Experimental study on the bond performance between ultra-high performance concrete and steel bar under freeze-thaw cycles

Abstract

To study the bond performance of ultra-high performance concrete (UHPC) and steel bar after freeze-thaw cycles (FTCs), the eccentric pull-out test of 10 groups of reinforced UHPC bond specimens, the compressive test of 24 cube specimens and the splitting tensile test of 24 cube specimens were carried out. The degradation of UHPC mechanical properties and bond performance of UHPC and steel bar after FTCs were studied. The influence of UHPC strength, cover thickness, and bond length on bond strength after FTCs was analyzed. The relationship between mechanical and bond properties is established by using compressive strength and average bond strength as indexes. A formula for calculating average bond strength of UHPC after FTCs was developed. The results show that the elastic modulus loss, compressive strength loss, and splitting tensile strength loss after FTCs increase slowly at first and then rapidly. With the increase of FTCs, the relationship between dynamic elastic modulus and compressive strength, compressive strength, and splitting tensile strength showed strong linear characteristics. UHPC strength is an important factor affecting the average bond strength after FTCs, followed by the cover thickness. After 600 freeze-thaw cycles, the failure mode of the UHPC bond specimen changed. The compressive strength and the average bond strength show a strong linear relationship in the process of 900 FTCs. The average bond strength between UHPC and steel bar decreased by 13.76 ∼ 17.23 % after 900 freeze-thaw cycles.

Keywords

• Ultra-high performance concrete
• Mechanical property
• Bond performance
• Average bond strength
• Freeze-thaw cycles