Pumpability evaluation of wet-mix shotcrete using paste rates and porosity

초록

In order to improve wet-mix shotcrete’s pumpability, the contemplated results of rheology and the basic properties of crushed sand shotcrete with pozzolanic materials were used in this study. The rheologcal properties of shotcrete with mineral admixtures such as silica fume and fly ash were compared and investigated in relation to each other. Also, the correlations of shotcrete between rheology and pumpability were investigated. The results were as follows: For the rheology test results using crushed sand, the torque viscosity (H) of shotcrete with pozzolanic materials decreased for all specimens compared to the control specimen, which will bring enhanced pumpability. The mixture with 20% fly ash showed increased flow resistance, which will bring enhanced build-up thickness. For the rheology test results using a natural sand, the torque viscosity (H) of shotcrete with pozzolanic material decreased for all specimens except those with silica fume and AE agent, while the flow resistance (G) values increased only in the samples with superplasticizer and AE agent. A comparative analysis of the results of the theoretical pumping values did not correspond to the real cement paste. Burns theory (2008), which assumes that all air in concrete during pumping is dissolved by pumping pressure, should be amended in the future. Among 11 variable samples, nine variable samples were capable of pumping and two samples with natural sand were not pumped because of the gap graded aggregates. Thus, it should be emphasized again the importantce of proper grades of mixed aggregates in shotcrete. ©2018 by Korea Concrete Institute.

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