フレッシュコンクリートのレオロジーモデルおよび試験方法に関する研究

抄録

 In this study, the author proposed rheological models to describe the rehological behaviors of fresh concrete before and after yield, based on the achievements of the author's past study about the shear stress-shear strain, shear strain rate relationships. Three rheological property indexes (RPI) were further suggested for fresh concrete, which are yield stress (shear failure limit stress), basic viscosity, and the shear stain rate under the yield stress (hereafter called briefly thixotropy index), respectively. The basic viscosity and the thixotropy index are experimentally determined on basis of the shear stress-shear strain rate relation that is measured when the mean particle contact angle of fresh concrete becomes zero. Furthermore, a ring shear apparatus (named RSNS) was developed to measure the three rheological property indexes and the rheological constants (RCs) in the rheological models. RSNS can measure the rheological performances of fresh concrete under a desired normal stress by either the stress-controlled test or the strain rate-controlled test. Test methods for the RPI and the RCs based on the RSNS rheometer were discussed. Finally, an experiment was performed to investigate the variation o fthe RPI and the RCs of high fluidity concrete with elapsed time.