Embed Size (px)
Citation preview
Testing Moisture Contentin Concrete Subfloors:Preventing Floor Coating Failures
J P C L N o v e m b e r 2 0 0 8 53www.paintsquare.com
Continued
e have seen a number of floor finish failures caused by moisture from the con-crete substrate. In many instances, moisture tests were conducted beforeinstalling the floor covering or finish to specifically assess the moisture content
of the concrete substrate. In many instances, results of the tests suggested the concrete was dryenough to install the flooring , but failure of the flooring still occurred, induced by moisture from
the substrate.All concrete slabs contain varying amounts ofmoisture from a number of sources: the waterused to mix, place, and cure the concrete; rainduring the construction phase of the building;leaks; or ground water. Flooring contractors areoften required to measure the moisture contentof the concrete slab before installing the floor fin-ish to assure that the concrete’s moisture contentmeets the manufacturer’s recommendations.
WDennis J. Pinelle,*Simpson Gumpertz and Heger Inc.
(above and below): Delamination and blistering caused bymoisture in concrete. All photos courtesy of the author *Now with Pinelle Construction Sciences, LLC
J P C L N o v e m b e r 2 0 0 854 www.paintsquare.com
ASTM F1869 and ASTM E1907.ASTM F1869 specifies three tests forthe first 1,000 sq ft of floor and one testfor each additional 1,000 sq ft of floor.ASTM E1907 specifies three test loca-tions for the first 500 sq ft of floor andone additional test for each additional
500 sq ft of floor. We do not normallysee test frequencies that comply witheither requirement, but we often seefrequencies on the order of one test per10,000 sq ft of floor area.There has been much discussion
about what the acceptable moistureemission (ME) or moisture vapor emis-sion rate (MVER) should be prior toinstalling a floor finish. ASTM E1907notes in the appendix that most flooringproduct manufacturers require a mois-ture emission rate of less than3 lb/1,000 sq ft/24 hr, butmanufacturer-published requirements can be higherdepending on the material; for example, agrowing number of manufacturers consid-er 5 lb/1,000 sq ft/24 hr acceptable forcertain products.
Research
However, as seen by the large number offlooring failures, these tests do notalways detect the levels of moisture thatare high enough to cause failure.The most common test method for
measuring moisture levels in concreteslabs involves placing a container ofanhydrous calcium chloride under adome sealed to the slab surface. The calci-um chloride is a desiccant and collectswater vapor that transmits from the con-crete surface into the sealed dome. ASTMInternational publishes two standardsthat use this technique: ASTM E1907,“Standard Practices for DeterminingMoisture-Related Acceptability ofConcrete Floors to Receive Moisture-Sensitive Finishes,” and ASTM F1869,“Standard Test Method for MeasuringMoisture Vapor Emission Rate ofConcrete Subfloor Using AnhydrousCalcium Chloride.”Another test method rapidly gaining
popularity, ASTM F2170, “StandardTest Method for Determining RelativeHumidity in Concrete Floor Slabs Usingin situ Probes,” involves drilling a holeinto the concrete and inserting a probeto measure the internal relative humidi-ty of the concrete.This article describes the calcium
chloride and relative humidity (RH) testprocedures, the significance of theresults, tips on interpreting the results,and the limitations of the test methods.The article also presents some other,less common techniques used to mea-sure moisture in concrete floor slabs.
