What mistakes to avoid when concreting?

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Construction work is no joke, one mistake can paralyze further work for several days, and its repair can cost a lot. Concreting is a step without which it is impossible to build a house. To make foundations, columns or ceilings concrete is essential. However, it is not the easiest material to work with, so many inexperienced builders have many problems with it. See what common mistakes to avoid when concreting.

Poorly prepared forms

To make an element out of concrete, you must first prepare an appropriate form for it, that is, a formwork. Most often they are made of boards or particle boards. Improperly formed and prepared formwork will deform under the weight of poured concrete – its one cubic meter weighs 2400 kg. Also important is their tightness. Under the influence of the concrete pressure the formworks can bend and unseal, which leads to deformation of the shape of elements poured in them. Then they have different dimensions and need to be “straightened”, which in some situations can affect the load bearing capacity (e.g. columns). When preparing the formwork for pouring the concrete elements, special attention should be paid to its strengthening and sealing, so that the defects in the forms do not delay further works

Incorrect vibration of concrete

It is extremely important that the concrete mixture fills the formwork thoroughly. That is why after the liquid concrete is properly and carefully placed in the forms, it should be compacted and vented. The liquid mixture should be poured in layers while simultaneously venting and compacting it with a compactor. When vibrating or compacting the concrete, air is drawn out of the mixture, which causes the concrete to spread evenly and have a homogeneous structure. This is a guarantee of achieving the assumed strength. Lack of mechanical vibration causes inaccurate filling of the formwork with concrete and presence of air bubbles. The result of poor vibration of the mix are surface damages called crawls, or voids, otherwise known as caverns.

When vibrating the mix, do not touch the reinforcement and formwork, as contractors sometimes do. because this can cause air bubbles to form around the bars. This adversely affects the bond between the concrete and the reinforcement, which is important to the strength of the element.

Poor care of the concrete during the work

After the elements are poured, the concrete setting process begins. During this time, the mixture dries out, which causes the dimensions of the elements to change, or more specifically, to shrink. The stresses that occur at this time are high enough to cause cracks and fractures. In order to prevent this, it is necessary to take proper care and make sure that the drying process does not occur too quickly. This involves maintaining the right temperature and humidity to reduce shrinkage of the concrete. The concrete surface should be regularly sprinkled with water, which also protects it from low temperatures. The result of improper drying of concrete is a porous structure and surface flaking. Poorly dried concrete is less durable, watertight and resistant to external factors.

Working with concrete is not the easiest task, it is easy to make mistakes, affecting the load-bearing capacity and durability of the material. When building a house, attention to details such as maintaining the dimensions of the concrete elements, proper drying and compacting of the mixture are extremely important for safety. Pay attention to these factors the next time you are pouring concrete

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Toby Kenney

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