Optimizing mixture proportions for flowable high-performance concrete via rheology tests

Several series of tests involving various binder combinations, water-binder ratios, and high-range water-reducing admixture-binder ratios were conduct ed to optimize mixture proportions for flowable high-performance concrete ( HPC). Test methods used include the standard slump, slump-flow spread, and rheology test procedures. Test samples were made with freshly mixed paste, mortar and concrete. Measured data were used to calculate volumetric fracti ons of coarse aggregate and filling ratios of sand and to correlate the flo w characteristics of tested paste, mortar, and concrete. The analytical res ults indicate that a slump value of at least 235 mm and slump-flow spread o f 500 mm or more under conditions where there is no aggregate segregation a re considered viable indicators for producing flowable HPC. In fact, flowab le HPC does behave like Bingham fluid, and its flow behavior can be charact erized by two Bingham parameters g and h that can be calculated from torque T and rotational speed of spindle N measured during the rheology tests usi ng the flow of HPC meter (FHPCM) of the authors' design. A slump range of 2 35 to 270 mm and a slump-flow spread range of 520 to 750 mm verified by rhe ology test data are recommended for reference in optimizing mixture proport ions for flowable HPC.