Enhancing UHPC Tensile Performance Using Polystyrene Beads: Significant Improvements and Mechanisms

Area of Science:

• Materials Science
• Civil Engineering
• Concrete Technology

Background:

• Ultrahigh-performance concrete (UHPC) exhibits superior mechanical properties but can benefit from enhanced tensile performance.
• Incorporating additives can modify concrete's internal structure and mechanical behavior.
• Understanding the role of artificial flaws and fiber orientation is crucial for optimizing UHPC.

Purpose of the Study:

• To investigate the effect of spherical polystyrene (PS) beads on the tensile performance of UHPC.
• To elucidate the mechanisms behind the observed improvements using X-ray computed tomography (CT) scanning.
• To correlate fiber orientation with UHPC tensile strength.

Main Methods:

• Uniaxial tensile tests were performed on dog-bone UHPC specimens with a 2% hooked steel fiber volume fraction.
• Three different dosages of PS beads were incorporated into the UHPC mix.
• X-ray CT scanning and AVIZO software analysis were used to examine the internal material structure and fiber orientation post-testing.

Main Results:

• Addition of PS beads resulted in a 33.4% increase in ultimate tensile strength and a 174.8% increase in ultimate tensile strain.
• CT analysis revealed PS beads act as artificial flaws, promoting matrix cracking.
• PS beads significantly optimized fiber orientation, leading to more uniform fiber distribution.

Conclusions:

• Spherical polystyrene beads effectively improve the tensile performance of UHPC.
• PS beads enhance UHPC by serving as artificial flaws and improving steel fiber distribution and orientation.
• A direct relationship exists between optimized fiber orientation and enhanced UHPC tensile strength.