Effect of Polypropylene Fiber on Flexural Strength and Impact Resistance of High Performance Concrete

Abstract: In this paper, the flexural strength, brittleness and impact resistance of high-performance concrete with different polypropylene fibers were studied. The flexural strength, brittleness, impact resistance and impact of high-performance concrete with fiber were discussed. The performance of cement-based fiber composites is reduced in brittleness and high in impact resistance. The test proves that the fiber blending in high-performance concrete can significantly reduce the brittleness of concrete and improve the flexural strength and impact resistance of concrete.

I. Introduction High-performance concrete not only has good strength properties, but also has excellent durability and suitable working performance to meet the construction needs of large-scale concrete projects at present and in the future. After extensive experimental research, we apply silicon. Ash and fly ash are used to formulate high-performance concrete. This concrete not only has high strength, but also has good workability, and the hardened concrete has excellent freeze-thaw resistance, penetration resistance and erosion resistance. However, brittleness and poor impact resistance are an important factor affecting the practical application of high performance concrete. Some studies have suggested that self-shrinkage cracking, wet expansion cracking and brittleness are important issues for high-performance concrete. This article will use polypropylene fiber to improve the brittleness and impact resistance of high performance concrete.

Second, the experimental method
1, raw materials
1. 1 Cement: 325# Pu-Si cement used by Sancha Bureau Xiaoyetian Cement Co., Ltd.
1. 2Incorporating all materials: The test uses the silica fume provided by the chemical addition agent factory, and the water reducing agent adopts the SN-II superplasticizer produced by the Wuyi agent factory.
1. 3 aggregate: 5-8mm quartz gravel is used for coarse aggregate, and standard quartz sand is used for fine aggregate.
1. 4 Polypropylene fiber: The new modified polypropylene fiber is used, and its physical properties are listed in Table 1.
Table 1 Physical properties of modified polymer fibers Water absorption No specific gravity 0.91
Fiber length (mm) 12-19
Melting point (°C) 160-170
Boiling point (°C) 590
Low conductivity, low thermal conductivity, high acid and alkali resistance, high compressive strength (Mpa) 560-770
Tensile strength (Mpa) 350
2. Test method Flexural and compressive strength test GB177-85 cement mortar strength test method. The water consumption is the standard consistency water consumption, and the standard consistency and setting time are all in accordance with GB134-77 cement standard consistency water consumption.
The wear-resistant test piece has a size of 15 cm × 15 cm × 7 cm. The wear test is carried out by GLM-200 steel wheel concrete wear tester. The test method is carried out according to GB/T12988-91 "Test method for wear resistance of inorganic floor materials". The abrasion resistance is represented by the anti-length L, the unit is mm, and the abrasion resistance test is 5 pieces per group, and the average value of the test is taken ten times.
The impact resistance size is 15 cm × 15 cm × 5 cm, and a total of 5 test pieces per group. The steel ball of 8 kg weight was freely dropped from a height of 25 cm. When the crack width of the test piece was greater than 3 mm, the number of impacts was recorded, and the test result took the average of the three data in the middle.

Third, the results and discussion
1. Effect of polypropylene fiber on brittleness of high performance concrete The strength and durability of high performance concrete are mainly affected by water-cement ratio and mineral polymer. When the water-cement ratio (w/c) is constant, the amount of mineral admixture will directly affect To various physical and mechanical properties of high performance concrete. Polypropylene-resistant fibers can improve the mechanical properties of high performance concrete. Table 2 shows the effect of high-performance concrete with fiber content (0, 0.1%, 0.15%) on concrete strength. Table 2 High-performance cement-based polypropylene fiber composite strength test piece silica fume content (%) fiber content (Kg Compressive strength flexural strength R3 R28 R3 R28
1 0 0 36.9 63.4 5.31 8.53
2 5 0 43.0 73.9 5.45 9.05
3 10 0 47.5 82.4 6.06 9.82
4 0 0.1 29.3 60.8 5.36 8.59
5 5 0.1 29.9 61.3 5.33 8.72
6 10 0.1 32.4 66.9 5.45 9.25
7 0 0.15 38.4 68.5 6.08 9.35
8 5 0.15 39.9 77.7 6.28 11.02
9 10 0.15 47.4 82.3 7.55 12.52

The experimental results show that when the water-cement ratio (W/C) is constant, the mechanical properties of the concrete increase with the increase of the amount of the concrete, and at the same time, the durability of the concrete is also greatly improved. However, the degree of influence of silica fume content on concrete compression and flexural strength is different. It can be seen from the data in the table that when the silica fume is increased by more than 30% from 0-10% concrete, and the flexural strength is only increased by about 15%, the brittleness of the high-performance mixing is significantly improved.

The test results show that the blended polypropylene fiber can improve the brittleness of high performance concrete. When the polypropylene fiber content is from (0-15%) high-performance concrete, the compressive strength hardly changes, and the flexural strength increases by more than 27%. The brittleness of the concrete is reduced from 8.39 to 6.5%. Therefore, the performance of high-performance concrete can greatly reduce the brittleness of concrete under the premise of ensuring the compressive strength and durability.

2. Effect of polypropylene fiber mesh on impact resistance of high performance concrete Polypropylene fiber has a great influence on the impact resistance of high performance concrete. It can be seen from the experimental data that the addition of fiber in high-performance concrete can significantly improve the impact resistance of concrete. The impact resistance of high-performance concrete increases with the increase of fiber content, and the impact resistance of concrete is proportional to the fiber content. In addition, the impact resistance of fiber high performance concrete is one of the main technical approaches for compounding high performance cement-based composites with concrete substrates.

3. Mechanism of polypropylene fiber for improving the folding and impact resistance of high-performance concrete In summary, the incorporation of polypropylene fiber into high-performance concrete can significantly improve the flexural strength of concrete and

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