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Concrete is generally considered to be a fire-resistant construction substance; however, it cannot withstand damage in extreme temperature. When subjected to fires with high temperatures, concrete may experience spalling, an explosive bursting of the surface material exposing reinforcement and causing the structure to collapse. Polypropylene fiber has come in as a very easy, but effective solution to this problem. Hebei Runhuabang New Material Technology Co., Ltd. is a company that deals with crushing, processing and distribution of non-metallic minerals such as polypropylene fiber. With the complete exploitation of local geographical and resource advantage, we provide polypropylene fiber which greatly enhances fire performance of the concrete structures.
Understanding Explosive Spalling in Concrete Fires
Explosive spalling is a phenomenon which takes place when a fire is subjecting concrete to heat at a very high rate. The high temperature makes the free water and chemically bound water of the concrete matrix evaporate and form steam. Low permeability of concrete does not allow the steam to escape rapidly. Pressure is accumulated in the concrete till it overcomes tensile strength of the material leading to a violent breakout. This spalling exposes steel reinforcement bars to the fire and structural integrity is easily destroyed. The spalling of the tunnel fire, pillars of the buildings and the high rise buildings can transform a fire that can be controlled to a catastrophe within a few minutes. Hebei Runhuabang New Material Technology Co., Ltd. understands that not only the performance of the material, but also the saving of lives and property is the focus of spalling prevention.
How Polypropylene Fiber Prevents Spalling
The root cause of spalling is alleviated by polypropylene fiber that forms an escape net to the steam pressure. Polypropylene fibers are incorporated into fresh concrete whereby they are evenly dispersed in the matrix. Polypropylene fibers melt at a relatively low temperature of about 160 to 170 degrees Celsius as the concrete is heated by fire. This melting leaves behind small capillary channels in the concrete. These avenues serve as an outlet of pressure, so that steam is released without accumulating any destructive internal pressure. The outcome is that concrete does not melt and thus it still offers much-needed structural support even in situations where it is exposed to extreme fire. Contrary to the steel fibers which do not move, the polypropylene fibers fade away at the time when they are most required. To produce uniform pressure relief throughout the whole concrete element, Hebei Runhuabang New Material Technology Co., Ltd. manufactures polypropylene fiber with uniform melting properties.
Optimal Dosage and Fiber Properties for Fire Resistance
Polypropylene fibers are not as fire resistant. The most important parameters are fiber length, diameter and dosage rate. Micro fibers of less than 50 microns in diameter and 6 to 20 millimeters in length are generally the most effective to stop spalling. The typical recommended dosage is 1 to 3 kilograms per cubic meters of concrete. Increased doses will not always be more protective, and will influence workability. The fibers should also evenly spread out in the mix since any lumps will leave loopholes in the mix that lack the pressure relief network it requires. Hebei Runhuabang New Material Technology Co., Ltd. has polypropylene fiber with a specific geometry and surface treatment to enhance uniform dispersion in applications in fire resistance.
Testing Standards for Fire-Resistant Concrete
A number of international testing standards have been established to test concrete spalling behavior when there is fire. The Hydrocarbon Curve test, RWS (Netherlands) test and RABT (Germany) simulate real fire conditions including the rapid increase in temperature. Concrete samples embedded with polypropylene fiber were heated under these heating regimes and spalling and residual strength were measured. Many tunnel linings and high-rise building cores and critical infrastructure were mandated to be able to perform under this heating and spalling environment. Hebei Runhuabang New Material Technology Co., Ltd. assists the customers by supplying polypropylene fiber, which has been tested to assist the concrete to satisfy these challenging needs. The quality control measures under strict control of our organization make sure that all the batches have the same melting behavior and dispersion properties.
Combining Polypropylene Fiber with Other Fire Protection Measures
Polypropylene fiber can be most useful as a component of an overall fire protection plan. It does not eliminate the necessity of a sufficient concrete cover over reinforcement, mix design and structural fireproofing in extreme situations. But polypropylene fiber offers an added level of protection which is passive and does not require maintenance or monitoring. The fiber when installed is always there and prepared to become active in case of an event of fire. Polypropylene fiber is commonly designated by many engineers where tunnels, parking garages, high-rise buildings, and any other concrete structure where fire safety is paramount. Hebei Runhuabang New Material Technology Co., Ltd. collaborates with concrete manufacturers and construction companies to incorporate polypropylene fiber into their normal mix formula to use in the fire resistant construction.
Conclusion
Polypropylene fiber is a special and unsubstitutable material in improving fire resistance properties of concrete. These small fibers allow concrete to hold its own shape through explosive spalling by melting under heat to make pressure relief channels and allow concrete to retain its shape during fire. Good choice of fiber geometry, dosage and dispersion quality is a prerequisite to a reliable performance. Hebei Runhuabang New Material Technology Co., Ltd. integrates the use of modern production technologies and a highly-complicated multi-tiered management system to provide polypropylene fiber to address the challenging needs of fire-resistant concrete. We invite both local and foreign entrepreneurs to speak about the cooperation and further development