Fiber Reinforced Concrete . Do You Know???

This article will give you more information the Fiber Reinforced Concrete. Since the advent of fiber reinforced concrete in the agreement of 1940, a large amount of testing has been performed in various fibrous materials to determine the true features and benefits of each product. This article will examine some of these fibers, their applications and some problems.

Portland cement concrete is considered a relatively fragile material. When subjected to tensile stressed mass concrete and does not crack. Since the steel reinforcing of mid 1800’s was used to solve this problem. Like composite, reinforcing steel is supposed to carry all the tensile loads. When the fiber reinforcement and added to the concrete mix can also add to the tensile load capacity of the composite system. In fact, research has shown that the shear strength of concrete can be increased to five times by the addition of fiber reinforcement.

In the American Concrete Institute report entitled “State-of-the-art report of fiber reinforced concrete, the characteristics of fiber reinforced concrete are discussed in detail.
Reinforcing fibers extend over concrete under load. Therefore, the system consisting of fiber reinforced concrete is supposed to work as if it were closer to reaching its “first crack strength. It is from this point that fiber reinforcement is responsible and has the concrete.

For reinforcement fibers, the maximum load capacity is controlled by the fibers to withdraw from the fiber composite reinforcement, because it has a deformed surface as the largest steel reinforcing bars. This condition limits the performance to a point much lower than the yield strength of the fiber itself. This is important because some fibers are more “slippery” than others when used as reinforcement and affect the hardness of the concrete product in which they find themselves. Tenacity is based on the total energy absorbed before competing failure.

The main properties that affect the hardness and the maximum fiber-reinforced concrete are:
– Type of the fibers used.

– Volume percent of the fiber.

– Aspect ratio (the length is divided by the diameter of the fiber).

– Orientation of the fibers in matrix.

The materials that are used in reinforcing fiber such as asbestos, acrylic, cotton, nylon, glass, polyester, polyperpylane, polyethylene, rayon, steel and rock wool.  Of these, the acid-resistant glass as well as the steel fibers has received more attention. The plastic fibers have proved of little value in the concrete until recently. The natural fibers are subject to alkali attack as well as are also determined to be of little value. Nylon is making a form on the slab at grade technology. Most of the test data, however, focuses on the use of steel fibers and fiberglass.

The percentage of fiber in the concrete mix is based on the volume and is expressed as a percentage of the mixture. Tests ranging from 1.7 percentages – 2.7 percentages are common. When using the volumes that are greater than 2 percentages the concrete could be difficult to mix. When the concrete is placed by means other than a truck-mixed concrete, the fiber may be higher. This is an example of using the concrete shot. The volumes of 2.3 percentages have been used successfully. In some prefabrication operations by using the fiber reinforced concrete percentage’s volume has been used up to five percentages. In general, if all of the other properties will become equal, the resistance increases linearly with fiber volume of concrete.

Aspect ratio is simply the fiber length divided by its diameter. This property is used to represent the amount of fiber surface against the concrete mix. This aspect is necessary for another reason. It has been found that fiber balls in the mixture increases with increasing aspect ratio. An aspect ratio of about hundred for steel fibers proved to be optimal. The fiber orientation will be generally random, simply because they are placed one by one in a straight line. The fibers are added spray on a form or to dry cement and covered with wet concrete mixture. Both procedures will help you to produce a random pattern of fiber reinforcement. Tests with steel fibers, however, have shown they could be aligned by the use of magnets and the resulting concrete will have a better resistance to breakage. This process is used in the manufacture of precast columns and beams.

Since the year 1940, many applications for fiber reinforced concrete have been discovered, and most of them have used fibers from either glass or steel fibers. The steel fibers have found their place in the paving, the stabilization of the rock to form inside the tunnels. Methods include direct placement of a dump truck mix concrete, and at work on airport and roads runways, and shotcreteing for other civil construction projects, which includes the water flows and spillways.

Nylon is considered a plastic material, and as such growth has not received the glass and steel have. Most of the plastic fibers are thought to contribute little to the static strength of concrete, however, polypropylene and nylon can increase the impact strength and flexural. These fibers are also naturally resistant to alkali. This is also a new product being developed by Nycon Inc. that is used in concrete slabs on grade in car repair workshops and warehouses. The manufacturers indicate that the fibers could even replace welded wire fabric in these plaques.

Glass fiber reinforcement also has shown greatest development from the last twenty five years. Principles of the glass fibers were not successful as the alkali in Portland cement that attacked and destroyed the fibers. In the year 1967 Dr. AJ Majumdar, from “UK Building Research Institute”, tested the use of zirconia-containing glass. It is from their efforts that have been developed alkali resistant glass fibers. The “Pilkington Brothers Ltd.”, from England, took over the worldwide rights to market this new material under the name of “CEM-FIL”. In the year 1975, “CEM-FIL Corporation” was founded in Nashville. This company began to manufacture glass products AR. “Fiberglass Owens-Corning Corporation” was also granted the license to produce the patented product glass.

