Cor-Tuf UHPC Production and Piling Test Results – LBM Research Associates

Amazing! Cor-Tuf UHPC Production and Piling Test Results – LBM Research Associates

Information about Cor-Tuf UHPC Production and Piling Test Results – LBM Research Associates

Phil Puccio

Ultra High Performance Concrete (UHPC) is a cementitious concrete material with a specified minimum compressive strength of 21,500 pounds per square inch (psi). UHPC is stronger and more resistant than conventional concrete due to the fibers integrated into the mix. The fibers vary from polyester to steel to stainless steel, with different types of fibers giving the end product more strength.

Cor-Tuf vs. Conventional UHPC: Why Cor-Tuf Is Superior

Conventional UHPC offers many advantages and can revolutionize concrete construction. The benefits include:

  • Longer service life – UHPC has an estimated lifespan of more than 75 years. Ordinary concrete usually only lasts 15-25 years before it needs to be replaced.
  • Lighter weight – Concrete wall panels designed with UHPC are 25-33% thinner. This means that less material is required for the construction of the panels and the requirements for the foundation of the support structures are reduced.
  • strength – Ordinary concrete has a compressive strength of 4,000 pounds per square inch (psi). UHPC has a compressive strength of 30,000 psi when fully cured. Some mixing techniques can even reach more than 50,000 psi. It also has a tensile strength in excess of 1,700 psi.
  • Extremely resistant to environmental degradation – Conventional concrete begins to deteriorate after just 28 freeze-thaw cycles. UHPC can withstand more than 1,000 freeze-thaw cycles and storms.
  • flexibility – UHPC is more flexible than normal concrete. This makes it ideal for making structures that incorporate more complex, architectural designs while still providing strength and durability.
  • Moisture resistant – UHPC has a higher density than normal concrete. This makes it practically impervious to liquids, abrasives, and all kinds of oxidizing agents.
  • Adhesiveness – In contrast to normal concrete, UHPC is ideally suited for bonding. It can be used for adhesive bonds with other materials, such as

Despite these advantages, it has not always been easy for contractors and contractors to use conventional UHPC on the construction site. Many conventional UHPC products cannot be mass-produced in large numbers. Mixing small batches takes additional time – time that adds up throughout your project.

Mixing small batches also opens up the potential for inconsistencies in your structure. If you’re building a bridge and need to mix lots of small batches of UHPC, you’re more likely to have margins for error in weighing, adding water, and other components.

Cor-Tuf UHPC is different. It’s an ultra-high performance concrete originally developed by the US Army Corps of Engineers to meet the need for a harder, yet lighter weight material to protect personnel and weapons systems from explosions and intruders.

This innovative concrete technology combines excellent compressive strength (up to 30 times stronger when thermosetting than conventional concrete) with impermeable elasticity. It is unlike any other concrete product and outperforms other UHPC products on the market.

More importantly, it can be mixed and poured like conventional concrete, making UHPC just as easy to use. Cor-Tuf UHPC offers the advantages of improved compressive and tensile strength and durability without having to change the way you work with concrete.

Cor-Tuf UHPC in action

We have conducted numerous tests to demonstrate these and other revolutionary properties of Cor-Tuf UHPC and are pleased to share the results of some of our latest efforts.

Recent testing was conducted at Dura-Stress Incorporated of Leesburg, Florida. We produced two 30-foot post-tensioning piles and one 100-foot post-tensioning post. The Cor-Tuf UHPC used in the tests was manufactured in a large series production facility. This is a major milestone for a UHPC product and one of the key features that set Cor-Tuf UHPC apart.

Other UHPC vendors can only supply UHPC in 50 pound bags, but Cor-Tuf UHPC is mixed in bulk (super bags that hold roughly a ton of material) and then put into a tuckerbilt truck. In our tests, like conventional concrete, our product is poured directly from the Tuckerbilt into the pile mold.

Other UHPC products also take longer to mix – typically twenty minutes. When you combine the longer mixing time with the small batch production, there are consistency issues in your end product and lots of gaps (downtime) in the production cycle that hold up work and slow down a project.

Small batch production has limited the use of UHPC, making it difficult to build large structures like bridges and piles. With Cor-Tuf UHPC, large-scale production of large structures is not only possible, it is also clearly advantageous.

