agregados (0.116-2,0 H kg/kg). Em relação à qualidade da água, os fluxos mais críticos -Zinco, Chumbo, Nitrato, Óxidos de nitrogênio e Dióxido de enxofre-foram identificados com base na contribuição destes fluxos para os potenciais impactos ambientais, o controle ou a influência que o produtor de concreto tem sobre as atividades onde esses fluxos aparecem e a viabilidade para medir esses fluxos no local. A pegada de água de concreto varia devido à formulação, rotas tecnológicas, localização e escolha do método de avaliação de impacto. Os resultados são de interesse para a comunidade de pesquisa, bem como para as partes interessadas das indústrias de cimento e concreto e uma contribuição para a construção sustentável, uma vez que o estudo da pegada hídrica é fundamental para melhorar a eficiência da água.

O estudo da reciclagem de pavimentos de concreto para utilização em novos pavimentos tem se mostrado de grande importância haja vista a quantidade de materiais necessários para a reconstrução dessas vias. Além do ganho ambiental, devido a uma menor extração de agregados, obtém-se um ganho econômico, com menor custo de transporte e de aquisição de materiais. O agregado proveniente da britagem de antigas placas de concreto se mostrou, historicamente, apto a ser utilizado para a produção de um novo pavimento de concreto. Entretanto, existem certas limitações, pois o seu uso não resulta em um concreto com características totalmente idênticas àquelas do concreto convencional. O presente trabalho apresenta resultados da análise das características dos agregados produzidos através da britagem de antigas placas de pavimentos de concreto do Rodoanel Metropolitano Mário Covas em britador de mandíbula e em britador de impacto, bem como a influência do uso de agregados reciclados nas propriedades mecânicas do concreto. No estudo comparativo entre os tipos de britador foi verificado que agregados obtidos por britador de mandíbula e por britador de impacto possuem características muito semelhantes. No estudo das características mecânicas dos concretos a resistência à tração na flexão, a resistência à tração na compressão e o módulo de elasticidade diminuíram conforme se aumentou a absorção de água ponderada dos agregados. No que se refere à resistência à compressão, contudo, não foi observada queda ao se substituir somente a fração de agregados graúdos na mistura. Quando se procedeu com a substituição da fração miúda, porém, a resistência ficou abaixo daquela do concreto de convencional. The study of concrete pavement recycling for its use in new pavements has shown to be of great importance considering the quantity of materials that are necessary to reconstruct these roads. Besides the environmental gain, due to a lesser extraction of aggregates, there is also an economic gain, with smaller transportation and material purchasing costs. The aggregate originated from the crushing of old concrete slabs has historically been shown to be able to be employed in the construction of a new concrete pavement. However, there are limitations, since its utilization does not result in a concrete with the exact same properties of the conventional concrete. The present work presents the results from the analysis of the characteristics from the aggregates produced through the crushing of old concrete slabs using a jaw crusher and an impact crusher, as well as the influence of the use of recycled aggregates on the concrete mechanical properties. The crusher type comparative study has shown that aggregates obtained from a jaw crusher and from an impact crusher have very similar characteristics. The concrete mechanical characteristic study reveals that flexural strength, indirect tensile strength and modulus of elasticity decrease as the aggregates water absorption increase. Concerning compressive strength, however, there was no observed decrease when only coarse recycled aggregates were used. Nevertheless, when fine recycled aggregates were employed besides coarse recycled aggregates, there was a decrease in compressive strength.

Nesta dissertação buscamos aplicar o modelo das interações entre as atividades científicas e os valores de Hugh Lacey ao campo das pesquisas tecnocientíficas sobre o cimento, a fim de verificar suas principais teses. Dois tipos de abordagens foram adotadas: a análise interpretativa de episódios-chave do desenvolvimento científico e tecnológico do cimento à luz do modelo teórico de referência; e a análise interpretativa das iniciativas do setor, em termos de processos tecnológicos e de estratégias de pesquisa, para reduzir suas emissões de gás carbônico até 2050. As principais conclusões a que chegamos com essas abordagens são: o campo de pesquisas sobre cimentos tem elementos para corroborar o modelo laceyano, na medida em que é caracterizado por pesquisas tecnocientíficas sob estratégias descontextualizadoras, fecundas e úteis, em relações mutuamente reforçadoras com as perspectivas de valor do progresso tecnológico e do capital e mercado, que preservam a imparcialidade, mas que não asseguram nem a autonomia nem a neutralidade no campo; e as iniciativas do setor cimenteiro para reduzir suas emissões de CO2 baseiam-se na conjunção hierárquica das perspectivas de valor do progresso tecnológico, do capital e mercado, e da sustentabilidade, cujas pressuposições até o momento carecem de comprovação empírica. In this dissertation we undertake the application of Hugh Laceys model of interactions between values and scientific activities to the field of cement techno-scientific research with the purpose of verifying its basic theses. Two approaches are followed: an interpretative analysis of the key episodes of the scientific and technological development of cements in the light of the model; and an interpretative analysis of the cement sector initiatives, in terms of technological processes and scientific strategies, for reductions of CO2 emission up to 2050. The main conclusions are: the field holds elements for corroboration of the model as it is characterized for techno-scientific research based on materialist strategies, fruitful and useful, in mutual relationship with value perspectives of technological progress and of capital and market, that preserves imparciality but neither autonomy nor neutrality in the field; and the cement sector initiatives for CO2 mitigation are based on an hierarchical conjunction of value perspectives of technological progress, of capital and market, and of sustainability, whose presuppositions so far lacked empirical corroboration.

