Controlling moisture in concrete slabs can be tricky, but it's one of the most important factors a contractor needs to focus on. Here are some tools, materials, and words of advice to help you keep your concrete from becoming all wet.
From choosing the right mix design and materials before construction begins, to keeping moisture in check after concrete placed, moisture control is crucial to a successful slab.
If a finished concrete slab suffers from serious moisture problems, the situation can be difficult-if not nearly impossible-to fix. However, if contractors control humidity in concrete at the outset, then monitor it on a regular basis, they'll head moisture troubles off at the pass.
One consultant helping contractors with moisture problems on a regular basis is Lee Eliseian, president of Independent Floor Testing and Inspection, who likens his work to dentistry.
'Most of our new clients come in because they have a toothache-they're in pain,' he says. 'We can help relieve the pain for their particular condition, but it's much better to be proactive, so they won't run into problems down the road.'
Eliseian's Concord, Calif. Company provides soup-to-nuts assistance to concrete contractors and slab owners-from mix design, to testing existing slabs, to remediation. His experienced clients (which include contractors for Wal-Mart, Bed Bath and Beyond, and other national retailers) are savvy enough to concern themselves with controlling moisture early on, and call specialists like him at the very first sign of problems. It's the smaller project owners and contractors that wait to pick up the phone until problems have become severe-sometimes waiting until lawyers are involved. Even then, however, it's not to late to turn the tide.
'There are a number of alternatives,' says Eliseian. 'We recommend solutions appropriate to the situation-it can be anywhere from an alternative adhesive to a moisture sealing system. Sometimes, it just takes time.'
The primary reason high humidity is a problem is that floor coatings can't be applied on the slab. Excess moisture wreaks havoc on floor-coating adhesives, blisters epoxy-based coatings, and fosters microbial growth. If a slab is too wet to lay down floor coating, the structure can't open for business-one reason why improper floor drying is a significant cause of non-payment by a project owner owner.
Pinpointing moisture problems calls for testing. According to Howard Kanare, senior principal scientist at Skokie, Ill.-based CTLGroup, the popular anhydrous calcium chloride test used to gauge moisture vapor emission rates on the surface relied upon since the 1940s is outdated and inaccurate.
For a quick estimate, manufacturers have developed pin, and other test methods remain in use. These procedures should only be used as general guidelines-possibly for rapid, preliminary results before more accurate moisture tests.
Most floor experts agree that the relative humidity (RH) testing method offers greater accuracy and precision. As a result, ASTM F-2170, which spells out the issues surrounding RH testing, has become the preferred standard of moisture-testing concrete humidity.
Independent Floor Testing and Inspection offers a variety of nationwide services, including moisture testing concrete slabs, visual inspections, risk assessment, and certified analysis and reporting.