How to leave construction joints? What is the best position for the construction joint?

construction joints. It refers to the joints formed between the concrete poured first and later due to the design requirements or the need for sectional pouring in the concrete pouring process.

The construction joint is not a real "joint", it is only because the post-poured concrete exceeds the initial setting time, and there is a joint surface between the concrete poured first, which is called the construction joint.

How to retain construction joints?

The position of the construction joint should be set at the shear force of the structure.

Smaller and easy to construct parts, and should comply with the following provisions:

Horizontal joints should be left for columns, and vertical joints should be left for beams, plates, and walls.

The construction joints should be left on the top surface of the foundation, beams or crane beams.

The underside of the corbel, the top of the crane beam, and the underside of the column cap of the beamless floor slab.

For the large-section beam that is connected with the floor slab, the construction joint should be left at 20mm 30mm below the bottom surface of the slab. When there is a beam bracket under the slab, it is left in the lower part of the beam bracket.

For one-way slabs, the construction joints should be left anywhere parallel to the short side of the slab.

The floor slab with the main and secondary beams should be poured in the direction of the secondary beam, and the construction joint should be left in the range of 1 3 in the middle of the secondary beam span.

The construction joint on the wall should be left in the door opening lintel span 1 3

range, it can also be left at the junction of the vertical and horizontal walls.

The construction joints on the stairs should be left at 1 3 places of the tread board.

The construction joint of the pool wall should be left 200 above the surface of the bottom plate

mm～500

mm on the vertical wall.

Two-way stressed floor slabs, large volume of concrete.

For arches, shells, silos, equipment foundations, multi-layer rigid frames and other complex structures, the location of construction joints should be set up according to the design requirements.

I don't particularly agree with what you said downstairs, because.

Take the shear beam with a span of 10m as an example, its bending moment is the largest.

At 5m, the place where its shear force is greatest is at 1 4 near the support.

If you choose a construction joint.

Then choose 2 10

And. 3 10 instead of 1 3, you know!

In this way, it is possible to avoid both the places where the bending moment is the greatest and the places where the shear force is the largest, including the above.

The problem of waterproofing of construction joints is another problem.

The waterproof problem of the construction joint, that is, the waterproof steel plate or waterstop, is also a secondary grouting connection problem, first of all, the reserved position of the construction joint and the stubble, watering water, the wind is clean, the concrete slurry is brushed at the hair, and the rear is poured.

The principle that horizontal joints must be ensured for construction joint retention, and vertical joints must be left for the gaps between beams, floor slabs and walls; The position of the seam is usually on the top surface of the foundation, below the beam, above the beam of the crane room and below the two-column cap, and the width of the seam is usually about 20-30 cm.

Column: It should be left on the top surface of the foundation, floor slab, beam, beam corbel, beam and crane beam, and below the column cap of the beamless floor slab; The large-section beam (more than 1m high) that is connected with the plate as a whole is left at 20 - 30mm below the bottom surface of the plate, and when there is a beam support under the plate, it is left at the lower part of the beam support; It can be left in the middle of the lintel span 113 of the door opening, and can also be left at the junction of the vertical and horizontal walls.

Construction requirements for concrete construction joints for building construction:

1. In order to ensure the quality of concrete and shorten the pouring time, it is best to use concrete transported by pump when constructing the basic project and the main structure.

2. Before pouring, the wooden mold should be fully watered with water, and the surface should be cleaned up, and there should be no dust and other impurities on the surface.

3. When pouring concrete, the method of layered pouring should be used to complete the method step by step, and the pouring method of the concrete that naturally flows into the slope will be more suitable for the pumping method, which can avoid the disassembly and extension of the pipeline in the process of transporting the concrete, so as to ensure the quality of the concrete.

Principle: Stay in the part of the structure that is less stressed and easy to construct.

Specific parts: 1) Column construction joints: the top surface of the foundation, under the beam or corbel.

2) The large cross-section beam connected with the plate as a whole is left 20-30mm under the bottom of the plate.

3) the floor slab with the main and secondary beams, the concrete is poured in the direction of the secondary beam, and the construction joint of the side wood is left in the middle of the secondary beam span within the range of 1 3.

4) Construction joints of other complex parts shall be retained according to the design requirements.

5) The foundation of the equipment bearing the power effect, the basement with impermeability requirements, should not leave construction joints.

Treatment of concrete construction joints.

1. First of all, it is necessary to determine the reserved position of the construction joint, under normal circumstances, the wall can be reserved for vertical construction joints, and the roof and floor can not be reserved for construction joints, etc. The wall construction joints can be reserved to smash the horizontal and longitudinal wall junctions and so on.

2. When the concrete is initially set, the surface needs to be chiseled at the position where the construction joint is set, and the excavation depth is about 20 to 30 mm, and the concrete coarse aggregate needs to be exposed.

3. After the concrete is chiseled, it needs to be rinsed with a water gun and other tools before trembling, and the plain cement slurry should be painted.

4. Pour concrete again according to the requirements.