CTIOA


CERAMIC TILE INSTITUTE OF AMERICA, INC.

12061 Jefferson Blvd., Culver City, CA 90230-6219





CTIOA FIELD REPORT 2001-6-01

SUBJECT: THE ELEMENTS OF MOISTURE AND EFFECTS ON CERAMIC TILE AND STONE INSTALLATION
By: Claudia Lezell, CTC

INTRODUCTION                  
                             
As the cost of floor covering failures sore into the billions of dollars, the floor covering and concrete industry as a whole has been forced to evaluate the relationship between floor covering failure due to the elements of moisture and chemical relationships in- concrete. Research performed over 30 years ago such as the H.W. Brewer's study' through the Portland Cement Association has resurfaced to help answer some key questions being asked today. From just a quick glance at the dates of some of the past research on this subject matter, one quickly realizes that this is not a new topic, but would definitely be considered one of the hottest topics being faced by the floor covering industry to date.
                             
DISCUSSION                      
                             
THEN & NOW                    
                             
    • Moisture emission testing established decades ago by the Rubber Manufacturer Association has now been revised and adopted into the current ASTM Designation: F1869-98, Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.
                             
    •   As recent as the summer of 2000, under the direction of Gary Wasmund World Floor Covering Association Chairman of the board, an ad hoc Task Force of interested professionals was formed and has written a draft2 titled the "White Paper" addressing the issue of responsibility of Moisture Emission Testing prior to floor covering placement.
                             
    • In relationship to the ceramic tile industry, recent meetings have been held amongst members of the Ceramic Tile Institute Of America (CTIOA) Concrete Slab Committee (CSC), extensively discussing the issue on moisture transmission in concrete slabs'.
                             
1 "Moisture Migration-Concrete Slab-on-Ground Construction," Bulletin D89, May 1965, H.W. Brewer, Portland Cement Association, Skokie, 111.  
2 Revised 9/23/00, Distribution date 10/31/01          
3 Minutes from the CT10A Concrete Slab Committee (CSC) meetings dated: October 24, 2000, November 28, 2000, January 23,200 1, February 27, 2001, and April 24, 2001    
WHY NOW?    
         
The question most asked and often heard amongst members of the related industries is what has happened in our industry to change all of this and why are we starting to see more floor ,overing failures than ever before. Of course, let's never forget that quality is never helped by Factors such as material shortages, being in too big of a hurry - "fast track construction" and trying to do things inexpensively - "value engineering". Compounding the complexity of this situation the following has occurred:
         
    The Federal Clean Air Act Amendments of 1990 gave the U. S. Environmental Protection Agency (EPA) authority to control VOC (Volatile Organic Compounds) emissions for products. VOCs combine in the atmosphere with other chemicals to form ground-level ozone.
         
  •   In December of 1995, the EPA eliminated production of chlorinated solvents in the country. Today the adhesives are mostly water-based.   This caused them to become more moisture and alkali sensitive.
         
  •   Asbestos was removed from most flooring materials by the mid to late 80's  
         
    For those who are not aware, environmental restrictions have also imposed some stringent rules and regulations concerning emission of kiln gases into the atmosphere. As a result, there have been some definite changes in the composition of cement, affecting the properties of concrete and the control of alkali.
         
  •   Manufacturers are also no longer allowed to manufacturer products for use in the U.S. exceeding the EPA specified VOC emission limits. For the concrete industry, the following materials will be affected: form release agents, curing compounds, damp proofing membrane materials, wall and floor coatings and primers, membranes, sealers and water repellents.
SOURCES OF MOISTURE  
   
THE QUESTION OFTEN PONDERED BY MANY... WHERE CAN MOISTURE COME FROM AND HOW DOES IT GET THERE?
   
Leakage: Moisture migration in the form of leakage is simply liquid water traveling from a higher to a lower elevation due to the force of gravity. It appears as either free water on the interior surfaces of wall or floors or by damp spots when the leakage is less severe. Such water can surround and flood the area below the slab when crushed stone is used to interrupt capillary action. Very often we find that landscaping, driveways or paved parking lots pitched toward a building will direct such free water to these areas. Water intrusion can occur when the slab, particularly the edge, is in contact with wet soil from sources such as rain, irrigation systems and broken plumbing. Excessive watering of plant beds or of raised planters both inside and surrounding a building is a source of water that can leak either directly into a slab or into the ground beneath it. Leakage into a building is caused by free water, which finds its way through cracks or openings, honeycombed concrete, porous masonry units, imperfect water resistant coatings, or poorly constructed or punctured water-resistant membranes. Shrubbery should be at least 6" away from exterior walls. Many moisture intrusion-related problems result from poor grading, irrigation, and/or property owners blocking swales and changing the lot grading to suit their tastes.   Lateral (from the side) moisture intrusion is an extremely common cause of job failure.
   
