Development and Evaluation of Vibrating Kelly Ball Test (VKelly Test) for the Workability of Concrete Peter C. Taylor, Xuhao Wang, Xin Wang, and Robert Steffes Background Objective Phase 3 – Validate Results Slipform paving is strongly influenced by the workability of the mixture, which in turn is susceptible to small changes in mix proportions. Develop and assess a workability test method for slip form paving concrete that is: Cheap Stable Portable Static and dynamic test Simulate paving process Repeatable Rheology Results and Discussion Rheology – the study of the liquid flow looks at 3 parameters: Yield stress (getting it going) Viscosity (keeping it going) Thixotropy – effect of vibration Slump only measures the first parameter Slipform paving is governed by the third parameter Phase I – Lab investigation Slump vs. Vpaste/Vvoids; VKelly index vs. Vpaste/Vvoids Base mixture: 564 pcy ordinary portland cement 5% total air content 45/55 fine/coarse aggregate ratio 0.45 w/cm ratio Variables: Class C fly ash - increments of 10% (+1, +2, and +3) Water – increments of 1 gallon/cubic yard (+1 and +2) VKelly test apparatus: A Kelly ball with an added vibrator Sample plot of VKelly test: Depth vs root time. The slope indicates response to vibration Box test visual rate versus VKelly index Conclusions VKelly test appears to be a suitable workability test for slip-formed paving mixes. Multiple operator error: up to 8.31%. VKelly index above 0.8 seems a reasonable criterion for slipform paving mixes. Effect of Class C fly ash, and Water Content on Workability Phase 2 – In-situ applications Nine slip-formed paving jobsites in MN and MO Mostly 20% class C fly ash ~550 pcy cementitious