Quantitative AnhydrousCalcium Chloride Tests
The anhydrous calcium chloride test isfairly simple, and typically, the flooringcontractor conducts the test andreports the results to the flooring man-ufacturer. Both ASTM E1907 andASTM F1869 use a small container ofanhydrous calcium chloride placedunder a dome that is sealed to the floor.The container of calcium chloride isweighed at the beginning and end of the
test. A desiccant, the calcium chloridetheoretically collects the water vaporemitted from the concrete surface overa 60- to 72-hour time frame (Fig. 1).ASTM E1907 provides a procedure
for measuring the moisture emissions(ME) from a concrete subfloor. ASTM
F1869 measures the moisture vaporemission rate (MVER). The two proce-dures are similar, but the methods ofcalculating the ME and MVER differslightly. ASTM F1869 requires the areaof the calcium chloride container to besubtracted from the dome area whencalculating the MVER, while ASTME1907 does not call for subtracting thearea of the container when calculatingthe ME.Commercially available calcium chlo-
ride test kits usually provide a calcula-tion that incorporates the areas of theplastic dome and calcium chloride con-tainer. The calculation produces themoisture emitted in pounds per 1,000sq ft per 24 hours, which is the unitspecified under both ASTM procedures.Sampling frequency differs between Continued
Fig. 1: Calcium chloride test in place
High Performance, Ultra-low VOC,Cost Efficiency. Pick ALL three...
Binding. Bonding. Coating. Leading.
With Hexion’s new EPIKURE™ Curing Agent 8547-W-60 formulators don’t need to sacri�ce high performance or face increased costs to meet the most stringent VOC regulations—even those in the SCAQMD (South Coast Air Quality Management District).
With the best viscosity pro�le in the industry, EPIKURE™ 8547-W-60provides superior ease of handling and a de�nable end of pot life. Why not offer your customers ALL of these bene�ts using a break-through product from the pioneers in WB curing agent technology. To learn more, e-mail us at [email protected] or contact your Hexion account representative.
© 2008 Hexion Specialty Chemicals, Inc. hexion.com
Introduced at the AMERICAN COATINGS SHOW in Charlotte
Click our Reader e-Card at paintsquare.com/ric
J P C L N o v e m b e r 2 0 0 8 57www.paintsquare.com
Research
ASTM F2170,Internal Relative Humidity Testing
ASTM F2170, “Standard Test Method for DeterminingRelative Humidity in Concrete Floor Slabs Using in situProbes,” is gaining popularity as an alternative to calciumchloride testing. The procedure involves drilling a hole intothe concrete. The depth of the hole is determined by whetherthe slab is allowed to dry from both the top and bottom orjust from the top. For a slab that can dry from the top andbottom, the hole depth is to be 20% of the slab thickness. Ifthe slab can dry from the top only (e.g., slab-on-grade withvapor retarder or an elevated slab on a metal deck), then thehole is to be drilled to a depth of 40% of the slab thickness.The hole is sealed with a special plug for three days to
allow the internal RH inside the hole to equilibrate with themoisture in the surrounding concrete. A RH probe is theninserted down into the sleeve in the hole, which is self seal-ing around the probe. The internal RH is read from a meterconnected to the probe (Fig. 2). We have also used self-seal-ing probes connected to data loggers to monitor the drying ofconcrete slabs over longer periods of time (Fig. 3).
Continued
The frequency of testing that ASTM F2170 specifies isthree tests for the first 1,000 sq ft of floor area and one testfor each additional 1,000 sq ft. However, we have not nor-mally seen internal RH testing done with this frequency.Budget and traffic limitations usually make the frequency oftesting to comply with the ASTM standard difficult.Similar to the discussion about allowable limits for mois-
ture emission levels using calcium chloride, there is much dis-cussion about allowable internal RH levels. Depending on thefloor finish, the slab’s maximum allowable RH is usually inthe range of 75% to 80%.One of the advantages of this test is that the probes can be
wired to data loggers, and data can be collected over time. Datacollected over time can be useful for determining how fast a slabis drying. Also, if the project allows long-term monitoring, theimpact of seasonal variations can also be determined.
