In the constant search for finding new ways to better manage environmental resources and to provide “greener” building technology, it is understandable that research into new and innovative technologies and materials have been forefront in industry news. This has applied to concrete in a number of ways – experimental aggregates, changes to sealants and adhesives, and a variety of admixtures that serve both functional and decorative purposes.
We’d also like to add a reminder to the discussion: If any concrete is installed with proper attention given to moisture measurement during the drying process, it ultimately benefits the environment, the industry and the individual professionals that rely on concrete in their trades. Doing it right the first time significantly minimizes the negative impact that moisture-compromised concrete will always present in terms of environmental stewardship.
The same significant changes that have swept through the concrete industry have also been happening in the science of understanding moisture measurement. Concrete has certainly proven its ability to withstand the tests of time, but as we understand more about what lets it reach its strongest, more research has been directed at the first stages of concrete installation – the curing and drying stages.
Curing, or hydration, is simply the chemical change that happens as the three main ingredients of concrete combine – the water, the cement and the aggregate. That chemical reaction is the first step in concrete’s proven strength and durability.
Drying is the next crucial step in the process and is the period of time after hydration when the excess moisture from the concrete mixture must make its way to the surface and evaporate away. It is during this time that the strength of the slab is established, and rushing the drying process can significantly impact the concrete’s performance.
So how have we typically determined that the concrete is dry?
While we don’t know how the ancient Romans decided concrete was dry, we do know several test methods that have been used over the past century.
One of the first applications to really demonstrate the difference that choosing the right concrete moisture test method can make was with the introduction of lightweight concrete.
Lightweight concretes were developed with several benefits in mind. They reduce the load weight of the concrete structure with a minimal loss in strength (depending on the specific batch ingredients), are lighter to transport (providing a cost savings when moving precast elements), and can be mixed with a variety of natural aggregates. They were also found to provide improved fire resistance and thermal properties.
Where they did not provide a benefit was in situations where calcium chloride (CaCl) testing – a time-honored standard in the concrete industry – was used to determine if the slab was dry enough to proceed with a flooring application. What was an acceptable margin of error with standard concrete suddenly became a liability to flooring professionals receiving callbacks to fix moisture-related flooring problems. Eventually, the limitations of CaCl testing for lightweight concrete proved problematic enough that the ASTM specifically disallowed CaCl testing for lightweight concrete applications and indeed, called its credibility into question for all concrete types.
In the meantime, relative humidity (RH) testing provided a much more specific, and scientifically-backed, understanding of the drying cycle of concrete and the moisture conditions inside a drying concrete slab. In addition, RH testing didn’t face the same limitations as CaCl testing or other surface-based test methods for lightweight concrete because it tests within the slab at the correct depth proven to give actionable readings.
What does this mean for other “greener” concrete types? With the variety of admixtures and aggregates on the market today, RH testing still provides the best possible test method for accurately measuring the moisture conditions in any concrete slab. RH testing, like the Rapid RH®, allows up-to-date, repeatable testing of moisture conditions IN the slab so that flooring professionals and building specialists can accurately determine not only the correct condition of the slab, but also the most viable options for flooring adhesives and products necessary to meet the building schedule.
Moisture-related problems in concrete cost the building industry millions of dollars every year. Whether that’s osmotic blistering in a concrete surface or flooring failure in a gymnasium, every time excess moisture in a concrete slab puts the installed flooring at risk, there are costs in materials, labor and even health for occupants – all of which place a burden on the environment in the long run. Damaged materials must be dumped or recycled, and additional products are required for repair or remediation.
Of course, concrete is actually recyclable and can be crushed for re-use as an aggregate itself (or can be made with recycled by products from other sources), but ultimately, the longer it can stay in service, the lower its overall impact on the environment. With accurate RH testing, the lifespan of any flooring system installed over concrete can be protected for optimal strength and performance.
The real secret is making sure any concrete is designed, mixed and installed for optimal performance and minimal moisture-related damage. When it’s done right at the beginning, it will serve its purpose far into a sustainable future.
Accurate, affordable RH testing serves as insurance against the costs, both financial and environmental, of moisture-related problems in concrete. That’s green that is worth investing in.