The use of Ultra-High-Performance Concrete (UHPC) in beams has been growing rapidly in the past two decades due to its superior mechanical and durability properties compared to conventional concrete. One of the areas of interest to designers is the elimination of transverse reinforcement as it simplifies beam fabrication/construction and could result in smaller and lighter beams. UHPC has a relatively high post-cracking tensile strength due to the presence of steel fibers, which enhance its shear strength and eliminate the need for transverse reinforcement. In this paper, UHPC shear test data were collected from the literature to study the effect of the following parameters on the shear strength of UHPC beams without transverse reinforcement: compressive strength, tensile strength, level of prestressing, longitudinal reinforcement ratio, and fiber volume fraction. Statistical analysis of test data indicated that level of prestressing and tensile strength are the most significant parameters for prestressed UHPC beams, whereas longitudinal reinforcement ratio and tensile strength are the most significant parameters for non-prestressed UHPC beams. Additionally, shear strength of the tested UHPC beams was predicted using five models: RILEM TC 162-TDF, 2003, fib Model Code, 2010, French Standard NF P 18-710, 2016, PCI-UHPC Structures Design Guide, 2021, and Draft of AASHTO Guide Specification for Structural Design with UHPC, 2021. Comparing measured against predicted shear strength indicated that the French Standard model provides the closest prediction with the least scatter, where the average measured-to-predicted strength was 1.1 with a standard deviation of 0.38. The Draft of AASHTO provided the second closest prediction where the average measured-to-predicted strength was 1.3 with a standard deviation of 0.64. The other three models underestimated the shear strength.

The goal of this research is to evaluate whether it is possible and effective to detect honeycombing of concrete pavement using a ground-penetrating radar (GPR) during construction. The motivation is that identifying honeycombing of concrete during construction would help avoid the spread of consolidation problems in large pavement sections, which are costly and time consuming to repair. GPR has been used as a tool for concrete quality control and detection of delamination in reinforced concrete elements since the 1980s, but it has not been used for the early detection of relatively small air voids. In this project, first, preliminary field testing was conducted to determine the possibility of detecting honeycombs in existing concrete pavement. Then, air voids of different sizes, shapes, and depths were artificially created using spray-foam in several laboratory specimens and detected using a high-frequency GPR antenna at different times after concrete placement. Cores were extracted to validate GPR readings and determine the capability of this technique. Another field testing was conducted to evaluate the efficiency and economy of using GPR as a nondestructive quality control tool. Field and lab test results indicated that GPR could be efficiently used to detect air voids as small as 32 mm (1.25 in.) and as deep as 102 mm (4 in.) from the surface of the concrete pavement as early as the initial set of concrete. These findings suggest that GPR is an effective, efficient, and economic quality control tool for this application.