T54: Avoiding Problems with Floor Finishes on Concrete Slabs 1 April 2014 4:00 pm to 5:30 pm Emily R. Hopps, P.E. Peter E. Nelson, P.E.

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Presentation Goals 1. Identify industry changes and current practices that may result in elevated concrete moisture levels or vulnerable finish floor installations. 2. Design and construct concrete floor slabs that will reduce the chance for high concrete moisture levels and floor finish failures. 3. Specify and interpret the results of current moisture test methods for concrete, and recognize the limitations of the different test methods. 4. Select and evaluate preventative measures to mitigate high moisture levels.

Imagine This… • New 3-story outpatient hospital facility • Various resilient flooring materials • Adhesive migration and material debonding • 30 trip-and-fall incidents • Replace all flooring five years after opening – 2 years of construction – Only 30% of cost is labor and materials for floor replacement

Or What about This… • New 17-story academic building in urban location • High-end epoxy terrazzo flooring installed in hallways and lobbies • Terrazzo begins to lift and curl; trip-and-fall incidents ensue • Replace all terrazzo flooring – Cost nearly 6x’s original installation – Phased construction over 1-1/2 yrs.

Or Maybe This… • New 300,000 sq. ft. facility currently under construction • Moisture test results presented at a project meeting that exceed flooring manufacturer maximum limits • Change order presented to provide moisture mitigation prior to floor installation – $2,000,000 price tag – 2 to 3 month delay

Many Types of Flooring Have Failed on Concrete • Vinyl – VCT – Sheet – Simulated Wood • Hardwood – Oak – Ash – Maple – Bamboo • Carpet – Broadloom – Carpet Tile

• Terrazzo – Cementitious – Epoxy • Coatings – Epoxy – Urethane – MMA – Vinyl Ester • Rubber Tile • Silicates • Stains • Underlayments

Adhesive Staining on VCT Tiles

Discolored Artificial Stone Tiles

Stains on Engineered Wood Flooring

Ruts in Sheet Vinyl

Bubbles in Sheet Vinyl

Adhesive Under Hospital Beds

Delamination of Simulated Wood Vinyl Floor

Bleed-Through of Marking

Epoxy Terrazzo Blisters and Surface Deposits

Carpet Failures

Why have we seen so many failures now? • Change in materials (government regulations)

Asphalt Cut-Back Adhesive

SCAQMD Rule 1168 (2005)

Carpet Policy Dialogue

VOC Regulations by State or Region

CASE STUDY: Investigation of Carpet and VCT Failure in Office Space

Investigation Moisture Measurements • MVER ranged from 3.75 to 10.20 lbs • In-situ RH ranged from 58% to 93%

Why have we seen so many failures now? • Change in materials (government regulations) • Blended cement (fly ash) concretes

Concrete with and without Fly Ash Concrete microstructure without fly ash at 200X magnification.

Concrete microstructure with 20% fly ash at 200X magnification.

Why have we seen so many failures now? • Change in materials (government regulations) • Blended cement (fly ash) concretes • Use of lightweight concrete

Normal Weight vs. Lightweight Concrete • 110 to 115 pcf vs. 145 to 150 pcf • Expanded slate and shale aggregate

Normal-Weight vs. Lightweight Concrete

From Concrete Construction, November 2000

Normal-Weight vs. Lightweight Concrete

Figure from ACI 302.2R-06

Normal-Weight vs. Lightweight Concrete

From Concrete International, January 2012

Normal-Weight vs. Lightweight Concrete

Material (and Unit Cost) Structural Steel Framing (assume $4,000/ton) 4,000 psi Composite Slab (assume $105/CY NWC and $135/CY LWC) Headed Stud Shear Connectors (assume $2/stud) Total

Normal-Weight Concrete (A)

Lightweight Concrete (B)

Cost Ratio (A/B)

$12.40/sq ft

$9.53/sq ft

1.30

$1.78/sq ft

$1.77/sq ft

1.01

$0.17/sq ft

$0.23/sq ft

0.74

$14.35/sq ft

$11.53/sq ft

1.24

Why have we seen so many failures now? • • • •

Change in materials (government regulations) Blended cement (fly ash) concretes Use of light weight concrete Fast track construction

