Improving Flexural Performance of Ultra-High-Performance Concrete by Rheology Control of Suspending Mortar


This study develops a rheology control method to improve steel fiber distribution and flexural performance of ultra-high-performance concrete (UHPC) by adjusting the rheological properties of the suspending mortar of UHPC before steel fibers are added. Correlations among the plastic viscosity of the suspending mortar, the resulting steel fiber distribution, and flexural properties of UHPC are established. This was done by changing the dosage of viscosity modified admixture (VMA) for investigated UHPC mixtures. The optimal plastic viscosity of the suspending mortar that allows for the optimized fiber distribution and flexural performance of UHPC is determined. The plastic viscosity is correlated with the mini V-funnel flow time, which provides a simple alternative to evaluate the plastic viscosity. For a UHPC mixture with 2% micro steel fibers, by volume, the optimal mini V-funnel flow time of suspending motar was determined to be 46 ± 2 s, which corresponded to the optimal plastic viscosity (53 ± 3 Pa s) that ensures the greatest fiber dispersion uniformity and flexural performance of UHPC. However, increasing the VMA dosage retarded the hydration kinetics and reduced the degree of hydration, compressive strength, and the bond properties of the fiber-matrix interface of UHPC.


Civil, Architectural and Environmental Engineering


This study was funded by RE-CAST Tier-1 University Transportation Center at Missouri University of S&T [grant No.DTRT13-G-UTC45] and the Energy Consortium Research Center at Missouri University of S&T [grant No. SMR-1406-09].

Keywords and Phrases

Bending strength; Compressive strength; Concrete beams and girders; Concretes; Elasticity; Fibers; Hydration; Mixtures; Mortar; Steel fibers; Viscosity; Fiber distribution; Flexural properties; Mini-V funnel; Plastic viscosity; Ultra high performance concretes; High performance concrete; Ultra-high-performance concrete (UHPC)

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Article - Journal

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© 2017 Elsevier, All rights reserved.

Publication Date

01 May 2017