Ultra-high performance concrete (UHPC) is relatively a new generation of concretes optimized at the nano and micro-scales to provide superior mechanical and durability properties compared to conventional and high performance concretes. Improvements in UHPC are achieved through: limiting the water-to-cementitious materials ratio (i.e., w/cm < 0.20), optimizing particle packing, eliminating coarse aggregate, using specialized materials, and implementing high temperature and high pressure curing regimes. In addition, and randomly dispersed and short fibers are typically added to enhance the material¡¦s tensile and flexural strength, ductility, and toughness. There is a specific interest in using UHPC for precast prestressed bridge girders because it has the potential to reduce maintenance costs associated with steel and conventional concrete girders, replace functionally obsolete or structurally deficient steel girders without increasing the weight or the depth of the girder, and increase bridge durability to between 75 and 100 years. UHPC girder construction differs from that of conventional reinforced concrete in that UHPC may not need transverse reinforcement due to the high tensile and shear strengths of the material. Before bridge designers specify such girders without using shear reinforcement, the long-term tensile performance of the material must be characterized. This multi-scale study provided new data and understanding of the long-term tensile performance of UHPC by assessing the effect of thermal treatment, fiber content, and stress level on the tensile creep in a large-scale study, and by characterizing the fiber-cementitious matrix interface at different curing regimes through nanoindentation and scanning electron microscopy (SEM) in a nano/micro-scale study. Tensile creep of UHPC was more sensitive to investigated parameters than tensile strength. Thermal treatment decreased tensile creep by about 60% after 1 year. Results suggested the possibility of achieving satisfactory microstructural refinement at the same temperature input despite the maximum temperature applied. For the first time, the presence of a 10 Ým (394 micro inch) wide porous fiber-cementitious matrix interface was demonstrated by nanoindentation and SEM for non-thermally treated UHPC only. Tensile creep at 90 days increased by 64% and 46% upon eliminating fibers for thermally and non-thermally treated UHPC, respectively. Increases in creep upon reducing the fiber content suggested that fibers carry part of the sustained load and thus reduce creep. Tensile creep strain was proportional to the stress applied up to 60% of the ultimate strength. No tensile creep failure occurred for a period of 1 year for pre-cracked UHPC under stress level of 40%. Also, no tensile creep failure occurred for a period of 90 days under stress level of 60%. Tensile creep failure occurred at stress levels of 70% and 80%. This study showed that fibers cannot be accounted for as shear reinforcement in lieu of stirrups unless micro-defect-free fiber-matrix interface is achieved.

Submitted by Biblioteca Central (biblioteca@unicap.br) on 2018-01-29T17:34:49Z No. of bitstreams: 1 maria_conceição_aguiar_nascimento.pdf: 3804537 bytes, checksum: aea07399e9de24f9fafa6060e4c467bd (MD5) / Made available in DSpace on 2018-01-29T17:34:49Z (GMT). No. of bitstreams: 1 maria_conceição_aguiar_nascimento.pdf: 3804537 bytes, checksum: aea07399e9de24f9fafa6060e4c467bd (MD5) Previous issue date: 2016-12-15 / Brazil is the world's largest non-sugar-alcohol complex that has been expanding in recent times, driven by the advent of bioenergy, exerting a leadership in all segments. The residue generated at the end of the sugarcane bagasse milling process is used for the generation of energy by burning in boilers. At the end of the burning as residual ash are released into the environment inadequately, and may cause environmental problems due to the generation of waste as a sugarcane bagasse ash. The interest of the research is to justify the demand through a job offer from the sugarcane bagasse ash (CBC) in concrete structures, due to the large volume of generation and the concern with the environment. The objective of this research is to evaluate the performance of the conventional contract made of sugar cane residues proved from mills. The results were reported with a 0%, 20% and 40% substitution of natural sand by BCC, where this mixture may contribute to a compound more difficult than conventional concrete. It is also concluded that although the use of CBC has not significantly reduced the final value of m³ of concrete, the gain in relation to the mechanical performance was higher. It can be concluded that the specimens produced have obtained sufficient mechanical strength to be dismantled, transported and conditioned prior to use, in the same way as the referents. / O Brasil é o maior produtor mundial no complexo sucroalcooleiro que vem se expandindo nos últimos tempos, impulsionado pelo advento da bioenergia, exercendo a liderança em todos os segmentos. O resíduo gerado ao final do processo de moagem do bagaço da cana-de-açúcar é utilizado para a geração de energia por meio da queima em caldeiras. Ao final da queima as cinzas residuais são lançadas no meio ambiente de forma inadequada, podendo causar problemas ambientais em decorrência da geração de resíduos como a cinza do bagaço de cana-de-açúcar. O interesse desta pesquisa justifica-se pela necessidade de se avaliar a possibilidade do emprego da cinza do bagaço da cana-de-açúcar (CBC) em estruturas de concreto, devido ao grande volume de geração e a preocupação com o meio ambiente. O objetivo desta pesquisa é avaliar o desempenho do concreto convencional confeccionado de resíduos de cana-de-açúcar proveniente de usinas. Os resultados foram apresentados com a substituição de 0%, 20% e 40% da areia natural por CBC, onde essa mistura pode contribuir para um composto mais durável que o concreto convencional. Conclui-se, também, que apesar do uso da CBC não ter diminuído significativamente o valor final do m3 do concreto, o ganho em relação ao desempenho mecânico foi maior. Pode-se concluir que os corpos-de-prova produzidos obtiveram resistência mecânica suficiente para serem desmoldados, transportados e acondicionados antes do uso, da mesma forma que os de referência.