Tips on Using the TestsASTM F1869 and F2170 state that before testing the con-crete slab, the floor shall be maintained at a temperature andhumidity consistent with the intended use for 48 hours. If a
48-hour pretest period is not possible, then ASTM F1869specifies that the space be kept at 75 F ±10 degrees F and50% ±10% RH for 48 hours prior to testing. We have seeninstances where the ambient conditions have an impact onthe test results, particularly in refrigerated areas in food pro-cessing facilities. In cool areas, the calcium chloride test willalmost always measure a low MVER, even if there is sub-stantial moisture in the concrete. In one food processing facil-ity, we observed standing water under the slab, but mea-sured a MVER of less than 2 lb/1,000 sq ft/24 hr.If possible, moisture testing should be done at a tempera-
ture and humidity consistent with the intended use of the
Fig. 2: RH meter in use
Fig. 3: Data logging RH
44--88 NNOOZZZZLLEERREECCYYCCLLEERRSS,,IINN SSTTOOCCKK AANNDDRREEAADDYY FFOORRDDEELLIIVVEERRYYIINN DDEECCEEMMBBEERR 22000088
AND THANKS TO UNCLE SAM, THEY’RE TAX-DEDUCTIBLE TOO
(CONSULT YOUR ACCOUNTANT FOR DETAILS!)
copyright 2008
Click our Reader e-Card at paintsquare.com/ric
S
J P C L N o v e m b e r 2 0 0 8www.paintsquare.com
ResearchClick
ourR
eadere-Card
atpaintsquare.com/ric
Continued
There’s never been asmarter time to invest in a newsteel grit blast system from AdvantageSPS. TheEconomicStimulus Actof 2008 letsyou expensethe first$250,000 ofcapital invest-ment purchases made by December 31,2008— and investments higher than$250,000 can be coupled with accelerateddepreciation so you could qualify for asmuch as a $400,000 first-year deduction!
You’ve bid smart and tough all year long— now, it’s time to redistribute the wealthto yourself with a machine that costs afraction to run versus the competition, andthat offers the greatest reliability andsimplicity to operate: Advantage SPS, LLC.
“Savvycontractors
will jump onthe biggesttax break
in history.”
800-800-7761www.surfaceprep.com
email [email protected]
We Keep It Simple
Non-Bank Financing Available
space, not the generic conditionsdefined in ASTM F1869, or error mayresult. Also, the 48-hour precondition-ing period is too short if the ambientconditions change substantially (e.g.,temperature is lowered from 75 F to 40F). The time required for the concrete torespond to such changes is typicallylonger than 48 hours.If there is a pre-existing floor finish,
the ASTM standards require removingit and allowing the concrete floor slab tovent (i.e., stay open to the air) for 24hours. This requirement may be diffi-cult because the tester must arrive twodays before testing to prepare the testareas, return to place the testkits/equipment, and then return againin three days to collect the kits andrecord the results.In some of the investigations we have
done where there is a pre-existing floorfinish, we have measured the in-servicemoisture condition by removing only asmall sample of the flooring and quicklyinstalling the anhydrous calcium chlo-ride test. The amount of moisturetrapped just under an existing floorcovering evaporates quickly, and evenafter just 24 hours, much is gone andwill not be detected if an anhydrous cal-cium chloride test is done a day later.This practice is a modification of thepretest 24-hour venting (drying out)Fig. 4: Moisture levels within concrete flooring
assemblies change over time.
Fig. 5: MVER vs. hours after coating removal
J P C L N o v e m b e r 2 0 0 860 www.paintsquare.com
ResearchCl
ick
our
Rea
der
e-Ca
rdat
pain
tsqu
are.
