1. Secondary pressing method
Shrinkage cracks in newly poured concrete often appear on the surface of structural components that are newly poured and exposed to the air. There are shrinkage cracks such as plastic shrinkage, settlement shrinkage, drying shrinkage, carbonation shrinkage, and condensation shrinkage. Such cracks are not deep and can not be wide; the processing method is as follows:
1) If the concrete still has plasticity, you can apply it by pressing it once and strengthening the maintenance.
2) If the concrete has hardened, cement slurry can infiltrate the cracks and then be smoothed and compacted with an iron trowel.
2. Surface application mortar method
During treatment, roughen the concrete surface near the crack or cut a groove 15-20mm deep and 100-200mm wide along the crack, sweep it clean, and sprinkle water to moisten it. First, apply cement slurry (applicable interface agent approved by the owner) once, then use 1:1~2 cement mortar in 2~3 layers, and apply a total thickness of 10~20mm and calendar. When there is water leakage, 4-5 layers of cement slurry (thickness 2mm) and 1:2.5 cement mortar (thickness 4-5mm can be mixed with 1-3% ferric chloride waterproofing agent based on the weight of the cement) should be applied alternately. Cover and sprinkle with water for curing 3-4 hours after application.
3. Apply epoxy glue (or paste epoxy glass cloth) on the surface
Before application, clean the surface near the cracks (oil stains should be scrubbed with acetone or xylene) and dry. Use epoxy cement to fill wider cracks, and apply the glue evenly on the surface of the crack to a width of 80-100mm. When it is difficult to dry the base layer, epoxy coal tar mastic can be used. When epoxy glass cloth needs to be pasted, the glass cloth must be desodiumized and dried first. Depending on the specific situation, it can be made into one cloth and two oils (or two cloths and three oils. The perimeter of the second layer of cloth should be 10 to 15mm wider than the next layer).
4. Surface groove inlay method
When cracks are rare but deep, dig a V-shaped or U-shaped groove along the cracks in the concrete. The inner surface of the groove should be smoothed, cleaned, and kept dry. Rigid materials such as cement mortar and epoxy glue are embedded in the groove, or flexible materials such as polyvinyl chloride glue and asphalt paste are filled and sealed. Before embedding the sealing material, apply a dilute paint of concrete to the material (the surface can be used as a mortar protective layer or not). The specific method is shown in Figure 1.
Figure 1 Treatment method of repairing cracks by gouging the surface
a) General crack treatment
b) Treatment of water seepage cracks
c) Active crack treatment
d) Situation after active cracks expand: 1—crack; 2—cement mortar or epoxy cement; 3—polyoxyethylene; 4—1:2.5 cement mortar or five-layer rigid waterproofing method; 5—sealing material; 6—isolation Buffer zone; B—trough width; δ—fracture activity distance
Note: For cracks on the surface of construction joints, before the concrete is poured in the construction section connected to them, a V-shaped or U-shaped groove can be drilled at the crack position according to the requirements of the surface groove embedding method, and no other grooves will be filled in the groove. The filler is filled with structural concrete poured in the connection construction section to ensure concrete at the construction joints.
5. Surface sticker method
For live cracks where the movement range of the crack is not limited to one plane and has waterproofing requirements that are inconvenient to drill and repair, a flexible polybutadiene rubber sealing strip can be placed on the crack, and the periphery can be bonded to the concrete with a polybutadiene rubber adhesive. (See Figure 2), so that the middle part of the sealing strip can move freely with the movement of the crack. Long cracks can be segmented for bonding. The connection of the segmented sealing strips is made of polybutadiene rubber, and the overlap should be pressed up and down. Cut into bevel overlaps, length 100mm.
Figure 2 Surface pasting of flexible sealing tape
1—Crack 2—Linoleum or plastic isolation layer; 3—Polybutadiene rubber sealing strip; 4—Adhesive
1. Cement grouting method
Drilling: Use pneumatic drills to drill holes. The hole spacing is 1-1.5m. Except for shallow holes that use straddle holes, they generally occupy a 30-45·oblique angle between the hole axis and the crack (see Figure 3). The hole depth should pass through the crack surface by more than 0.5m. , when there are two or more rows of drill holes, they should be arranged in a cross or plum blossom shape.
Figure 3 Drilling diagram
1—crack, 2—flat seam opening, 3—oblique hole
Rinse: After drilling is completed, rinse with water, hole by hole, from top to bottom, in a vertical arrangement.
Sealing: After rinsing the joint surface, apply 1:1 to 2 cement mortar or epoxy cement on the crack surface.
Buried pipe: Generally, a ø19-38 steel pipe is used as a grouting pipe (the upper end of the steel pipe is processed with a thread). Before installation, the outer wall of the steel pipe is tightly wrapped with raw tape and then screwed into the hole. The gap around the pipe wall in the hole is filled with cement mortar or sulfur. The mortar is sealed to prevent grout from coming out or the grout pipe from punching out.
Pressure test: Use 0.1-0.2MPa pressure water for the water seepage test; use the methods of grouting hole pressure and drainage hole drainage to check cracks and pipe smoothness, then close the vent hole to check the grouting and leakage blocking effect, and wet the joint surface. To facilitate bonding.
Grouting: Qualified injectable cement used for filling joints approved by the design, the net water-cement ratio of the cement is 0.4, and the grouting pressure is 0.3-0.5MPa. After the entire crack is treated, the hole should be filled with clean slurry filled with clean sand and tamped with a rod.
2. Chemical grouting method
Drilling: Use pneumatic drills to drill holes. The hole spacing is 1-1.5m. Except for shallow holes that use straddle holes, they generally occupy a 30-45·oblique angle between the hole axis and the crack (see Figure 3). The hole depth should pass through the crack surface by more than 0.5m. When there are two or more rows of drill holes, they should be arranged in a cross or plum blossom shape;
Sealing: After rinsing the joint surface, apply 1:1 to 2 cement mortar or epoxy cement on the crack surface.
Buried pipe: Generally, a ø19-38 steel pipe is used as a grouting pipe (the upper end of the steel pipe is processed with a thread). Before installation, the outer wall of the steel pipe is tightly wrapped with raw tape and then screwed into the hole. The gap around the pipe wall in the hole is filled with cement mortar or sulfur. The mortar is sealed to prevent grout from coming out or the grout pipe from punching out.
Pressure test: Use 0.2-0.3MPa compressed air to conduct pressure experiments;
Grouting: Use epoxy resin grout for grouting.
TRUNNANO is a supplier of Cement Anti-crack Agent-Preventing Cracks in Foam Concrete(which is one of concrete additives) with over 12 years experience in nano-building energy conservation and nanotechnology development. It accepts payment via Credit Card, T/T, West Union and Paypal. Trunnano will ship the goods to customers overseas through FedEx, DHL, by air, or by sea. If you are looking for high quality concrete crack reducing admixture, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com).
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