Comparative Test of Vacuum Suction Process Xiao Fei\Zhang Taiping2 Chen Shaozhen3(1. Guangzhu West Line Expressway Co., Ltd., Shunde, Guangdong52831* 2. Guangdong Hualu Transportation Technology Co., Ltd., Guangzhou 510420; 3. China Railway XIV The four companies of the Bureau Group, Linyi 276003, China) has been widely used in the construction of beams. Combined with the construction practice of the Guangzhu West Line Expressway, a comparative experiment was conducted on the vacuum suction method and the general pressure method to verify the superiority of the vacuum suction process.
1 Overview The vacuum suction method is a new technique in the construction of post-tensioned prestressed concrete structures and has been gradually applied in the construction of large-scale bridges.
When the cement slurry has a small water-cement ratio and a high consistency, the grouting can still be completed smoothly.
In this paper, combined with the construction practice of the Guangzhu West Line Expressway, a comparative test of vacuum suction grouting and ordinary grouting is introduced.
2 Construction Process 2.1 Vacuum Suction Method The main supporting equipment UBL3 screw grouting pump; SZ-2 water ring vacuum pump; OVM.ZKGJ vacuum grouting assembly; X * 40A jet cleaning machine; mortar mixer and so on.
2.2 Construction Process (1) After the prestressed tensioning is completed, remove the exposed steel strand (note that the exposed strand length is >30mm) and seal the anchor. Sealing anchors can be horizontally arranged in the following two types. The vertical prestressed pipes (50 mm round bellows) are arranged vertically. The two ends of the transverse steel strand are tensioned, and the middle part is positioned with steel bars. The upper end of the vertical rolling steel rebar is fixed by brackets and positioning steel bars. One end of the pipeline is equipped with a grouting pipe and the other end is equipped with a row (suction) pipe. Slurry diagram of horizontal pre-stressed pipe grouting for both grouting pipe and exhaust pipe (unit: cm) Schematic diagram of vertical pre-stressed pipe grouting (unit: cm) 3.2.2 Vertical mold pouring ç ¼ Installation of template around the installed corrugated pipe, pouringç ¼ ç ¼ æ£ å¹¶ 并, and vibrate.
First, the vacuum-assisted suction grouting method was used to grouting half of each type of pipe, and then the remaining pipe was grouted using the ordinary grouting method. The grout code M50, water-cement ratio 0.33, and consistency 17s used in this test were grouted for 7 days and the prestressed pipes were taken out. The cutting machine is used to cut along the cross section and peel the bellows to check the fullness, compactness and strength of the respective cement slurry.
3.3 Test results 3.3.1 Comparison of the appearance after peeling off the bellows After the peeling of the bellows, see the appearance of the vacuum suction paste. The appearance after peeling the bellows can be seen from the comparison, the slurry of the vacuum suction grouting can be good The ground is full of corrugated pipes, and the appearance is obviously denser than that of ordinary grouting. There is almost no looseness caused by bleeding. On the other hand, there are more blisters on the surface of ordinary sizing pastes, and the phenomenon of non-compactness is caused by bleeding.
3.3.2 Strength comparison of slurry After removing the slurry in the iron box at the end of the pipe, the compressive strength test is conducted after the standard curing for 28 days (the test data is shown in Table 1). Table 1 Compressive strength test Piping type No. Vacuum grouting resistance Compression strength / MPa No. Ordinary grouting compressive strength / MPa Transverse vertical average 3.3.3 Test conclusion From the peeling of the bellows after the appearance can be seen, vacuum assisted suction grouting process slurry fullness and stability Higher than ordinary grouting process.
The vacuum-assisted suction grouting process slurry generally has higher compressive strength than conventional grouting. Due to the need to take care of ordinary grouting, the consistency of the slurry and the water-cement ratio of the slurry are relatively large. When vacuum grouting is used in practical applications, the consistency and water-cement ratio of the slurry can be smaller, so that the compressive strength of the slurry will be higher.
4 Conclusion The vacuum suction process is more complex than ordinary grouting, and it needs to be equipped with special equipment, but it has obvious improvement on the density and strength of the slurry, and can significantly improve the construction quality of grouting. Especially for vertical prestressed holes and prestressed long bundles and certain shaped key positions (such as curved U-shaped Yang Zhengyu. Vacuum suction method | J. Highway, 1998 (10) 15~17. I3 Zhou Minghua. Vacuum assisted pressure Slurry technology in Nanjing Yangtze River Bridge
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