Os finos de resíduos cimentícios (previamente hidratados) podem ser reciclados através de tratamento térmico, tornando-se um ligante alternativo. Quando tratados termicamente em temperaturas inferiores a 550ºC, o processo não gera emissões de CO2 relativas à descarbonatação do calcário. Esta pesquisa teve como objetivo reativar o cimento Portland de alto forno (CP III) previamente hidratado, desidratando-o em temperatura de 500°C com patamar de 2h e reidratando-o com teores de água e de dispersante variados. Inicialmente foram realizadas caracterizações a fim de comparar as características físico-químicas do cimento desidratado com o cimento anidro. Posteriormente, foram analisadas as transformações de fases observadas com a hidratação, desidratação e reidratação do cimento. A segunda parte do estudo foi de otimização das pastas reidratadas e hidratadas, onde foram definidas condições ideais de dispersão, com a saturação ideal de dispersantes e teores mínimos de água resultado em pastas com volume de poros menores e consequentemente resistências mais elevadas. Os resultados obtidos comprovaram que o cimento desidratado se reidrata e forma fases similares às fases formadas na hidratação, como C-S-H, portlandita, hidrotalcita, etc. O cimento de alto forno carbonata mais do que o cimento Portland (CP V). Devido à área superficial elevada (14 vezes superior ao do cimento anidro), o cimento desidratado libera calor de molhagem elevado, consequencia da recombinação da água com as fases desidratadas. Observou-se ainda que, é possível controlar a resistência à compressão da pasta reidratada, otimizando o volume de poros presentes nas pastas. As resistências das pastas reidratadas com dispersante aos 28 dias foram 2,37 vezes maiores quando comparados com sistemas aglomerados. Com relação a porosidade, há indícios que é possível obter níveis de porosidade para as pastas reidratadas semelhantes com a pasta hidratada. The fines of cementitious wastes (previously hydrated) can be recycled through heat treatment, becoming an alternative binder. When heat treated at temperatures below 550°C, the process does not generate CO2 emissions relative to limestone decarbonation. The objective of this research was to reactivate the previously hydrated Portland cement (CP III), dehydrating it at a temperature of 500°C with a 2-hours plateau and rehydrating it with varying water and dispersant contents. Characterization was initially performed to compare the physicochemical characteristics of dehydrated cement (DC) with anhydrous cement (AC). Subsequently, the AC-HP phase transformations for DC-RP were analyzed. The second part of the study was the optimization of rehydrated (RP) and hydrated (HP) pastes, where ideal dispersion conditions were defined, with optimum dispersant and water minimum contents, resulting in pastes with smaller pore volumes and consequently more compressive strength high. The results confirm that the DC rehydrates and forms phases similar to the phases formed in the hydration, such as C-S-H, portlandite, hydrotalcite, etc. The blast furnace cement carbonate more than Portland cement (no additions). Due to the high surface area (14 times higher than that of the AC), the DC releases high wetting heat, due to the recombination of the water with the dehydrated phases. It was also observed that it is possible to control the compressive strength of the rehydrated paste by optimizing the pore volume present in the pastes. The strengths of dispersed pastes with additives at 28 days were 2.37 times higher when compared to agglomerated systems. With respect to porosity, there are indications that it is possible to obtain porosity levels for the similar rehydrated pastes with the hydrated paste.

