Fiber Reinforced Concrete Casting

The video above is about the casting of steel fiber reinforced concrete. In the casting, they are also using steel rebar for an even higher resistance to stresses. I wanted to show a video like this for one reason. That reason is that, the fibers don't change much for the casting of concrete forms. When pouring the concrete into the cast, it still acts somewhat fluid, like standard concrete, and allows for the ability to mold to any shape that is needed for the structure. This is very important since, in every aspect except for cost, the fiber reinforced concrete is a feasible replacement to standard concrete and, due to its higher strength, is an even better material to use in the near future.

Ultra High Performance Concrete

Ultra High Performance Concrete (UHP) is a very interesting material. Standard concrete slabs for things such as roads or driveways are designed to resist a minimum stress of about 5000 psi. This material however, is designed to resist stresses of 21800 psi. A study on this material can be found here. The conductors of this study tested the effects of different lengths of steel fibers in the material. During this study, they found that, without cracking, the different lengths of fiber didn't effect the overall strength of the material. When the material started cracking, the longer fibers actually bridged the cracks and kept up the strength of the material better than the shorter fiber. This is something I would like to include in my paper. While it doesn't use composite fibers like the other studies I have read about, it can still be considered a flexible concrete. I wanted to write about the possibility of writing about using concrete in ways that it couldn't normally be used, like beams and girders. This UHP concrete allows for a very different use of concrete in those ways.

Economic Feasibility of Fiber-Reinforced Bridge Decks

Remember all that time ago we went to the library to learn about the databases and figure out different ways to search for our topic? Well, another term for flexible concrete is fiber reinforced concrete and the Federal Highway Administration shared a study conducted in the West Virginia University that tests the economics of using the concrete as a bridge deck. Unfortunately, the link for this study is a direct download of a word document to the study. So, if  you follow the link here it will bring you to the google search i conducted. Then, the second listing titled, "Economic Evaluations of Fiber-Reinforced Polymer Bridge..." is where the document can be found. After jumping through all these hoops to get the article, the conducted study is actually extremely interesting. For this study, the researchers checked the life cycle cost of the bridge deck. The life cycle cost includes construction and demolition costs, which are the initial cost to build the material and the final cost of the material during its removal. This cost also includes the repair costs that may occur throughout the life of the material. The issues that they ran into within their study is that, due to the extremely high initial cost of the flexible concrete it, currently, can not be competitive with standard concrete. However, they conducted an estimation of the future initial costs of the material and found that, due to the curve sets of data, the material should become economically feasible to use as bridge decks within 10 years. This isn't exactly what I wanted to see in the study, honestly. I was hoping to see that, based on the life cycle data, that the flexible concrete would be economical to use. Unfortunately, that is not the case. But, 10 years, is an extremely short amount of time and with the way technology is always changing nowadays, it could occur much quicker.

Standard Concrete vs. Flexible Concrete

Much earlier in the semester I gave an example of how concrete acts when loaded (similar to a granola bar) but have never actually shown it. The two videos below show stress tests of, first, standard concrete and, second, flexible concrete. In the standard concrete video, failure of the material occurs at the 1:59 mark showing just how rapidly a concrete structure can go from standing and bearing the load, to immediate failure and a risk to human life. In comparison, the flexible concrete doesn't show signs of total failure under similar conditions. This is due to the higher ultimate strength which means that complete failure will, eventually, occur but at a much higher load capacity. Now, the benefit to the flexible concrete in these examples is that, by bending so greatly and still carrying the applied load, the engineer who notices the extreme bending still has time to redesign the concrete and replace the beam that is being effected without the structure collapsing. While the beam in use would still be mathematically safe to carry the loads applied, having that large of a bend within the concrete would not make people within the building feel safe because bending is a sign of imminent failure. Definitely check out the videos below. It's amazing to see how, by changing the materials in the concrete, it effects the performance of the finally designed material.

Starting the Paper

Well the semester is coming to a close and, while it has been a very busy one, there is still more for me to do in all my classes. Now that I have a day, it'll be good to get a start on the paper. Recently, in class, we were assigned to put together a small outline of our paper. This actually helped a lot in figuring out what to do for the research paper. The style of the assignment was to have an argument about a topic which, due to the nature of my topic of choice, was something that didn't really have two or more sides and arguments. Due to this, I had always been thinking on what I should write about because there isn't really an argument against flexible concrete. However, by doing that in-class assignment, I realized that there is an argument against it. The material is actually fairly expensive when compared to standard concrete. While, there is no one actively stating, "We can't use flexible concrete because it is overly expensive," it is something that every individual who is conducting the studies on the material has kept in mind and have attempted to find ways to save on cost, including studying about using recycled fibers (discussed in another blog post). So this helped me in setting up the paper and discussing the counter argument about cost and helped me to have an argument against the counter argument which is that the cost over time would be smaller due to the possibility of less construction to fix potholes or cracks.