com
/ric
Clic
kou
rR
eade
re-
Card
atpa
ints
quar
e.co
m/r
ic
Continued
requirement of ASTM F1869.However, the kits placed immediate-
ly after removing the flooring provideuseful information about the amountof moisture that will accumulate whenequilibrium is reached on that particu-lar slab under a f loor cover-ing/coating.A common misconception is that the
calcium chloride test generally detectsmoisture coming through the slab. Thetest appears to actually measure themoisture in the top inch or less of theconcrete subfloor. The implication ofthis finding is that moisture deeper inthe slab, or in wet materials below theslab such as insulation, is not alwaysaccurately detected by the calcium chlo-ride test.Use of calcium chloride and RH tests
on a slab-on-grade with no vaporretarder beneath is not meaningful andwill not predict the anticipated highmoisture levels in the future. Whenthere is no vapor retarder under a slab-on-grade, water vapor from the soilsbelow can diffuse up into the floorassembly over time. Also, most floorcovering materials will impede vaporemissions from the top of the slab, trap-ping moisture in the slab and under theflooring after installation. (Figs. 4 and 5on the previous page). Trapped moisturehas been found to cause a number of dif-ferent types of floor failure.Using either the calcium chloride or
the RH test on a concrete slab providesno information about how future mois-ture levels change over the seasons orhow outside moisture sources enter theflooring systems. Computer modeling ofwater vapor migration through thefloor assembly, as well as long-termmonitoring, can detect or predict sea-sonal moisture changes and may behelpful in determining future moisturecontents after the new moisture equilib-rium is established under the installedflooring.In refrigerated environments, we
Contact our sales department for further information on available grades.
Email: [email protected]
Coarse grade garnetfor heavy blasting
applications.
Not Cutting �rough?You Need A New
Coarse of Action.
MOHAWKGARNETINC.808 Hwy 17 East, Wahnapitae, Ontario, P0M 3C0, Canada
Toll Free 866-642-7638 www.mohawkgarnet.com
Click our Reader e-Card at paintsquare.com/ric
Research
have found that the calci-um chloride test is ineffec-tive. The cold air tempera-ture above the slab willslow the amount of vaporemitted from the surfaceof the slab. Also, the calci-um chloride itself losesthe ability to absorb mois-ture in cold environments.Combined, these two fac-tors produce low testresults that are almostalways below 3. In aninvestigation of a refriger-ated food processing facili-ty, our calcium chloridetests were all below 3. Wecored the slab and found it was insulat-ed with cork, which was sitting in liquidwater. The calcium chloride test in thiscase gave us no indication that therewas a potential high level of moisture in
the insulation under the slab.The standard calcium chloride test
does not always detect internal mois-ture levels in lightweight concrete slabs.We have found that internal RH mea-
surements are a more reli-able way to determine theinternal moisture levelsfor lightweight concrete.We have often found lowmoisture levels as mea-sured by the calcium chlo-ride test, but high levels ofmoisture deeper in thelightweight concrete, astested with the RH test.
Interpreting Test ResultsAs already stated, whenthere is no vapor retarderbeneath a slab-on-grade,we do not rely on themoisture tests to predict
future moisture levels, and we assumethat future levels will be high enough toinduce a moisture-related failure.For elevated slabs or slabs-on-
Continued
Calcium chloride tests alone are
not always effective in accurately
detecting moisture in light-
weight concrete. Measuring the
internal RH in conjunction with
the calcium chloride tests can
better measure the moisture in
lightweight concrete
“
“
J P C L N o v e m b e r 2 0 0 862 www.paintsquare.com
Clic
kou
rR
eade
re-
Card
atpa
ints
quar
e.co
m/r
ic
Research
Continued
ground with a vapor retarder, we nor-mally conduct both the calcium chlo-ride and the RH tests to assess a con-
crete floor slab’s moisture contentbefore installing a new floor finish. Ingeneral, this means we can get four dif-
ferent combinations of test results,which are listed on p. 64.
