For millennia, concrete remains a centerpiece of construction science and still provides the foundation for thousands of structures around the world. Its naturally-curated strength and durability beget its universal popularity, yet its frequent mishandling has seen the destruction of countless facilities. While many components play into the quality of a particular concrete mix, one specific factor trumps all others — the management of moisture.
The failure to properly apply and manage moisture in concrete can devastate the integrity of a facility. Understanding the ways moisture interacts with concrete, as well as the dangers of its presence in excess, will grant much-needed insight into what separates a quality concrete mix to a not-so-excellent mix. Likewise, what separates a quality installation process from a shoddy one.
The Multi-Pronged Dangers of Excess Moisture
Water is an essential component of concrete that, when mixed with cement, binds the aggregates together via hydration (a chemical reaction in which the cement forms chemical bonds with the water to form hydrates). Excess water results in moisture that hasn’t chemically combined with the cement, eventually becoming trapped and causing flooring failures. Additionally, a poor water-to-cement ratio (w/c) results in an especially porous cement, forming a weaker concrete more susceptible to cracks and erosion.
Problem 1: Water Vapor Pressure
Depending on the porosity and moisture content of the concrete, there can be dramatic differences in water vapor pressure for a given concrete slab. This is measured as moisture vapor evaporation rate (MVER). An acceptable industry MVER typically sits at 3 pounds in 24 hours though some concrete can have an MVER of 13+ pounds per 24 hours. Unchecked, especially high levels of water vapor pressure destroy topical moisture mitigation methods and eventually flooring materials.
Problem 2: High-pH levels and alkalinity
Calcium hydroxide is a natural alkaline product of cement formation. This natural alkalinity means the internal pH levels of a concrete slab will reside around 12.5 to 13.8 pH (by contrast, pure water will have a neutral reading of roughly 7 pH). Ideally, the pH level at the surface of the concrete slab is 9 pH or lower before the installation of flooring. If pH levels remain high when the flooring is installed, the high-pH moisture (resulting from hydroxide ions dissolved in the concrete’s water content) rising from the slab can compromise the flooring’s adhesion to the concrete.
Moisture Mitigation and Proper Evaluation
Though some moisture mitigation methods can be effective at reducing flooring risks, they should not replace thorough moisture-detection testing. If RH levels or MVER levels are too high, be mindful not to apply your moisture mitigation solution too soon in the process. Similarly, if pH levels are too high for an adequate flooring or moisture mitigation solution, err on the side of caution and wait before you install. Using this process further elevates the risk of construction delays.
A rapid-drying concrete solution for moisture mitigation will eliminate the need for a moisture mitigation application. With rapid-drying concrete, the moisture mitigation has been taken care of when the concrete is placed, completely eliminating these types of delays.
Concrete requires moisture for its development, an obvious requirement before the installation of flooring. Ironically, moisture — once-friend-turned-foe — can be the means of a flooring’s demise. Use a self-desiccating, rapid-drying concrete to eliminate moisture related issues all together.