Why is Water — A Necessary Component of Concrete — So Dangerous?

Posted by ARIDUS Rapid Drying Concrete on Oct 3, 2016, 1:05:00 PM

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Water is an absolutely necessary component for the formation of concrete. When mixed with cement, a chemical reaction known as hydration creates bonds between water molecules and cementitious materials to form hydrates. This natural reaction gives concrete the strength and durability that has made the building material the foundation of construction for millennia. Moisture in excess within concrete, however, can lead to a myriad of issues and the erosion of flooring materials. But why is something so essential to concrete’s formation the cause of so much trouble?

Water-to-Cement Ratios, Porosity and Alkalinity

The water-to-cement ratio (w/c), alongside the quality of cementitious materials used, is among the most important factors in concrete formation. Too little water, and the concrete will not have an opportunity to strengthen. Too much water, and the concrete will become overly porous, leading to compromises in durability and strength. Porosity also increases the moisture evaporation rate within the concrete, creating additional, and potentially problematic, pressure on the surface. Since concrete naturally produces calcium hydroxide, the resulting moisture is high alkaline and can easily erode poorly installed topical moisture mitigation treatments or flooring materials.    

Cupping and Flooring Expansion

The pressure caused by the buildup of moisture at the concrete-flooring interface can lead to a multitude of flooring issues. Cupping occurs when the sides of the flooring rise to levels higher than the center (emulating a cup). This can occur in residential and commercial facilities with relative ease if moisture mitigation methods or rapid-drying concrete aren’t used. Flooring expansion, a moisture and climate-induced problem, can create cracks in the flooring, as well as the concrete itself. In the cases of both cupping and flooring expansion, a disparity in moisture levels between the top and bottom of a slab can devastate a floor.

Sick Building Syndrome

Porous concrete with excess moisture creates a breeding ground for the buildup of bacteria and mold. If left uncontrolled, this buildup can become a health hazard for the occupants of a facility. There are many causes for sick building syndrome beyond the moisture in concrete slabs, but concrete moisture can still be a major contributor to the problem. Well-installed and maintained ventilation can help stymie any potential problems, but preventing moisture from becoming an issue in the first place is the best preventative measure. This begins with diligence in removing the moisture issue in concrete.  

Rapid-Drying Concrete as a Solution

Rapid-drying concrete’s advantage, in addition to its ability to reach target relative humidity (RH) levels within 45 days, is uniform drying. Cupping and floor expansion, two common moisture-caused flooring issues, are avoided since the concrete doesn’t dry from the top down. Since the concrete self-desiccates so quickly, high alkaline moisture and evaporation pressure become non-issues within a month’s time, allowing construction crews to begin flooring installation sooner than later.

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Topics: Moisture Mitigation, Rapid-Drying Concrete