Link To Latest Report : Coming Soon.
Background :
Many culverts installed during the 1950s and 1960s are approaching the end of their service life. Culvert failure can lead to serious environmental problems and cause road closures, resulting in major delays, inconveniences, and high costs of repair. Thus, it is essential to maintain and upgrade their integrity to minimize disruptions caused by aging, deterioration, and increased traffic demands. Ultra-high-performance concrete (UHPC) shotcrete has emerged as a potential solution for the rehabilitation, repair, and retrofit of steel culverts. However, when applying UHPC to upgrade steel culverts, the exterior surface often exposes steel fibers.
To address this challenge, this research proposes using sprayable, grout-like self-healing concrete as a second layer over the sprayed UHPC. Self-healing concrete autonomously repairs cracks through mechanisms like microbial activity or encapsulated healing agents, improving durability, reducing maintenance costs, and enhancing sustainability. Specifically, bacteria-based self-healing concrete can precipitate calcium carbonate, which seals cracks and enhances both the mechanical strength and durability of concrete structures. The incorporation of bacteria into shotcrete has been shown to significantly enhance water absorption resistance and permeability, thus improving durability.
Objectives :
The objectives of this research are to demonstrate:
- Investigate the mechanical and durability properties of a system that consists of sprayed UHPC and self-healing concrete.
- Through numerical analysis develop set of approaches for design of two-layer system.
- Develop experimental data for comprehending the design and construction steps, necessary for utilizing two-layer system
- Develop set of recommendations for design and construction, for strengthening deficient steel culvert using the two-layer system described here.
Scope :
Task 1 – Literature Review.
This task involves conducting a comprehensive review of existing literature on steel culvert rehabilitation, UHPC shotcrete applications, and self-healing concrete. The review will cover case studies, current practices, and standards to establish a solid foundation for the project.
Task 2 – Mix Design Testing.
This task involves developing and testing UHPC shotcrete and sprayable self-healing concrete mixtures with varying compositions and properties. The variations will focus on optimizing strength, workability, and adhesion for spray applications.
Task 3 – Steel Culvert with Two – Layer Full-Scale Testing.
This task involves conducting full-scale testing of steel culverts with a two-layered (UHPC + self-healing concrete) protective system. The tests will focus on developing a set of recommendations for sequence and methodologies for application of second layer of self-healing liner.
Task 4 – Steel Culvert with Two-Layering Lining Small-Scale Testing.
This task involves conducting small-scale testing of steel culverts with a two-layered (UHPC + self-healing concrete) protective system. The tests will focus on calibrating the numerical models and developing design tools.
Task 5 – Durability Testing.
This task involves conducting Freeze/Thaw tests on small-scale steel culverts with a two-layered (UHPC + self-healing concrete) protective system. These tests should provide information to assess the durability of the proposed two-layer system.
Task 6 – FEM Analysis.
This task involves creating finite element models to simulate the behavior of steel culverts with a UHPC shotcrete layer and an additional sprayed self-healing concrete layer. Non-Linear finite element analysis will allow to better comprehend the performance of two-layer system and development of design and rating approach.
Task 7 – Self-healing UHPC Testing.
This task involves testing small-scale specimens where cracks are incorporated into the first sprayed UHPC layer. The specimens will be used to assess the characteristics of self-healing spray to repair cracks.
Task 8 – Development of Guidelines.
This final task involves a full assessment of the findings, data, and analyses from the previous tasks into a comprehensive final report. The report will include procedural guidelines for the rehabilitation, repair, retrofit, and maintenance of steel culverts using the developed two-layered system. Additionally, it will include design and rating guidelines based on both experimental and theoretical analysis.
Research Team:
Princiapal Investigator : Atorod Azizinamini, Ph.D., P.E.