Author Archive: Omid Sarmad

Ultra High-Performance Concrete (UHPC) Applications in New Jersey – An Update

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UHPC for Bridge Preservation and Repair is a model innovation that was featured in FHWA’s Every Day Counts Program (EDC-6).  UHPC is recognized as an innovative new material that can be used to extend the life of bridges. Its enhanced strength reduces the need for repairs, adding to the service life of a facility.   

This Q&A article has been prepared following an interview with Jess Mendenhall and Samer Rabie of NJDOT, who provided an update on the pilot projects of UHPC around the state. The interview has been edited for clarity. 

Q.  While EDC-6 was underway, we spoke with your unit about the pilot projects being undertaken with UHPC.  Some initial lessons were shared subsequently in a featured presentation given to the NJ STIC.  Can you update us on results of those projects, and did they yield any benefits in the fields of safety or environmental considerations?

For the NJDOT Pilot Project, the thickness of the overlay was limited by the required depth for effectiveness, as well as the cost of the UHPC material and environmental permitting. To mitigate environmental permitting, we avoided any modifications to the existing elevations and geometry of the structure. Essentially, any removal of asphalt and concrete needed to be replaced to its original elevations.

UHPC overlays can significantly extend the service of bridge decks and even increase a structure’s capacity. Although safety improvements were not the primary objective of this application, there were rideability and surface drainage considerations in the design to enhance the conditions for the road users.

The environmental impacts of structural designs must be compared on the cradle-to-grave use cycle of the design at a project scale.  Having a focus on sustainability is imperative; however, it is more meaningful when resiliency is also considered.  While the greenhouse gas emissions of a volume of UHPC are higher than those of the same volume of concrete, UHPC enables the reduction in the amount of material required in structural designs and improves the durability of structures. Its exceptional compressive strength and toughness allow for the reduction of material usage. By minimizing maintenance requirements and extending the lifespan of infrastructure, UHPC reduces the consumption of materials, energy, and resources over time.

For example, we installed this overlay on 4 bridges as a preservation technique. Had we done nothing, they would have lasted approximately 10 more years. During that time they would have needed routine deck patching resulting in further contamination of the decks and in a condition that is no longer preservable and requires total deck replacement, with large volumes of concrete and much more environmental impact.

UHPC allowed us to take these decks that are still in decent shape and preserve them now with a relatively thin layer to make them exceed the service life of the superstructure and substructure.

Q. Has UHPC been incorporated into the design manual?

Figure 1. UHPC being placed by workers

It is not in our current design manual, but we are working on the revised design manual. UHPC is presently being used for all closure pores between prefabricated components, overlays, and link-slabs. I don’t think we are ready to standardize it quite yet. We used it on the 4 bridges and it will continue to be used, but we will not standardize it until the industry is more predictable and we get more experience to develop thorough guidelines and specifications. It is incorporated into projects as a special provision with non-standard items.

Q. Have you been receiving more requests to use this technology from around the state?

It is much more commonly specified by designers or requested for use on many of our projects. We have responded to nationwide inquiries from state transportation agencies and universities seeking our specifications or input on specific testing and procedures.

Q. What efforts do you think can be taken to encourage more adoption amongst local agencies, counties, etc.?

We are keen on inviting the counties to any training or workshop that we are hosting as well as sharing our lessons learned thus far.  I think they are aware of it.

Q. What kind of hurdles do you think exist that may limit widespread adoption?

It is possible that initial cost and industry experience with the material are still major limiting factors in adoption. We have also learned from specialty UHPC contractors that the innovation and availability of construction equipment geared for UHPC implementation are also lacking.  Bringing into focus the life cycle costs and with more implementations, we think many of these hurdles will be overcome. Additionally, once UHPC is used more in routine maintenance the implementation would be more frequent and widespread; we know there is interest specifically in UHPC shotcrete once it is available.

Q. Are you familiar with any training, workshops, or conferences that have been done for staff or their partners on this topic?

We participated in the Accelerated Bridge Construction (ABC) conference in Miami, Florida, the International Bridge Conference (IBC) in Pittsburgh, Pennsylvania and the New York State DOT Peer Exchange. In Delaware, we presented at the Third International Interactive Symposium on UHPC. We also participated in the development of a UHPC course for the AASHTO Technical Training Solutions (TTS formerly TC3) which is now published on the AASHTO TTS portal and available on our LMS internally. 

Q. Do you think there is any special training needed for the construction workforce to start using this technology?

Absolutely, the AASHTO TTS course and the EDC-6 workshops are geared towards the design and construction, TTS is more focused in the Construction. It’s an introduction to what to expect and how to implement it. UHPC is often used for repair projects, and many contractors may not have the experience or comfort with using the material.

