How to Repair Wide Cracks  in Concrete

What is concrete?

Concrete is a composite material consisting of fine and coarse aggregates bonded together by liquid cement (cement paste) that hardens (cures) over time. Concrete is the second most used substance in the world after water and is the most widely used building material. Its use worldwide, in tons, is twice that of steel, wood, plastic, and aluminum combined.

What is a concrete crack?

Concrete cracking is the result of the combined effects of mechanical loads and environmental conditions.29 Concentrated chloride exposure is one of the most severe and aggressive forms of environmental exposure of all. possible forms for concrete structures. 30 Severe concrete deterioration is often initiated by cracking of the concrete under conditions of stress concentration or limited shrinkage, leading to rapid penetration of aggressive, subsequent corrosive agents. of embedded reinforcement and peeled concrete shell. 31–34 Maximum allowable crack width is therefore required in various codes and specifications for the design of reinforced concrete structures exposed to aggressive chloride environments.

Why concrete crack?

The formation of internal cracks can be due to many causes. Some of the main reasons are as follows:

•  Shrinkage cracks
•  Thermal – hydrothermal cracks.
•  Thermal cracks- due to temperature changes in the structure.
• Structural cracks.
• Chemical reactions cracks.

How to Repair Wide Cracks of the road in Concrete?

The trick to repairing large concrete cracks is to hollow out the sides of the crack so that it has an inverted “V” shape. This helps the repair material “sink” into the crack, creating a mechanical bond in addition to a chemical bond between the repair material and the concrete.

1. Punch the crack with a hammer and chisel to widen the base of the crack and dislodge any loose material from the old concrete.
2. Remove any debris from the crack with a wire brush. If desired, clean the crack with a pressure washer or garden hose and nozzle.
3. Remove all water and debris from the crack with a wet/dry brush or brush attachment. Work carefully to remove all dust and sand from the crack. It’s okay if the surface is wet, but there should be no puddles.
4. Mix the concrete patch mix according to the manufacturer’s instructions.
5.  Apply compound to the track float into the compound to remove air pockets and help patch the material deep into the crack. Fill the crack on the surrounding concrete surface.
6.  Use a trowel to smooth the surface of the patch, allowing the mixture to adhere to the surrounding concrete.
7. Brush the surface of the patch compound with a dry paintbrush to create a texture, if desired.
8. Allow the compound to cure as directed.
9. Paint or seal the patch surface and surrounding area, if desired.

How to Repair Wide Cracks of  Basement Concrete Wall?

Basement walls must remain structurally intact; otherwise, even the smallest amount of water passing through can rot the building materials, create mold, and make the space uninhabitable. Even tree roots and plants have a way of getting through cracks in basement walls. So before you finish your basement – or even for an uninhabited but dry basement – part of your waterproofing plan should be fixing cracks in concrete walls.

Basement wall crack repair :

Basement wall crack repair falls into one of two categories: non-structural or structural repairs. Non-structural repairs, the focus of this guide, restore the appearance of concrete walls, prevent moisture infiltration and retard subsequent cracking. The structural repair will glue the wall back together to make it stronger or even stronger than it was in its original state.

Non-Structural Repair of Concrete Walls

Cracks in concrete walls can be repaired with liquid or paste elastomers. The compound is injected into the crack with a bottle or with a knife scraping the crack.

Cracks up to 1/2 inch wide and 1/4 inch deep, inside out, can be repaired this way. This compound can usually be coated with latex-based paint if desired.

Easy, inexpensive, and user-friendly, the main purpose of this concrete repair is to prevent water from seeping into the basement. This will prevent the edges of the crack from further chipping, but it will not prevent the wall from cracking or splitting.

Structural Concrete Wall Repair:

Structurally stable concrete walls can be repaired by low-pressure crack blasting. The purpose is to bind the concrete together and prevent water from seeping in.

1. Plastic injection ports are inserted into the crack every 4 to 6 inches.
2.  Holes are sealed in concrete with epoxy paste.
3. An epoxy adhesive is spread throughout and beyond the crack, leaving the top of the openings.
4. An epoxy or urethane binder is introduced slowly into the crack, starting at the bottom hole and working upwards. With the ports clogged, the epoxy acts as a shield to force the adhesive into the crack.
5. After 24-48 hours, the epoxy chipped and the ports cut or broke off the wall.

How to Repair Wide Cracks of Concrete Room Wall?

We repaired an 8-meter-long cracked foundation wall that leaked water into the basement during heavy rains. To seal the crack permanently, we used an epoxy spray system from Polygem, called the Liquid Concrete Repair Kit ($60).