Uma das aplicações dos agregados provenientes da reciclagem dos resíduos de construção civil (ARC) é na fabricação de concretos no slump. Este tipo de concreto é utilizado na fabricação de peças conformadas por vibração e vibro compactação. Porém, as características dos agregados de ARC dificultam a dosagem desse tipo de concreto, pois ocorrem variações na trabalhabilidade dependendo da morfologia e absorção de água. O estudo da dosagem de ARC é importante pois ao ser utilizado altera as propriedades do concreto, em especial do concreto no slump, devido à necessidade de manter a forma imediatamente após a desmoldagem. Desta forma, o presente trabalho tem como objetivo avaliar o efeito do agregado ARC nas características do concreto no slump, com a avaliação da influência do processo de fabricação na forma das partículas e da pré-molhagem do agregado nas propriedades reológicas e na resistência mecânica à compressão. Para isto, foram estudadas composições de concretos utilizando agregados reciclados com diferentes teores de excesso de pasta e diferentes relações água/cimento (a/c), além da composição sugerida pela ABCP para concretos utilizados em meio fio com agregados naturais. Com a composição que apresentou os melhores resultados e com o traço de referência foi realizada a análise do custo de fabricação de uma peça de meio-fio com cada um dos concretos, a fim de se avaliar o impacto econômico da substituição do agregado. Observou-se diferenças entre os agregados reciclados e naturais, tanto em relação as propriedades quanto a morfologia, fatos que resultaram em características distintas também nos concretos obtidos. No estudo da pré-molhagem foi possível observar que diferentes taxas de pré-molhagem resultaram em comportamentos distintos tanto no estado fresco como no endurecido, sendo obtida variação de 60% na resistência à compressão entre os teores de 75 e 65% de pré-molhagem. Com a obtenção de traços variando o excesso de pasta e a/c pode-se observar que a composição com a/c de 0,35 e teor de pasta de - 5% foi a que resultou em melhores características para a produção de peças submetidas à vibração. Apesar desta composição atingir o mínimo de 11 MPa exigido por norma para a fabricação de meio-fio, o custo para fabricação de uma peça de concreto com agregado reciclado foi 17% maior do que o custo com agregados naturais, resultado ligado ao maior consumo de cimento exigido pelo concreto com ARC para atingir a resistência exigida. / One of the applications of aggregates from the recycling of civil construction waste (CCW) is in no slump concrete manufacturing. This type of concrete is used in the manufacture of parts shaped by vibration and vibrocompression, for example. However, the characteristics of CCW aggregates make it difficult to measure this type of concrete, since there are variations in the workability depending on the morphology and water absorption. The study of CCW aggregate is important because its use changes the concrete properties, especially in no slump concrete, due to the necessity to maintain the form immediately after the demolding. Therefore, the present work aim to evaluate the effect of the CCW aggregate on the no slump concrete characteristics, with the evaluation of the influence of the particle formation process and the pre-wetting of the aggregate on the rheological properties and the compression strength. For this, concrete compositions were studied using recycled aggregates with different contents of excess paste and different water/cement (a/c) ratios, in addition to the composition suggested by ABCP for concrete used in curb with natural aggregates. With the composition that presented the best results and with the reference mix design it was performed the analysis of the manufacturing cost of a piece of curb with each of the concretes, in order to evaluate the economic impact of the replacement of the aggregate. It was observed differences between the recycled and natural aggregates, both in relation to the properties and morphology, facts that resulted in different characteristics also in the concretes obtained. In the pre-wetting study, it was possible to observe that different pre-wetting rates resulted in different behaviors in both the fresh and hardened state, with a 60% variation in the compressive strength between 75 and 65% pre-wetting rates. By obtaining traces varying the excess of paste and a/c it can be observed that the composition with a/c of 0.35 and paste content of -5% was the one that resulted in better characteristics for the production of vibration pieces. Although this composition reached the minimum of 11 MPa required by standard for the production of curb, the cost for manufacturing a piece of concrete with recycled aggregate was 17% higher than the cost with natural aggregates, a result linked to the higher consumption of cement required by concrete with CCW to achieve the required strength.

