How should slope concrete slabs be handled during pouring?
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During the pouring of concrete slabs on slopes, vibration can cause the concrete to slide; otherwise, the concrete won’t be compacted properly. What should be done in such cases?
Delayed vibration is possible, as is vibration outside the mold.
External vibrators: Also known as attached vibrators, these are typically fixed to formwork using bolts or clamps. The vibration energy from the vibrator is transmitted to the concrete through the formwork, thereby compacting the concrete. The vibration effect of external vibrators does not extend far, so they are used in structures where the rebar is densely packed and the thickness is small, situations where insert-type vibrators are not suitable. When using external vibrators, their vibration radius is around 250 mm. When the size of the structural element is large, vibrators need to be installed on both sides of the element to carry out vibration simultaneously. Generally, the vibrators are turned on after the concrete has been poured into the formwork. The pouring height of the concrete should be higher than the location where the vibrators are installed. When the rebar is dense or the cross-section of the element is deep and narrow, it is also possible to vibrate while pouring. External vibrators must be firmly connected to the formwork, and the spacing between them should be determined through testing; generally, one vibrator is placed every 1–1.5 meters. The vibration time should be adjusted until no more bubbles appear in the concrete and its surface becomes level.
Surface vibrators: When in use, surface vibrators need to vibrate continuously at each location for a certain period of time, usually 25–40 seconds, until slurry appears on the surface of the concrete and it stops sinking. When moving the vibrator, it should follow a specific path, with overlapping areas of 30–50 mm in all directions to prevent missed areas from being vibrated. The effective vibration depth of surface vibrators is approximately 200 mm in unreinforced or single-reinforced slabs, and about 120 mm in double-reinforced slabs. When vibrating an inclined concrete surface, the vibrator should move gradually from lower to higher areas to ensure proper compaction of the concrete.
Surface vibrators: When in use, surface vibrators need to vibrate continuously at each location for a certain period of time, usually 25–40 seconds, until slurry appears on the surface of the concrete and it stops sinking. When moving the vibrator, it should follow a specific path, with overlapping areas of 30–50 mm in all directions to prevent missed areas from being vibrated. The effective vibration depth of surface vibrators is approximately 200 mm in unreinforced or single-reinforced slabs, and about 120 mm in double-reinforced slabs. When vibrating an inclined concrete surface, the vibrator should move gradually from lower to higher areas to ensure proper compaction of the concrete.
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Methods for pouring concrete on slopes: The water-cement ratio should not be too high; it is necessary to control the fluidity of the concrete. Another important factor is the formwork, which must have an appropriate slope on its top surface. Thirdly, there is the matter of treating the concrete’s surface – using rollers is a good method. This post was last edited by microman88 on 2008-6-7 at 12:02