Este trabalho visa estudar o emprego da escória de aciaria a oxigênio (EACN) na construção civil. Para isso, elaborou-se um programa experimental em seis etapas: a primeira compreendeu a caracterização da EACN, do cimento, do clínquer e do gesso; na segunda, a EACN foi cominuída até valores de tamanho de partículas inferiores a 0,075mm; em seguida, caracterizada física, ambiental, química, mineralógica, microestrutural e termicamente, e teve a sua atividade pozolânica determinada; a terceira compreendeu a ativação da escória com hidróxido de sódio; na quarta, foram realizados ensaios de pega expansibilidade, resistência axial à compressão e durabilidade de argamassas de cimento CP V-ARI com substituição parcial do cimento por EACN; na quinta, obteve-se uma primeira escória de aciaria modificada (EACM1) mediante o processo pirometalúrgico da EACN em forma de pó, para alterar a composição química e estrutura para amorfa, tornando-a mais reativa, sendo submetida aos mesmos ensaios da quarta etapa, à exceção dos ensaios de pega e expansibilidade; na sexta e última, obteve-se uma segunda escória modificada (EACM2) pirometalurgicamente: a composição química próxima da escória de altoforno e amorfa. A carga desse processo pirometalúrgico foi calculada pelo software Factsage. Parte dessa escória modificada foi cominuída adicionalmente, de modo que foram obtidas amostras sem moagem adicional (EACM2a) e com moagem adicional (EACM2b). A escória modificada foi submetida aos ensaios da quinta etapa, mais o grau de vitrificação e a reatividade por microscopia de luz transmitida. Os resultados obtidos mostraram que argamassas em que parte do cimento CP V-ARI é substituída por escórias de aciaria (naturais ou modificadas) atendem às especificações de resistência à compressão nos seguintes casos: escória natural e modificada 1: substituição de até 10% do cimento CP V-ARI; escória modificada 2a, substituição de até 20% de cimento; escória modificada 2b, substituição de até 40% do cimento. Observou-se que a escória modificada 2b apresentou resistência à compressão superior ao traço referência nas idades de 28 dias e 91 dias. Apresenta-se ainda a utilização da EACM2b com o clínquer. Outros ensaios e comparações são apresentados para discutir o comportamento observado das escórias em estudo. / This study aims at employing BOF steel slag (EACN) in civil construction. Thus, the study developed an experimental program in six stages: the first one comprised the characterization of BOF steel slag, cement, clinker and gypsum; in the second stage BOF steel slag was reduced to particles sized less than 0.075mm; then, it was physical, environmental, chemical, mineralogical, microstructural and thermally characterized, it also had its pozzolanic activity determined; the third stage comprised the activation of BOF steel slag with sodium hydroxide; during the fourth stage, we carried out setting time, expansibility, axial compressive strength and durability tests for mortars made with cement CP V-ARI and partial substitution with BOF steel slag; in the fifth stage, we obtained the first modified BOF steel slag (EACM1) through pyrometallurgical process of powdered BOF steel slag so as to alter its chemical and structural makeup, making it more reactive to be submitted to the same tests of the fourth stage, except the setting time and expansibility tests; in the sixth and final stage, we obtained the second pyrometallurgically modified BOF steel slag: chemical makeup close to blastfurnace slag. The load of this pyrometallurgical process was calculated using software Factsage. Part of this modified slag was ground additionally, so that samples without additional grinding (EACM2a) and with additional grinding (EACM2b) were obtained. The modified slag underwent the fifth-stage tests, and the degree of vitrification and transmitted light microscopy reactivity. The results obtained show that mortars in which part of CP V-ARI cement was replaced with BOF steel slag (natural or modified) meet the compressive strength specifications in the following cases: Natural and modified slag 1: substitution of up to 10% of CP V-ARI cement; Modified slag 2a, substitution of up to 20% cement; Modified slag 2b, substitution of up to 40% cement. We observed that modified slag 2b showed higher compressive strength than the reference mix at ages 28 and 91 days. We also present the use of EACM2b as clinker. Other tests and comparisons are presented so as to discuss the observed behaviors of the study slags.