2022 fanden die 9. Jahrestagung des Deutschen Ausschusses für Stahlbeton (DAfStb) sowie das 61. DAfStb-Forschungskolloquium am 26. und 27. September in Dresden direkt im Vorfeld der 14. Carbon- und Textilbetontage statt. Gastgeber waren die Institute für Baustoffe (IfB) und Massivbau (IMB) der Technischen Universität Dresden. Thematische Schwerpunkte waren Impaktbelastungen, Ingenieurbau, Ermüdung und Dauerhaftigkeit, Frischbeton und Rheologie, additive Fertigung und Sensorik sowie Carbonbeton. Der vorliegende Tagungsband enthält alle Beiträge in deutscher oder englischer Sprache.:Themenschwerpunkt Impakt Cesare Signorini, Viktor Mechtcherine: Mineral-bonded composites for enhanced structural impact safety: The vision of the DFG GRK 2250 Ahmed Tawfik, Viktor Mechtcherine: On the shear behavior of mineral-bonded composites under impact loading Lena Leicht: Charakterisierung von mineralisch gebundenen Kompositen zur Impaktdämpfung Franz Bracklow: Rückseitige Verstärkung von Stahlbetonplatten unter Impaktbeanspruchung Themenschwerpunkt Ingenieurbau Steffen Marx: Ingenieurbau im Bestand Conrad Pelka: Sanierung von Gewölbebrücken Max Herbers: Langzeitverformung semi-integraler Talbrücken – Messung und Simulation Fabian Klein: Modellierung der Torsionstragfähigkeit segmentierter Betontürme auf Basis der Wölbtheorie dünnwandiger Stäbe Jan-Hauke Bartels: Robuste, lebensdauerumfassende Monitoringkonzepte für Offshore-Windenergieanlagen Themenschwerpunkt Ermüdung und Dauerhaftigkeit Dominik Junger, Viktor Mechtcherine: Ermüdungsverhalten von hochduktilem Kurzfaserbeton Raúl Beltrán: Untersuchung von ermüdungsbedingten Veränderungen der Ultraschallgeschwindigkeit in Beton Marc Koschemann: Rissbreitenentwicklung unter Langzeitbelastung anhand lokaler Verbundbeziehungen Daniel Gebauer: Rissbildung und Rissbreitenentwicklung bei Stahlbetonbauteilen unter verformungsinduziertem Zwang Michaela Reichardt, Steffen Müller, Viktor Mechtcherine: Erhöhung der Dauerhaftigkeit von Wasserbauwerken durch faserbewehrte, zementgebundene Komposite Themenschwerpunkt Frischbeton und Rheologie Rolf Breitenbücher, Udo Wiens, Mirsada Omercic: Wandel im Betonbau – Aktuelle Herausforderungen Daniil Mikhalev, Viktor Mechtcherine, Dario Cotardo, Michael Haist: Pumpverhalten und Blockierungsneigung von Beton: Erkenntnisse aus Großversuchen Irina Ivanova, Silvia Reißig, Viktor Mechtcherine: Vergleich von Bewertungsmethoden für die rheologischen Eigenschaften von frisch gedrucktem Beton Slava Markin, Viktor Mechtcherine: Rissbildung in 3D-gedruckten Betonelementen infolge plastischen Schwindens: Ursachen und Quantifizierungsmethoden Steffen Müller, Viktor Mechtcherine: Alternative mineralische Baustoffe – Potentiale und Eigenschaften Themenschwerpunkt Additive Fertigung und Sensorik Viktor Mechtcherine: Additive Fertigung mit Beton Tobias Neef, Viktor Mechtcherine: Additiv gefertigter Carbonbeton mit mineralischer Tränkung der Garne Egor Ivaniuk, Viktor Mechtcherine: Formwork-free, continuous production of variable frame elements for modular shell structures Markus Taubert, Viktor Mechtcherine: 3D-druckbarer Normalbeton mit grober Gesteinskörnung Sebastian Hegler, Marco Liebscher, Viktor Mechtcherine, Dirk Plettemeier: Rissdetektion und -lokalisierung in Betonstrukturen mittels Auswertung elektromagnetischer Hochfrequenzwellen Themenschwerpunkt Carbonbeton Norbert Will: DAfStb-Richtlinie „Betonbauteile mit Nichtmetallischer Bewehrung“ – Von Forschung und Pilotprojekten zum Regelwerk Nazaib Ur Rehman, Harald Michler: Existing codes and guidelines for durability design of FRP reinforcement Peter Betz: Carbonbeton unter Druck – Einfluss von Querdruck und Querzug Enrico Baumgärtel: Untersuchung von Stäben und Gelegen aus rezyklierten Carbonfasern Iurii Vakaliuk: Use of pervading internal shell-type substructures to dissolve compact components / 2022, the 9th Annual Conference of the Deutscher