Title:
Rheology Control of UHPC
Author(s):
Meng
Publication:
Web Session
Volume:
ws_S24_Meng.pdf
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
3/23/2024
Abstract:
This research study presents an innovative approach to enhance the distribution of steel fibers and improve the flexural performance of ultra-high-performance concrete (UHPC) by manipulating the rheological properties of the suspending mortar prior to introducing the steel fibers. By establishing correlations among the plastic viscosity of the suspending mortar, resultant steel fiber distribution, and flexural characteristics of UHPC, the study seeks to optimize the overall performance of this advanced concrete material. Traditionally, UHPC's remarkable properties are derived from precise mixture proportions and material quality. However, achieving uniform dispersion of steel fibers throughout the matrix has been a challenge due to their tendency to agglomerate. To address this, the study explores the utilization of a viscosity-modifying admixture (VMA) to tailor the rheological behavior of UHPC's suspending mortar. This approach aims to achieve the optimal plastic viscosity that results in the best distribution of steel fibers and subsequently enhances the flexural properties of UHPC. Nevertheless, the introduction of higher dosages of VMA had contrasting effects. While it improved fiber distribution and flexural performance, it also had adverse impacts on other properties. Hydration kinetics slowed down, leading to decreased compressive strength and compromised bond properties at the fiber-matrix interface. This highlights the complex interplay of factors when manipulating the rheology of UHPC. Furthering the investigation, the research explores the effect of rheological control on UHPC with varying steel fiber volumes. By incorporating Welan gum and a high-range water reducer, the study managed to achieve optimal rheological properties that facilitated superior fiber distribution. A novel concept, the fiber distribution coefficient, was introduced to characterize the dispersion and orientation of fibers within the matrix.