Title:
Linking Flow-Induced Fiber Orientation in Fresh UHPC and Hardened UHPC Tensile Characteristics: A Numerical Framework
Author(s):
Bhaduri
Publication:
Web Session
Volume:
ws_S24_Bhaduri.pdf
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
3/23/2024
Abstract:
UHPC exhibits significantly higher tensile strength and post-cracking ductility compared to conventional concrete. This is attributed to fiber bridging efficiency in the principal directions of tensile cracking. However, the self-consolidating nature of UHPC influences fiber orientation during fresh UHPC flow. Consequently, tensile strength is not an intrinsic mechanical property of UHPC. In addition, conventional steel fiber is one of the expensive constituents of UHPC. Therefore, a seamless integration of fresh UHPC flow with its hardened state mechanical property is crucial to ensure optimal use of fiber crack-bridging efficiency. Nevertheless, in a structural-scale conventional casting process, such integration via experiments or modeling can be difficult and expensive. Recently, a novel nozzle-based casting was proposed to better align fiber in UHPC flow. This device was built based on two key ideas - a) creating a converging gravity-driven laminar flow for UHPC pouring to orient fibers along flow and b) then adding a nozzle exit width less than fiber length to ensure rotation of any left unrotated fiber. An experimental campaign with direct tension and flexural tension tests were designed to evaluate efficiency of this device. Experimental results showed a significantly higher tensile strength for the direct tension samples compared to randomly cast samples. Similar observations were made for the flexural tension test done on a slab specimen. In current work, a numerical framework is proposed to predict stochastic state of fiber orientation via nozzle-based flow. This predicted fiber orientation was used to calibrate fiber orientation factors in a discrete mesoscale model called lattice discrete particle model for fiber-reinforced concrete (LDPM-F). Finally, both direct tension and flexural tension tests were simulated in LDPM-F framework. Very good agreement was observed from numerical simulations.