Study On Affection Of Polypropylene Fiber To Concrete Cracks In The Early Age

The application of the high strength and performance concrete is increasinglycommon along with the the development of high building and mass foundation,butthe high strength and high performance concrete generat e early age crackseasily.Now the main methods of control early age cracks have lower dosage ofcement concrete in order to reduce the hydration heat and mixed with expansionagent resistance contraction.These methods have their own limitations. Add lowdosage of polypropylene fibers in concrete can effectively improve theanti-cracking ability. This paper studied the polypropylene fiber concrete’sperformance and it’s suppression of early cracking. Paper’s work and achievementsinclude in the following aspects:1. Polypropylene fiber concrete workability and mechanical properties of theinfluence. Polypropylene fiber enhanced concrete mixtures’s cohesiveness come tovariation, its water retention become better and less slump loss. Whenpolypropylene fiber dosage is under1.5kg/m3, concrete mixtures’s slump with theincrease of dosage was reduced obviously. At low water binder ratio,polypropylene fiber can not only improve the compressive strength of the concrete,and the improved tensile/compressive strength ratio reflects the toughening effectof polypropylene fiber on concrete.2. Through the experimental of sclerosis concrete and plastic concrete foundthat the most outstanding concrete’s shrinkage occurs in the early days, in the first3days could reach80%of the total; At low water-binder ratio the reduce shrinkageeffect of polypropylene fiber is significant. When the dosage under1.0kg/m3polypropylene fiber reduce concrete’s plastic shrinkage effect is remarkable.Ifdosage is more than1.0kg/m3the reduce plastic shrinkage effect become smaller.3. The strength grade of simulation column is high.Even if the cement dos agehas been the minimum to ensure that strength, the hydration heat is stillsignificant.With0.5kg/m3of polypropylene fibers in400kg cement,140kg slagpowder and30kg of beads powder per cubic, the concrete gain highperformance.This concrete has low cement contents and make full use of industrialwaste residue of innocuity demand. Temperature monitoring display the simulationcolumns temperature reached80℃, but the concrete mixed with polypropylenefibers effectively improve the concretes anti-crack ability.simulation column had asmooth surface and free of cracks. At the same time that ultrasonic testing showedthat the internal of concrete close-grained.4. Economic benefit analysis of polypropylene fiber concrete showed thatwhen construct buildings and structures the polypropylene fiber concrete canincrease durability,reduced repair cost.