What can I do to minimize the chance for failure? • Use low w/c ratio concretes without fly ash – Be aware of extra moisture in lightweight concrete

Concrete Mix Design • Water/Cement Ratio – 0.40 W/CM for normal weight slabs – 0.45 W/CM for lightweight slabs

• Consider using water-reducing admixtures – Superplasticizers / high-range water reducing admixtures

• Prohibit addition of water in the field

What can I do to minimize the chance for failure? • Use low w/c ratio concretes without fly ash – Be aware of extra moisture in lightweight concrete

• Use a vapor retarder under slabs-on-ground – Use a product intended for the purpose – Make sure it gets installed properly

Slab-on-Ground without a Vapor Retarder

Slab-on-Ground without a Vapor Retarder

Slab-on-Ground with a Vapor Retarder

Location of the Vapor Retarder

From ACI 302.2R

CASE STUDY: Flooring Failure in Elementary School

Flooring Deterioration

46

Existing Floor System

VCT

VAT

47

Floor Vent Pipes

Sub-Slab Construction • Concrete floor slab is 5 in. thick • Sub slab soil is sandy-clay with 1 in. and larger stones • Moisture content of the soil about 8% (dry soil typically has less than 2% moisture) • No vapor retarder beneath concrete (to depth of 17 in.) • Site drainage system functions adequately • Water table at least six feet below surface

49

Moisture Measurements

Room 5 15 Library 11 Gym

MVER (lbs) 5.9 5.7 7.9 9.8 8.2

RH (%) 95 95 96 97 92

50

Floor Venting System • Direction of air movement through vents is into building, regardless of roof-top vent fan performance, so floor system receives outside air on a continual basis. – When outside air is warmer than floor, potential for condensation within floor system exists. – When outside air is cooler than floor, flooring system can cool, increasing potential for condensation to occur on surface of flooring.

51

Buildings Mechanical System • Interior dew point tracks with outside temperature and humidity. • Air flow is into building, drawing exterior humidity into rooms and corridors. • Dew point occasionally becomes higher than floor temperature in late fall and in spring, potentially causing condensation on floor surface.

52

Sources of Moisture in and on Flooring • From concrete, and soil beneath concrete • From roof venting system • From open doors and windows

53

Repair Recommendations • Remove flooring and tile to expose concrete surface (requires asbestos abatement) • Shotblast concrete to remove residual adhesive • Seal surface of concrete with a topical moisture mitigation membrane – including floor beneath cabinets and heating units. • Apply finish flooring system (leveling layer, adhesive, tile) • Adjust / replace doors and fixtures as needed • Repair openings left in roof from discontinued vents • Review mechanical system operation and balance building – Install make-up air system to classrooms – Dehumidify air (either make-up or ambient)

54

Floor System Demolition

55

Concrete Surface Preparation

56

Floor Patching Requirements

57

Mitigation Coating Application

58

Finish Installation

59

What can I do to minimize the chance for failure? • Use low w/c ratio concretes without fly ash – Be aware of extra moisture in lightweight concrete

• Use a vapor retarder under slabs-on-ground – Use a product intended for the purpose – Make sure it gets installed properly

• Avoid blotter layers

Installation of Sand Blotter Layer Sand Blotter Layer

Vapor Barrier

Preparation for Compaction of Blotter Layer

In Progress Construction

Slab-on-Grade with Blotter Layer

Slab-on-Grade with Blotter Layer

Slab-on-Grade with Blotter Layer

Location of the Vapor Retarder

From ACI 302.2R

Slab-on-Grade and Curling Rebar near top of slab to prevent curling and arrest cracking Saw-cut control joint

Shrinkage-compensating admixture in concrete

What can I do to reduce moisture levels? • Use low w/c ratio concretes without fly ash – Be aware of extra moisture in lightweight concrete

• Use a vapor retarder under slabs on ground – Use a product intended for the purpose – Make sure it gets installed properly

• Avoid blotter layers • Consider the concrete curing method

Concrete-Curing Methods • Moisture Addition (water curing or wet covering) – Adds water to system. – May stain or discolor the slab.

• Liquid Membrane-Forming Curing Compounds – Do not allow concrete to begin drying until removed. – Act as a bond-breaker and prevent adhesion of finishes.

