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Concrete Dec 2017

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10 CONCRETE COVERED 2017 COATINGSPROMAG.COM what is causing the concrete to look the way it does," Wienczkowski advised. "Is it excess moisture, a combination of freezing and thawing, a bad concrete mixture that may be causing it to crumble, excessive use, or chemicals? Or is it a combination of all of the above?" If moisture is abundant and a slab is not sufficiently dry, that can cause a new coating, sealant, or overlay not to function as intended. Moisture may have also caused corro- sion of the rebar. But before acting to fix those problems, it is crucial to pinpoint the precise cause. "We all teach our kids, when crossing the road, to look both ways," said Ronan Carrigy of Tramex, a provider of nondestructive testing (NDT) instruments and in situ relative humidity (RH) probes. "It would be foolish to look only one way and possibly ignore a serious problem coming from the other direction. Moisture problems in concrete flooring can originate from various sources and can affect floor coverings in different ways. e origin of a moisture-related problem could be from construction moisture within the slab or from moisture that has been introduced to the slab from, for example, ambient site condition sources, such as condensa- tion." According to Carrigy, there has been a tendency by many to oversimplify moisture testing and for installers to rely on a "one-size-fits-all " test. However, when making critical decisions based on single pieces of data, other critical infor- mation can be overlooked. "In situ RH testing, as per ASTM F2170, is arguably the best method for determining the moisture condition within the body of a slab," Carrigy said. "e moisture content of the concrete is indirectly measured by measuring the relative humidity of an air space in the probe, which itself is in equilibrium with RH in the concrete. e results are therefore considered independent of any variables that may be present in the concrete." Similarly, NDT moisture testing, as per ASTM F2659 when using a concrete moisture meter, can be a practical complement to the RH testing and provide data on moisture conditions that an in situ test alone cannot necessar- ily provide. "Reading up to 0.75 inches [1.9 cm] into the slab, the non-destructive moisture content test not only allows for very rapid preliminary moisture mapping of the slab and identification of moisture problems from within the concrete, but it also shows the wettest areas and where best to place in situ RH probes," Carrigy said. "By comparing the moisture map with the on-site ambient relative humidity readings and surface temperature, this test allows us to identify moisture issues originating from the surface, such as dew point or condensation issues. ese distinct moisture issues can then be dealt with separately." As a result, the use of different testing methods can give contractors a more complete picture of the moisture condi- tions both in and on the concrete subfloor, as well as the ambient moisture conditions. e Paul N. Gardner Company (GARDCO), Extech, Wagner Meters, and Lignomat, which offers the RH BluePeg system, are among other industry providers offering moisture and physical testing instruments. On some concrete substrates, extra protection may be needed to deal with moisture and ensure structural integ- rity. Companies, including 3M, can supply vapor barriers to protect a building envelope from moisture intrusion, while W. R. Meadows offers the water-based penetrating chloride screen INTR AGUARD — a water-repellent sealing compound for exterior concrete and masonry surfaces. e proprietary blend of silane and siloxane penetrates into the pores of concrete to protect the surface from scaling and water ingress. Cementing Success After safety, moisture takes top priority. It can cause serious problems in concrete. There's no "one-size-fits-all" test for moisture, according to Ronan Carrigy of Tramex, which offers nondestructive testing and in situ probes. Part of the mystery comes down to where the moisture originated. Ambient moisture conditions can help paint the picture and tools, such as from Lignomat, can help test the area around the concrete.

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