For mature reinforced concrete structure, there is always a cracks appear that make the owner or who are using the building  afraid to live on it.

Then you need to do some repair for this structure to be safe in use. The first step usually is to do a site visit to see what is the cracks shape and nature, PLEASE in this stage and specific for junior engineers advice this statement should be in your mind. “DO NOT JUMP TO THE CONCLUSION”. As the engineers is happy to tell the people that he has a solution in their problem to be self satisfaction. But please take care and take your time by collecting the required data and then define the solution after studying in the office with a cup of coffee and take time of thinking. I know that, they are always pushing you to provide a solution during your site visit, but you should be professional in dealing with it.

Mature structure like an old man when he goes to the doctor, can you imagine if the doctor diagnosis is wrong, so the medicine shall be wrong. The result is DEATH. This is the same situation as we face in the old building. The treatment should be match with his existing condition same as in our case. The repair procedure you can find it in any text book but the challenge is to choose the best method to your structure

Even in case of corrosion as its repair procedure is known and easy, but you should know the reason of the corrosion as there are many reason, as it may be due to carbonation, chloride and even in case of chloride attack it should be defined if it is from outside or inside. Some times it will be  from bacteria as in case of foundation.

The type of epoxies and repair procedure is varied depending on diagnosis to define the reason of that cracks. The repair procedure  depends on the as-is-condition of the structure itself; in some cases the structures was failed during the repair.

It is very important to study and do your calculation precisely based on the collected information about the building to define the location of the temporary supports. As you need to define the load path of the load and do some sort of risk assessment if any of the element fail.

There are many ways of repair which are summarized in these 4 methods:

• Traditional method

In this method we can add steel reinforcement or not add more steel depend on the remaining diameter of the steel bar as a rule of thumb if the reduction is more than 20% it is mandatory to add steel bars.

• Using epoxy injection method

This technique is used to fill the cracks in the wall and also it can be used with CFRP to close the cracks on the wall from opening. This methods should be applied by higher professional team to have a good repair.

• Using strengthening by steel sections

This method is very fast by using steel sections and plates to fix the concrete member or increase its strength; as example in the below photos but the thickness of the member will increase and you need some decoration and finishing scenario to cover its ugly shape.

• Using CFRP

 The CFRP can be used in repair and also in strengthening for any members based on some constrain and the design of CFRP is follow ACI 440.

The old method of strengthening is to use hot rolled sections but its applications is not  reliable and it increases the member thickness however CFRP its thickness measure by mm so there is no increasing in member dimensions, and it is not easy in application but it need a professionalism during the application.

These methods of repair are described in detail in this link.

The best repair method shall be defined based on the good assessment. At the END ” DO NOT JUMP TO THE CONCLUSION“

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