Material conditions necessary for strengthening concrete structures

Concrete is one of the most widely used building materials in the world fact it is estimated that in 2006 there was as much as 7.5 billion cubic meters of concrete made in a year.

Of course it is understandable, concrete is an incredibly versatile and strong substance but even concrete can start to weaken as it ages. However, this doesn't mean that you need to tear down concrete structures instantly. It is possible to strengthen aging concrete in order to extend the life of the building.

All you need is the right material conditions.

Inspection & Control

The first step in dealing with a suspected concrete issue is to have a reputable firm, such as Corrims inspect and assess the situation. They will be able to advise you of what the issue is, how bad it is and the remedial steps that can be taken.

Strengthening Materials

One method that has been used for many years is to bond new concrete in place of the old. This is referred to as external bonding. Unfortunately this has led to another issue; de-bonding. Effectively the new concrete will peel away.

This is not to say it is an ineffective method but there is still room for improvement.

Metal

A viable alternative is to use metal to strengthen the concrete. However precautions need to be taken when inserting metal into concrete. One of the biggest issues is the addition of moisture into the concrete. This will cling to the metal and start it corroding. Ultimately your building could then develop concrete cancer; the most obvious sign of this is rust marks on the outside of your walls.

If possible a steel plate is mounted across the weakened area to provide support. In fact this is one of the most common approaches.

Sprayed Concrete

This method has been used for in excess of 90 years. There are two definitive approaches to spraying concrete onto an existing structure:

1. Dry Mix

Dry mix means the dry ingredients are mixed and the water is added as the ingredients leave the spraying nozzle.

2. Wet Mix

In contrast a wet mix is prepared beforehand and sprayed from the nozzle as it is.

Wet mix requires a simple pump and pipe whereas dry mix needs a water regulator at the pump end. However, the dry mix approach is the more common one; perhaps because it is easier to store and transport the dry mix. As long as it is kept dry it can be stored almost indefinitely.

Ferrocement Laminates

This approach mixes metal and cement mortar.

Effectively the cement mortar, which is the same mix as traditional concrete, is sprayed thinly onto the weakened area. Wire mesh is then placed over it and another layer of cement mortar. This process is continued until the necessary strength is received.

In all cases the damaged concrete will need to be removed and a bonding agent used to ensure the new concrete adheres to the old surface. This is the only way to ensure damage does not spread and the building can retain its structural integrity for years to come.