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Repairing of concrete cracks

The methods of repairing concrete cracks are dependant on crack types. We have two types of cracks: dead and live crack. The concrete cracks that are stagnant and not growing, known as dead cracks. While if the cracks growing in size, it is known as live cracks. The repairing of dead cracks is easier. Once the dead cracks are appropriately repaired, there is a lower chance that the concrete will crack again. Concrete cracks can reduce the durability of the structure. Cracks will work as a passage of harmful chemicals such as chloride. The ingress of chloride will accelerate the corrosion of reinforcement, and this can cause concrete spalling and excessive cracking of concrete.  

Figure 1

 Dead cracks are caused by a previous event such as concrete shrinkage or accidental overloading of the structure. Cracks wider than 1 mm can be sealed by filling them with cement grout. For finer cracks or those in the soffit or vertical surfaces, Polymer can be used to seal them. Epoxy resin or polyester resin can be used to protect reinforcement, restore structural integrity, and it can be used when there is moisture. The injecting of epoxy resin can be done under gravity or pressure.  Polymer injection of a crack should start at one end and continue progressively until it reaches the second end. For vertical or inclined cracks, the grouting should begin at the lower end and proceed upwards. We should not forget to clean the cracks by wire brush and air blower before injecting the grout. Injection points will be fixed along the crack length. Then the grout will be injected from the first point, once the grout starts flowing from the second point. The first point will be sealed off, and the grout will be injected from the second point and so on until the grout flow from the last point. The distance between injection points will depend on various factors such as crack width, crack depth, and properties of grouting material. 
The surface of cracks between the injection points should be sealed temporarily until the injection of grout is completed. The injection point can be drilled with a normal drill. The use of a normal drill can block the crack due to dust generated during the drilling process. This problem can be overcome if hollow drills with an applied vacuum are available. Once the drilling of hollos is completed, the injection nipples will be fixed in the drilling locations, and the process of polymer injection can start.

Figure 2


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