New Active Rheometer for Flowable Concrete

Based on the flow characteristics of cementitious materials as well as the relative relations of deformation and stress of materials at flowing process, this research develops an apparatus capable of inducing flowable concrete to form a stable annulus flow field from which the angular deformation, angular velocity, and torque can be measured. Because no external stress is applied on the material during deformation, the apparatus is named an "active rheometer" (ARM). The measured data were automatically recorded by computer and the results were calculated and analyzed using rheological theories to directly convert into fluid characteristics of shear stress and shear strain rate. Comparison of the test results measured by the ARM and the standard Brookfield viscometer prove that the ARM has relatively better reliability and accuracy. The test results have shown that ARM is sensitive enough to measure the rheological parameters of flowable concrete.