subject: Concrete Drying Through Dehumification [print this page] Concrete Drying Through Dehumification Concrete Drying Through Dehumification
Application:Concrete Drying
Frequently Faced Problems
Presence of high moisture level on the concrete floor hampers the epoxy laying procedure thereby delaying the project completion. Life & quality of coating gets hampered if it is done in the presence of high moisture level,instead of adhering to the substrate ie concrete,the coating adheres to water lowering its life.
Concrete gains its strength due to presence of water molecules inside. However only 50% of this water is hydrated and rest remains as free moisture. Further as concrete takes around 28 days to cure,it is kept under 100% RH or under wet condition till hydration is complete. This process increases the free moisture to around 7-8%,which is not acceptable for the application of coating. Coating manufacturers do not guarantee their products if the moisture content is at that level.
General Recommendation
Moisture level in the concrete should be maintained at 3-5%.
Solution
Drying of concrete i.e. reduction of moisture can be done with the help of Dessicant based dehumidifiers. Dehumidification is the most effective and quickest method of moisture removal. Dehumidification involves lowering the dew point of the air surrounding the concrete so as the water starts to migrate from concrete to the dry surrounding air. Dehumidification helps to achieve and maintain the Level of Moisture to prevent coating failure while concrete coating.
For inside coating of concrete floor/wall, dehumidified air can be fed through duct from the machine. In case of outside concrete painting in open atmosphere, a vapour barrier surrounding the job is created and dehumidified air is passed inside the vapour barrier through duct.
The desiccant based dehumidifier removes moisture from the air by chemical attraction rather than condensation. Humid air is directed across a desiccant material that acts as a drying agent. The moisture is collected on or in the desiccant rather than as a liquid. The moist desiccant is dried using second hot air stream that heats the desiccant and releases the moisture. Then the desiccant is reused to dry more air. In a continuous process the air is dried by the desiccant at the same time the moist desiccant is dried for reuse so that dry air is available at all times continuously.
TDS Application(Author is an employee of TDS)
The Problem
The client had to lay acid resistance tiles on the floor having moisture level of 12-16 % in two weeks time.
Presence of high moisture level has severe effects in laying of tiles in floors and posed problem in the life of the coating on concrete. The moisture present in the concrete was 12-16% which had to be reduced to 3-5 % for proper sticking of acid resistant tiles.
Our Solution
For bringing down moisture levels to 3-5 % , services of TECHNICAL DRYING SERVICES(TDS) were hired. Dehumidifiers of various capacities were installed for reducing the moisture level. The temperature was increased to about 45 degree Celsius on the floor covered by plastic sheets for making vapour barrier and continuously dry air was supplied in the covered area.
Concrete was dried as per client expectation and moisture content was brought down to,between 3-5% in two weeks time,by weight from initial 12-16% and the floor was ready for laying of acid resistant tiles. Client could finish off the work in relatively 50 percent less time than by conventional drying method.
The Advantages:
Better coating performance
No problems like coating failure and improper adherence, which increases building downtime.
Project time and cost reduced by appr. 35%.
Coating possible at any time of the year and can accurately program the downtime.
No downtime for bad weather and no adhesion problems
