Estudo do comportamento do concreto no estado fresco contendo areia britada
AUTOR(ES)
Paula Medeiros Rodolpho
DATA DE PUBLICAÇÃO
2007
RESUMO
The crushed sand possesses different characteristics from the natural one, mainly due to the high fine materials contents, particle size distribution, shape, roughness and lithological types. It is formed during the process of comminution of rock, and its able to suffer classification and improvement of the particles shape. Such characteristics affect, in larger scale, the fresh concrete properties. In this research, it has been studied the behavior of fresh concrete with crushed sand and natural sand. One of the crushed sand shape was improved, providing equidimensional particles with less angular edges. The comparative analysis of three methods leaded to the mixture proportioning of the concrete by the Faurys Method. The effects variang fine material content in the sand, water/cement ratio and the use, or not, of additive has been investigated. Considered as Binghams fluid, the concrete with consistency of 120+10 mm was characterized by the rheological parameters yield stress and viscosity. For that way, it was used the Modified Slump Test, proposed by Ferraris &De Larrard (1998). The yield stress of the concretes mortar was also determined by Vane Test, supplying a good correlation between the methods. Moreover, the mass of concrete per unit volume, the incorporated air content, the bleeding and the compressive strength of concrete has been evaluated. It was concluded that the influence of type and fine material content in sand in the rheological behavior of concrete, for a given consistency, is dependent on the paste content of concrete mixture, limited by a cement concentration. It is the paste content that determines the fine or coarse particle contribution in the shear strength, either for friction, cohesion or lubrication effect. The paste content is determined by density packing of granular mix, influenced by particular characteristics of investigated sand and fine material content combinations. At last, it was verified that it is possible to dose concrete with 25% of fine material in the sand. Amongst analyzed sands, the crushed sand with shape treatment conferred the best results to concrete.
ASSUNTO(S)
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