Viabilidade da estimativa de vazão de concreto autoadensável por meio de correlações com parâmetros do ensaio de espalhamento
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Data
2023-01-31
Autores
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Para tentar contribuir com o desenvolvimento do controle de volume de concreto entregue na obra, o presente trabalho mostra um estudo inicial para verificar a possibilidade de medição de vazão (e consequentemente o volume, considerando que o tempo de vazão pode ser medido) de concretos autoadensáveis que escoam dentro de um tubo de volume conhecido, a partir da correlação entre a velocidade média de espalhamento (obtida por meio dos ensaios de espalhamento) e a velocidade de escoamento, obtida pelo ensaio de vazão sugerido. Para tal, quatro traços-base foram desenvolvidos (nomeados I a IV) e quatro combinações de aditivos superplastificantes e modificador de viscosidade foram aplicadas em cada um deles (resultando em dezesseis “situações”, nomeadas “S1” a “S16”). Os resultados revelaram dezesseis traços estáveis, sendo oito classificados como SF1 e oito como SF2 (de acordo com a NBR 15823-1). Após as correlações da velocidade de espalhamento com a velocidade de vazão, foi possível desenvolver quatro cenários para mensurar a vazão: o primeiro, utiliza a classificação de espalhamento SF1 e SF2 e a velocidade média de espalhamento medida até a marca de 500 mm. Essa combinação resultou uma equação capaz de estimar uma relação média de 1,00 entre a vazão estimada/vazão ensaiada dos traços, com desvio padrão de 0,15. No segundo cenário, em que a classificação de espalhamento da norma não foi considerada (e a velocidade média de espalhamento medida até a marca de 500 mm), a relação média foi de 1,01 e o desvio padrão de 0,23. No terceiro cenário (que considera a classificação de espalhamento da norma) e no quarto (que não separa os traços pela classificação de espalhamento), a velocidade média de espalhamento está vinculada ao diâmetro final que o concreto atinge no término do ensaio. Nesses cenários, a relação média entre a vazão estimada/ vazão ensaiada dos traços foi de 1,00 e 1,01, respectivamente, com desvio padrão de 0,17 e 0,25.
Attempting to control the delivered volume of concrete on construction sites, the present work shows an initial study to verify the possibility to measure self-compacting concrete flow rates (and consequently the volume, considering that the flow time can be measured) inside a tube of known volume, by correlating the spreading diameter average speed (obtained from slump cone tests) and average flow speed, obtained by the abovementioned flow rate test. To do this, four standard-mixtures were developed (named I to IV) and four combinations of superplasticizer and viscosity modifier admixtures were applied to each (resulting in sixteen “situations”, named “S1” to “S16”). The results revealed sixteen stable mixtures, eight classified as SF1 and eight as SF2 (according to NBR 15823-1). From the average speed of the spreading diameter and flow rate average speed correlations, it was possible to develop four scenarios to determine the flow rate: the first uses the SF1 and SF2 spreading classifications and the average spreading diameter speed, determined when the concrete reached the 500 mm mark. This combination resulted in an equation capable of estimating one average relation between the estimated flow rate/tested flow rate of 1.00, with a standard deviation of 0.15. The second scenario, in which the spreading classifications were not considered (and the average spreading diameter speed was determined when the concrete reached the 500 mm mark), the average relation was 1.01 with a 0.23 standard deviation. For the third scenario (which considers the spreading classifications) and the fourth (which does not separate the mixtures by the spreading classifications), the average speed of the spreading diameter is related to the final diameter that the concrete reached at the end of the test. For these scenarios, the average relations between the estimated flow rate/tested flow rate were 1.00 and 1.01, respectively, and the standard deviation were 0.17 and 0.25.
Attempting to control the delivered volume of concrete on construction sites, the present work shows an initial study to verify the possibility to measure self-compacting concrete flow rates (and consequently the volume, considering that the flow time can be measured) inside a tube of known volume, by correlating the spreading diameter average speed (obtained from slump cone tests) and average flow speed, obtained by the abovementioned flow rate test. To do this, four standard-mixtures were developed (named I to IV) and four combinations of superplasticizer and viscosity modifier admixtures were applied to each (resulting in sixteen “situations”, named “S1” to “S16”). The results revealed sixteen stable mixtures, eight classified as SF1 and eight as SF2 (according to NBR 15823-1). From the average speed of the spreading diameter and flow rate average speed correlations, it was possible to develop four scenarios to determine the flow rate: the first uses the SF1 and SF2 spreading classifications and the average spreading diameter speed, determined when the concrete reached the 500 mm mark. This combination resulted in an equation capable of estimating one average relation between the estimated flow rate/tested flow rate of 1.00, with a standard deviation of 0.15. The second scenario, in which the spreading classifications were not considered (and the average spreading diameter speed was determined when the concrete reached the 500 mm mark), the average relation was 1.01 with a 0.23 standard deviation. For the third scenario (which considers the spreading classifications) and the fourth (which does not separate the mixtures by the spreading classifications), the average speed of the spreading diameter is related to the final diameter that the concrete reached at the end of the test. For these scenarios, the average relations between the estimated flow rate/tested flow rate were 1.00 and 1.01, respectively, and the standard deviation were 0.17 and 0.25.
Descrição
Palavras-chave
Concreto autoadensável, Reologia, Vazão de concreto, Self-compacting concrete, Rheology, Concrete flow