Experimental Study On Frost Resistance Properties Of Polypropylene Fiber Concrete Subjected To High Temperature

High performance concrete due to its good workability, high strength and highdurability advantages has been widely used. High performance concrete with highdensity and low permeability extremely easy to burst when suffered with hightemperature or fire. The results show that, the addition of polypropylene fiber canimprove concrete anti high temperature and anti crack performance, addingpolypropylene fibers in concrete has become an effective means of crackingresistance and temperature difference compensation. In the concrete engineering fieldof our country, we research more about the strength and structure stiffness of concretematerials after high temperature, but it is not always arouse enough attention for theinfluence of fire to the durability of the structure.The article took polypropylene fiber concrete as the researchobject; Experimental study on frost resistance of polypropylene fiber concrete afterhigh temperature research was conducted, through the combination of macro andmicro research on polypropylene fiber concrete after freeze-thaw apparent damage,quality, strength, elastic modulus, microstructure changes. Mastering frostresistance durability gradation trend of polypropylene fiber concrete after hightemperature, revealing the freeze-thaw damage mechanism of high temperaturedamage of polypropylene fiber concrete. Aiming at provide theoretical foundation forthe further promotion and application of polypropylene fiber concrete. Details are asfollows:（1）Frost degradation regularity of polypropylene fiber concrete after hightemperatureUsing high-temperature resistance furnace for heating the concrete temperatureinto the normal temperature,200℃,400℃,600℃and800℃, followed by thecompletion of polypropylene fiber concrete after high temperature rapid freeze-thawtest, observe the polypropylene fiber concrete temperature and freeze-thaw damageapparent characteristics; analysis under high temperature and freezing corner of polypropylene fiber concrete strength, quality, and dynamic elastic modulus variationtrend with the number of freeze-thaw variation.（2）Study the mechanism of polypropylene fiber concrete damage under hightemperature and freezing thawing cyclesBy SEM scanning methods, Research the micro-scale level of polypropylenefiber concrete microscopic morphological influence under high temperature andfreeze-thaw cycles, revealing damage mechanism of high temperatures andfreeze-thaw corner cooperation with polypropylene fiber concrete.The results show that: Mixed proper amount of polypropylene fiber caneffectively improve the high temperature performance of concrete, and inhibitspalling of polypropylene fiber concrete surface layer cement mortars, Slow down themass loss rate of concrete after high temperature and freezing and thawing, reduce therate of relative dynamic elastic modulus and compressive strength, the antifreezeperformance of concrete is improved after high temperature. Larger fiber contenthave an adverse influence on concrete antifreeze performance under the action ofhigh temperature (400℃or more), but for polypropylene fiber reinforced concreteunder normal temperature and low temperature (200℃or less) to improve theperformance of concrete frost effect.