Moisture Issues in Concrete Floors Part 3

HOW TO TEST FOR MOISTURE
Or Start from the begining

There are 3 common tests:

ASTM F 1839

This test measures the (moisture vapor emission rate) “MVER”.  It is done with a kit and a small amount of calcium chloride that is placed in a plastic dome and sealed for 60-72 hours.  The calcium chloride then absorbs the moisture leaving the concrete slab.  The MVER is translated to test the pounds of water leaving the slab in a 24 hour time frame.  Rates for most floor coverings are 3-5 lb.

 

A 20×20” area is needed for the test.  The area must be properly cleaned.   The International Concrete Repair Institute (ICRI) requires a light sanding of the area, then vacuum and wipe clean.  The area should be exposed to the conditions that it will see in the building when it is put into service.  This includes:

o Fans

o Air conditioners

o Heat

o Lights

o Normal operating temperature

Although this is the most widely used test, there are some concerns:

o It only measures the moisture in the top ½” of the slab.

o Curing compounds and how the floor was toweled will affect the test.

o How carefully the test concrete area was prepared.

o Ambient temperature and humidity.

o The test also requires that the vapor barrier is properly installed.

ASTM F 2170:  INTERNAL SLAB RELATIVE HUMIDITY

This is considered to be the most accurate test for testing moisture throughout the slab.  It requires three tests to be done for the first 1000 square feet and one more for each additional 1000 square feet.

A hole is drilled (dry drilling only) and completely cleaned of any dust.  A small sleeve is inserted to the bottom of the concrete slab and left for 72 hours.  A probe is inserted and the humidity at the bottom of the slab is recorded.  The results can be used to see if the floor covering can be safely installed.

Note:  All surface preparation must be done dry.

ASTM F 710:  PH TESTING

High PH levels at the concrete surface can result in failures of adhesives and coatings.  New concrete has PH levels of about 12.5.  As the hydration process continues, these levels will drop to around 7.5-8.5.  This PH reading is about 1/8” deep and can be changed by surface preparation methods.  When aggressive methods are used the PH should be checked after the preparation and not before.  For most installations levels of 7-10 will be fine.

PH testing should be done at each place a moisture test is done.  When testing PH levels the area should be sanded and cleaned.

Before installation of coatings begins, floors must also be properly prepared.  This can be done with liquid cleaning (which may require large amounts of water) or by mechanical means (several of these methods, especially the older methods, also require the use of water).  New dust free methods now greatly reduce clean up by water cleaning.

ICRI Guideline #03732 gives a surface preparation instruction on what profiles should be done for almost any floor coating containing both polymers and epoxies.  This includes an inspection of the concrete for both soundness and MVP before work begins.  The guideline uses nine different profiles for coatings and preparation.  Methods range from coating of a sealer, polymer overlay, detergent scrubbing and milling.  In most cases, the concrete will be the weakest link in the overlay process and requires that both moisture tests and surface preparation be done correctly to provide for successful overlays.

Note:  ICRI will begin offering a certification program that will involve both written and performance tests.

References:

o       Guide #03741 – Guide for Design, Installation and Maintenance of Protective Polymer Flooring Systems for Concrete.

See Part 4, Concrete Curing and Resolving Moisture Issues 

 

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