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Background:
For any aging infrastructure, its probability of failure increases with time. There are a multitude of ways to repair and rehabilitate deteriorating pipes, and as the infrastructure system continues to age, it is important to understand and promote the use of effective and durable materials for retrofit. Fiber reinforced polymer (FRP) composites have shown to offer an attractive alternative to replace the deteriorating steel in structural corrugated metal pipes (CMPs). FRP composites have significantly improved durability characteristics compared to steel, which will reduce maintenance costs and improve lifecycle costs. Other materials such as HDPE slip liners for retrofit are in existence but their durability and improvement to load carrying capacities is under question. Past experimental work has shown GFRP to be a suitable material for developing composite action with corroded steel using a polymer grout. Longitudinal testing of corroded CMP with glass fiber reinforced polymer (GFRP) slip liners has garnered interest of the New Mexico DOT. However, field conditions are more circumferential dominant behaviors, and no data exist on this performance measure for CMPs with GFRP slip liners. The proposed work will help evaluate the parameters obtained from circumferential bending necessary to develop design for field
implementation using GFRP slip liners with different grouts for corroded culvert retrofit.
Objective:
The project will focus on evaluation of a retrofitted system in a field dominated behavior. Information on three main aspects of behavior will be provided by the activities in this project: (a) circumferential behavior of retrofitted CMPs with combination of GFRP slip liner and different grout systems, (b) isolated behavior of the bonding material from the slip liner behavior and composite system behavior after retrofit, and (c) stiffness factor and load capacity design parameters to retrofit CMPs with GFRP slip liner using different grouts. Currently, there is no standardized approach [e.g., an ASTM or a Canadian Standards Association (CSA) standard] to evaluate the load-carrying capacity of a slip-lined CMP, but instead, engineers typically apply standards for similar systems or industry guidelines, which are often very conservative or not appropriate. In this project, an evaluation system used for HDPE pipes will be used to evaluate load carrying capacities of GFRP slip lined corroded metal pipes with different grout systems. The evaluation will be carried out in 56 tasks.
Scope:
A literature review will be performed with emphasis on materials to retrofit existing corroded CMPs and methods used. In addition, Review of existing published research on the role of different grouts in the bonding action with retrofit materials and existing CMP will be conducted.
Task 2 – Mix design and compressive testing of grouts
The properties of a low-strength and a high strength grout will be characterized using compression tests. A low-strength grout and a high strength grout will be studied. Compressive strength of the grouts will be measured using three 4 in by 8 in cylinders using ASTM C39 Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens and ASTM C579 Standard test methods for compressive strength of chemical-resistant mortars, grouts, monolithic surfacings, and polymer concretes.
Task 3 – Preparation of test setup
A two-point loading test protocol will be prepared for testing the composite action of the retrofitted CMPs. One specimen per grout type will be fabricated and tested for un-corroded and corroded CMP retrofitted with GFRP slip liner. The test protocol will follow similar testing for HDPE as there are no established ASTM standards currently.
Task 4 – Fabrication of test specimens.
Four specimens will be fabricated: (a) corrugated steel pipe with low strength grout slip lined with GFRP, (b) corrugated steel pipe with high strength grout slip lined with GFRP (c) corroded corrugated steel pipe with low strength grout slip lined with GFRP and (d) corroded corrugated steel pipe with high strength grout slip lined with GFRP. Corrosion will be achieved using an accelerated 30- day corrosion cell and the retrofit will be conducted following corrosion.
Task 5 – Testing
A series of circumferential bending pipe tests will be conducted to determine the load-carrying capacity and stiffness of a corroded and non-corroded CMP with grouted GFRP slip liners.Linear potentiometers (LPs) will be used in all test specimens to measure the diameter changes during the test. Additionally, a load cell is used to measure the applied load. The LP and loadcell measurements will be recorded using a data acquisition system. Shrinkage will be monitored to observe bond with corrugations in steel after fabrication and during testing.
Task 6 – Analysis
Analysis will be conducted to investigate grout action on composite behavior and which combination results in improved load carrying capacities. Load vs diameter change graphs will be developed and used to calculate capacities and parameters. Shrinkage analysis will be performed.
Research Team:
Principal Investigator: Shreya Vemuganti, Ph.D., Assistant Professor, CEES, OU.
Co-Principal Investigator: Royce Floyd, Ph.D., P.E., S.E., Lloyd G. and Joyce Austin Presidential Professor, CEES, OU.