• Moisture-Retaining Covers – Can be removed as soon as cure is complete. – Can be a nuisance and potential hazard during construction.

What can I do to reduce moisture levels? • Use low w/c ratio concretes without fly ash – Be aware of extra moisture in lightweight concrete

• Use a vapor retarder under slabs-on-ground – Use a product intended for the purpose – Make sure it gets installed properly

• Avoid blotter layers • Consider the concrete curing method • Plan ahead

Planning Ahead for Flooring Installation Preconstruction Building Occupancy

Start Construction HVAC Operational

Flooring Installed

Concrete Placed Building Enclosed

REWETTING

Typical Construction Timeline

DRYING

What can I do to reduce moisture levels? • Use low w/c ratio concretes without fly ash – Be aware of extra moisture in lightweight concrete

• Use a vapor retarder under slabs-on-ground – Use a product intended for the purpose – Make sure it gets installed properly

• • • •

Avoid blotter layers Consider the concrete curing method Plan ahead Perform proper moisture testing

ASTM Moisture Test Standards • ASTM F1869 – Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride • ASTM F2170 – Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes • ASTM F2420 – Standard Test Method for Determining Relative Humidity on the Surface of Concrete Floor Slabs Using Relative Humidity Probe Measurement and Insulated Hood • ASTM F710 – Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring

ASTM F1869 – Moisture Vapor Emission Rate

ASTM F1869: Procedures to Note • • • •

Remove existing floor material. Space at operational temperature and humidity. Grind concrete surface. Three tests for first 1,000 ft2, one test for each additional 1,000 ft2 (10 yd3 truck covers 800 ft2 at 4 in. thick). • Do not concentrate test sites. • Seal dome to concrete. • Test duration of 60 to 72 hrs.

ASTM F1869: Results • MVER = (52.91 * ΔM) / (A * T) • MVER = lbs / 1,000 ft2 / 24 hrs (lbs) • Maximum MVER = 3 lbs (per ASTM F710) • Report should include the following: – Any variations from the test standard. – Ambient conditions during test. – Identify any venting requirement.

ASTM F1869: Limitations of Test • No documented scientific basis • No calibration procedures or standard reference • Only measures thin layer (1/2 in.) on surface of – Not a good indication of trapped moisture in lightweight concrete

ASTM F2170 – Internal Concrete RH

ASTM F2170: Procedures to Note • Space at operational temperature and humidity. • Select appropriate depth for holes. – Slab Drying from Top Only: 40% Depth from Top of Slab – Slab Drying from Top and Bottom: 20% Depth from Top of Slab

• Clean holes. • Seal sleeve. • Three tests for first 1,000 ft2, one test for each additional 1,000 ft2. • Do not concentrate test sites. • Test duration of 72 hrs.

ASTM F2170: Results • RH =

Water Vapor in Air (at a specific temp.) Maximum Water Vapor in Air (at same temp.) • RH = % • Maximum RH = 75% (per ASTM F710) • Report should include the following: – – – –

Depth from top of slab, slab thickness, “drying conditions.” Ambient temperature and humidity. Make and model of instruments used. Last calibration and calibration procedures.

ASTM F2170: Limitations of Test • Newer method. • Limited thickness of slab. • Different probes give different results.

Variation in RH Measurement Equipment

Variation in RH Measurement Equipment

ASTM F2170 Changes

Figure from ASTM F2170-11

ASTM F2170: Limitations of Test • Newer method. • Limited thickness of slab. • Different probes give different results.

ASTM F1869 vs. ASTM F2170 • So I conducted the tests properly, what do the results mean?

ASTM F1869 vs. ASTM F2170

High RH High MVER Low MVER

Low RH

ASTM F1869 vs. ASTM F2170

High RH

Low RH

High MVER Low MVER

• Average calculation not applicable, maximum value must be below limit. – Can consider breaking floor up into zones, but must be clearly defined by floor, concrete pour, etc.

ASTM F2420 – RH with Insulated Hood

Other Moisture Measuring Tools

ASTM F710 – pH Testing

ASTM F710: pH Test Procedure 1. 2. 3. 4. 5. 6.