Hydrostatic Pressure: This term, used to describe water pressure beneath a below-grade slab is (to some degree) a misnomer. Hydrokinetic, hydrodynamic, or even hydraulic are words more descriptive of the water frequently encountered under the below-grade slab. It is moving water.   It is forced up through the slab by the weight of the water in the soil surrounding the foundation.   If there is no effective barrier beneath the slab, no relief through drains, large quantities of water will pasE through the slab, through cracks and joints and all other perforations in the slab (from pipes, conduit, columns, etc.) Water pressure, or hydrostatic pressure, is most often suspected in transmission problems where the structure is below the surface of the ground, or "below grade" The driving forces of gravity and momentum are the key forces in hydrostatic pressures. Designers and builders are advised to influence the magnitude or source strength of the transmission by proper site selection, controlling the number of openings or holes in the building enclosure, by specifying drains to carry groundwater away from the building and to lower the groundwater table immediately adjacent to the building.   Water proofing techniques, such as surface coatings on the outside of the building, are often recommended.
   
Capillarity (in relation to concrete)-Capillary Action: The rising or lowering of the surface of a liquid which is in contact with a solid of small bore like a capillary tube.   Caused by surface tension of the liquid and adhesive forces between the liquid and solid.   Passage of water through concrete from a "non-hydrostatic"(no pressure) source as "vapor emission" is an example of capillarity.   Unlike leakage, moisture may travel from a lower to a higher elevation. The amount of mixture that can be transmitted from the ground by capillary action
is often underestimated.   Tests have indicated that as much as 12 gallons of water per 1000 sq.ft. per day can be transmitted through a concrete slab and evaporated into the air. Capillary action usually takes place 24 hours a day every day over the entire area of a slab, so that a tremendous amount of water may migrate into a building by capillarity alone. Chemical solution has also been found to migrate through the concrete to the surface by capillary actions and through microcracks in the concrete caused from dry shrinkage cracks. Water rising to the bottom of the slab from ground water can also occur by capillary action or wicking. The degree of saturation of the subgrade depends on the fineness of the soil and the depth of the water table. Capillary water will saturate the subgrade and move through the concrete slab. Fine-grained soils can draw water from considerable distances while coarse sand or gravel will not sustain this flow.
     
Residual Moisture: Moisture in the slab from the original concrete mixing water. It may take anywhere from six weeks to one year or longer for a concrete slab to dry out to an acceptable level under normal conditions.
     
Vapor Transmission/Vapor Pressure: All concrete surfaces, regardless of age, elevation or location, emit some degree of moisture in the form of a gas vapor. This process of moisture emission is natural, necessary and driven by nature through capillaries within the concrete. Water vapor always migrates from a cool wet environment(concrete slab) to a warm dry environment(building interior) through a process known as diffusion, following the basic laws of physics of a higher pressure moving to a lower pressure.   Moisture movement can occur from capillarity, absorption and gaseous diffusion. Vapor pressure is governed only by temperature and humidity differences. Vapor pressure can be measured, but not calculated(predicted). Concrete permeability and porosity govern vapor emission levels. Voids in the vapor retarder or lack of a vapor retarder can also affect vapor emission levels.
     
OTHER MOISTURE RELATED PROBLEMS THAT CAN OCCUR AFTER PLACEMENT OF CONCRETE
     
Problems in concrete after placement that can contribute to moisture and sources of intrusion for soluble salts:
     
  Over Troweling Problems-Steel Trowels/Power Trowels-trap moisture just under the finished surface. As a result, the upper surface may delaminate from the bulk of the slab after a period of time.
     
  Excessive bleeding -results from using a high water/cement concrete  
  Finishing of concrete slabs while there is bleed water on the surface, or finishing slabs before bleeding has stopped. In some cases where a floor covering fails (due to moisture) after being installed over a green slab, water of convenience (bleed water) is likely the cause.
     