Figure 2. UHPC Testing at Rutgers’ CAIT

Q. What are the results of the pilot projects of UHPC?

This Pilot projects program demonstrated that UHPC overlays can be successfully placed on various structures, the work can be completed rapidly to minimize traffic impacts — we estimated roughly four weeks of traffic disruption per stage, and the benefits of UHPC can help preserve the existing infrastructure. Compared to deck replacement, UHPC overlays can rehabilitate a bridge deck at exceptional speeds with unique constructability and traffic patterns, as implemented in all four structures. However, limitations exist, and further research is necessary to investigate the issues identified in the pilot project, but the potential of this material outweighs the existing limitations.

Q. Has there been long-term testing data developed to gather performance data?

To assess the performance of the UHPC overlay, we put together a testing program to include NDT as well as physical sampling and lab testing. This objective will be accomplished by first establishing baseline conditions through an initial survey followed by periodic monitoring of the UHPC-overlaid bridges over succeeding years. This will help NJDOT assess the performance of UHPC as an overlay. Overall, the results show the overlay bond is performing well.

Q. Has the data from the pilot project been used to research further applications?

Further applications for UHPC overlay are on new bridge decks/superstructures, and the data from UHPC overlay research project are being used for these projects. There is an interest in header reconstruction with UHPC. If deck joints need to be replaced, they should be constructed with conventional HPC with UHPC at the surface to provide the same overlay protection over the entire structure. Also, self-consolidating and self-leveling UHPC was preferred for the full-depth UHPC header placement to ensure proper consolidation around tight corners and reinforcement. This will be further explored for maintenance operations as well.

For future projects, in lieu of full-depth header reconstruction in a single lift, a partial depth header removal and reconstruction or alternatively two lifts of header concrete should be evaluated to coincide with the deck overlay, in which case the benefits of the fast cure times from UHPC can still be realized. Two of the four bridges experienced air voids throughout the placement. A UHPC slurry with no

fibers was placed in the identified air voids; since the voids contained exposed fibers, they were considered to create adequate bonding with the UHPC slurry.

Resources

NJDOT Technology Transfer (2021, November). Stronger, More Resilient Bridges: Ultra High-Performance Concrete (UHPC) Applications in New Jersey.  Interview with Pranav Lathia, Retrieved from:  https://www.njdottechtransfer.net/2021/11/29/uhpc-stronger-more-resilient-bridges/

Mendenhall, Jess and Rabie, Samer. (2021, October 20). UHPC Overlays for Bridge Preservation—Lessons Learned. New Jersey Department of Transportation. https://www.njdottechtransfer.net/wp-content/uploads/2021/11/NJDOT-UHPC-Overlay-Research-Project-EDC-6-Workshop.pdf

New Jersey Department of Transportation. (2021, October 20). NJDOT Workshop Report. New Jersey Department of Transportation. https://www.njdottechtransfer.net/wp-content/uploads/2021/11/NJDOT-UHPC-Workshop-Final-Report.pdf

Rabie, Samer and Jess Mendenhall (2022, December). Design, Construction, and Evaluation of UHPC Bridge Deck Overlays for NJDOT.  NJ STIC Presentation and Recording.  Retrieved from:  https://www.njdottechtransfer.net/2022/12/18/nj-stic-4th-quarter-2022-meeting/

Q&A: What’s EPIC2 about Internally Cured Concrete?

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Enhancing Performance with Internally Cured Concrete (EPIC2) is a model innovation in the latest round of the FHWA’s Every Day Counts Program (EDC-7). EPIC2 is recognized as an innovative new technique that can be used to extend the life of concrete bridges and roads. Internal curing increases concrete’s resistance to early cracking, allowing the production of higher-performance concretes that may last more than 75 years.

This Q&A article has been prepared following an interview and follow-up correspondence with Samer Rabie and Jess Mendenhall of the New Jersey Department of Transportation. The Q&A interview has been condensed and edited for clarity.

Q. What is Internally Cured Concrete, and how does it differ from traditional concrete?

A common issue with high performance concrete (HPC) bridge decks is that soon after the curing is done, they develop fine shrinkage cracks spread throughout the deck. Even this fine cracking can reduce the service life. In the past, we have used crack sealing materials as a mitigation effort, but when we learned about internally cured concrete, we shifted our focus to see if we could adopt it in New Jersey.

Figure 1. Illustrating the difference between conventional and internal curing

Autogenous or chemical shrinkage is specific to HPC concrete, where the w/c ratio is less than 0.42. It is due to self-desiccation, which is water consumed by the cementitious materials after setting, and that is one where internal curing can help.

