Rapid Repair and Strengthening Procedures for Plain, Reinforced, and Prestressed Concrete Structural Elements
Creators: name: Yagnik, Hardik Bhaskarbhai
Publisher: name: No Publisher Supplied
Year: 2025

description: Concrete has become the most widely consumed material on Earth after water. The volume of concrete consumed globally has tripled during the last two decades as more developing countries are expanding their infrastructure. In the developed countries, continuous efforts are made in the maintenance of the built environment. The prominent use and maintenance of concrete is in transportation and industrial infrastructure. The results presented in this dissertation focus on maintenance, mainly, repairing and strengthening the plain, reinforced, and the prestressed concrete structures. The information is developed primarily using the bridge structures. The three focus areas of the study are the cementitious repair materials with short fibers, reinforced concrete, and prestressed concrete. The repair and maintenance in concrete bridges is needed due to the damages induced by weather conditions, overloading, and vehicle collisions. Most common damages in the concrete are patches or potholes on the pavements, bridge decks or girders. Incidents involving structural damage due to vehicle collisions may also represent emergency scenarios leading to traffic closure and requiring immediate repair beyond a patch repair owing to the loss of reinforcement. The cementitious repair materials used according to the current standards are known to disintegrate over longer periods. Additionally, there is a lack of thorough guidelines and fundamental understanding for structural repairs of bridge girders damaged with loss of reinforcement during service. In lieu of such guidelines, transportation agencies are left with limited repair solutions either primitive or advanced. Practical, robust, fast, and low-cost structural repair solutions along with durable repair materials for damaged concrete in general, are thus necessary for safety and serviceability of concrete structures. The first goal of the study was to identify the most efficient cementitious repair materials. Based on the extensive literature and experimentation, material groups with three cement matrices were identified. The focus was to provide a workable repair material with good toughness characteristics achieved through addition of discrete polyvinyl alcohol (PVA) fibers. Compositions were developed with higher fiber dosage of 3 - 4 % and with lower dosage of 0 – 2% for application in horizontal, vertical, and overhead repair applications. Selected formulations were evaluated for their durability including cracking resistance with samples in field exposure in New Jersey. Detailed design procedures based on first principles of bending theory are developed using the current code of practice for structural repair of damaged prestressed and reinforced concrete girders using carbon fiber reinforced plastics (CFRP). The application of the proposed repair procedures on available experimental studies from literature is verified. Non-linear analysis of cracked prestressed girder along with modified equation for cracking moment capacity of standard prestressed girders is also proposed. The experimental results provided three formulations with toughness characteristics in bending with calcium sulfo-aluminate (CSA) cement-based matrix suited for horizontal repairs. A total of three other formulations for overhead and vertical repairs with two other rapid setting cements are identified entirely preventing the restrained shrinkage cracking as observed during nearly 3 years of age in field conditions. Other formulations in field exposure with CSA cement reported total crack widths of as low as 0.004 inches. The application of design procedures developed for structural repairs and strengthening using CFRP are reported to be in good standing with published experimental studies. The debonding of FRP at the debonding strain of 0.005 is identified as most probable mode of failure. The design procedures can be used to satisfy the ductility requirements of current codes of practice. Significant increase in cracking moment capacity of standard AASHTO girders is observed using the modified approach to serviceability analysis of prestress concrete girders.