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Abstract(s)
O protótipo do betão auto-compactável surgiu no Japão na década de oitenta, por proposta
do Professor Hajime Okamura, como forma de combater um défice de durabilidade em
resultado de uma deficiente compactação do betão vibrado, decorrente do decréscimo na
mão-de-obra especializada. As suas potencialidades já foram provadas pela sua grande
aplicação por todo o mundo. No entanto, o conhecimento das suas propriedades no estado
endurecido ainda não é completo. O conhecimento e previsão correctos das propriedades do
betão auto-compactável no estado endurecido permitem prevenir problemas futuros nas
construções, bem como elevar ainda mais a sua potencialidade e aplicabilidade.
De forma a contribuir para um maior esclarecimento deste tema foi elaborada a presente
dissertação, que contempla, numa primeira fase da revisão bibliográfica, uma comparação
das propriedades no estado endurecido entre o betão auto-compactável, o betão corrente
vibrado e o betão de alta resistência. Na segunda fase da revisão bibliográfica são ainda
compilados e comparados entre si diferentes modelos de previsão das propriedades no estado
endurecido do betão corrente vibrado e é avaliada a viabilidade de aplicação destes modelos
ao betão auto-compactável, através da comparação dos valores obtidos com recurso a estes
modelos e os valores experimentais obtidos em diferentes estudos recentes. As propriedades
como a resistência à compressão, resistência a tracção, módulo de elasticidade, módulo de
ruptura, retracção e fluência são tratados nesta dissertação.
Comparados os valores de previsão dos códigos aplicados ao betão vibrado corrente com os
valores experimentais obtidos no betão auto-compactável, concluiu-se que todos os códigos
podem ser aplicados, no entanto, alguns são mais apropriados para a estimativa de
determinadas propriedades que outros. Os modelos propostos pelo ACI são os que melhor se
aproximam dos valores obtidos experimentalmente para a resistência à compressão,
resistência à tracção, módulo de elasticidade e módulo de ruptura, enquanto os modelos do
CEB-FIP 90 se adequam melhor à estimativa dos valores de retracção e de fluência.
The prototype of self-compacting concrete has emerged in Japan in the eighties, proposed by Professor Hajime Okamura, as a way to combat lack of durability as a result of poor compaction of vibrated concrete due to the decrease of skilled labor. Its potentialities were proven by its wide application throughout the world. However the knowledge of its properties in the hardened state is not yet complete. Knowledge and correct prediction of the properties of self-compacting concrete in the hardened state allow prevent future problems in constructions as well as further increase its capability and applicability. This dissertation has been prepared in order to contribute to a clarification of this issue, which includes, in a first phase of the literature review, a comparison of the hardened properties between the self-compacting concrete, the current vibrated concrete and the high-strength concrete. In the second phase of the literature review are also compiled and compared different prediction models of the hardened properties of the current vibrated concrete and the feasibility of applying these models to the self-compacting concrete is also evaluate by comparing the obtained values using these models and the gathered experimental values from different recent studies. The properties such as compressive strength, tensile strength, modulus of elasticity, modulus of rupture, shrinkage and creep are treated in this dissertation. Compared the forecast values of the codes applied to vibrated concrete with current experimental values obtained for the self-compacting concrete it was concluded that all codes can be applied. Nevertheless, some of these are more suitable for prediction of some properties than others. ACI models are the best approach to the values experimentally obtained for compressive strength, tensile strength, modulus of elasticity and modulus of rupture, whereas CEB-FIP 90 models are more congruous to predict values of shrinkage and creep.
The prototype of self-compacting concrete has emerged in Japan in the eighties, proposed by Professor Hajime Okamura, as a way to combat lack of durability as a result of poor compaction of vibrated concrete due to the decrease of skilled labor. Its potentialities were proven by its wide application throughout the world. However the knowledge of its properties in the hardened state is not yet complete. Knowledge and correct prediction of the properties of self-compacting concrete in the hardened state allow prevent future problems in constructions as well as further increase its capability and applicability. This dissertation has been prepared in order to contribute to a clarification of this issue, which includes, in a first phase of the literature review, a comparison of the hardened properties between the self-compacting concrete, the current vibrated concrete and the high-strength concrete. In the second phase of the literature review are also compiled and compared different prediction models of the hardened properties of the current vibrated concrete and the feasibility of applying these models to the self-compacting concrete is also evaluate by comparing the obtained values using these models and the gathered experimental values from different recent studies. The properties such as compressive strength, tensile strength, modulus of elasticity, modulus of rupture, shrinkage and creep are treated in this dissertation. Compared the forecast values of the codes applied to vibrated concrete with current experimental values obtained for the self-compacting concrete it was concluded that all codes can be applied. Nevertheless, some of these are more suitable for prediction of some properties than others. ACI models are the best approach to the values experimentally obtained for compressive strength, tensile strength, modulus of elasticity and modulus of rupture, whereas CEB-FIP 90 models are more congruous to predict values of shrinkage and creep.
Description
Keywords
Betão auto-compactável Betão auto-compactável - Propriedades Betão auto-compactável - Resistência à compressão Betão auto-compactável - Resistência à compressão Betão auto-compactável - Endurecido