| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 3.01 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
A trabalhabilidade do betão auto-compactável durante o enchimento das cofragens em obra é determinante para a maior ou menor compacidade do produto final, uma vez que este betão é aplicado sem qualquer vibração ou outra forma de compactação. Tem sido referido que os processos de produção, transporte e colocação do betão auto-compactável podem afectar as suas propriedades no estado fresco e que, comparativamente com um betão corrente, a trabalhabilidade deste tipo de betões é mais sensível à variação dos materiais, variações na dosagem de água, sequência e duração da amassadura, temperatura ambiente, condições e duração do transporte, condições de colocação, entre outras. No processo de transporte deverá observar-se qualquer possível efeito de segregação dos agregados, mas especialmente relevante será a avaliação da retenção da trabalhabilidade ao longo do tempo.
A presente dissertação avaliou a influência que o tipo de cimento, a temperatura de amassadura e a dosagem de superplastificante exercem na capacidade de retenção ou manutenção da trabalhabilidade de betões auto-compactáveis ao longo do tempo decorrido após amassadura. Esse estudo foi realizado em argamassas adequadas à produção e betões auto-compactáveis e a trabalhabilidade foi avaliada de forma indirecta através dos ensaios de espalhamento (slump-flow) e de fluidez (Funil-V).
Os resultados obtidos proporcionaram uma análise comparativa e crítica da influência relativa dos vários parâmetros seleccionados. Os dados obtidos experimentalmente foram promissores no que respeita à análise da retenção de trabalhabilidade em argamassas. Verificou-se que todos os parâmetros analisados influenciaram a retenção da trabalhabilidade das argamassas, sendo que uns são mais preponderantes que outros. As misturas com o cimento de endurecimento lento, menor temperatura de amassadura e maior dosagem de superplastificante foram as que registaram menores perdas de trabalhabilidade ao longo do tempo decorrido após amassadura, sendo que a dosagem de superplastificante se revelou o factor mais preponderante.
The workability of self-compacting concrete when filling the formwork on site is critical to a greater or lesser compactness of the final product, since this concrete is applied without any vibration or other form of compaction. It has been reported that the processes of production, transportation and placement of self-compacting concrete may affect its fresh properties and that, compared with a normal vibrated concrete, the workability of this type of concrete is more sensitive to variation of materials, variations in water dosage, sequence and duration of mixing, temperature, conditions and duration of transport, conditions of placement, among others. In the process of transportation it should be pointed out any possible effect of segregation of the aggregates, but especially relevant is the assessment of the workability retention over time. This thesis evaluated the influence that the type of cement, mixing temperature and dosage of superplasticizer exercise in the retention capacity or maintenance of the workability of self-compacting concrete along the time after mixing. This study was conducted on mortars adequate to the production of self-compacting concrete and workability was assessed indirectly through tests of slump flow and fluidity (Funnel-V). The results provided a comparative and critical analysis of the relative influence of various parameters selected. The experimental data were promising as regards the analysis of the retention of workability in mortars. It was found that all measured parameters influenced the retention of the workability of mortars after mixing, and some are more predominant than others. The mixtures with the cement of low heat of hydration, the lower temperature of mixing and higher dosage of superplasticizer were those that revealed the smallest loss of workability over time elapsed after mixing, and the dosage of superplasticizer emerged as the most dominant factor.
The workability of self-compacting concrete when filling the formwork on site is critical to a greater or lesser compactness of the final product, since this concrete is applied without any vibration or other form of compaction. It has been reported that the processes of production, transportation and placement of self-compacting concrete may affect its fresh properties and that, compared with a normal vibrated concrete, the workability of this type of concrete is more sensitive to variation of materials, variations in water dosage, sequence and duration of mixing, temperature, conditions and duration of transport, conditions of placement, among others. In the process of transportation it should be pointed out any possible effect of segregation of the aggregates, but especially relevant is the assessment of the workability retention over time. This thesis evaluated the influence that the type of cement, mixing temperature and dosage of superplasticizer exercise in the retention capacity or maintenance of the workability of self-compacting concrete along the time after mixing. This study was conducted on mortars adequate to the production of self-compacting concrete and workability was assessed indirectly through tests of slump flow and fluidity (Funnel-V). The results provided a comparative and critical analysis of the relative influence of various parameters selected. The experimental data were promising as regards the analysis of the retention of workability in mortars. It was found that all measured parameters influenced the retention of the workability of mortars after mixing, and some are more predominant than others. The mixtures with the cement of low heat of hydration, the lower temperature of mixing and higher dosage of superplasticizer were those that revealed the smallest loss of workability over time elapsed after mixing, and the dosage of superplasticizer emerged as the most dominant factor.
Description
Keywords
Betão auto-compactável Betão auto-compactável - Trabalhabilidade Retenção da trabalhabilidade Betão auto-compactável - Ensaios reológicos Betão auto-compactável - Composição