How is concrete vibration compacting carried out in construction?

The vibrator must move vertically, up and down, and when operating it it should be inserted quickly and pulled out slowly (to avoid creating holes); moreover, the insertion points should be evenly distributed, at a distance of 300–400 times the radius of the vibrator rod. Multiples of 1.5 times the radius! Be sure not to miss any spots when inserting it (to avoid a lack of vibration); move it up and down to keep the vibrator in motion (50–100 mm, to compact the concrete). Each layer should overlap the one below it, with an overlap of 150 mm being ideal, ensuring good bonding. The time should be between 20 and 30 seconds, so that the concrete does not settle, no bubbles form, there is no slurry on the surface, and the surface remains flat with the best possible density. It must not touch the formwork when vibrating. Vibrate for 0.5 hours, then rest for 5 minutes; do not curl the hose. After 200 hours, lubricate the vibrator. This post was last edited by daqing01 on 2009-4-7 18:16]

General requirements for concrete pouring and vibration: 1. The free fall distance of concrete from the bucket mouth shall not exceed 2 m; if the pouring height exceeds 3 m, special measures must be taken, such as using buckets in series or chute pipes. 2. When pouring concrete, it should be carried out in segments and layers in a continuous manner. The height of each pouring layer should be determined by taking into account factors such as the concrete supply capacity, the volume to be poured at one time, the initial setting time of the concrete, the structural characteristics, and the density of the rebar; generally, it is 1.25 times the length of the area that can be reached by the vibrator. 3. When using an insert-type vibrator, it should be inserted quickly and removed slowly. The insertion points should be arranged evenly, moving from one point to another in sequence without any omissions, to ensure even compaction. The moving distance should not exceed 1.5 times the radius of vibration action (usually 30–40 cm). When vibrating the upper layer, it should be inserted 5–10 cm into the lower layer to ensure a strong bond between the two layers of concrete. During vibration, the vibrator rod must not touch the rebar or formwork. The moving distance of the surface vibrator (also known as the plate vibrator) should be such that the plate of the vibrator covers the edges of the compacted area. 4. Concrete pouring should be carried out continuously; if interruption is necessary, the duration of such interruptions should be kept as short as possible, and the next layer of concrete should be poured before the previous layer has begun to set. The maximum interval time should be determined based on the type of cement used, temperature, and the conditions under which the concrete sets; generally, if it exceeds 2 hours, it should be treated as a construction joint. (When the setting time of concrete is less than 2 hours, the initial setting time of the concrete shall be used.) 5. When pouring concrete, it is necessary to regularly check whether the formwork, rebar, pre-existing holes, embedded components, and reinforcement bars have moved, deformed, or become blocked; any issues detected must be addressed immediately, and the work must be completed properly before the poured concrete starts to set.

Depending on the method by which vibration is transmitted to the concrete, concrete vibrators can be divided into four categories: insert-type internal vibrators, attached external vibrators, plate-type surface vibrators, and vibration platforms. When using a concrete vibrator, the following points should be noted: (1) A leakage protection device should be installed on the power supply of the plug-in vibrator; the fuses used must meet the required specifications, and the grounding system must be safe and reliable. Electric motors that are not grounded or have poor grounding must never be used. (2) Operators should possess basic knowledge of safe electricity use. When operating a vibrator, it is necessary to wear rubber shoes and insulated rubber gloves. (3) When the vibrator is no longer in use, the motor should be turned off immediately. The power supply should be disconnected when moving the vibrator to ensure safety. Do not pull or drag the motor using wheel pipes or cables. (4) There should be no exposed parts on the cable; it must be placed in a dry and well-lit area. Other items are not allowed to be piled on top of the cable, vehicles are not permitted to drive over it, and the cable must not be used to hang devices such as vibrators. (5) When the vibrator is in use, the bending radius of the hose must be no less than 50 cm, and the hose must be free of cracks. (6) When starting the vibrator, it must be controlled by the operator; the vibrating rod used for starting should not be placed flat on hard surfaces such as steel plates or cement slabs, to avoid damage and potential hazards. (7) It is strictly prohibited to use a vibrator rod to pry rebar and formwork, or to use it as a hammer. During operation, ensure that the tip of the vibrator rod does not get caught between rebar or other hard objects and get damaged. (8) When using a rope to pull a flat vibrator, the pulling rope should be dry and insulated; do not kick the motor with your foot when moving or changing direction. The vibrator and the plate should be kept firmly connected; the power cord must be fixed to the plate, and the power switch should be located on the handle. (9) When several attached vibrators are used simultaneously on a single object, all vibrators must have the same frequency. (10) After use, cleaning and maintenance must be carried out properly. The vibrator should be placed in a dry area.

