Analysis of the tensile fracture properties of ultra-high-strength fiber-reinforced concrete with different types of steel fibers by X-ray tomography

Abstract

This study is concerned with the analysis of the tensile properties of an ultra-high-strength fiber-reinforced concrete manufactured with short and long steel fibers. The analysis involve using different techniques - from mechanical tests to X-ray computed tomography - to relate the observed variation of the mechanical properties of the mixes with their porosity. A comprehensive study of the porosity distribution was conducted on the basis of the analysis of X-ray computed tomography images and porosimetry. The study shows the influence of the type of fiber used in the reinforcement on the pore size and distribution of the concrete matrix and consequently on its tensile properties. The tensile properties are obtained with an inverse analysis method available in the literature that yielded the first-cracking tensile strength (ft) and the ultimate tensile strength (ftu) and related with the inner structure of the concrete matrix. Our results prove that the tensile properties, especially the first-cracking strength, vary depending on the fibers used. These findings help mix designers make a decision about the type of fibers that should be used when a high first-cracking tensile strength is needed and make it possible to quantify the effect of the fiber. Keywords: Ultra-high-strength concrete, X-ray computed tomography, Steel fibers, Concrete matrix, Tensile behavior, Fracture behavior