Lessons Learned from Condition Evaluation of UHPC Overlays
Presented By: Andrew Foden
Affiliation: WSP USA
Description: In a pilot program, four bridges in New Jersey were treated with ultra-high-performance concrete (UHPC) overlay. The overlay installation included complete removal of the existing bridge asphalt overlays, partial removal of the existing concrete deck surface, and a complete resurfacing of the bridge with a UHPC overlay. Prior to this pilot program, UHPC was not used as a bridge deck overlay in the state of New Jersey. To assist NJDOT in assessing the quality of the UHPC overlay, a nondestructive evaluation (NDE) testing plan was developed to assess the baseline conditions through an initial survey of the deck, followed by a periodic assessment of the UHPC-existing concrete bond over a two-year period. Impact echo and ultrasonic tomography were used. Additionally, pull-off tests were used to assess the bond quality between UHPC and original concrete. This study presents the results of the first year’s condition assessment.
Non-Destructive Evaluation of a Large-Scale Laboratory UHPFRC Beam
Presented By: Thomas Schumacher
Affiliation: Portland State University
Description: Ultra-high performance fiber reinforced cement-based composite (UHPFRC) material has superior strength and is virtually impermeable compared to traditional concrete. Thus, it is used to rehabilitate and strengthen reinforced concrete structures, in particular bridges. It is also used to construct entire new bridges. Because UHPFRC is still in its early use phase, large-scale laboratory as well as field testing are necessary to ensure that the serviceability and durability of structures built with this material are as expected. This presentation introduces UHPFRC and discusses non-destructive evaluation techniques to determine material properties and structural performance. A large-scale experiment of a UHPFRC beam equipped with embedded ultrasonic transducers is presented and preliminary results are discussed.
A Durability Study of FRC in Bridge Deck Applications
Presented By: Carl Labbe
Description: The service life of concrete and its long-term durability is an ever-growing concern. New materials and practices used to increase the expected service life of concrete are never fully evaluated until these have been in place, in their environment, under loading conditions, for an extended duration of time to validate their actual impact and influence on the associated concrete members. This presentation reviews a few bridge decks’ surfaces where FRC (Fiber Reinforced Concrete) has been applied and in-place for 15 to 20+ years.
Concrete bridge decks have historically required continual maintenance with cracks, surface wear, joints, worn approaches, freeze thaw, pop-outs, etc. One of the technologies that is increasingly deployed is three-dimensional reinforcement using fibers. The strategy of incorporating fibers in concrete bridge decks is to reduce the number of cracks and the widening of cracks and improve overall toughness and durability. Although reinforcing fibers have been around for centuries, no one fully understands all the benefits and synergies acquired when using fibers in conjunction with bar reinforcement. Can fiber extend the life of a bridge deck? At what dosage rate of fiber is effective or optimal? What types of fibers are used? What performance indicators can be applied for specification requirements? Many of the answers to these questions are continually being refined due to advancements in product technology, testing, and new standards within our concrete industry.
Performance Evaluation of Polymer Concrete Overlays
Presented By: Mohamed ElBatanouny
Affiliation: Wiss, Janney, Elstner Associates, Inc.
Description: The Iowa Department of Transportation (DOT) has used concrete bridge deck overlays to extend the service life of their bridge decks since the 1970s. While portland cement and high-performance concrete overlays are currently standard practice in Iowa, they require extensive deck preparation and three days of moist curing, resulting in undesirably high traffic control costs and long traffic disruptions to users. While relatively more expensive in terms of material cost, polymer concrete overlays are an attractive alternative because they may be completed over a weekend or overnight in some cases. As such, the Iowa DOT decided to install two polymer concrete overlays and conduct a case study to document their performance and the lessons learned. This presentation provides a summary of the completed work that included initial deck evaluation to document the pre-existing condition of the two bridge decks before overlay installation, construction documentation, and post-installation inspections over a period of 3-years to evaluate the performance of the overlays.
In-Situ Examination of GFRP Bars in Bridge Decks after Two Decades of Field Exposure: How Durable Are They?
Presented By: John Myers
Affiliation: Missouri S&T
Description: Since the late 1990’s Fiber Reinforced Polymer (FRP) bars have been deployed into Bridge Deck applications in the field. While numerous laboratory tests have been undertaken over the past three decades to examine the durability performance of various FRP bar products under accelerated laboratory testing, there is much more limited field-based data that has examined the performance of these products under field conditions. In particular, eleven bridges have been studies that were constructed between fifteen to twenty years ago. The study examines both microscopic as well as physical property tests from extracted GFRP bar samples from the aforementioned number of bridges. These tests include constituent content, maximum water absorption, as-received moisture content, glass transition temperature, short bar shear strength and tensile strength were evaluated. Scanning electron microscopy and energy dispersive spectroscopy were also performed. The fiber mass content of all bars was evaluated. Scanning electron microscopy and energy dispersive spectroscopy was assessed along with short beam shear strength and non-standard limited tensile testing.
Application of Inorganic Resins for Bond of CFRP-Retrofit Systems
Presented By: Wajdi Ammar
Affiliation: University of Colorado Denver
Description: This presentation discusses the time-dependent interfacial behavior of near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) strips bonded to a concrete substrate using inorganic resins. Four types of bonding agents (mortar, polyester-silica, ultra-high performance-concrete (UHPC), and geopolymer) are tested to appraise the potential for NSM application with a focus on rheological and mechanical performance during a curing period of 28 days. Unlike the case of the mortar and geopolymer resins, the rheological resistance of the polyester-silica and UHPC resins increases within 30 min. owing to an evolved setting process. The hydration of mortar continues for up to 28 days of curing in line with assorted chemical reactions. The compressive strength of polyester-silica gradually ascends to 35 MPa (5,076 psi) at 28 days, while that of UHPC rapidly rises to 95.3 MPa (13,822 psi) at 3 days. Contrary to the stabilized interfacial capacity of the specimens with mortar and geopolymer after 7 days, the capacity of the specimens with polyester-silica steadily develops until 28 days. Unlike the failure mode of other cases over time, a shift in the plane of failure is noticed for the mortar-bonded interface. The post-peak response and energy dissipation of the interface are controlled by the resin type and curing period. Analytical modeling quantifies the level of hazard and clarifies the functional equivalence of the interface with the inorganic resins against conventional organic epoxy resins.