Project Description:

Advancements in manufacturing methods and the growing demand for high-strength materials in reinforced concrete have led to the development of steel reinforcing bars with strengths exceeding 100 ksi. These ultra-high-strength bars hold significant promise for bridge construction, as they could extend feasible span lengths beyond those achievable with conventional reinforcement while still meeting strength and serviceability requirements. Their use can also reduce girder depth, leading to material savings and lower overall construction costs. However, successful implementation requires addressing key concerns regarding serviceability and durability. Critical factors include corrosion resistance, structural behavior, and ductility of beams reinforced with these high-strength bars. 
The primary objective of the proposed work is to investigate the durability (corrosion resistance) and serviceability of concrete girders reinforced with very high-strength reinforcement, by testing bond-slip relationship between corroded and non-corroded steel rebars and concrete. 12 medium-span (8 in x 12 in x 10 ft) concrete beams will be cast and tested for strength and ductility (Figure 1). Six of the 12 beams will be subjected to accelerated corrosion. Under controlled conditions, we will test the strength and ductility characteristics of the beams reinforced with these bars. 
This study directly supports the mission of the Center for Healthy and Durable Transportation (CHDT), a University Transportation Center (UTC), whose primary research focus is enhancing the durability and service life of transportation infrastructure through innovative construction materials and techniques. By addressing the performance of very high-strength reinforcing bars in reinforced concrete girders and their behavior under corrosive conditions, this project advances the application of durable, next-generation materials for transportation infrastructure.

Fig. 1 Conceptual schematic of longitudinal cracking at an ABC shear key and its mitigation using ECC

The project activities include: 

• Phase 1 – Mix screening (4 candidates → 2–3 down-selected): evaluate flow/slump-flow, set time, early f′c, and fiber dispersion; refine HRWR and mixing sequences.
• Phase 2 – Material characterization: compression (1/7/28 d), direct tension (dog-bone or coupon) to obtain σ–ε, tensile strain capacity (εt), number of cracks and crack-width statistics at service-level strains; companion flexure for toughness indices if needed. 
• Phase 3 – Joint-mimicking flexural validation: fabricate precast ECC beams with realistic joint configurations; conduct four-point bending comparing load–deflection, ductility/residuals, and crack maps to a conventional joint control. 
• Phase 4 – Analysis of experimental test results: synthesize compression/tension/flexure outcomes; establish thresholds and compare ECC vs. control. 
• Phase 5 – Final report: prepare and submit the project final report with datasets and figures. 

US DOT Priorities:

This project directly supports U.S. DOT priorities by advancing durable and sustainable solutions for accelerated bridge construction (ABC) with improved service life. By enabling ECC joints that resist wide cracking and corrosion-driven deterioration, the research improves durability and extends service life, reducing the frequency of disruptive repairs. The project enhances efficiency by developing constructible joint materials that achieve required fresh and early-age properties to support rapid fabrication, installation, and reopening of transportation corridors, minimizing work zones and user delays. Finally, economic feasibility is addressed by incorporating optimized/recycled fibers and by limiting maintenance, material consumption, and associated environmental burdens across the lifecycle.

Outputs: 

• A down-selected set of constructible ECC mix designs with documented fresh, mechanical, and crack-width control properties.
• Structural performance results from joint-mimicking beam tests, including load–deflection response, residual capacity, and crack mapping.
• A feasibility assessment with go/no-go criteria linking material behavior to ABC joint performance requirements.
  Implementation guidance and a short Next Phase Plan outlining steps toward pilot or field deployment if feasible.
• A concise written final report and technical documentation suitable for transportation agency review and future specification development.

Outcomes/Impacts:

This research will demonstrate whether ECCs can deliver durable, constructible joint performance for Accelerated Bridge Construction (ABC), enabling transportation agencies to make informed adoption decisions. Successful outcomes will extend the service life of precast bridges by mitigating corrosion and crack-related deterioration, reducing maintenance frequency and associated user delays. Improved constructability and early-age performance will support faster, more efficient project delivery, lowering work zone exposure and enhancing worker and traveler safety. Collectively, these impacts advance resilient, cost-effective, and environmentally responsible infrastructure across the U.S. transportation network.