  Adverse effects of certain curing compounds (e.g. use of calcium chloride accelerators) and admixtures
  •   Improper application of curing compounds        
                 
  •   Shrinkage and curling of slabs            
  • Durability- the ability of concrete to withstand exposure to weathering and traffic without surfacing
                 
  •   Scaling- is a local flaking away of the near-surface portion of hardened concrete. Depth 1/8
                 
    Freezing and thawing of the concrete.          
                 
    Dusting-The development of a powdered material at the surface of hardened concrete. Random Cracking  
                 
    Segregation- aggregates separating from the rest of the concrete (Honeycombed surface). If the aggregates, cement, sand and water are not evenly distributed throughout the concrete, the parts of the concrete with the most water will be the weakest and will shrink most. Those parts will settle more and are a primary cause of "bird baths" and excessive curl in slabs on grade. A condition known as laitance (which is the weak top surface of a slab) can also develop.
  •   Pop-outs occur when internal pressure causes a small part of the concrete surface to break away, usually leaving a cone-shaped hole. Pop outs range in size from 1/4" or less in diameter to 2" or more.
                 
SOURCES OF SOLUBLE SALTS AND RELATED CHEMISTRY      
                 
WHERE DO THE SALTS COME FROM AND WHAT HARM CAN THEY DO?    
                 
Several researchers and applicators claim that as water vapor collects and condenses (turning from a gas to a liquid) at the bond line of the adhesive, this newly liquefied moisture is relatively neutral in pH. As this relatively "pure" moisture collects at the bond line of the floor covering material, the existing moisture in the concrete begins to move toward it. Technically speaking, this activity is compelled by osmotic forces (a solution of higher solids will move toward a solution of lesser solids) to "infect" this moisture at the bond line. Usually most alkaline salts are the first to enter this area. These salts are capable of raising the alkalinity of the condensed moisture to pH levels of 11-13 or greater, the moisture is then transformed into a caustic solution that is harmful to virtually all types of adhesives (The pH scale starts at a value of 7, which is neutral, and increases on a logarithmic basis (each succeeding value is 10 times greater than the previous). Adhesive starts to fail (re-emulsify, crystallized and/or even in some cases become "soapy" from saponification) at a value of 9-10. Others state that soluble salts are accumulated through moisture movement and are left behind on the surface after evaporation has occurred.   When salts are deposited and accumulated within the surface pores, as they dry, they also expand, with crystallization pressures strong enough to damage the concrete.   The concrete slab is best suited for a moist environment with an elevated pH (12.5 or higher). The flooring materials are best suited for a dry environment where the pH is (7.010.0). Studies have shown that water in contact with concrete forms strongly alkaline solutions due to the reaction of water with the salts (mominally oxides) of sodium, potassium and calcium, which are present in cement. Calcium hydroxide in this solution has been found to
contribute to the alkalinity to a lesser extent. These alkaline solutions readily absorb carbon dioxide from the air to form bicarbonate solutions, which in turn form carbonate and sequicarbonate. Such solutions have been found to be in high levels of concentration on the surface of the concrete involving adhesive bleeding and debonding of various floor covering materials.
   
MORE ON SALTS, ELEMENTS OF MOISTURE AND CONCRETE CHEMISTRY...  
   
Efflorescence:   The changing of certain crystalline compounds to a whitish powder crust
through loss of water.   A deposit of soluble slats, usually white in color, appearing on the surface of the concrete and masonry construction.   A reaction also referred to as whiskering and saltpetering.
   
Note: Even when optimum construction techniques are used, it is still possible that a slab will dry with a layer of salt or will develop such a layer under floor covering regardless of the moisture conditions. The salts should be removed before installation or replacement of floor covering. To accomplish this, some recommend using a Hydrochloric (Muriatic) Acid Wash/ followed by water rinse. Others suggest only a clean water rinse and if necessary diluted phosphoric acid. Naturally, surface treatment with acid does not affect salts in bulk of the slab and these can be carried to the surface later if moisture becomes available.
   
Sulfate Attack: Salts foreign to concrete derived from the soil through moisture intrusion can adversely affect concrete and floor covering materials.
   
Carbonation: The neutralization of the protective alkalinity of concrete caused by the absorption of carbon dioxide and moisture. Carbon Dioxide forms carbonated water with the moisture contained in the concrete. Since the newly formed carbonated water (carbonic acid) is a mild acid, it neutralizes the protective alkaline calcium hydroxide in the concrete by a chemical reaction forming water and calcium carbonate(chalk). After a time these seemingly harmless reactions may lead to severe corrosion problems.
   
