Concrete Repairing (Evaluate the Extent of Damage)

Concrete repairing is critical and requiring experience people. Proper repairing of concrete surface will ensure sustainable repairing. After determining the cause of damage. We need to evaluate the extent of the damage. At this stage, we will determine how much the concrete damage and how the damage will affect the structure serviceability. To determine the extent of damage we should answer the following question (how long, how wide, how deep, and how much of the structure involved). 

FIgure 1

The extent of damage can change by the change of the cause. Sulfate exposure, alkali-aggregate reaction, and cyclic freezing and thaw will cause similar damage. The extent of damage caused by cyclic freezing and thaw is lesser than others.

The reason behind the difference in severity is the fact that only 90% saturated surfaces can be affected by cyclic freeze and thaw. Therefore the damage caused by freeze and thaw will develop on the outdoor surface. Alkali and sulfate reaction will affect a larger portion of the structure.

One of the easiest techniques to determine the extent of damaged concrete is sounding concrete with a hammer. Hollow and drummy sounds means damaged concrete. Experience personnel can provide useful information using this simple method. In sounding a suspected disbanded or delaminated concrete. Deep delaminated or delamination that causes a small separation will not produce a drummy sound. For this case, concrete quality can be determined by blowing a hammer to the concrete surface. Hammer will rebound smartly from good concrete, and a distinct ring will form on the concrete surface. Hammer will rebound slightly, and a dull sound will be generated for low quality concrete.

There are several non-destructive tests. Schmidt Rebound Hammer is one of the cheapest and easiest tools. Schmidt Rebound Hammer will provide relative quality information. This information can be useful if compared to a different part of the structures. For old structures using rebound hammer considered ineffective, and the pieces of information provided are unreliable. It is more useful for the newer structure that has not experienced much weathering or deterioration.  

Figure 2

Ultrasonic pulse velocity and acoustic pulse-echo devices is another non-destructive test. These devices will measure the time required by a sound wave to travel through a concrete section and rebound. The travel time of the sound wave inside a concrete section will be compared with the travel time in sound concrete. The difference in traveling time means the concrete is damaged. 

The data acquired from these technologies is not sufficient, and it will be considered misleading without testing cores from the damaged concrete. Cores should be taken from the damaged concrete. Cores will be tested to determine the concrete strength, and also it can be used to determine the deterioration of concrete subsurface. 

The areas of deteriorated or damaged concrete discovered by these methods should be mapped or marked on drawings of the affected structure. This will provide information for subsequent calculations of the area and volume of concrete to be repaired, as well as for the preparation of repair specifications.