All too often in construction when we gather around a set of plans, we immediately come up with some really good ideas to improve constructability. This can be detailing alterations which may make things easier on the laborer in the field, providing a safer alternative approach, or realizing a time savings alternative where components can be made in advance and connected simply, quickly to get out of a hazardous project or even meet a demanding schedule. However, even in our best, most well thought out approaches to simplify processes, durability is always a primary concern. We need longevity and resiliency in our structures, and it is the responsibility of all parties to ensure that we meet these goals.
Ultra High Performance Concrete (UHPC) offers a unique opportunity to improve constructability and provide even greater durability than the current methods of doing business.
Let’s explore one example. We do a lot of precast, prestressed marine concrete piers and wharves on concrete or steel piling. Typically, this is comprised of precast, prestressed caps spanning multiple piles and closures made between the ends of the concrete section. These piers can be several hundred feet long and the precast elements anywhere from 30 ft to 80 ft depending on crane capacity. The reinforcement projecting out of the ends of the members vary from #8’s up to #11’s. In some challenging projects, we have used headed #18 bars. The normal concrete closure is typically 4 ft to 6 ft long as illustrated in Figure 1.
A lot of these projects are on sites not easily accessible as the sites by land are typically congested and require special clearance and water even more complex yet each one of these closures only amounts to 2 or 3 yards of concrete. Filling these joints are also a critical path item where waiting for a large placement by a pump truck may or may not be possible and in some cases this all has to be coordinated with the tide. (Figure 2)
Enter UHPC as the alternative. Pre-bagged material may be shipped in advance and batching may commence onsite as needed for this critical connection. Studies are underway where bars up to #11’s may only require a 12” UHPC closure to fully develop the bar. This greatly reduces the volume required resulting in less loose material delivered to the job site as well. More importantly, this delays the requirement of normal concrete delivered to the job site until after the deck planks are set. Therefore, traditional concreting occurs only when there is a large platform for crews to walk on, safely and more efficiently.
The same value added occurs in bridges as well. If a precast, prestressed cap is used which is large or heavy, then a UHPC closure provides the connection thereby delaying the delivery of ready mix concrete until after the girders and stay in place forms are set.
Future of UHPC Caps in a Marine Environment
An entire new level of utilizing UHPC in marine environments is a shell structure as utilized in Malaysia (Figure 4). These are much lighter allowing for a smaller crane and enough capacity for the connection to the pile and dead load of the deck and infill concrete. The infill concrete can be placed from safely above doing away with the need for any extra formwork in the field where continuity reinforcement is placed inside the shell. A discrete corbel at the outside of the shell may support transverse caps or a continuous ledge may support deck slabs greatly simplifying the construction process and taking UHPC from predominately a connection material to a cost effective, value added component.
Enhancing safety while encouraging constructability, UHPC
provides a rare opportunity to think outside the box with inherent durability in
the material or the connection thus changing the approach to construction.
The following is shared from a Press Release from August 21, 2019 via PRWeb
Cor-Tuf UHPC is proud to formally announce a partnership with Precast Systems Engineering. This collaboration allows for new, innovative progress in ultra-high performance concrete development and application.
Cor-Tuf is the exclusive licensed producer of Cor-Tuf Ultra-High Performance Concrete (UHPC) in the United States and the world. Cor-Tuf UHPC is an extremely strong and durable new concrete material developed by the U.S. Army Corps of Engineers (U.S. patent No. U.S. 8016938 B2) to fill a demand for a stronger and more resilient material to protect personnel and weapons facilities from blasts and intrusions.
Cor-Tuf will help PSE develop the UHPC mixing technology for project-specific uses, using local supplemental constituents (sand, cement, and other materials as appropriate). PSE will support Cor-Tuf as a structural engineering resource to advance the technology and promote the continued development of Cor-Tuf.
“I have been excited for many months about how I envisioned the potential ‘union of forces’ between Cor-Tuf and Precast Systems Engineering,” says Rich Burgess, president of Cor-Tuf. “Our two companies have already started working together on several large projects and are in discussions concerning many more. We anticipate this new agreement will be mutually beneficial to both organizations. This is just the tip of the iceberg.”
About Cor-Tuf UHPC
Cor-Tuf UHPC was founded in 2016. The company is the exclusive licensed producer of Cor-Tuf Ultra High-Performance Concrete (UHPC) in the United States and the world. Cor-Tuf UHPC is a new concrete technology that is exceptionally strong and durable, displaying a compressive strength that is 10 times that of traditional concrete. This innovative concrete is impervious to water, demonstrates superior freeze/thaw resistance, and has a longer useful life of more than 75 years.
Cor-Tuf UHPC is replacing traditional concrete in such projects as bridge construction and repair, precast concrete deck panels, and field-cast connections between prefabricated bridge components.
About Precast Systems Engineering
JP Binard, a professional engineer registered in several states along the East Coast from New York to Florida, is the owner and manager of Precast Systems Engineering, LLC, specializing in construction engineering primarily focused on precast, prestressed concrete for buildings, marine structures, and bridges utilizing UHPC in components and connections.
The firm’s business model is based on teaming up directly with contractors, engineers, and owners in order to streamline fabrication or placement, facilitate communications throughout the design and casting process, and provide the best overall project delivery in terms of durability and performance.
For more information, contact: Douglas Darling, Founder and Chairman, Cor-Tuf UHPC email@example.com 703.656.1445
PSE partnered this summer with Cor-Tuf in Leesburg, FL for this Cor-Tuf UHPC three-day testing event, pouring two 30′ beams, one 63′ beam, and two 30′ H pilings. This video produced by Cor-Tuf illustrates the process and findings.
The Second International Interactive Symposium on Ultra-High Performance Concrete (2IIS-UHPC) will be held in Albany, New York, USA from June 2 to 5, 2019. Building on the success of the first symposium held in July 2016, the symposium is bringing together the UHPC Community for more learning, networking, and advancement of this innovative technology. The interactive symposium will afford professionals working on all aspects of UHPC to:
share knowledge about applications and opportunities,
broaden technical depth,
identify knowledge gaps and
grow the UHPC family dedicated to truly working together to achieve similar goals.
Cost is a primary impediment but also
confidence in execution. Perceived risk by both contractors and precast
fabricators circle around being unable to perform reliably in the field
or at the plant and ultimately lose too much money with such an
expensive material. Currently this fear outweighs the gain in market
share for most.