Papers by Keyword: Polypropylene (PP) Fiber

Abstract: Based on the evaluation of fibrous concrete materials and the experiments of freezing-thawing resistance home and abroad, the present experiment takes relative dynamic modulus of elasticity and rate of mass reduction as an analytical index to conduct a comparative study on the effects of the mixing of four kinds of polypropylene fiber on the cement concrete freezing resistance. The results show that different kinds of polypropylene fiber have different influences on cement concrete freezing resistance. And some polypropylene can improve it while others may make it decreased.

Abstract: Pumice, polypropylene fiber, steel fiber and fly ash were used to compound fiber reinforced lightweight aggregate concrete (LWAC). The effect of fibers on frost resistance durability of LWAC is studied, which including freezing-thawing in 5% Na₂SO₄ solution and in water. The test results show that the strength loss of LWAC is reduced with the increase in fiber fraction, but the impact of mass loss is not obvious by mixing fiber. LWAC freezing-thawing deterioration is even more serious in salt solution than in water. SEM photo show that polypropylene fiber has more stronger cementing bond with paste than steel fiber. the mass loss and strength loss are decreased significantly. By introduction silica fume can improve Interfacial Transition Zone（ITZ）and the frost resistance of fibers reinforcement LWAC dramatically.

Abstract: In order to study the influence of modified polypropylene (PP) fiber on the physical and mechanical properties of curing sludge, the same amount of cement and different content of polypropylene fiber were mixed into the sludge. Unconfined compressive strength tests, water content tests and shear strength tests were carried out on different specimens with different curing time. The results show that the sludge curing effect is markedly improved by the addition of the polypropylene fiber. As to the curing sludge with the same curing time, when the content of the polypropylene fiber increases, the unconfined compressive strength and the cohesive strength greatly increase, and the internal frictional angle decreases.

Abstract: Impact property of concrete containing nano-particles (TiO₂ or SiO₂) for pavement is experimentally studied and compared with that of plain concrete, concrete containing PP fibers and concrete containing both nano-TiO₂ and PP fibers. The test results indicate that the impact property of concrete is enhanced when the amount of nano-particles is smaller. However, the impact property of concrete is reduced when the amount of nano-particles is larger. The impact property of concrete containing PP fibers is improved, and the impact property of concrete containing both nano-TiO₂ and PP fibers is decreased. There is a significant linear relationship between impact property and flexural strength of pavement concrete.

Abstract: With numerical modeling in meso level, impaction of incorporating polypropylene fibers with two different geometry dimensions on flexural strength and toughness of hybrid fiber concrete has been studied in this paper. Mechanism of such hybrid fiber reinforcement has also been analyzed. The results show that hybrid of fibers with different geometric dimensions would bring about synergy, thus fiber enhancement effect could be demonstrated. Furthermore, the closer the incorporation ratio of these two kinds fibers are to each other, the more evident the enhancement will be produced. The most optimized hybrid ratio is in between 2:1 and 1:1.

Abstract: Early shrinkage of concrete includes plastic shrinkage before the final setting, drying shrinkage during hardening process and autogenous shrinkage. Concrete drying shrinkage which is caused by evaporation is a major factor for the concrete volume change. By ring constrained test and free shrinkage CONCEN test, this paper studies the impact of polypropylene fibers on the shrinkage properties of concrete at the early age. The test shows that the polypropylene fibers can significantly reduce the early shrinkage of concrete, the best content of C30 concrete should be 0.9kg/m³.

Abstract: The authors experimentally studied the size effect of axial compressive properties of concrete cube and slenderness ratio of 2:1 prism with cross-section side length of 100mm to 800mm in this paper. Commercial concrete was used for test specimens. Specimens were cast and cured outdoors. To highlight the size factors, accumulation of sand on the end surface of the specimen was used to eliminate the end cyclo-hoop effect. The test results show that, in the case of eliminating the end restraint, failure modes of the prism and the cube are the same. There isn’t determined relationship between the cubic compressive strength and cylinder axial compressive strength of concrete, in the case of the specimen slenderness ratio not more than 2 to 1. However, the decline trend of cylinder axial compressive strength with size is slightly greater than the cubic strength. Fly ash concrete, ordinary concrete without fly ash and fiber reinforced fly ash concrete show different size effects. Size effect for concrete with 40% fly ash replacement of cement significantly reduced. The experimental results also show that, strength, elastic modulus and ultimate strain of concrete are all size-dependent. But there are different size effect trends between strength and deformation properties. Ultimate strain of concrete decreases as size increases, and more attention should be taken to this point.

Abstract: As the composite of materials, fibers compositing, which can give full play to synergism of each fiber’s reinforcement, will become an inevitable trend. Calcium carbonate whisker is a kind of green environment-friendly fibrous powder filler with high strength, high modulus and excellent thermal stability, which has been proven that it has obviously toughening and reinforcing effects on cement-based materials. In this paper, CaCO3 whiskers composite with polypropylene fiber were added into concrete as reinforcement. Effect of different content of whiskers and fibers on the mechanical properties of concrete was investigated. The results shows that the composite of CaCO3 whisker and polypropylene fiber (PP) has better toughening and reinforcing effects than that of single filler. The strength of whiskers/PPF-reinforced concrete can be obviously improved compared with that of pure concrete, whisker concrete and PPF concrete. These increases could be correlated to the synergism of PPF and CaCO3 whisker, which are different in size, aspect ratio, elastic modulus, and reinforcing role in concrete.

Abstract: As a kind of monocrystal reinforcing material, CaCO3 whisker has good characteristics of high strength, high module and high thermal stability. This research aims to optimize the microscopic structure of fiber cement mortar by adding CaCO3 whiskers and improve the macroscopic mechanical properties. The results showed that CaCO3 whiskers increased the flexural and compressive strength of cement mortar at 3d age by 29.5% and 19.8% at maximum respectively, which fell to 7.2% and 13.0% at 28d age; when CaCO3 whiskers content was 10% and polypropylene fibers content was 0.05%, compared with the pure cement mortar, the flexural and compressive strength were increased by 32.4% and 29.4% at 3d age and 7.6% and 4.6% at 28d age respectively; when the fiber length was 9mm, the composite effect of whiskers and fibers was more ideal; through the SEM analysis, the reinforcing mechanisms of CaCO3 whiskers and polypropylene fibers in cement mortar were discussed.

Abstract: This paper presents the experimental investigation carried out to study the behavior of polypropylene fiber reinforced concrete (PPFRC) under compression and flexure. Crimped polypropylene fibers and twisted polypropylene fiber were used with 0.0%, 0.2%, 0.4% and 0.6% volume fractions. The influence of the volume fraction of each shape of polypropylene fiber on the compressive strength and flexural strength is presented. Empirical equations to predict the effect of polypropylene fiber on compressive and flexural strength of concrete were proposed using linear regression analysis. An increase of 27% in flexural strength was obtained when 0.6% volume fraction of twisted polypropylene fiber was added. It was also found that the contribution of fiber in flexural strength is more effective when twisted fibers were used. The compressive strength was found to be less affected by polypropylene fiber addition.