Alkali Carbonate Reaction (ACR): Reaction of alkalis occur within certain limestone aggregate and the alkaline pore solutions (liquid). This can cause expansion and extensive cracking in concrete.
   
Alkali-Silica Reaction (ASR): Reaction of alkalis with aggregate (sand and/or rock) occurs with poorly crystalline and reactive, silica. Aggregate of this type may cause distress to the concrete when present in amounts as little as 1 % to 5 %.
MOISTURE TESTING                
                     
OKAY WE KNOW WE GOT IT NOW HOW DO WE TEST FOR IT?    
                     
They're a variety of recognized dynamic, static, quantitative and qualitative testing procedures A few of them are.......
                     
  •   Mat Test4                   
                     
  •   Electrical Resistance Test4             
                     
  •   Electrical Impedance Test'            
  •   Qualitative/Quantitative Anhydrous Calcium Chloride Test'      
  •   Primer or Adhesive Strip Test'          
  •   Hygrometer or Relative Humidity Test'        
  • Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride. ASTM Designation: F1869-98
  • Phenolphthalein                
                     
THE EFFECTS OF THE ELEMENTS OF MOISTURE ON CERAMIC TILE AND STONE INSTALLATIONS
                     
WHAT ROLES DO THE ELEMENTS OF MOISTURE PLAY ON CERAMIC TILE AND STONE INSTALLATION FAIL URES?
                     
From general polling and discussion amongst various members of the ceramic tile industry and from a very limited amount of available documented informations most seem to agree, since tile and mortar are both inorganic, that moisture itself generally does not cause a problem. However, most agree that when "moisture" passes through the slab it dissolves the salts and carries them to the surface. Alkaline salts can also come from mud beds and bond coats. These alkaline salts can cause staining and if left untreated alkaline salts can break down tile and mortar installations. The ceramic industry also does appear to agree that vapor transmission and related chemistries can adversely affect membranes and organic adhesives. However, as observed and listed on page 9 of this document, a very limited amount of documented information relating to the elements of moisture, vapor transmission and vapor emission compliance levels was able to be obtained by this author.
                     
4 Standard Practices for Determining Moisture-Related Acceptability of Concrete Floors to Receive MoistureSensitive Finishes ASTM Designation: E 1907-97  
4 ASTM Designation: E 1907-97 4 ASTM Designation: E 1907-97 4 ASTM Designation: E 1907-97 4 ASTM Designation: E 1907-97 4 ASTM Designation: E 1907-97              
5 Ceramic Tile Consultant Course, CTIOA Review Questions Moisture Intrusion      
  ANSI AN-2.6.3.26-Concrete slabs, existing ceramic tile, and terrazzo states, "Floor surface shall be dry, structurally sound, and free of wax, curing compounds, or other coatings. Slabs-on-grade subject to moisture transmission are not suitable for ceramic tile set with organic adhesive.
  ANSI AN-2.5.1.2.3 6 -The architect or specifier shall design exterior walls that are to receive tile on exterior or interior face to prevent moisture from collecting behind the tilework. This may include flashing, coping, membranes, vapor barriers, and weep holes as required.
     
  A recent article in the Tile Design & Installation publication states, "Over the past several years, I have observed numerous tile and stone floor failure due to excessive vapor emission through concrete slabs. It amazes me how many installations are started without taking a very important step; the vapor emission test. "'
  From various conversations with consultants, experts, leaders and inspectors in the ceramic tile industry, it does appear that an assumption has been made that ceramic tile set with an inorganic setting material on a concrete substrate has failed from poor setting techniques to defective materials and not from moisture. No apparent published forensic studies involving this subject matter have been found by this author to support or disclaim this theory.
  One personal forensic inspection performed by this author involving vapor emission testing (VET) and scanning electron microscopy(SEM) showed severe debondment of 12"x12" porcelain tile from a gypsum patching compound installed over a cementious setting bed on a on grade concrete substrate. The cause of this failure was found to be from a combination of elevated vapor emission levels and an Ettringite crystalline formation.
     
