Link to Report: Coming Soon
Background :
Bridge decks across the United States continue to experience deterioration due to reinforcement corrosion, environmental exposure, and increasing traffic demands. Traditional overlay materials such as normal-strength concrete and some polymer-based systems often exhibit limitations related to durability, bond performance, curing time, or long-term crack resistance. Sileto, as a viable material for bridge deck overlays, has demonstrated promising mechanical and durability characteristics in preliminary studies conducted by FIU and Construction Technologies Laboratories (CTL), with compressive strengths approaching 12,000 psi at 28 days and durability behavior comparable to UHPC. However, its feasibility and performance as a bridge deck overlay system has not yet been validated through comprehensive structural testing. To this end, the research will combine small-scale material-level tests and large-scale structural tests to establish bond behavior, durability, abrasion resistance, long-term performance under cyclic loading, and overall structural capacity. The scope includes (1) direct bond testing on small specimens to evaluate surface preparation methods and overlay thickness effects; (2) freeze-thaw durability and long-term bond assessment; (3) abrasion resistance testing in accordance with ASTM C944; and (4) large-scale testing of a steel-girder-supported concrete deck upgraded with a Sileto overlay, including five million load cycles followed by ultimate load testing and post-test forensic evaluation. The results will provide critical performance data, recommended construction protocols, and preliminary guidance for implementation of Sileto as a practical overlay system. Outcomes of this project directly support the IBT/ABC-UTC mission by introducing fast-curing, durable, and field-deployable material that can reduce construction time, minimize traffic disruption, and significantly enhance the service life of aging bridge infrastructure.
Objectives :
The main objectives of this research are as follows.
- Evaluating the bond performance between Sileto and conventional concrete under both direct tension and long-term cyclic conditions.
- Characterizing durability properties, including freeze–thaw resistance and abrasion behavior, to assess long-term durability of Sileto.
- Investigating structural performance of Sileto overlays through large-scale cyclic and ultimate load testing, including assessment of bond integrity and shear capacity.
- comparative analysis of Sileto against conventional materials (e.g., normal strength concrete (NSC) and UHPC), leading to preliminary design guidelines and identification of potential application areas.
- Developing practical recommendations and preliminary guidelines for implementation of Sileto as a bridge deck overlay material.
Scope :
Task 1- Small scale test specimens for direct bond test
These specimens will be in the form of flat slabs with Sileto overlay. These specimens will be constructed to establish the bond between substrate consisting of normal strength concrete with Sileto overlay. The bond capacity will be established using direct tension test as depicted in Figure below. To this end, it is critical that the concrete substrate onto which Sileto will be applied achieves a 28-day compressive strength of approximately 5000 psi.
Several different parameters will be investigated using these flat slab test specimens, as follows:
a) Different methods of preparing the surface conditions to establish the most effective way to bond Sileto to NSC,
b) Effect of thickness of Sileto on bond capacity
Task 2- Investigating long term bond capacity
The objective of this task is to investigate the long-term bond capacity between Sileto and substrate NSC. This objective will be achieved by preparing numerous small scale test specimens that can be placed inside freeze/thaw chamber and subject to hundreds of cycles of freeze/thaw. The long-term bond would be investigated through visual observation and performing direct pull-out tests. The size of test specimens could be different than standard ASTM tests, to allow placement of specimens consisting conventional concrete with Sileto as overlay. Figure below shows the freeze/thaw chamber.
Task 3 – Abrasion test
Abrasion tests will be conducted in accordance with ASTM C944 standard test. Following equipment will be purchased to conduct these tests.
Task 4- Large Scale Experimental Tests to Assess long term performance of Sileto as an overlay to strengthen deficient concrete bridge deck
This test is essential to study the long-term performance of Sileto as bridge deck overlay.
After conducting small scale tests as described under Task 1 through Task 3, one large scale test specimen that will consist of two steel girders with bridge deck overlay using Sileto will be constructed. Figure below shows a similar test specimen, tested by Dr. Azizinamini in the past, except that two steel rolled shapes will be used to support the deck.
The deck will consist of normal strength concrete with a layer of reinforcement embedded in it. An additional layer of steel will be placed over the roughened normal strength concrete portion of the deck and Silto will be applied as overlay. This will simulate a condition in the field where deficient bridge deck needs strengthening. Placement of the Sileto over NSC deck will be achieved by Sponsor.
The test specimen will be subjected to at least five million (5,000,000) cycles of loads before conducting ultimate load test. Cyclic tests will be conducted from 8:00 a.m. to 5:00 p.m. every week days. Tests will be conducted at one cycle per second rate. This translates to 162,000 cycles per week. The completion of test will require about 8 months of continuous testing.
During the cyclic load tests, at some interval (about every 150,000 cycles) impulse response test will be carried out to investigate qualitatively the bond between Sileto and concrete deck.
After completion of cyclic tests, following tests will be carried out.
a) direct tension test at various locations along the length of the test specimen to investigate the bond between Silto and concrete deck. By comparing these data with those obtained from Task 1, data could be generated to comprehend the long-term bond performance of Sileto as bridge deck overlay.
b) punching shear test at several locations. Punching shear tests will be carried out at various locations along the specimen.
For the sake of safety and following FIU’s safety protocol, a sub-contractor will be employed to remove the test specimen from structures laboratory, after conclusion of the test and disposing it.
Task 5- Final Report, Progress Reports and Recommendations for Using Sileto as Bridge Deck Overlay
Research team at FIU will conduct, once a month, an online meeting to brief Sileto on project progress. Additionally, a quarterly progress report will be submitted to Sileto.
Results of Tasks described above will be used to develop the final report and set of recommendations for use of Sileto as a material for bridge deck overlay. Draft of this document will be submitted 30 days prior to conclusion of the research project. Recommendations will also include description of the work that needs to be carried out to address connections between strengthened bridge deck and expansion joints.
Research Team :
Principal Investigator: Atorod Azizinamini, Ph.D., P.E.