Effect of shrinkage-reducing admixture on biaxial flexural behavior of ultra-high-performance fiber-reinforced concrete

• Lower autogenous shrinkage of UHPFRC is obtained by including SRA.
• The use of SRA deteriorates compressive strength and fiber pullout resistance.
• The use of SRA decreases load carrying capacity and toughness of UHPFRC panel.
• First cracking point of UHPFRC under biaxial flexure is suggested.
• Deflection-hardening ratio and crack pattern are seldom influenced by SRA content.

This study aims to investigate the effect of shrinkage-reducing admixture (SRA) on the mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC). Three different SRA to cement weight ratios (0%, 1%, and 2%) were considered using the UHPFRC including 2% of smooth steel fibers by volume. The specimen without SRA exhibited the best performance in almost all aspects of the mechanical behaviors in compression, fiber pullout, and biaxial flexure including load carrying capacity, strain capacity, and energy absorption capacity (pullout energy and toughness). The mechanical performances deteriorated with the increase in the amount of SRA up to 2%. Finally, a suggestion was made to define the first cracking point of deflection-hardening UHPFRC under biaxial flexure stress.