There are multiple methods to implement internal curing. The method that we are considering involves  modifying a conventional concrete mixture to an internally cured concrete mixture by replacing a portion of the fine aggregate (sand) with lightweight fine aggregate. This lightweight fine aggregate (LWFA) is saturated with internal curing water, typically estimated at 7lbs of water for every 100lbs of cementitious materials used in the mixture. Next, the amount of LWA required for this amount of internal curing water is determined based on the mass of the internal curing water and the absorption of the LWFA. Once the total volume and mass of lightweight aggregate are determined, the volume (and mass) of the fine lightweight aggregate are adjusted so that the volume of LWFA and fine aggregate in the internally cured mixture is equal to the volume of the fine aggregate in the original mixture.

The LWFA will provide internal curing water within the concrete mix during curing, and prevent a condition that occurs in low W/CM ratio systems where the capillary water within the concrete matrix pores will be consumed without complete cement hydration, which can lead to cracking of the concrete matrix.

Q. How does Internally Cured Concrete improve performance?

Internal curing improves the performance of concrete by increasing the reaction of the cementitious materials and reducing internal stresses that typically develop in high-cementitious content mixtures if insufficient internal curing water is present. However, in addition to conventional curing which supplies water from the surface of concrete, internal curing provides curing water from the aggregates within the concrete. This provides a source of moisture from inside the concrete mixture, improving its resistance to cracking and overall durability.

Q. Are there any limitations on the use of internally cured concrete?

Internal curing is extremely versatile and  can generally be used anywhere traditional concrete is used. Most of the process is the same, and aggregates can be pre-saturated as needed. It follows the norms of industrial concrete production, making it accessible to any producer already familiar with the state of practice. Most of the implementation process is similar to conventional concrete.

Figure 2. Workers applying internally cured concrete to a bridge deck.

Q. What New Jersey sites were picked for use in internally cured concrete, and why?

We started with a list of all of our bridge projects, specifically projects that needed deck replacement and superstructure replacement. We then further targeted projects that allowed us to focus on implementation and quick delivery time rather than constructability and other additional challenges. We looked at projects with straightforward staging and geometry and prioritized projects with twin bridges (for example, northbound and southbound). This would allow us to do one bridge with traditional HPC and the other with internally cured HPC, providing us with an excellent controlled opportunity to study and compare the results.

Various sites have been screened throughout the state. Currently, eight bridges are under consideration, with a project scope of work of deck and superstructure replacement. The rationale included the project scope of work, CIP deck slabs, project schedule, staging constraints, and avoiding heavily skewed bridges.

Q. Have any life cycle cost analyses been performed?

We have not prepared one ourselves, but we do plan on doing so in the future. First, we will need to get these projects out to construction and get actual cost data. We’re expecting higher upfront costs, but if cracking is reduced then the life cycle costs and future maintenance and reconstruction needs can be significantly reduced.

Q. In what ways do you think people can be better educated on the implementation of EPIC2?

We have presented to many of our stakeholders in our capital program to discuss the topic, and now that it is an EDC initiative,  decision makers are acknowledging its value. The Federal Highway Administration is also planning on conducting workshops and peer exchanges between contractors, concrete suppliers, and other agencies like New York State DOT, which have already done this. All of these are extremely valuable.

We first heard about internally cured concrete during a peer exchange in 2021 with the New York State DOT. It was under the banner of EDC-6, and they took us out on several bridges where we noted that they have significantly reduced the typical shrinkage cracking that is common with High Performance Concrete. So that was an eye opening experience for us, and I know it would be valuable to others. The fact that it is now its own initiative in EDC-7 helps facilitate implementation.

Q. Is special training needed for contractors to work with internally cured concrete?

From our research and experience with other agencies, the finishing should not be significantly different from conventional HPC. The process at that point will be almost identical to placing traditional concrete, so there won’t be any learning curve or time spent on getting workers to learn how to deal with a new material. In fact, most contractors say that the mixture is easier to work due to improved pumpability as the material is quite smooth. I think the crucial step will be to coordinate with concrete production plants that are creating the mixes.

Figure 3. States that have implemented EPIC2 on their roads or bridges

Q. Where else has internally cured concrete been implemented?

So far it has been used in bridge decks in many states, including New York, Ohio, and North Carolina, among others. It has also been used in pavement and pavements in Kansas, Texas and Michigan.

Q. What is the future of internally cured concrete in New Jersey?

We hope these projects will be successful, and that our current crop of projects will result in some valuable lessons learned. In the long term, I believe the goal would be that all of the bridge decks would use an internally cured mixture. I can also see this being used for patching and deck repair jobs. But ultimately, the goal would be for this to become the new standard for bridge decks across the state.

