WHEN MOISTURE IS TORTURE !

In this column, we will share with you regularly our experience on major application areas where usage of dehumidification is both extensive and essential.

Concrete Coatings
Moisture Related Problems

Concrete coatings, today, are becoming very popular and are being applied at an increasing rate in various applications to prevent corrosion. Concrete itself is considered a corrosion resistant material and is often applied over steel. However, due to its reactive

Excess Moisture in concrete has caused many coating failures, disrupting building operations necessitating expensive repairs !

Hence, it is important to remove this excess moisture from concrete within a reasonable period.

characteristics, it requires protection from many common conditions found in the Industrial and marine areas, throughout the world. Thus, coatings are needed to provide this protection. However, applying coating to concrete is more complex and difficult then other surfaces. There are some physical and chemical properties of concrete that have a direct bearing on coatings. Some of them include excess moisture, cracking, alkalinity, freezing and thawing, porosity and soluble salts, corrosion of steel in concrete and reactive aggregates.

Effect of Excess Moisture on Cement Coatings

Concrete gains its strength due to the presence of the water molecules inside. To achieve proper strength and bonding the concrete has to be hydrated to around 70 % before drying is started. It takes around 28 days for concrete to hydrate to this level. However, it would take around six months for the concrete (6” thick) to dry before coating can be applied.This can lead to eventual delay in projects. In addition, moisture has severe effect in the performance and life of the coating. It inhibits initial cure and coating adhesion. When moisture travels to surface and tries to escape after coating has been applied it causes fish eye or bubbling on the coating.

Excess Moisture in concrete has caused many coating failures, disrupting building operations necessitating expensive repairs !

Hence, it is important to remove this excess moisture from concrete within a reasonable period.

The Solution !!

The various techniques available to remove the excess moisture from concrete include ventilation, heating and dehumidification. Ventilation and heating, are often used in conjunction with the most effective and quickest methods of moisture removal i.e. dehumidification. Dehumidification involves lowering the dew point of the air surrounding the concrete so that the water starts to migrate from concrete to the dry air surrounding it. However, depending on the amount of moisture

Effect of Excess Moisture on Cement Coatings

Concrete gains its strength due to the presence of the water molecules inside. To achieve proper strength and bonding the concrete has to be hydrated to around 70 % before drying is started. It takes around 28 days for concrete to hydrate to this level. However, it would take around six months for the concrete (6” thick) to dry before coating can be applied.This can lead to eventual delay in projects. In addition, moisture has severe effect in the performance and life of the coating. It inhibits initial cure and coating adhesion. When moisture travels to surface and tries to escape after coating has been applied it causes fish eye or bubbling on the coating.

in concrete, location and concrete type, a judicious mix of the three can be used for quick drying.

Bry-Air Desiccant Dehumidifier is the most economical and reliable method of concrete drying as it removes moisture from the air, through a process of continuous physical adsorption, and can effectively maintain the humidity conditions required as it is capable of maintaining RH as low as 1% or even lower at a constant level, regardless of ambient conditions.

–- Ask for a free copy of the technical paper “Concrete Coatings - Moisture Related Problems” presented at NACE* seminar.