A study on prediction method of quality change for fresh concrete under pressure of pumping

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In order to develop a prediction method of quality change for fresh concrete under pressure of pumping, it is necessary that the mechanism of quality change have been evaluated. In this study, three experimental series were carried out following ;1.A study on mechanism of flowability under pressureIn this study, in order to evaluating mechanism of flowability change under pressure, time-depending-change tests of cement paste and lime powder paste under statistic pressure were carried out. For lime powder, which is not active powder, viscosity kept steady. On the other hand, viscosity increased and grain size of particles grew for ordinary portland cement. It was considered that hydration was accelerated under pressure for cement paste.2.A study on prediction method of viscosity under static and dynamic pressureIn this study, a prediction method of viscosity under static pressure was established assuming that interaction between cement particles was decreased by hydration of cement. Under dynamic pressure on real site, it was considered that we might predict viscosity by evaluating pressure with mean value.3.A study on application of prediction model to real pumping on siteIn order to evaluating the application of prediction method of viscosity under pressure, a site research was carried out. It was appeared that unit contents of mix proportion were not change by pumping, but, flow time in V funnel was decreased for concrete and viscosity of mortar was decrease too. A presented model may predict time-dependent-change of viscosity between time of producing concrete and time of arriving to site. But this model may not predict correctly decreasing viscosity under pumping.