Fracture behavior of interfaces between ultra-high performance concrete and high-performance concrete
Date
2022
Authors
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Publisher
University of Delaware
Abstract
The adoption of ultra-high-performance concrete (UHPC) to connect precast (high-performance concrete or HPC) bridge deck panels has resulted in improvements in the constructability and structural performance of such connections. However, recent field evidence suggests that UHPC connections are susceptible to HPC/UHPC interfacial cracking under service loads. While such cracks may not compromise the structural strength of these bridges in the short term, concerns were raised about the impacts of interfacial cracks on the serviceability and long-term durability of the connections. This work presents the development of a fracture mechanics test method to accurately characterize the cracking propensity of interfaces between the HPC and UHPC. The experimental program consisted of splitting tensile tests and notched-beam tests that were conducted on monolithic HPC and HPC/UHPC interfaces. Closed-loop feedback was implemented in notched beam tests to ensure stable crack growth and control the crack-opening displacement (COD) during the test. HPC substrate hygric state (dry and saturated surface dry (SSD)) and surface tortuosity (as-cast and exposed aggregate finish) were varied to evaluate the effect of substrate condition on the fracture energy and tensile strength of the interface. Tension-softening curve parameters for HPC/UHPC interfaces were generated by implementing an inverse analysis approach. The data indicate that HPC/UHPC interfaces are characterized with an on-average decrease in splitting tensile strength of between 50 and 66%, and a reduction of fracture energy ranging from 63 to 86% compared to neat HPC. Moreover, no significant difference was observed in fracture energy and tension-softening curve parameters between the ‘SSD’ and ‘dry’ interfaces with exposed aggregate surface finish. While there was no statistically significant difference in splitting tensile strength between as-cast and exposed aggregate surface finish groups, the fracture test data indicated that HPC/UHPC interfaces in as-cast group are significantly more brittle. ☐ Keywords: concrete, precast, bridge, HPC, UHPC, bond, interfaces, fracture mechanic
Description
Keywords
High-performance concrete, Bridge construction, Fracture mechanics, Interfaces, Precast concrete, UHPC, Cracking propensity