Este trabalho visa estudar o emprego da escória de aciaria a oxigênio (EACN) na construção civil. Para isso, elaborou-se um programa experimental em seis etapas: a primeira compreendeu a caracterização da EACN, do cimento, do clínquer e do gesso; na segunda, a EACN foi cominuída até valores de tamanho de partículas inferiores a 0,075mm; em seguida, caracterizada física, ambiental, química, mineralógica, microestrutural e termicamente, e teve a sua atividade pozolânica determinada; a terceira compreendeu a ativação da escória com hidróxido de sódio; na quarta, foram realizados ensaios de pega expansibilidade, resistência axial à compressão e durabilidade de argamassas de cimento CP V-ARI com substituição parcial do cimento por EACN; na quinta, obteve-se uma primeira escória de aciaria modificada (EACM1) mediante o processo pirometalúrgico da EACN em forma de pó, para alterar a composição química e estrutura para amorfa, tornando-a mais reativa, sendo submetida aos mesmos ensaios da quarta etapa, à exceção dos ensaios de pega e expansibilidade; na sexta e última, obteve-se uma segunda escória modificada (EACM2) pirometalurgicamente: a composição química próxima da escória de altoforno e amorfa. A carga desse processo pirometalúrgico foi calculada pelo software Factsage. Parte dessa escória modificada foi cominuída adicionalmente, de modo que foram obtidas amostras sem moagem adicional (EACM2a) e com moagem adicional (EACM2b). A escória modificada foi submetida aos ensaios da quinta etapa, mais o grau de vitrificação e a reatividade por microscopia de luz transmitida. Os resultados obtidos mostraram que argamassas em que parte do cimento CP V-ARI é substituída por escórias de aciaria (naturais ou modificadas) atendem às especificações de resistência à compressão nos seguintes casos: escória natural e modificada 1: substituição de até 10% do cimento CP V-ARI; escória modificada 2a, substituição de até 20% de cimento; escória modificada 2b, substituição de até 40% do cimento. Observou-se que a escória modificada 2b apresentou resistência à compressão superior ao traço referência nas idades de 28 dias e 91 dias. Apresenta-se ainda a utilização da EACM2b com o clínquer. Outros ensaios e comparações são apresentados para discutir o comportamento observado das escórias em estudo. / This study aims at employing BOF steel slag (EACN) in civil construction. Thus, the study developed an experimental program in six stages: the first one comprised the characterization of BOF steel slag, cement, clinker and gypsum; in the second stage BOF steel slag was reduced to particles sized less than 0.075mm; then, it was physical, environmental, chemical, mineralogical, microstructural and thermally characterized, it also had its pozzolanic activity determined; the third stage comprised the activation of BOF steel slag with sodium hydroxide; during the fourth stage, we carried out setting time, expansibility, axial compressive strength and durability tests for mortars made with cement CP V-ARI and partial substitution with BOF steel slag; in the fifth stage, we obtained the first modified BOF steel slag (EACM1) through pyrometallurgical process of powdered BOF steel slag so as to alter its chemical and structural makeup, making it more reactive to be submitted to the same tests of the fourth stage, except the setting time and expansibility tests; in the sixth and final stage, we obtained the second pyrometallurgically modified BOF steel slag: chemical makeup close to blastfurnace slag. The load of this pyrometallurgical process was calculated using software Factsage. Part of this modified slag was ground additionally, so that samples without additional grinding (EACM2a) and with additional grinding (EACM2b) were obtained. The modified slag underwent the fifth-stage tests, and the degree of vitrification and transmitted light microscopy reactivity. The results obtained show that mortars in which part of CP V-ARI cement was replaced with BOF steel slag (natural or modified) meet the compressive strength specifications in the following cases: Natural and modified slag 1: substitution of up to 10% of CP V-ARI cement; Modified slag 2a, substitution of up to 20% cement; Modified slag 2b, substitution of up to 40% cement. We observed that modified slag 2b showed higher compressive strength than the reference mix at ages 28 and 91 days. We also present the use of EACM2b as clinker. Other tests and comparisons are presented so as to discuss the observed behaviors of the study slags.

