Behavior, Modeling, and Impact of Bond In Steel Reinforced High-Performance Fiber-Reinforced Cement-Based Composites

High-performance fiber-reinforced cement-based composites (HPFRCCs) are a class of cement-based materials that exhibit a psuedo strain-hardening behavior in uniaxial tension after first cracking, and retain residual strength in compression after crushing. The unique mechanical properties of HPFRCCs have led researchers to investigate their use in structural applications where damage tolerance and energy dissipation is needed. Research on structural applications of steel reinforced HPFRCCs members has shown enhanced damage tolerance, shear capacity, flexural strength, inelastic deformation capacity, and life cycle performance.

Recent research has focused on the interaction between mild steel reinforcement and HPFRCCs for modeling and design purposes. When reinforced HPFRCCs have been subjected to direct tension, early strain hardening and reinforcement strain localization have been observed caused by short debonded lengths, as opposed to long debonded lengths in traditional reinforced concrete. Short debonded lengths caused the HPFRCC reinforcement to fracture at lower levels of specimen deformation compared to reinforced concrete. This recent research indicates that bond strength between reinforcement and HPFRCCs may be higher than that of traditional reinforced concrete. Additionally, reinforcement tensile strains may be an important consideration for design and modeling of reinforced HPFRCC structural components.

In this dissertation, the bond behavior between steel reinforcement and HPFRCCs is presented through experimental testing and numerical simulations. Bond experiments were conducted under monotonic and cyclic loading conditions where the HPFRCC material surrounding the reinforcement was in a flexural tension stress state. Monotonic test results show that bond strengths are 37% higher, on average, in reinforced HPFRCCs than in reinforced concrete. Additionally, bond-slip toughness (i.e., the area under the bond stress versus reinforcement slip curve) is higher in reinforced HPFRCCs than in reinforced concrete.