Application of Microsilica Fume in Bridge Concrete

The ordinary concrete bridge deck pavement is brittle due to its thinner design thickness (80, 150mm). In the process of driving. Under the action of bending and tensile load, impact fatigue load, temperature and humidity deformation and other factors, it is easy to cause cracking, damage, and waterproof failure of ordinary concrete bridge deck pavement. Polypropylene fiber can enhance the fatigue resistance, impact resistance, wear resistance, crack resistance and crack resistance of concrete. As well as improving toughness and impermeability, it can effectively prevent the expansion of internal and surface cracks in concrete or delay the appearance of cracks. It is an ideal material for bridge deck paving. Therefore, polypropylene fiber concrete is used in the design of the bridge deck concrete material. At the same time add micro silicon powder. To compensate for the shrinkage, extend the bridge deck joint spacing. Further improve the crack resistance and seepage resistance of concrete.

1. Experiment

1.1. Raw materials

The main raw materials are: ①The cement adopts 42.5 ordinary Portland cement produced by Qinhuangdao Asano Cement Plant. The strength is: 3d flexural resistance 5.9MPa, compression resistance 28.8MPa; 28d flexural resistance 8.8MPa, compression resistance 54.8MPa. ②The admixture adopts Shenyang Fulang FL superplasticizer (powder). ③ Coarse aggregate is long gemstone limestone crushed stone with a continuous gradation of 5.20mm. ④ The fine aggregate is coarse river sand in Xiaogudong River, with a fineness modulus of 2.88. ⑤Expansion agent adopts micro-silica powder produced by Tianxian Special Material Research Institute of Ningxia Agricultural District. ⑥The fiber adopts polypropylene mesh fiber produced by Hongruilai (Beijing) Technology Co., Ltd., and its main physical and mechanical performance parameters are: density O. 919/cm3, melting point 165°C, ignition point 590%, no water absorption, no toxicity, no aerial tensile strength 560～770MPa. The tensile limit is 15%, the elastic modulus is 3500MPa, and the fiber length is 19mm.

1.2. Concrete mix ratio for experiment

   Concrete design requirements: the slump of the concrete mixture is about 50ram, and the cohesion and water retention meet the construction requirements; the concrete strength grade is C50. The compounding strength is 64.1MPa, and the impermeability grade is above W22. According to the design requirements, after a large number of experiments, the two mixture ratios listed in Table 1 were determined for further comparison experiments.

1.3. Experimental methods

The concrete compressive strength test uses cubic concrete specimens with a size of 150mmx150mmx150mm. According to JTJ053-94 highway engineering cement concrete test regulations.

The concrete impermeable strength test adopts a circular table concrete specimen with a top diameter of 175mm, a bottom diameter of 185mm, and a height of 150mm. The test was carried out in accordance with literature [11]. The concrete abrasion strength test adopts a concrete specimen with a size of 150mmx150mmx150mm, which is carried out in accordance with the document "11."

The concrete impact strength test adopts a diameter of 150mm. The circular pie-shaped concrete specimen with a thickness of 64 ram is carried out in accordance with the "drop weight method" recommended by the ACl544 committee, and f2]. The concrete flexural strength test adopts a small beam concrete specimen with a size of 150mmx150mm×550mm, according to the document "11 in Italy It was carried out on the 50-C0066/S01 universal pressure testing machine produced by Controis.

2. Experimental results and analysis

The results of various performance tests of concrete are shown in Table 2. From the slump of the concrete mixture. No. 2 mix ratio is compared with No. 1 mix ratio. After adding 20kg of microsilica fume and 0.9k of polypropylene fiber per cubic meter of concrete. The reason for the formation of ettringite due to the "support" function of polypropylene fiber and the rapid hydration reaction of microsilica powder. The slump of the concrete mixture is greatly reduced (about 100mm). From the results of concrete strength and impermeability. Both mixing ratios meet the design requirements of C50 compounding strength and W22 impermeability grade. In terms of flexural strength, impact toughness and abrasion resistance and other mechanical properties. No. 2 mix ratio is better.

The main function of adding expansive agent and polypropylene fiber to concrete is: an appropriate amount of microsilica can compensate for the shrinkage of concrete and improve the compactness of concrete, thereby preventing cracking and improving concrete impermeability. Every unexpected problem may cause the project's implementation status to deviate from the established goal, so schedule, cost, and quality control are the core of modern engineering, especially highway engineering construction management. Since the success of a project first depends on whether it meets the functional value stipulated in the contract, this article puts the quality goal at the top of the three major goals in the highway construction project. At the same time, project management is not to pursue the highest quality and the most perfect project as the goal, but to make the quality of the project meet the contract requirements, ensure that it is qualified and leave a proper margin.