What are the treatment methods of construction joints and the treatment methods of construction join

The treatment method of construction joints is as follows:

1. If the construction joints in the horizontal position are treated, the garbage and dirt in the construction joints should be cleaned up first, and the old concrete needs to be chiseled, and it is necessary to use clean water to moisten it. Secondly, the position of the rebar should be adjusted well, and it also needs to be cleaned. Then use cement mortar of the same strength grade to pour at the construction joint in the horizontal position, and the pouring thickness can be kept between 10 mm and 15 mm.

2. If the post-pouring joint is caused by structural design reasons, expansion concrete can be used to pour the construction joint position. If the construction joints between the cast-in-place concrete and the precast beams and columns are treated, then some cement mortar should be dried in the horizontal joints, and some expanded concrete should be poured in the vertical joints.

If the construction exhaustion time does not exceed the initial setting time of the cement used (determined according to the test, when there is no test data, it should not exceed 2 hours), when the concrete is continued to be poured, the new concrete can be poured evenly, cover the first poured concrete, and then use a vibrating tool to pass through the new concrete to reach the poured concrete layer 5 10cm, the new and old concrete are compacted together, and form a whole.

If the construction exhaustion time exceeds the initial setting time of the cement used, the strength of the poured concrete must not be less than when the construction can be continued.

The construction joints of beams and columns should be perpendicular to the axis of beams and columns, and the construction joints of slabs and walls should be perpendicular to the slabs and walls, and should not be made into slope shapes.

Problem handling. 1. Chiseling method on the surface of the vertical seam.

After the final setting of concrete, the baffle is removed, the surface is chiseled with an axe or a steel rod, and the loose stone is cleaned up, the concrete strength is very low at this time, and the depth of the chisel is 20 30mm is easier, when the concrete is poured twice, the seam surface is washed clean with pressure water in advance, and the cement slurry is brushed while pouring, so as to enhance the bite force.

2. Increase the coarse aggregate method.

The large volume of beams and plates causes the thickness of the retention joints to be large, and the slurry layer and water leakage layer on the surface are also correspondingly thick, and the treatment of the construction joints is difficult; If the slurry on the surface is scraped off or the secondary vibration effect is not good, the method of adding coarse aggregate can be used to sprinkle the graded clean gravel into the slurry and re-vibrate to prevent the concentration of stones.

In this way, the coarse and fine aggregates of the concrete poured at the joint will be uniform when the volume is larger, the cement slurry will not be lost and the strength will not be reduced, and the cohesion and occlusion force of the old and new interfaces can also be improved.

3. Removal of floating slurry method.

When the volume of concrete is small, the simple method is to scrape off a layer of floating slurry on the surface with an iron trowel with a depth of 25mm, and dig out the stripes, which can improve the bonding quality of the horizontal construction joints and benefit the combination of new and old concrete.

Construction

joint) refers to the joints formed between the concrete poured first and later due to the design requirements or construction needs to be poured in sections during the concrete pouring process.

The construction joint is not a real "joint", it is only because the concrete is poured first for more than the initial setting time, and there is a joint surface between the concrete poured after the initial setting, and the joint surface is called the construction joint.

The connection method of the construction joint should meet the design requirements. design without specific requirements, for plain concrete.

structure, the connecting steel bar with a diameter of not less than 16mm should be buried at the construction joint. The depth at which the rebar is buried.

And the exposed length should not be less than 30d of the diameter of the steel bar, and the spacing should not be greater than 20cm.

Semicircular standard hooks should be set at both ends, and hooks can be omitted when using ribbed steel bars. The treatment of concrete construction joints should also meet the following requirements:

1. When the old concrete surface and exposed steel bars (embedded parts) are exposed to cold air, the new distance should be dealt with

Old concrete construction joints within the range of old concrete and length within the range of exposed reinforcement (pre.

embedded parts) for cold protection and insulation.

2. When the concrete does not need to be heated and cured, and it will not freeze within the specified curing period, it will not freeze for non-freezing.

Expansive foundation or old concrete surface, concrete can be poured directly.

3. When the concrete needs to be heated and cured, the newly poured concrete and the adjacent hardened concrete or rock and soil.

The temperature difference between the media shall not be greater than 15°C; The temperature of the foundation surface in contact with the concrete must not be lower than 2°C.

The temperature at the beginning of the curing of the concrete should be determined by thermal calculation according to the construction plan, but not low.

At 5°C, the thin cross-section structure should not be lower than 10°C.