Fig. 6: Low RH and high calcium chloride results
J P C L N o v e m b e r 2 0 0 864 www.paintsquare.com
ResearchCl
ick
our
Rea
der
e-Ca
rdat
pain
tsqu
are.
com
/ric
1. Calcium Chloride—Low; RelativeHumidity—Low
2. Calcium Chloride—High; RelativeHumidity—High
3. Calcium Chloride—Low; RelativeHumidity—High
4. Calcium Chloride—High; RelativeHumidity—Low
The first two conditions are easy tointerpret. If both are low, the moisturelevel is low; if both are high, the mois-ture level is high.The third andfourth conditionsrequire someinterpretation. Ifthe calcium chlo-ride test is lowbut the RH test ishigh, then it islikely that thefloor finish can-not be installed.The relativehumidity test isdetecting mois-ture deeper in theconcrete, whichthe calcium chloride test cannot detect.The moisture within the concrete canredistribute after the flooring isinstalled and cause a failure. We see thisoften with lightweight concrete slabs,but we have obtained test results likethis in normal weight concrete too. Ifthe RH test indicates high levels ofmoisture, hold off on installing theflooring or consider a moisture mitiga-tion system (for both normal and light-weight slabs).If the RH test results are low and the
calcium chloride test results are high(Fig. 6), then there may be a couple ofreasons for this condition. The top of theslab may have been lightly wetted butnot enough to saturate the slab, and thetests were run not long after. In newconstruction, low RH and high calciumchloride readings can also mean the slabis “almost” dry and you just need towait a little longer. In general, this com-
bination of test results indicates there issome level of moisture in the surface ofthe slab, but the “core” of the slab is dry.In other words, the slab is almost dry,but the top surface needs a little moretime to dry.Of the four possible combinations of
test results, we see combinations 1, 2,and 3 most often. When the results pro-duce combinations 3 and 4, some pro-ject-specific interpretation is likely
needed, and more testing may be neces-sary.When possible, we prefer to take core
samples from the concrete slab. Coresamples allow us to assess the quality ofthe concrete and to look under the slab. Acore hole does allow us to see if there is avapor retarder and capillary breakbeneath or if there is some other materiallike insulation present. This informationis useful in interpreting test results.Also, consider the ambient conditions,
which, as we have noted, can affect thetest results. But other problems can becreated by the ambient air conditions.For example, the ambient air conditionsbelow an elevated slab could produce avapor drive up into an elevated slab. Weencountered one situation in whichthere was a steam generation operationunder an elevated slab, and the spaceabove was occupied. The warmmoist airbelow the slab drove moisture up
When possible, we prefer
to take core samples
from the concrete slab.
Core samples allow us
to assess the quality of
the concrete and to look
under the slab.
“ “
J P C L N o v e m b e r 2 0 0 8 65www.paintsquare.com
Clickour
Reader
e-Cardatpaintsquare.com
/ricClick
ourR
eadere-Card
atpaintsquare.com/ric
Research
Continued
through the perforated metal pan. Eventhough we obtained results that indicat-ed the elevated slab was dry as it satwithout a floor finish, we treated thisparticular slab like a slab-on-groundwith no vapor retarder. We took thisapproach because, over time, moisturecould accumulate in the slab from belowafter the floor finish was installed.
Other Moisture TestsWhile the calcium chloride and RHtests currently seem to be the most pop-ular moisture tests, there are other testprocedures and equipment. Most ofthese are simple meters that are placedon the concrete, and the moisture levelis read directly off the meter.One proprietary unit reads the mois-
ture level of the concrete using an elec-trical eddy current. By measuringchanges in the impedance of the cur-rent, the meter produces a moisturereading. The scale goes from 0 to 6%,and the percentage reading is supposedto represent the moisture content as apercent by weight of the concrete.Another type of unit has pins that are
pressed into the concrete, and electricalcurrent is passed through the concretebetween the pins. Using the measuredelectrical resistance, the meter convertsthe reading to a moisture content on anarbitrary scale, such as 1 to 40. Thisunit is not as popular with flooringmanufacturers as the meter that mea-sures the impedance current, but wehave seen it used occasionally.A newer meter on the market uses
radio waves. The meter interprets theeffect on the radio waves and producesa moisture reading on a scale of 1 to1000. In general, once readings reachthe 180 to 200 range, the concrete isdetermined to be “wet.” While the resultobtained is a number, we find this testuseful when used as a qualitative mea-sure. The test is very useful in assessingwhat parts of a large floor are wetterthan other areas, but the scale is not
J P C L N o v e m b e r 2 0 0 866 www.paintsquare.com
Clic
kou
rR
eade
re-
Card
atpa
ints
quar
e.co
m/r
ic
Research
always reliable in finding concrete thatis too wet to receive a floor finish.One other test that we have seen late-
ly appears to be gaining popularity.Referred to in ASTM E1907, the testinvolves placing a sealed box on the topsurface of the concrete floor slab. AnRH probe is placed through the side ofthe box, and the RH change inside thebox is read over time. This test has beenused in other countries, but it is still notvery popular in the U.S. One of the chal-lenges faced with this test is how tointerpret the results. There is somedebate about interpretations. Not verymany flooring manufacturers refer tothe test in their data sheets, but it maybecome more popular in the future.
