Cracks in concrete. Part 2: The main causes of cracks in concrete, their impact and solution

If cracks are identified in the structural part, this is a worrying indication. Now, if the cracks are only on the walls, it is necessary to observe whether they are increasing in size or not.

How do you make this observation accurately? A super tip! Do the following test to see if the crack is really increasing or not.

For cracks in internal areas: Prepare a paste of plaster and fill the crack with a spatula or even with your finger, covering completely.

For cracks in external areas: Prepare a paste of lime, cement and water, in equal proportions, and pass in the same way as in the internal area.

Keep it under observation for a week. If it remains the same, you can arrange for its final closure. If it opens, it could be a sign that the structure is in trouble. Call an expert urgently to assess.

We’ll now look at the various kinds of cracks, their impact and eventual solution.

1. Foundation settlement

Differential foundation settlements are some of the most recurrent causes of cracks and cracks in buildings. The main manifestation of this pathology is cracks at an approximate angle of 45o in the corners of windows and doors. This happens when there is a difference in the density of the soil, and thus different parts of the building “lower”. The greater the difference in settlement points, the greater the problem for the construction.

When should I worry?

It is practically impossible to predict all foundation settlements. That's why lintels in the openings (doors and windows) are made to minimize the effects. When the cracks start to get bigger and bigger, this shows that the situation is serious. First, because these openings are critical infiltration points, and can compromise the wall both internally and externally. Also, large cracks are indicative of more serious foundation problems.

What should I do?

The first steps that the professional must take are related to identifying the cause and real severity of the problem. In general, it is necessary to take care to correct and subsequently seal the cracks, especially to avoid problems arising from water infiltration.

2. Thermal variation

Thermal variation is the most common cause of active cracking. Differences in temperature cause expansion and contraction of materials and, when expansion joints are not made, cracks appear. It is possible to notice this type of cracks on the walls, and especially on the ceiling where the incidence and area is greater. It is very common to see cracks occur near the meeting of the slabs with the masonry.

When should I worry?

Again, these are somewhat expected cracks. What cannot happen is the constant increase in these cracks, so that the masonry is irreversibly compromised. The professional should investigate the causes of the cracks, and assess how they are behaving.

What should I do?

If expansion joints were not made during the construction of the structure, it is essential that they be made at this time. The joints act as a stress relief point, and the structure can move without compromising the safety and stability of the building.

3. Concrete Retraction

Concrete and mortar in general, as we know, must undergo a curing process, during which there’s a very rapid loss of water which causes retraction, and consequently cracks. That is why it is recommended to keep the slab surface moist after concreting.

When should I worry?

Plaster cracks due to excessive shrinkage during the curing process do not present a structural risk but can end up compromising the finish. In relation to slabs and other structural elements, cracks can represent critical points that can lead to exposure of reinforcement and structural risk.

What should I do?

When cracks in the walls and ceiling are noticeable, it is a good practice to redo the coating. However, for cracks in structural elements, the recommendation is to seek professional help to carry out the risk assessment.

IMPORTANT: Cracks in the Structure

Regarding cracks in structural elements (beams, columns, slabs and foundation) it is necessary to understand that this could be a very serious problem.

Cracks can arise for a variety of reasons, in addition to those already mentioned, execution failure, the use of low-quality materials, lack of preventive maintenance, natural phenomena such as heavy rain, wind, earthquakes, among others.

Therefore, when identifying large cracks in structures seek professional help immediately – if you are a building manager, be sure to inspect the building periodically to identify cracks as soon as possible. And above all, contact a professional to assess and also repair the cracks.