4. The cement mortar and loose layer on the surface of the poured concrete should be chiseled out, and the fresh mix exposed after chiseling should be removed.

The concrete area is not less than 75%. When chiseling, the strength of the concrete should meet the following requirements:

1) When using artificial chiseling, not less than.

2) When chiseling with wind turbine and other machinery, it should not be less than 10MPa.

5. The concrete surface treated by chiseling should be washed with water, but there shall be no stagnant water. In pouring new.

Before concrete, a layer of cement slurry should be brushed on the old concrete surface for vertical construction joints, and horizontal construction joints.

It is advisable to lay a layer of 10mm thick 20mm on the old concrete surface, and the ratio of glue sand slightly smaller than the water-glue ratio of concrete is 1:

2. The cement mortar, or a layer of concrete with a thickness of about 30cm, should be less coarse aggregate than the newly poured concrete.

10% less. 6. When the construction joint is an inclined plane, the old concrete should be poured or chiseled into a stepped shape.

Construction joints refer to the joints formed between the concrete poured first and later due to the requirements of the bending meter or the need for sectional pouring of construction in the process of concrete pouring. There are many factors that affect the quality of construction joints, and there are many treatment methods for construction joints.

Various factors that affect the quality of construction joints.

1) The reasons for the engineering design drawings and the construction process, such as the construction joints left in the area where the stress concentration may be generated; Too much or too little structural reinforcement or deviation from the shear zone.

2) Reasons for concrete materials: the mud content of post-cast concrete sand and gravel is too large; uneven gradation of aggregate particles, unreasonable cement varieties and dosages; Improper selection of concrete mineral admixtures and admixtures or failure to add as required, increasing the shrinkage of concrete; The vibrating method is incorrect during construction; Pouring concrete at high altitude, the wind speed is too large, the scorching sun is blowing, and the concrete shrinkage value increases, which correspondingly causes cracks to the construction joints.

3) On-site construction reasons: the vibration method is incorrect during construction; The loose concrete and stones at the construction joints are not removed in place, the dust is not cleaned, and the construction joints are not watered and moistened before the second concrete is re-poured; When the weather is hot, failure to take protective measures leads to excessive water loss of concrete; Before pouring concrete, the debris and garbage falling into the joints are not checked and cleaned up in time, resulting in the formation of a sandwich between the old and new concrete; The blanking method is improper, and the aggregate is concentrated at the bottom or one place of the construction joint; Expansion waterstops or waterstop steel plates are not placed or not properly placed in the construction joints; Micro-expansion concrete is not used, resulting in the joint parts cannot be tightly connected. Bi finger stuffy.

4) Construction site maintenance and environmental reasons: the newly poured concrete should be cured, covered, windproof and other protective measures should be taken in time to prevent the concrete from losing water too quickly, and the site formwork is not easy to dismantle too early.

5) The cracks caused by the construction joints due to the use of the main ones are: due to the uneven settlement of the structure; The use load exceeds the design regulations; Adopt barbaric decoration, dismantle load-bearing walls or chisel walls, beams, columns, etc.; The surrounding environment, acid, alkali, salt and other erosion of the structure, cause the accelerated aging and cracks of the construction joints.

How to deal with construction joints.

On the hardened concrete surface (the concrete strength is required to reach the point of continuing to pour concrete, the garbage, loose sand and weak concrete layer on the surface of the cement film should be cleaned up. At the same time, the surface should be chiseled. Rinse with water and moisten fully, generally the wetting time should not be less than 24h.

Residue in coagulation.

Concrete pouring should be continuous, and the pouring interval of more than 2 hours shall be treated according to the construction joint.

1. The bottom plate generally does not leave construction joints or post-pouring belts according to the design requirements.

2. The horizontal construction joints of the wall should be left on the wall not less than 200mm above the surface of the bottom plate, and if there is a hole in the wall, the construction joint should not be less than 300mm from the edge of the hole.

3. Convex joints (wall thickness greater than 30cm) or stepped joints and straight joints should be used in the form of construction joints, and metal waterproof sheets (wall thickness less than 30cm) should be added when there are waterproof requirements.

4. The construction joints should be made tongue and groove joints, and the vertical construction joints should be treated with water-stopping strips, and the construction joints should be combined with post-pouring belts and deformation joints.

5. Before pouring concrete on the construction joint, the concrete surface should be chiseled, debris, washed and wetted, and then a layer of 2 3cm thick cement mortar (that is, the original mix ratio removes the stones) or the same mix ratio of reduced stone concrete, and then pour the next step of concrete.