Resources

Federal Highway Administration. 2023 Internally Curing Concrete Produces EPIC2 Results. https://www.fhwa.dot.gov/innovation/innovator/issue98/page_01.html

Federal Highway Administration. 2023. Enhancing Performance with Internally Cured Concrete. https://www.fhwa.dot.gov/innovation/everydaycounts/edc_7/docs/EDC-7FactsheetEPIC2.pdf

Federal Highway Administration. (2018, June). Concrete Clips: Internal Curing. https://www.youtube.com/watch?v=b6WREFmacaM

New York State DOT Standard Specifications (2021). Standard Specifications. New York State DOT. https://www.dot.ny.gov/main/business-center/engineering/specifications/busi-e-standards-usc/usc-repository/2021_9_specs_usc_vol2.pdf

National Concrete Pavement Technology Center Internal Curing Resources. (2022). Internal Curing. Iowa State University. https://cptechcenter.org/internal-curing/

Internal Curing. (2020). Oregon State University. https://engineering.oregonstate.edu/CCE/research/asphalt-materials-performance-lab/materials-research-concrete-materials/Internal-Curing

Pacheco, Jose. (2021, October). USDOT Workshop Report, Bureau of Transportation Statistics. Wisconsin Department of Transportation. https://rosap.ntl.bts.gov/view/dot/62607

Weiss, Joseph. (2015, July). Internal Curing Technical Brief. Federal Highway Administration. https://www.fhwa.dot.gov/pavement/concrete/pubs/hif16006.pdf

Orthotropic Bridge Deck Design

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Steel orthotropic deck

On July 9th, Dr. Sougata Roy discussed the benefits of using orthotropic bridge decks, focusing on their design, fabrication, and construction. He addressed a room of NJDOT employees, highlighting significant projects that have utilized orthotropic bridge decks, including the first such bridge designed by NJDOT.

An orthotropic bridge deck is one in which a steel deck plate is supported by longitudinal ribs and transverse crossbeams. The ribs and crossbeams give the deck different stiffness in the transverse and longitudinal directions, allowing it to distribute weight effectively.

Dr. Roy first posited the advantages of using these bridge decks, emphasizing their light weight and structural efficiency, and their estimated life span of over 100 years. Orthotropic bridge decks are lighter due to the reduced need for concrete, which minimizes the total dead load carried by the rest of the structure. Estimates are that up to 25 percent of a bridge’s total mass can be saved by reducing the deck weight, and those weight reductions can extend to cables, towers, piers, and so forth. Orthotropic decks are prefabricated and their modular form allows for accelerated bridge construction and higher quality control. The bridges can be erected more quickly, thus minimizing the impact on New Jersey’s motorists. The maintenance requirements for orthotropic bridges are expected to be much lower as there would be no need to re-deck the bridges every few decades. While Dr. Roy acknowledged that there are high initial construction costs associated with orthotropic bridges due to the complex welds involved, such costs would be offset by the lower maintenance costs over the life of the bridge.

Dr. Roy suggested that the orthotropic bridge deck design could help address some of the state’s greatest transportation infrastructure needs related to bridge condition, maintenance, as well as overall traffic congestion. To demonstrate this, Dr. Roy used data from the Route 7 Wittpenn Bridge between Kearny and Jersey City, which is the first bridge constructed by NJDOT to use an orthotropic bridge deck.

Bridge deck in transit to New Jersey

The 300-foot deck was shipped in one piece via the Panama Canal from Portland, Oregon and arrived at the Wittpenn Bridge in July, 2017. For an illustrated depiction of the Wittpenn Bridge deck’s trip to Kearny, see Oregon to New Jersey: The Journey of New Jersey Department of Transportation’s First Orthotropic Deck.

The current work on the bridge is proceeding quickly as the steelwork for the bridge is less impacted by cold weather than a typical concrete bridge deck would be. The new bridge will be twice as high as the current Wittpenn, and will feature wide lanes and shoulders.

Dr. Sougata Roy presents Cost Effective Design for Orthotropic Bridge Decks

For related information, please view the report, Design and Fabrication of Orthotropic Deck Details. The objectives of the research were to verify the design and fabrication of the orthotropic deck details proposed for the lift bridge, for infinite fatigue life. Multi-level 3D finite element analyses (FEA) of the proposed deck were performed to determine the critical stresses at the connections, the corresponding load position, and the deck specimen. To develop cost-effective connection details, three variations of rib-to-floor beam and rib-to-deck plate connection details, including the influence of different fabrication parameters, were explored in full-scale, small-size mockups. Subsequently, the infinite life fatigue performance of the connection details were evaluated by laboratory testing of a full-scale prototype. The fatigue testing was conducted under simulated rear tandem axle loading of the American Association of State Highway and Transportation Officials (AASHTO) fatigue truck with adequate boundary condition. The prototype testing was runout after 8 million cycles, verifying the infinite life fatigue performance of the deck design.