Abstract
Abstract
This study presents a material characterization of large-diameter 36-mm (No. 11) glass fiber–reinforced polymer (GFRP) reinforcing bars produced by two manufacturers, referred to as Type A (sand-coated) and Type B (deformed ribbed). With the expanding use of GFRP bars in concrete infrastructure and the recent investments, an urgent need has emerged to validate the performance of larger bar sizes and the initial provisions proposed in the Florida Department of Transportation (FDOT) specifications, which are not yet explicitly covered in existing ASTM and AASHTO specifications. A series of standardized tests were performed to evaluate key properties, including fiber content, glass transition temperature, degree of cure, cross-sectional area, tensile strength and modulus, transverse and horizontal shear strength, and bond strength. Results revealed that both bar types met most expanded FDOT performance criteria. The study also discusses how surface treatments and manufacturing variations affect bar performance. Recommendations are provided for revised provisions for 36M (No. 11) bars in FDOT specifications and manufacturer qualification requirements, plus consideration for addition to ASTM material specifications, including proposed updates to allowable tolerances, strength thresholds, and testing protocols.
Practical Applications
This study provides a mechanical and physical characterization of large-diameter No. 11 (36-mm) glass fiber–reinforced polymer (GFRP) reinforcing bars, a bar size that has not previously been fully evaluated or documented in existing specifications. Because most current ASTM, American Concrete Institute (ACI), and AASHTO provisions were developed primarily for smaller bar sizes, there has been limited verified data available to support the use of No. 11 GFRP reinforcement in infrastructure projects. To establish reliable material property benchmarks for this large-diameter bar, a rigorous experimental program including fiber content, glass transition temperature, degree of cure, moisture absorption, cross-sectional area, tensile strength and modulus, shear strength, bond performance, and durability testing, was carried out in this research. The results provide transportation agencies, designers, and manufacturers with validated performance data to confidently incorporate No. 11 GFRP bars into structural applications such as bridge substructures and coastal infrastructure. Most importantly, the findings directly support the inclusion of No. 11 bar properties in the Florida Department of Transportation (FDOT) specifications and manufacturer qualification requirements, plus consideration for relevant ASTM material and ACI/AASHTO design specifications, thereby closing an existing gap in national and international standards.