Abstract
During concrete pumping, the migration and redistribution of particles occur in a pipe and the lubrication layer that forms between the bulk concrete and the pipe wall is the governing factor determining the flow behavior. In order to identify flow behavior of pumping, in this study, the viscoelastic properties related to the microstructural behavior of a flocculated suspension were examined by using dynamic oscillatory measurements. Cement paste is assumed to be a constituent material of the lubrication layer and ten cases of mixing design are employed by changing the proportions of mineral admixtures. The relationship between the yield stress obtained from the steady shear test and the dynamic modulus resulted from the oscillatory shear measurement was derived and the implications of the correlation are discussed. Moreover, based on the investigation of the viscoelastic properties with oscillatory measurements, the initial behavior of pumped concrete was analyzed systematically.
Highlights
Concrete pumping involves the flow of a complex fluid under high pressure in a pipe, and predicting flow behaviors of concrete pumping is challenging research area
In addition to the steady shear measurements, the rheometer is capable of continuous strain sweep and frequency sweep
The following conclusions were obtained: (1) Due to the migration and redistribution of particles in a pipe under shear by the pumped pressure, the lubrication layer could be considered as being similar to the constitutive cement paste in concrete pumping
Summary
Concrete pumping involves the flow of a complex fluid under high pressure in a pipe, and predicting flow behaviors of concrete pumping is challenging research area. For the characterization and prediction of the flow of concrete pumping, the fundamental understanding of various factors is needed, which include rheological properties, dynamic segregation, stability of constituent materials, geometry of a pumping circuit, slip layer formed between bulk concrete and a pipe wall, and relationship between the pressure and flow rate. The primary difference is that concrete is a yield stress fluid. Most researches on concrete pumping in the literature account for the yield stress and the existence of the unsheared zone
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