Impacts of Fine Aggregate Gradation on the Workability of Slip-Formed Concrete

Widespread gradations of aggregates have been blended together to produce concrete mixtures with adequate performance; yet, poor performance of some of the concrete mixtures has been instigated by certain gradation characteristics. This work investigates how fine aggregate gradation impacts the workability and finishability of a concrete mixture for slip-formed pavement. The Box Test AASHTO T 396, Slump Test ASTM C143, and a hand float for surface finishability will be used to measure workability and quantitatively compare how the different gradations impacted workability. The results establish fine aggregate gradation sieve size limits based on workability performance for sieve sizes of 4.75 mm (#4) through 0.075 mm (#200). The research also establishes volume limits for coarse sand [2.36 mm (#8) through 0.6 mm (#30)] and fine sand [0.6 mm (#30) through 0.075 mm (#200)]. The coarse sand volume of the combined gradation was shown to not only impact surface finishability but influence the cohesion within the mixture, which leads to segregation and edge slumping. The fine sand volume contributes to allowing the concrete to have a smooth surface finish and to properly consolidate the concrete through vibration, but deficient fine sand volume promotes segregation and excessive fine sand volume reduces workability. These guidelines can be utilized to aid producers in designing concrete mixtures with improved cost, durability, and sustainability with a mixture procedure called Tarantula Curve.