[pt] A indústria siderúrgica no Brasil gera atualmente cerca de 5 milhões de toneladas/ano de escória de aciaria LD. Estudos preliminares recentes têm mostrado ser promissora a produção de cimento mediante tratamentos térmicos e modificações químicas capazes de gerar fases com propriedades pozolânicas com resistência a compressão semelhantes às do cimento Portland. Dentro deste contexto o presente trabalho teve como objetivo investigar a viabilidade de utilização da escória LD na produção de um cimento Portland classe E por meio de ajuste químico composicional e tratamentos térmicos da escória ainda liquida utilizando análises químicas por ICP-OES e testes de resistência à compressão segundo a norma NBR 7215. Além disso, a presente pesquisa realizou estudo de correlação utilizando várias gamas de misturas e um fator de correlação entre os corpos de prova especificados pela norma (5x10cm) e corpos de prova menores (1x2cm), a fim de adequar um equipamento mais apropriado ao projeto. Os resultados mostraram que a mistura formada por 75 por cento Cimento Portland II F-32 e 25 por cento Novo Clínquer (escória de LD química e termicamente tratada) e a mistura com a relação 50-50 desses mesmos materiais, foram as que atenderam plenamente a condição exigida pela norma para a resistência à compressão dos Cimentos Portland Tipo II, Classe E, decorridos 28 dias de cura. Além disso os resultados mostraram viabilidade na correlação dos corpos de prova, dessa forma sendo possível a realização dos testes mecânicos com corpos de prova com dimensão de 1x2 cm. / [en] Nowadays the steel industry in Brazil generates about 5 million tons of LD steel slag annually. Recently some studies with its use in cement production have shown promise, once that after heat treatment and chemical modifications it can present phases with similar hydraulic properties to Portland cement and equivalent compressive strength as well. In this context, the present work aimed to investigate the feasibility of using LD slag for production of a Portland cement Class-E, in the face of chemical modifications of the liquid slag followed by a fast-cooling heat treatment and chemical analysis carried out by ICP-OES techniques and also a compressive strength test according to the NBR 7215 standard. In addition, based on the results of the compression test and to optimize the amount of material used, a correlation study was carried out between specimens in accordance with the standard (5X10cm) and smaller specimens (1X2cm), in order to use an appropriate lab compressive machine. The results showed that the mixtures using 75 percent Portland II Cement F-32 and 25 percent Novo Clinquer (chemical and heat-treated LD slag) and that one with 50-50 ratio using the same materials, were the mixtures that fully satisfied the minimum compressive resistance condition required by the NBR standard, concerning Type II Class Portland Cements, after 28 days of curing. In addition, the results showed feasibility in the correlation of specimens, thus making it possible to perform mechanical tests with specimens with a dimension of 1x2 cm.

