Link to Latest Report: Coming Soon
Background:
Corrosion is a critical phenomenon that occurs to metallic. In reinforced concrete structures corrosion occurs due to chloride (namely, chloride-induced corrosion) or carbonation (namely, carbonation-induced corrosion). Carbonation of concrete [4] occurs due to chemical reaction between Calcium hydroxide (Ca(OH)2) in cement matrix and carbon dioxide (CO2) from atmosphere that chemical reaction results in formation of calcium carbonate (CaCO3) which fills the pores. In addition, pore water pH drops to below 9.0 leading to disturbance to the passive layers which lead to initiation of corrosion if sufficient oxygen and water are present around the reinforcement. Due to corrosion, the interface between concrete and reinforcement experiences growth of expandable corrosion products that cracking of concrete that may hamper the serviceability of structures. In the United States, the annual direct cost of corrosion in highway bridges alone is roughly $8.3 billion, including maintenance, repair, replacement, and the cost of capital.
This project aims to upgrade the capacity of existing concrete bridges and protect concrete bridge columns against both chloride-induced corrosion and carbonation-induced corrosion. The proposed technique utilizes a full wrapping of bridge columns (circular and square) with full encasement of UHPC which includes longitudinal reinforcements. In addition to upgrading capacity and protection against corrosion, the proposed technique will enhance the column resistance against impact loading (e.g. vehicle collision)
Objective:
The proposed project objectives include:
- Development of rapid upgrade technique for existing concrete bridge columns using UHPC layer wrapped around existing column.
- Conducting experimental testing using the proposed technique for several column specimens with different cross-sections (square and circular) using both lateral loading in conjunction with constant vertical loading. PI has conducted many similar tests.
Scope:
The proposed project includes several tasks
- Task 1: Summarize the lesson learned from the preliminary work conducted at FIU
- In this task, the research team will comprehend the results of the limited testing conducted on concrete columns for buildings in Florida and will draw conclusions and areas of difference between concrete bridge columns and concrete columns for buildings.
- Task 2: Construction of test specimens
- In this task, the research team will construct several specimens with different cross-sections (circular, and square). The column will be designed according to AASHTO-LRFD bridge design specifications.
- The first step will be to cast the core concrete column, representing the existing columns. After hardening of the core concrete columns, the surface of the core concrete columns will be sand blasted, to create exposed aggregates. This roughened surface will be moist prior to casting the UPC layer around it. Additional steel reinforcements will be provided to increase the capacity of the upgraded column.
- It should be noted that the number of columns will be designed after discussion with project RAP members
- Task 3: Experimental Test
- In this task, the upgraded column will be subjected to constant axial load and cyclic lateral loads. Attempts will be made to have results of this study to be equally applicable to seismic and non-seismic regions. This will mainly be achieved by placing the transverse reinforcement within the constructed columns, at a spacing that meets AASHTO LRFD Seismic design provisions.
- Task 4: Numerical Analysis
- A calibrated non-linear finite element analysis will be developed to conduct parametric analysis to predict the capacity of upgraded column using UHPC wrap.
- Task 5: Final Reporting and Guide
- In this task, the results of the proposed work will be summarized in final report and publications. The research team will develop ABC-UTC guide for “upgrading concrete bridge columns and protection against corrosion”
Research Team:
Principal Investigator: Atorod Azizinamini