Each set contains two parts epoxy glue, and two parts 10 oz. Liquid Concrete Repair (LCR) tubes, a viscous epoxy supplied in a caulk-like cartridge, and seven resin injection ports deliver the LCR deep into the crack. There is enough material in each kit to repair a crack 1/16 inch long x 8 inch wide x 8 ft long.

Method:

1.   First, clean the cracks of any loose concrete, paint, or old plaster with a wire brush. Remove all dust and debris with a store vacuum cleaner.
2. Press 3 inches. (10 days) mid-finish nails due to cracks, 12″ apart individual. You will use them to align the injection ports with the crack.
3. Open both containers of Epoxy Crack Sealer and scoop out equal amounts of Part A and Part B; Use two separate sticks to avoid contamination.
4. Spread some glue on the base of one of the injection molding ports, being careful not to clog its hole. Slide the gate onto one of the nails sticking out of the crack and press it into the wall. Install the remaining ports in the same way.
5. Next, mix a slightly larger batch of epoxy sealant and cover the entire crack using a putty knife or 1 1/2″ wide margin trowel. Spread the sealant about 1/8th thick. inches and 1 inch. on either side of the crack. Alternatively, cover the entire flange of each spray port with crack sealant, leaving only the neck extension. Smooth the sealant and brush its edges with a paintbrush dipped in mineral spirits. If the other side of the wall is accessible, see if the crack is clean. If it is, seal it with a crack sealant. Let the glue cure for 6-10 hours before injecting the epoxy.
6. Mix the LCR epoxy thoroughly using the plunger bar supplied with the kit. Place the LCR cartridge in the freeze gun. Starting at the lowest spray port, distribute the epoxy into the crack.
7. Continue pulling the trigger until epoxy begins to flow from the port directly above. Remove the gun and plug it into the port you just filled in. Now insert the cartridge tip into the rust port and pull the trigger to dispense the epoxy. Repeat this process for the remaining ports; plug each one before moving on to the next
8. Let the CSF harden for five days, then slit the gate neck with a hacksaw. If desired, you can repair the cut ports with a little crack sealant.

3 common Methods of Wide Concrete crack Repair:

Epoxy Grout Injection :

It can follow the following procedure when repairing cracks in concrete with epoxy building mortar.

•  The crack may be penetrated to a certain depth or may penetrate the section.
   First, clean the area to repair concrete cracks. Coatings, dust, paints, coatings, etc. Must be removed. This should be done for a width of about 50mm.
• In general, repair of cracks with epoxy grout will be done by grouting with a little pressure
• Attach the nozzles. They can be placed at a maximum distance of about 300 mm. The distance can be selected according to the length of the crack.
•  Fill surface cracks with epoxy grout or a suitable adhesive. Once the crack has penetrated the section, the nipple can be placed on both sides. For example, in a slab, nipples can be placed on both sides to ensure that the entire crack is filled with grout.
•  It is possible to seal to a width of about 50mm and the thickness of the sealant to be applied to the surface is at least 2mm. It must be allowed to vulcanize as specified in the product specifications
•  Epoxy grout must be started from one end once the transverse cracks have been sealed. The injection/filling must be done until it looks like grout is coming out of the next nipple. Then repeat the process.
•  Epoxy grout must be started from the lower end when the longitudinal crack is sealed.
• The grout pressure can be maintained in the range of 0.1-0.5 MPa. However, this can be decided in consultation with the engineer and according to product specifications.
  
  Drilling and Patching Method
• Crack repair in concrete is not always possible because cracks do not develop in an irregular manner.
• This method is suitable for cracks forming almost in a straight line
• Suitable for longitudinal cracks.
•  One or more holes can be drilled through the crack.
•  It can then be filled with a suitable non-shrink construction mortar or epoxy grout.
• Longitudinal cracks formed in concrete walls can be treated by this method in most cases. It is a self-healing method for concrete cracks.

Autogenous Healing:

• Autogenous wound healing is the process by which calcium carbonate crystals [CaCO3] are formed.
•  Ca2 + ions on the crack surface react with water. They move through the crack and settle. It is a quick process.
• Spontaneous healing depends on the width of the fracture. According to British Standards, it is assumed that cracks less than 0.2mm wide will heal automatically.
•  Autogenous wound healing is affected by water pressure. However, the type of cement and the type of water did not affect the formation of calcium carbonate.
•  The formation of calcium carbonate will be accelerated by the high temperature of the concrete, the increase in the pH of the water, and the fall of the CO2 particles in the concrete.