Alkaline industrial wastes are considered potential resources for the mitigation of CO2 emissions by simultaneously capturing and sequestering CO2 through mineralization. Mineralization safely and permanently stores CO2 through its reaction with alkaline earth metals. Apart from natural formations, these elements can also be found in a variety of abundantly available industrial wastes that have high reactivity with CO2, and that are generated close to the emission point-sources. Apparently, it is the applicability and marketability of the carbonated products that define to a great extent the efficiency and viability of the particular process as a point source CO2 mitigation measure. This project investigates the valorization of iron- and steel-making slags through methods incorporating the carbonation of the material, in order to achieve the sequestration of sufficient amounts of CO2 in parallel with the formation of valuable and marketable products. Iron- and steel-manufacturing slags were selected as the most suitable industrial byproducts for the purposes of this research, due to their high production amounts and notable carbonation capacities. The same criteria (production amount and carbonation capacity) were also used for the selection of the iron- and steel-making slag types that are more suitable to the scope of this work. Specifically for the determination of the slag types with the most promising carbonation capacities, the maximum carbonation conversions resulting from recent publications related to the influence of process parameters on the conversion extent of iron- and steel-manufacturing slags, were directly compared to each other using a new index, the Carbonation Weathering Rate, which normalizes the results based on particle size and reaction duration. Among the several iron- and steel-manufacturing slags, basic oxygen furnace (BOF) and blast furnace (BF) slags were found to combine both high production volumes and significant affinity to carbonation. In the context of this research, two different procedures aiming to the formation of value added materials with satisfactory CO2 uptakes were investigated as potential BF and BOF slags valorization methods. In them, carbonation was combined either with granulation and alkali activation (BOF slag), or with hydrothermal conversion (BF slag). Both treatments seemed to be effective and returned encouraging results by managing to store sufficient amounts of CO2 and generating materials with promising qualities. In particular, the performance of the granulation-carbonation of BOF slag as a method leading to the production of secondary aggregates and the sequestration of notable amounts of CO2 in a solid and stable form, was evaluated in this work. For comparison purposes, the material was also subjected to single granulation tests under ambient conditions. In an effort to improve the mechanical properties of the finally synthesized products, apart from water, a mixture of sodium hydroxide and sodium silicate was also tested as a binding agent in both of the employed processes. According to the results, the granules produced after the alkali activation of the material were characterized by remarkably greater particle sizes (from 1 to 5 mm) compared to that of the as received material (0.2 mm), and by enhanced mechanical properties, which in some cases appeared to be adequate for their use as aggregates in construction applications. The maximum CO2 uptake was 40 g CO2/kg of slag and it was achieved after 60 minutes of the combined treatment of alkali activated BOF slag. Regarding the environmental behavior of the synthesized granules, increased levels of Cr and V leaching were noticed from the granules generated by the combination of granulation-carbonation with alkali activation. Nevertheless, the combination of granulation with alkali activation or that of granulation with carbonation were found not to worsen, if not to improve, the leaching behaviour of the granules with regards to the untreated BOF slag. The formation of a zeolitic material with notable heavy metal adsorption capacity, through the hydrothermal conversion of the solid residues resulting from the calcium- extraction stage of the indirect carbonation of BF slag, was also investigated in this project. To this end, calcium was selectively extracted from the slag by leaching, using acetic acid of specific concentration (2 M) as the extraction agent. The residual solids resulting from the filtration of the generated slurry were subsequently subjected to hydrothermal conversion in caustic solution of two different compositions (NaOH of 0.5 M and 2 M). Due to the presence of calcium acetate in the composition of the solid residues, as a result of their inadequate washing, only the hydrothermal conversion attempted using the sodium hydroxide solution of higher concentration (2 M) managed to turn the amorphous slag into a crystalline material, mainly composed by a zeolitic mineral phase (detected by XRD), namely, analcime (NaAlSi2O6·H2O), and tobermorite (Ca5(OH)2Si6O16·4H2O). Finally, the heavy metal adsorption capacity of the particular material was assessed using Ni2+ as the metal for investigation. Three different adsorption models were used for the characterization of the adsorption process, namely Langmuir, Freundlich and Temkin models. Langmuir and Temkin isotherms were found to better describe the process, compared to Freundlich model. Based on the ability of the particular material to adsorb Ni2+ as reported from batch adsorption experiments and ICP-OES analysis, and the maximum monolayer adsorption capacity (Q0 = 11.51 mg/g) as determined by the Langmuir model, the finally synthesized product can potentially be used in wastewater treatment or environmental remediation applications.