Title:
Practical Evaluation of the Tensile Properties of Tension-Hardening UHPC from Flexural Tests (Prepublished)
Author(s):
Zoi G. Ralli, Stavroula J. Pantazopoulou, and Ismail Mohammed
Publication:
Structural Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
fibers; inverse analysis; tensile stress-strain law; tension hardening; UHPC
DOI:
10.14359/51749166
Date:
9/10/2025
Abstract:
Inverse analysis methods proposed by current standards for extracting the tensile properties of tension-hardening cementitious materials from indirect tension tests (e.g., flexural prism tests) are considered either cumbersome and can only be performed by skilled professionals 1,2 or apply to certain configurations and specimen geometries. Significant discrepancies are reported between the results of direct tension tests (DTT or DT tests) and inverse analysis methods. This has eroded confidence in flexural tests as a method of characterization of tension-hardening Ultra-High Performance Concrete (UHPC) and has motivated its abandonment in favor of DT testing. Additional concerns are size sensitivity, variability, and lack of robustness in the results of some methods. However, DT tests are even more difficult to conduct, and results are marked by notable scatter. This is why some codes allow for bending tests at least for quality control of UHPC. To address the limitations of the bending tests in providing an easy and quick method for reliable estimation of the tensile characteristic properties of UHPC, a new practical method is developed in this paper, based on a Forward Analysis (FA) of third-point bending tests. A unique aspect of the approach is that it considers the nonlinear unloading that occurs in the shear spans of the prism after strain localization in the critical region. The method was used to derive charts for direct estimation of the tensile properties from quality control bending tests, for the commonly used flexural specimen forms and material types. The goal of the study is to provide a practical alternative in the characterization of tension-hardening UHPC materials. Results obtained using the proposed FA method are in good agreement with the tensile response from DT tests. However, it is noted that due to the presence of a strain gradient in bending tests and the larger strain gauge lengths employed in some DT tests, the strain values at localization from DT tests tend to be more conservative.