For decades, flooring contractors have conducted moisture tests to verify the appropriate “dryness” of a concrete slab, prior to installing finished floor products. The anhydrous calcium chloride provided a moisture vapor emissions rate (MVER) which was the industry benchmark since the 1950s. In the 1990s, experts raised methodology concerns and suggested that the calcium chloride test did not indicate a thorough enough measure of concrete moisture content. Since then, relative humidity (RH) testing has emerged as an alternative. Both tests may still be used, but many may ask: which one is best?
Calcium Chloride Test vs. Relative Humidity: Materials
The first place most businesses would look to answer that question is cost. And cost alone would make it seem that CaCl comes out ahead. If contractors apply the calcium chloride test in 13 locations of a 10,000 square foot slab, they pay a materials cost of $147.95, or $11.38 per test. In the building business, the calcium chloride test may appear to be cost-effective.
|Bottom Line||Calcium Chloride (CaCl)||Relative Humidity (RH)|
|Material Costs (13 tests)||$147.95||$600.00|
Calcium Chloride Test vs. Relative Humidity: Time
But time equals money, too, and it is there that the anhydrous calcium chloride test becomes a heavyweight. If contractors place in-situ relative humidity (RH) probes at 40% depth in 13 locations of a 10,000 square foot slab, they can obtain overall moisture content assessment in 94% less time than the anhydrous calcium chloride test. By deploying RH testing, contractors save 54.82 man hours of cost.
|Test Task||Calcium Chloride (CaCl)||Relative Humidity (RH)|
|Prepare test locations||65 minutes||0 min.|
|Prepare the test||65 minutes||0 min.|
|Place the test||65 minutes||65 minutes|
|Protect the test||120 minutes||0 min.|
|Obtain results||130 minutes||3.5 minutes|
|Cleanup||20 minutes||7 minutes|
|Time Required (13 tests)||4,320 minutes (72 hrs.)||120 minutes (2 hrs.)|
|Total Test Time||3,495 minutes (158 hrs. 15 min.)||205.5 minutes (3 hrs. 25.5 min.)|
Multiply the Savings
Contractors pay an extra $452.02 for a moisture content test based on relative humidity, and they save 54.82 man hours for it. Further, the calcium chloride test measures moisture vapor emissions at the slab surface. It does not indicate moisture content levels or moisture migration through the concrete slab. Measured by both time and test integrity, relative humidity concrete moisture testing appears to hold a long-term edge despite higher up-front costs.
What to do with 54.82 hours of budget? Hire contractors! Here’s how long you could employ the following trades people based on the amount saved on moisture testing ($452.02) multiplied by their average national wage in 2011:
Source: US Bureau of Labor Statistics (Web).
In a constrained budgetary world, the relative humidity (RH) moisture content test trumps the anhydrous calcium chloride test on both methodological and economic grounds. Concrete slabs and construction projects gain.