Flexural and Tensile Strength of Ultra-High-Performance Concrete with ZnPh-Treated Steel Fibers

Abstract

This study demonstrates the use of novel zinc phosphate (ZnPh)-treated steel fibers in ultra-high-performance concrete (UHPC), replacing the commonly used steel fibers. The effects of ZnPh-treated steel fibers on tensile and flexural strengths of UHPC were investigated through flexural and direct tension tests. The results showed that first cracking strengths were reduced by 9.7% and 0.5% in the flexural and direct tension test specimens, respectively. The ultimate strengths were increased by 16.8% and 18% in the flexural and direct tension test specimens, respectively. Also, in the direct tension test, the ultimate strain at the ultimate strength was increased by 113.1%. scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) analyses revealed that a weaker interface exists between the ZnPh covering and the fiber. This interface resulted in reduction of first cracking strengths, whereas the ZnPh covering improved ultimate strengths due to an increase in friction between the fiber and matrix after the ZnPh peeled off.