Com a crescente demanda do mercado de tintas por produtos mais sustentáveis, toda a cadeia produtiva tem se movimentado para oferecer soluções neste âmbito. Para contemplar o pilar ambiental da sustentabilidade, a redução de Compostos Orgânicos Voláteis (VOC), de alquilfenol etoxilados (APEO) e a substituição de matérias-primas de origem fóssil por vegetal nas formulações de tintas são algumas das práticas em expansão neste setor. No presente estudo, os perfis de impactos ambientais de duas tintas imobiliárias base água foram comparados aplicando-se a metodologia de Avaliação do Ciclo de Vida (ACV) (ABNT NBR ISO 14040 e 14044). Primeiramente, foram desenvolvidas duas fórmulas genéricas não comerciais de tinta standard (ABNT NBR 15079): \"Tinta A\" com matérias-primas de uso convencional e \"Tinta B\" com algumas matérias-primas alternativas, que hipoteticamente contribuiriam com um melhor desempenho ambiental do produto final. Em seguida, ambas fórmulas foram reproduzidas em laboratório, as amostras das tintas foram submetidas a testes de desempenho técnico e com os dados obtidos determinou-se os fluxos de referência para cumprir a unidade funcional definida por cobrir 36 m2 de parede de alvenaria interior por um período mínimo de 4 anos (ABN NBR 15575-1). A ACV tem quatro fases: objetivo e definição do escopo, análise de inventário, avaliação do impacto ambiental e interpretação. Com os objetivos e escopo do estudo definidos, foi realizada uma abrangente coleta de dados, majoritariamente secundários, para possibilitar a Análise de Inventário (ICV). Posteriormente, o ciclo de vida das tintas foi modelado e analisado no software SimaPro 8.2 e na fase de Avaliação de Impactos do Ciclo de Vida (AICV) foi selecionado o método ReCiPe Midpoint (H) v.1.12. Para as sete categorias de impacto analisadas, a \"Tinta B\" apresentou perfil de impactos ambientais reduzido em relação a \"Tinta A\": Mudanças Climáticas (-18,6%), Formação de Oxidantes Fotoquímicos (-19%), Toxicidade Humana (-17,7%), Ecotoxicidade (-30,5%), Depleção de Recursos Fósseis (18,8%), Depleção de Recursos Minerais (-21,4%) e Depleção de Recursos Hídricos (-18,7%). Os resultados do estudo, reforçam a importância da ACV como uma ferramenta eficaz para mensurar o desempenho ambiental de tintas. No entanto, a falta de disponibilidade de dados primários dos processos de toda a cadeia produtiva de tintas dificulta a execução de estudos e compromete a precisão dos resultados. Destaca-se ainda, que a perspectiva do ciclo de vida de produtos e processos foi incluída como requisito da nova versão da norma ISO 14001, que é do interesse de toda a cadeia de valor, portanto, vale considerar a aplicação da ACV na indústria de tintas. The demand for sustainable products in the paint market has been steadily growing and is pushing the whole production chain to offer solutions following this scenario. The reduction of Volatile Organic Compounds (VOC), alkylphenol ethoxylates (APEO) and the substitution of raw materials of fossil origin by vegetable in the formulations of paints are some of the practices increasing among this sector to meet the environmental sustainability pillar. In the present study, the environmental impact profiles of two water-based architectural paints were compared applying the Life Cycle Assessment (LCA) methodology (ABNT NBR ISO 14040 and 14044). Firstly, two generic non-commercial formulas of standard paint (ABNT NBR 15079) were developed: \"Paint-A\" with conventional raw materials and \"Paint- B\" containing some alternative raw materials, which would hypothetically contribute to a better environmental performance of the final product. Then both formulas were reproduced in the laboratory and the samples of the paints were submitted to technical performance tests. With the data obtained, the reference flows were determined to fulfill the functional unit defined by covering 36 m2 of interior masonry wall by a minimum period of 4 years (ABN NBR 15575-1). The LCA has four phases: goal and scope definition, inventory analysis, environmental impact assessment and interpretation. After goal and scope definition, a comprehensive data collection was carried to enable the Inventory Analysis (LCI). Afterwards, the life cycle of the paints was modeled and analyzed in the SimaPro 8.2 software and in the Life Cycle Impact Assessment (LCIA) phase the ReCiPe Midpoint (H) v.1.12 method was selected. Within seven impact categories analyzed, \"Paint-B\" presented a reduced environmental impact profile compared to \"Paint-A\": Climate Change (-18.6%), Photochemical Oxidants Formation (-19%), Human Toxicity (-18.5%), Ecotoxicity (-30.5%), Fossil Resources Depletion (18.8%), Mineral Resources Depletion (-21.4%) and Water Resources Depletion (-18.7%). The results of the study strengthen the importance of LCA as an effective tool for measuring the environmental performance of paints. However, the lack of availability of primary process data throughout the paint production chain makes it difficult to carry out studies and compromises the accuracy of the results. It is also relevant to highlight that the product and process lifecycle perspective was included as a requirement of the new version of the ISO 14001 standard, which is a matter of concern to the entire value chain, so it is worth considering the application of LCA in the paints industry.