Ausschusses für Stahlbeton (German Committee for Reinforced Concrete, DAfStb) and the 61st DAfStb Research Colloquium took place on 26 and 27 September in Dresden directly in the run-up to the 14th Carbon and Textile Concrete Days. It was hosted by the Institutes for Building Materials (IfB) and Concrete Structures (IMB) of the Technische Universität Dresden. The main topics were impact loads, civil engineering, fatigue and durability, fresh concrete and rheology, additive manufacturing and sensor technology as well as carbon reinforced concrete. The present conference proceedings contain all contributions in German or English.:Themenschwerpunkt Impakt Cesare Signorini, Viktor Mechtcherine: Mineral-bonded composites for enhanced structural impact safety: The vision of the DFG GRK 2250 Ahmed Tawfik, Viktor Mechtcherine: On the shear behavior of mineral-bonded composites under impact loading Lena Leicht: Charakterisierung von mineralisch gebundenen Kompositen zur Impaktdämpfung Franz Bracklow: Rückseitige Verstärkung von Stahlbetonplatten unter Impaktbeanspruchung Themenschwerpunkt Ingenieurbau Steffen Marx: Ingenieurbau im Bestand Conrad Pelka: Sanierung von Gewölbebrücken Max Herbers: Langzeitverformung semi-integraler Talbrücken – Messung und Simulation Fabian Klein: Modellierung der Torsionstragfähigkeit segmentierter Betontürme auf Basis der Wölbtheorie dünnwandiger Stäbe Jan-Hauke Bartels: Robuste, lebensdauerumfassende Monitoringkonzepte für Offshore-Windenergieanlagen Themenschwerpunkt Ermüdung und Dauerhaftigkeit Dominik Junger, Viktor Mechtcherine: Ermüdungsverhalten von hochduktilem Kurzfaserbeton Raúl Beltrán: Untersuchung von ermüdungsbedingten Veränderungen der Ultraschallgeschwindigkeit in Beton Marc Koschemann: Rissbreitenentwicklung unter Langzeitbelastung anhand lokaler Verbundbeziehungen Daniel Gebauer: Rissbildung und Rissbreitenentwicklung bei Stahlbetonbauteilen unter verformungsinduziertem Zwang Michaela Reichardt, Steffen Müller, Viktor Mechtcherine: Erhöhung der Dauerhaftigkeit von Wasserbauwerken durch faserbewehrte, zementgebundene Komposite Themenschwerpunkt Frischbeton und Rheologie Rolf Breitenbücher, Udo Wiens, Mirsada Omercic: Wandel im Betonbau – Aktuelle Herausforderungen Daniil Mikhalev, Viktor Mechtcherine, Dario Cotardo, Michael Haist: Pumpverhalten und Blockierungsneigung von Beton: Erkenntnisse aus Großversuchen Irina Ivanova, Silvia Reißig, Viktor Mechtcherine: Vergleich von Bewertungsmethoden für die rheologischen Eigenschaften von frisch gedrucktem Beton Slava Markin, Viktor Mechtcherine: Rissbildung in 3D-gedruckten Betonelementen infolge plastischen Schwindens: Ursachen und Quantifizierungsmethoden Steffen Müller, Viktor Mechtcherine: Alternative mineralische Baustoffe – Potentiale und Eigenschaften Themenschwerpunkt Additive Fertigung und Sensorik Viktor Mechtcherine: Additive Fertigung mit Beton Tobias Neef, Viktor Mechtcherine: Additiv gefertigter Carbonbeton mit mineralischer Tränkung der Garne Egor Ivaniuk, Viktor Mechtcherine: Formwork-free, continuous production of variable frame elements for modular shell structures Markus Taubert, Viktor Mechtcherine: 3D-druckbarer Normalbeton mit grober Gesteinskörnung Sebastian Hegler, Marco Liebscher, Viktor Mechtcherine, Dirk Plettemeier: Rissdetektion und -lokalisierung in Betonstrukturen mittels Auswertung elektromagnetischer Hochfrequenzwellen Themenschwerpunkt Carbonbeton Norbert Will: DAfStb-Richtlinie „Betonbauteile mit Nichtmetallischer Bewehrung“ – Von Forschung und Pilotprojekten zum Regelwerk Nazaib Ur Rehman, Harald Michler: Existing codes and guidelines for durability design of FRP reinforcement Peter Betz: Carbonbeton unter Druck – Einfluss von Querdruck und Querzug Enrico Baumgärtel: Untersuchung von Stäben und Gelegen aus rezyklierten Carbonfasern Iurii Vakaliuk: Use of pervading internal shell-type substructures to dissolve compact components