Study on Concrete Workability Based on Comparison between the Minimum Paste Demand and the Closest Packing Density

Abstract

The mixture design method (MDM) has been used to design the concrete workability with the three-graded stone. The results indicated that the proportion of the stone corresponding to the minimum paste demand (Pmin) can meet that corresponding to the approximate closest packing density (ACPDmax). When the workability reaches its maximum value, the paste thickness (Tpaste) and mortar thickness (Tmortar) do not reach their respective extreme values. Therefore, the combined effect of the Tpaste and Tmortar needs to be considered when evaluating concrete workability. Compared with concrete designed by the maximum packing density, the concrete designed by the Pmin + ACPDmax has a lower cost; however, stone surface area (Sstone) and the average particle size of the stone (DA-stone) are increased by 8.6% and reduced by 5.7%, respectively. Therefore, the contradictory weakening effect of an increase in the Sstone and a decrease in the DA-stone on the interface transition zone in both cases requires further investigation.