Grind or sand the floor. Clean the floor. Apply 1 in. dia. puddle. Wait 60 ±5 sec. Dip pH paper in water. Compare pH paper to chart.

pH of Concrete pH = - log 10 [H+ (in moles per liter)] p[H+] + p[OH-] = 14 Adhesive Tolerance = 7-10

1 Very acidic

7 Neutral

Fresh Concrete = 12-13

14 Very alkaline Carbonated Concrete = 9

ASTM F710: Limitations of Test • Readings from different types of pH paper or meters vary • Distilled or deionized water must be used • Time between water application and pH reading must be consistent

Who should do the moisture testing? • • • • • •

General Contractor? Owner? Floor Subcontractor? Concrete Subcontractor? Material Manufacturer? Independent Testing Agency?

• And, who should hire the tester? • Include tester requirements in the specification!

Tester Qualifications • • • •

Proper Testing Equipment Experience Performing Tests Experience Interpreting Results ICRI Concrete Moisture Testing Technician Certification – Training Seminar – Written Examination – Performance Examination

Moisture Levels are High, but I need to Install • Wait Longer

What about Vented Metal Deck?

From Concrete International, January 2012

Moisture Levels are High, but I need to Install • Wait Longer • “Accelerate” Drying of the Slab

“Accelerate” Drying of the Slab

Moisture Levels are High, but I need to Install • Wait Longer • “Accelerate” Drying of the Slab • Install a Moisture Mitigation System – Consider an allowance, alternate or unit price in budget.

Install a Moisture Mitigation System

Types of Moisture Mitigation

Type of Mitigation System

Typical Manufacturer Limitations

Typical Surface Preparation Requirements

Water-Based Acrylic Coating

Low

Cleaning.

Penetrating Treatment

Low

Cleaning and sanding.

Reactive Penetrant

Medium

General cleaning.

Loose-Laid Sheet

Medium

General cleaning.

Underlayment System

High

Shotblasting.

Modified Epoxy Coating

High

Shotblasting.

Concrete Admixture

NA

NA

What should I look for in a Mitigation System? • A long track record of success and a manufacturer that will work closely with you • Epoxy-based, topical products have best performance – – – –

Continuous coating High pH tolerant ASTM E96 < 0.1 perms ASTM F3010-13 (Two-Component Mitigation Coatings)!

• Clear, specific and simple installation instructions

What Else Should Be Considered? • Surface preparation (shot blasting). • Leveling underlayment / “blotter” layer. • Assume $5 to $10 per square foot. • Include in bid upfront.

1. 2. 3. 4. 5.

Concrete Mitigation Coating Underlayment Primer Cementitious Underlayment Flooring with Adhesive

Mitigation Systems to Avoid • Penetrating coatings • Water-based materials • Concrete admixtures

Concrete Admixtures • Where does concrete mix water go? – Either into cement hydration products – Or resides within pore spaces, available for evaporation • Designed to have a chemical reaction with the concrete to form a barrier to moisture migration.

Concrete Admixtures • Cannot use standard ASTM tests for moisture. • Studies show treated concrete is permeable. • No track record for long-term performance or compatibility. • Admixtures undetectable in hardened concrete. • May increase soluble alkalis and potential for ASR. • May increase surface pH of concrete. • Does not address cracks and joints in the concrete. • May create denser concrete with reduced ability for adhesive bond.

What Other Options Do I Have? • Chose a different, more-permeable flooring system • Upgrade adhesives.

Will there be more mitigation options soon? • Proprietary ready-mix concrete mix that reduces the drying time associated with excess moisture vapor in concrete slabs – Licensed ready-mix producers only – No lightweight concrete mix – $3 to $4 per square foot for 6 in. thick slab or less

• Waterproof and pH-proof adhesives – – – –

No moisture limits No testing requirements No abrasive surface preparation Fast cure

Summary • Understanding moisture is critical to preventing failure for flooring coverings and coatings on concrete, especially with today’s water-based and 100% solids adhesives and coatings. • MVER, RH, and pH are all important when determining if a substrate is suitable for installation of flooring, BUT the tests MUST be performed correctly. • Lack of a vapor retarder, installation of a blotter layer, use of fly ash, or use of light weight concrete will increase the amount of moisture in the flooring system. • Be cautious when selecting a moisture mitigation system; not all are created equal.

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