Today there is worldwide competition of over hundred manufacturers of fiberglass AR.
The concrete reinforced fiberglass has been used with great success since its inception in the year 1970. One of the best examples is the “Four Seasons Olympic Hotel” which is located in downtown Seattle. Glass fiber reinforcement concrete panels were used to simulate terra cotta in the addition of hotels and restoration project. At the entrance, Glass fiber reinforcement concrete interlocking panels over 6 x 16 gauge metal stud back-up flat rectangular modules simulate terra cotta. These groups were set up in sequence on bars as well as sealed joint sponsor of the perimeter. The entire surface was painted on the wall give a look that is made of terra cotta pebbles.

Ornamental forms, like capitals, columns, freezing as well as lintels is also done by using molds of the original terracotta or the construction of new molds of detailed design drawings of the architect. Glass fiber reinforcement concrete matrix was sprayed into the molds and the support steel frame anchored directly to the coating material by spraying additional Glass fiber reinforcement concrete in puddles on the edges of the frame. The individual elements supported by the masonry construction or steel frame are done for sealing the edges on the stand rod.

Many structures have been used as a substrate for different Glass fiber reinforcement concrete facing products such as thin brick, ceramic tile and other architectural concrete mixes. These composite panels have shown wall GFRC new behaviors that warrant careful study and understanding. If you have ever painted on the surface of a free-standing sheet of plywood or particle board may have noticed that, unless “Go paint” the reverse surface, the bow panel. This inclination is because of the surface tension of the coating surface, which in turn is caused by the tendency to decrease while the paint dries.

For painting plywood panel that has created a “composite structure” of painting and wood, and unless the wood is held securely to a wall, it will double. This is a rather simplistic example to illustrate some of the dynamics that will occur in the GFRC composite panels. That is, the composite panel can deform or bow under the efforts.

This issue is mentioned in an article titled, “Cracking and aging compounds GFRC Wall Panel Skins metal frames Stud in the United States”, by DW Pfeifer, EA Rogalla Wiss WJ Nugent. Their study shows that” when GFRC mixture is compounded with the face of conventional cement, brick, terracotta clay or ceramic tile, a large potential for off-level tilt occurs due to the expansion properties differential thermal.

Glass fiber reinforcement concrete can develop up to three to four times the potential of thermal expansion compared to other materials. WJE turns to Glass fiber reinforcement concrete contraction when applied decorative facing materials. His report shows the enormous potential of the tilt out of plane when the GFRC is attached to the ceramic tiles. When tested over GFRC concrete mixture against the results showed that, even though two of Portland cement-based materials shrink compounds are, the possibility of tilt is at least half that of the panel of ceramic tile.

The “Four Seasons Olympic Hotel” was not covered by using other decorative materials, except paint. This was probably a contributing factor in the behavior of the GFRC panel success in that project. In contrast to the process of direct attachment to metal stud linked GFRC preparation used in the Olympic Hotel, WJE recommends a sliding connection that allows Glass fiber reinforcement concrete to move. This connection will allow the panel to breathe during the transfer of gravity and wind loads to the building structure. This is not to limit the panel, or attempt to maintain thermal motion panel or moisture absorption. As a result, these panels GFRC moves and joints must be sized and designed accordingly.

Earlier this article will show how you could add fiber reinforcement concrete strength by holding together after the strength of his “first crack”. Concrete Fiberglass, however, has a tendency to “age” or the ductility loose over time. Tests conducted by WJE glass fiber reinforcement concrete show you can lose more than half its strength when subjected to aging tests, and when, of course, the testing samples with age and compare data when the sample was new. This is important when considering the use glass fiber reinforcement concrete the members who support the other members.

Glass fiber reinforcement concrete usually not considered a material that can support otherwise. For example, when a panel of the outer wall contains a window, the window should not be anchored to this type of concrete, but some members of support. Not enough to simply steel plate inside this concrete fit to include a file attachment. The only stress is GFRC return the supporting rod. Construction and design of Glass fiber reinforcement concrete has proved more complex than originally anticipated. When using composite materials, the panels can build underlines that cause panel. Moreover, the strength of the figures used in the design Glass fiber reinforcement concrete should be evaluated because of their propensity to age and become weaker.

Many of the standards in construction as Glass fiber reinforcement concrete “Precast / Prestressed Concrete Institute” (PCI) recommended the  practice for fiberglass reinforced concrete panels were written in the middle to late 1980’s and not up to date regarding the failures that have occurred in recent years. If you are planning to design a new building, it would be advisable to take on board as an expert who has WJE data beyond what is usually available through professional organizations.

It has been shown by laboratory tests that the addition of steel, glass and nylon fibers improves the strength and durability of concrete. These fibers can be used in concrete for added strength, impact resistance, and / or weight losses are desirable. GFRC has been used to cover the bare earth in the construction of prefabricated building panels and tunnels formed of lightweight concrete that would be too heavy. Nylon as well as other plastics is used to slabs on added strength, crack resistance and resistance to moisture. The fibers are also used to reinforce plaster and mortar. We will look at the new uses of these products are tested and improved. As always, caution is advised when using all the new ideas and technology. The fiber reinforced concrete can result in the outstanding architecture of lasting performance and beauty.

Tags: civil engineering, Concrete Technology, technology