When vibrating concrete, attention should be paid to the choice of vibrator. For concrete with larger stone particles, a vibrator with a lower frequency and greater amplitude is more effective; conversely, a vibrator with a higher frequency and smaller amplitude is more suitable. During concrete vibration, it is important to control the duration of each vibration cycle properly; the vibration time should neither be too long nor too short, as either option is unsuitable. Vibration is generally continued until the concrete is no longer deep, with no significant bubbles rising; a thin layer of cement slurry appears on the surface of the concrete, and the surface becomes sufficiently smooth. When using a attached vibrator, its low efficiency means that approximately two minutes is usually sufficient; whereas with an inserted vibrator, which is more effective, a vibration time of 15–30 seconds is appropriate. Using a plate vibrator, it is appropriate to keep it vibrating at each location for about 25–40 seconds.

Concrete vibration 1. Selection of vibration equipment Vibration equipment is classified according to its working method into internal vibrators, surface vibrators, external vibrators, and vibration tables (Figure 3-53). http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.3/IMAGE/3-53.GIF Figure 3-53 Vibration machinery a) Internal vibrator ； b) External vibrator ； c) Surface vibrator ； d) The internal vibrator in the vibration table, also known as an inserted vibrator (Figure 3-54), has a rod-shaped hollow cylinder as its working part; an eccentric oscillator is placed inside this cylinder, and it rotates at high speed driven by an electric motor, thereby generating high-frequency, low-amplitude vibrations. It is commonly used in compacted beams, columns, walls, thick plates, and mass concrete structures. http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.3/IMAGE/3-54.GIF Figure 3-54 Electric flexible-shaft planetary internal vibrator 1—Vibration rod ； 2—Flexible shaft ； 3—Reverse prevention device ； 4—Electric motor ； 5—Electrical switch ； 6—Supports: When vibrating the concrete with an internal vibrator, it should be inserted vertically and 50–100 mm into the concrete of the lower layer that has not yet set, in order to promote bonding between the upper and lower layers. There are two types of interpoint distribution: determinant and alternating (Figure 3-55). For ordinary concrete, the spacing between insertion points should not exceed 1.5R (where R is the radius of action of the vibrator); for lightweight aggregate concrete, it should not exceed 1.0R. http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.3/IMAGE/3-55.GIF Figure 3-55 Distribution of interpolation points a) Determinant ； b) Interleaved surface vibrator, also known as a flat plate vibrator, consists of an electric motor with an eccentric mass and a flat plate (wooden or steel plate), etc. It has a limited depth of action and is mainly used for vibrating the concrete surface; it is suitable for thin horizontal elements such as floor slabs, floors, roads, and bridge decks. An external vibrator, also known as a mounted vibrator, is fixed to the outside of the formwork using bolts or clamps, and it transmits vibration to the concrete mixture through the formwork; therefore, the formwork must have sufficient stiffness. It is suitable for vibrating components with small cross-sections and dense rebar, such as thin-web beams and box girder deck beams, as well as underground sealed structures in situations where insert-type vibrators cannot be used. Its effective range can be determined through practical measurement.

On-site, plug-in vibrators are generally used for vibration; they should be inserted quickly and withdrawn slowly, ensuring that no bubbles escape.