  A recent case study published in the Concrete Repair Bulletin$ addressed debondment of a cementious overlay on a concrete substrate that revealed a thin deposition of foreign material on the surface of the concrete. According to the findings, the solution must have migrated through the concrete to its surface by capillary action and through microcracks, where it precipitated as a salt. The existence of the debonded zone at the concrete-cementious layer interface was confirmed from scanning electron microscopy (SEM), which is known for its distinctly higher resolving power.
  The only other document found by this author addressing vapor emission compliance levels for ceramic tile and membranes, was in a TEC Technical Bulletin document9.
     
6 American National Standard Specifications For The Installation Of Ceramic Tile, 1999 6 American National Standard Specifications For The Installation Of Ceramic Tile, 1999  
Tile Design & Installation, January 1999, "Tile Installation Failure? Maybe It's the Substrate," Fredrick Hueston s Understanding Floor Covering Failure Mechanisms, Concrete Repair Bulletin: March April 1999, Shondeep L Sarkar
9 TEC Technical Bulletin March 12, 1997, Moisture Content of Concrete Acceptable Ranges for Various Flooring
RECOGNZIED INDUSTRY CERAMIC TILE AND STONE INSTALLATION FAILURES CAUSED FROM THE ELEMENTS OF MOISTURE:  
                         
So what ceramic the and stone installation failures do we know of that can be caused from the elements of moisture?
                         
CERAMIC TILE INSTALLATIONS                  
  •   Disintegration of porous tiles from sulfate (soil salt) attack on concrete      
  •   Debonding of impervious glass mosaic tile from vapor transmission          
  • Compromised organic membranes and adhesives "glue" from exposure to moisture and/or alkalinity
  •   Scaring of fired Terracotta from moisture                
                         
  • Continual reoccurrence of efflorescence in grout joints caused from soluble salts brought to the surface by capillary action where there is water or moisture present. The use of latex additives will help reduce efflorescence by slowing the transmission of water.
                         
  • Saltillo tiles are prone to alkali in the clay. To minimize problems during and after installation, Saltillos must be kept dry to keep the alkali from becoming active as efflorescence or lime pops.
  •   Debonding, inherent sheer bond strength and dimensional stability issues with properly installed concrete and porous tiles when exposed to moisture.
  • Bond failure and adverse effects on properly installed agglomerate marble tile installations from exposure to temperature and/or moisture.
                         
STONE INSTALLATIONS                    
                         
  • Curling of Verde Green, Mexican Black and Spanish Red marble tiles exposed to moisture
                         
  •   Loss of polish and dusting on the marble from moisture and alkalinity        
  •   Discoloration of light colored marble from moisture and alkalinity            
  • Crystallization of soluble salts (subflorescence in Historic masonry causes severe deterioration of the substrate. Problems associated with subflorescence can be diagnosed and identified by visual clues, such as spalling and rising damp).
  •   Iron staining in marble caused from oxidation from moisture              
                         
  •   Deleterious effects causing erosion of the veins from moisture and alkalinity    
                         
SUMMARY                      
                         
Obviously with the continued restrictions and mandatory environmental changes occurring with the EPA, much more stringent study and attention will have to be paid to this subject matter by the floor covering industry as a hole. It is obvious at this time that continuous case studies and sharing of information amongst the leaders of the ceramic tile, stone, and other related industries must occur in order to aid in the further investigation of the relationship between the elements of moisture to ceramic tile and stone installation failures. Information is the key and communication is the answer!
  Footnotes              
                   
"Moisture Migration-Concrete Slab-on-Ground Construction," Bulletin D89, May 1965, H.W. Brewer, Portland Cement Association, Skokie, Ill.
                   
Revised 9/23/00, Distribution date 10/31//01                
                   
Minutes from the CTIOA Concrete Slab Committee (CSC) meetings dated: October 24, 2000. November 28, 2000, January 23, 2001, February 27, 2001 and April 24, 2001
                   
Standard Practices for Determining Moisture-Related Acceptability of Concrete Floors to Receive Moisture-Sensitive Finishes ASTM Designation: E 1907-97      
                   
Ceramic Tile Consultant Course, CTIOA Review Questions Moisture Intrusion            
                   
American National Standard Specifications For The Installation Of Ceramic Tile, 1999        
                   
Tile Design & Installation, January 1999, "Tile Installation Failure? Maybe It's the Substrate"' Fredrick Hueston          
                   
Understanding Floor Covering Failure Mechanisms, Concrete Repair Bulletin March April 1999, Shondeep L Sarkar    
                   
TEC Technical Bulletin March 12, 1997 Moisture Content of Concrete Acceptable Ranges for Various Flooring