Cor-Tuf UHPC has a longer working time (approximately one hour) than other UHPC products on the market. It is also more fluid and flows like regular concrete. You get all of the benefits of UHPC in terms of exceptional compressive and tensile strength, but the applications and methods of mixing and pouring are the same as conventional concrete. This is not the case with other UHPC products, which makes Cor-Tuf UHPC a truly innovative concrete material that will revolutionize the concrete industry WITHOUT having to change processes or machines.

During the production phase of our tests, we wanted to prove that components prefabricated with Cor-Tuf UHPC, unlike other UHPC products, are free of voids and show no inward shrinkage during the curing of the component.

In collaboration with the Florida Department of Transportation, 15 strain gauges were installed in each pile. When the prestressed load at each end was released and transferred into the concrete, it was measured. As predicted, it showed no movement of the pre-stressed cables embedded in the pile.

When each pile was pulled out of its form, they were considered to be devoid of any voids. Other than a few light surface stains left by the mold, they were ideal otherwise. The surface stains were easily removed and were completely clean.

Additional tests were conducted on-site at the Florida Department of Transportation Structures Research Center in Tallahassee, Florida. This was the first of two directional compression tests designed to measure how much tension can be placed on a pile that can withstand extreme vertical loads before it ultimately fails.

In this test specifically, we put as much horizontal pressure as possible on one of our 18 “x18” x30 ‘UHPC piles to measure its full point of failure. In order to provide us with precise data, the FDOT used strain gauges and deflection gauges as well as a strand slip monitor to monitor the event. Prior to testing, the stack was predicted to fail around the 60,000 psi mark.

The tests were interrupted at various pressure levels so that the piles could be inspected by the FDOT team. Overall, the Cor-Tuf UHPC post was able to withstand a downward bending pressure of 84,000 psi and a deflection of 4.5 inches before failing. When the pile cracked, its fracture point was compacted into an area with no additional beam cracks along the sides of the pile.

In another demonstration, we installed our 18 “x18” x100 ‘piles into the ground at the Leware Construction Yard in Leesburg, Florida. As in our previous test, this post came with a full set of data acquisition sensors so we can monitor its condition during installation.

The Leware shipyard was chosen as the location for our installation because we had a full geotechnical report for the area prior to starting. This report would allow us to compare our results with the soil data for the area to get a complete picture of what is going on below the surface.

Two piling hammers were used in this test: a D36 and a D62. We started the piling installation with the D36 hammer. When installing the piles with the D36 hammer, we encountered very little subsurface drag until we encountered bedrock at the 70 foot mark.

When we hit bedrock, the decision was made to see how hard and fast we could hit the stake with the D36 hammer to make it fail. What we found was that the friction between the hammer head and the end of the post did not fail, but caused the pad (which was designed to cushion the blow of the hammer and was made of plywood) to catch fire and melt.

The real-time pile data report showed no significant changes in the pile’s stress weave pattern or structural continuity at this point. This, combined with the D36 hammer’s failure to produce any internal anomalies, prompted us to switch to the larger D62 hammer to try and make the ramming fail.

Regardless of which hammer was used or how hard or quickly we tried to hit the stake, our data from the event showed that the structural integrity of the stake never fell below 100 percent. We eventually got to a state where the test team ran out of cable length for the internal sensors. Aside from the residue from the burning hammer pad, the top of the stake is still in near-pristine condition.

The results of these tests clearly show the superior properties of Cor-Tuf UHPC. Please watch the video below to see these tests in action and see firsthand how easy it is to use our product on your next specific task – all without changing your machines or process have to.

Stay tuned for the videos and results of our next concreting work, including testing bridge girders, H-piles for sea walls and coastal protection, a new mix for use on bridge and highway overlays, and classified civil defense and anti-terror devices for a vastly improved public protection of both personnel and vital infrastructure.

Breaking Story – Cor-Tuf UHPC Production and Piling Test Results – LBM Research Associates

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Original Source: http://www.lbmresearchassoc.com/2019/12/19/bringing-uhpc-to-the-masses-cor-tuf-uhpc-production-and-piling-test-results/
Category – Concrete

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