1. 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