SummaryAll moisture tests provide useful data,but understanding the results and theirlimitations is important. Based on thefieldwork we have conducted, the fol-lowing summarizes some of our findingswith regard to testing concrete sub-floors for moisture:• Moisture testing is necessary todetermine when a concrete subfloor isdry enough to finish. The general guide-lines based on time, e.g., wait 60 daysafter pouring concrete, are not reliable.• Calcium chloride testing per ASTMF1869 and ASTM E1907, the mostpopular test methods, measures theamount of water vapor emitted fromthe surface of the slab over three days.The surface emission rate is not alwaysan accurate gauge of the internal mois-ture content or of how fast the slab isdrying.• Internal RH testing, ASTM F2170, isgaining popularity and provides a pro-cedure to measure the internal moistureof concrete subfloors.• Both the calcium chloride and inter-nal RH tests measure a moisture level ata specific point in time. However, inter-nal RH test probes can be attached todata loggers to measure long-termchanges. Seasonal differences in mois-
Buy and SellUsed Equipmentin the PaintSquare
Market Placewww.paintsquare.com
1-800-837-8303
J P C L N o v e m b e r 2 0 0 8 67www.paintsquare.com
Clickour
Reader
e-Cardatpaintsquare.com
/ric
Research
Dennis J. Pinellereceived his B.S. inchemical engineeringfrom the University ofRhode Island in 1984.Before joining Simpson
Gumpertz & Heger Inc. (SGH) in 2000,Mr. Pinelle worked as a materials engi-neer, a research and development man-ager, and a technical director in firmsthat manufactured construction prod-ucts. At SGH, he held the position of staffconsultant—materials, with particularinvolvement in investigating issues withcoatings, concrete repair materials, andreinforcing steel corrosion. Mr. Pinellehas authored numerous papers and hasgiven presentations at industry events ona regular basis. Mr. Pinelle is a memberof the American Concrete Institute (ACI)and the International Concrete RepairInstitute (ICRI), where he is a Fellow. Hechairs ICRI’s Corrosion Committee andcurrently is president of the Institute. Mr.Pinelle is also active on a number oftechnical committees in ACI and ICRI,including ACI 562, which is writing a newrepair code for concrete repair.
Answer YourTechnical QuestionsSearch JPCL articles onlinein the PaintSquare Library
www.paintsquare.com1-800-837-8303
ture contents are not detected unlessthe tests are done at different timesthroughout the year.• Calcium chloride tests alone are notalways effective in accurately detectingmoisture in lightweight concrete.Measuring the internal RH in conjunc-tion with the calcium chloride tests canbetter measure the moisture in light-weight concrete.• Calcium chloride tests are not usefulin cold (refrigerated) environments.• Neither the calcium chloride nor theRH test can predict whether moisturefrom other sources may enter the floorsystem. For instance, concrete slabs-on-grade without vapor retarders willaccumulate moisture because theimpermeable floor finish (vaporretarder) is installed on top of the slab.
