Fabrication of Polypropylene Fiber concrete- By adopting various techniques Polypropylene Fibers are added to the concrete in several different forms. The fibers can be incorporated into concrete as a continuous network of fibrillated film, as a short discrete chopped fibers, or as a woven mesh. The method of fabrication is decided by the form of the available fiber. Every method has its own limitation. The method is chosen based upon the percentage volume of the fiber that can be obtained during fabrication using a said technique. So also, by implementing a ' spray suction De-watering technique' concrete panels reinforced with chopped mono-filament polypropylene fiber is produced. 6% fiber volume content can be achieved by using the spray suction De-watering technique. Chopped fibrillated polypropylene film and composite incorporating chopped mono filament are produced.
Fibers |
Positives |
Negatives |
Fiber Reinforcement |
During mixing, can be added to concrete |
As the primary reinforcement, it is rarely used. |
Fiber Reinforced Polymer |
With regard to corrosion, it has a good durability. It can also be used in thin concrete members. |
It is greatly affected by degradation mechanism. e.g. salts and UV lights, rare technique which can lead to high cost
|
Conventional Reinforcement Steel |
With regards to design codes and guidelines it is easy to implement structural integrity which is widely used. Thermal expansion is almost equal to that of concrete. Not Expensive |
It is not suitable for very thin structures. For using such thin structures, specific concrete is needed. |
Limitations and Solutions-
When considered as a building material, natural fibers possesses some dis-advantages such as weakening due to alkaline environment of cement, cementious matrices, poor interface between natural fibers and polymeric, less durability due to high moisture and chemical absorption, variability in properties, generation of concrete cracks due to swelling and volume changes etc. Various modifications based on the fiber has been designed and reported in order to overcome the drawbacks of this natural fibers. some of the solutions include treatment with saline, alkali and numerous other water repelling agents. Recent reports on plasma modification of natural fibers are also there. By using this technique of plasma modification, we also reduce the water absorption of natural fibers either by removing lignin and hemicellulose or by imparting hydrophobicity. To improve the interface between natural fibers and various interfaces, various fiber modifications or techniques were also found. When designing load carrying concrete structures this study shows that conventional steel reinforcement cannot be easily set aside. Also, no other reinforcement types can provide such integrity in all applications. As the conventional reinforcement is well known and regulated standard worldwide, it increases the applicability of new construction. We also have an alternative reinforcement technique called as steel fiber reinforcement technique which can also be included to contribute an additional structural integrity in terms of ductility. As there were number of such alternatives being invented for reinforcement, it was all decided that the more better solution/technique should be tried to introduce for the continuous development of reinforcement solution for various applications such as load bearing, and tailor made concrete structures. This can be easily done by utilizing both the steel fiber reinforcement and conventional reinforcement separately or in combination. Of all these reinforcement techniques, textile reinforcement might be interesting. However, there are some limitations that are set by the exibility of the textile. It may simply be impossible for robots to handle such material.
Advantages of Composites-
Composite materials can achieve excellent stiffness to weight ratios and strength to weight ratios. For a given weight, a high performance can lead to fuel saving. This is expressed as strength divided by density and stiffness (modulus) divided by density. So it can also be called as either 'specific' strength and 'specific' modulus characteristics.
Ply buildup and laminate patterns in a part can be tailored to give the required mechanical properties in various directions.
For drag reduction it is easy to achieve smooth aerodynamic profiles. In one manufacturing operation complex double curvature parts with a smooth surface finish can be made.
Cost of production is reduced. By using a wide range of processes various composites may be made.
However, Composites offer excellent resistance to chemical attack, corrosion and outdoor weathering.But, some chemicals even harm or damage the composites (e.g. Paint, Stripper). Hence, to overcome this situation, various new types of paints and strippers are being developed. so also, to some solvents several thermoplastics are also not very resistant.
Dis-advantages of composites-
Composites are more brittle than wrought metal and hence they get damaged more easily. Cast metal also tend to be brittle.
Repairing emerges new problems for the following reasons-
Most Materials requires refrigerated transport for storage. But the storage has limited shelf lives.
Special equipment's are required for hot usage in most cases.
It may be hot or cold type of cutting, it takes time. When the last rivet has been installed the job is not yet finished.
Repairing at original temperature requires too long time and pressure.
As all resin matrices and some fibers absorb moisture, the composites must be dried before repair.