National Concrete Pavement Technology Center

Project description

Ultra-High-Performance Concrete (UHPC) is an advanced concrete material with outstanding mechanical properties and considerable potential for extending the life of bridges. While traditionally based on Portland cement and reinforced with steel fibers, UHPC formulations reinforced with Carbon Fibers (CFs) of different scales have been recently investigated. Pilot experiments show promising results. Common dispersion techniques allow for CF contents under 1% by weight of cementitious content to avoid dispersion-related issues, such as clumping and balling, which affect the homogeneity of the matrix and deteriorate mechanical performance. These techniques are inefficient to fully explore the potential of CF in UHPC and additional research is needed to examine the effect of high concentrations of CF reinforcement on these matrices in pursuit of tensile properties equal to or above what is obtained with steel fiber reinforcement. Additionally, rapid setting calcium sulfoaluminate cement and internal curing have significant potential for reducing the environmental impacts of UHPC, improving the speed of strength gain, and improving overall performance of UHPC bridge deck overlays while reducing the unit weight of the material. This study will investigate UHPC formulations reinforced with high concentrations of CF at multiple scales using a dispersion technique that allows fiber contents of up to 4% by weight. Additionally, UHPC formulations using alternative cementitious materials and curing methods to achieve reduced environmental impacts, light weight, and improved durability will be investigated. This research entails the investigation of multi-scale carbon fiber reinforcement of UHPC mix designs aiming to achieve flexural strengths and strain hardening behavior similar or superior to the levels typically obtained with steel fibers. It will also examine the impact of calcium sulfoaluminate cement and internal curing on the same behaviors and compare performance of the best mix designs when used as a structural overlay. Small-scale four-point bending tests will be conducted to measure the flexural strength and ultimate strain of UHPC specimens and overlay specimens will be tested in flexure with the UHPC portion on the flexural tension side. The following tasks will be pursued in this multi-institutional study. Task 1: Evaluation of carbon fibers (lead: TAMU); Task 2: Evaluation of calcium sulfoaluminate cement and internal curing (lead: OU); Task 3: SEM evaluation of microstructure (lead: TAMU); Task 4: Construction of overlay specimens (lead: OU and TAMU); Task 5: Bridge deck overlay specimen testing (lead: OU), and Task 6: Final report and dissemination of results (lead: TAMU and OU).