Elastomeric waterproofing membranes for parking garage decks

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Elastomeric waterproofing membranes for parking garage decks

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Ela st om e ric w a t e rproofing m e m bra ne s for pa rk ing ga ra ge de c k s

N R C C - 4 0 3 8 2

M a i l v a g a n a m , N . P .

O c t o b e r 1 9 9 6

A version of this document is published in / Une version de ce document se trouve dans:

Materials Performance, 35, (10), Oct, pp. 24-29, October 01, 1996

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COATINGS & LININGS

Elastomeric Waterproofing

Membranes for

/

Parking Garage Decks

/

NoelP.Mailvaganam

National Research Council,Canada, Ottawa, Canada KiA OR6

The slab of a parking garage serves as a structural diaphragm and wearing surface.11

also must provide protection for the space below. Those functions require a deckto be

imperviousto liquids and stop water from seeping through cracks. Depending on the

type of structure, North American Standards require, as a minimum, sealing the top surface of the deck with penetrating sealers or elastomeric traffic bearing membranes, with or without epoxy coated reinforcing steel. Elastomeric membranes are widely used

to prevent the ingress ofwater and chloride ions, both for new and existing structures. The durability of membranes is affected by a number of factors, including poor installation, variation in product uniformity, and exposure to, adverse in-service conditions. A study of six proprietary membranes showed many degradative agents encountered in the parking garage environment affected critical properties, serial/sly reducing short- and long-term performance Of the membranes.

I

n repairing and restoring park-ing garages, the general ap-proaches include patching and waterproofing; replacing the deterio-rated surface with concrete overlays; cathodic protection; and crack injec-tion with polymeric materials such

as epoxies.1_,2

Patching and waterproofing of-fer a medium term solution to deck deterioration problems. Delamina-tion and spalls are repaired by re-moving the affected concrete to below the level of the top steel, cleaning and coating the exposed surfaces with a corrosion inhibiting primer, and back filling with fast setting,

high-24

strength concrete. After patching is completed, a surface barrier (such as a elastomeric membrane or a penetrat-ing sealer) is applied. This substan-tially reduces the penetration of moisture and chloride ions.

I"

Elastomeric membranes provide an impervious barrier to the concrete surface, bridge cracks, and respond to thermal cycling without rupture. Sealers reduce moisture and chloride ion ingress by filling the concrete pores below the level of the concrete surface.Anadvantage of elastomeric membranes is that they are thin ad-hesive coatings, that are easy to ap-ply and provide a good seal of the

concrete surface, cracks, joints, and'

drains, regardless of the geometry of

the structure.2_,4

Moisture barriers for parking ga-rages are classified into two types, thin systems 0.7 to 1.5 mm (elasto-meric adhesive coatings) and thick systems (asphalt mastics). This article discusses the composition, properties, performance, durability, criteria for selection, and quality control of the thin systems. Performance and dura-bility characteristics are illustrated by results obtained from a study involv-ing six elastomeric coatinvolv-ing systems.'

Categories of Elastomeric Membrane Systems Elastomeric parking garage membrane systems vary in chemical composition, types of wear resistant top coats, and method of application. Various types available on the mar-ket include one component, moisture-cured polyurethane, two component catalyzed polyurethane, two compo-nent flexibilized epoxy-urethane, and water-based neoprene.

Many systems are liquid elas-tomers, usually cold applied in thin

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COATINGS & LININGS

FIGURE 1

Typical configuration of a parking garage coating.

TABLE 1

Chloride Ion Permeability of Coated and Uncoated (Control) Concrete Specimens According to AASHTO T227-831

Initial Charge (Coulombs) i

t

I' I I

!

<1 <1 143 17 2 <1 8,695 w/c=0.55 36 1 24

o

502 <1 10,940

Air Entrained Nonalr Entrained

'0 1 223 o 3 <1 4,170 w/c =0.45 <1 2 <1 2 135 <1 7,615

AirEntrained Nonalr Entrained

PDM1 PDM2 PDM3 PDM4 PDM5 PDM6 Control Coating System

of a primer, followed by the water-proofing coating, 30 to 60 mil (0.75 to 1.50 mm) thick overcoated with an abrasion resistant 60 mil wear coat containing aggregate. A tie coat is then sprayed over the aggregate to firmly bond it (Figure I).'

Membrane Properties

Properties critical to a mem-brane's performance and durability are tensile strength, elongation,

ad-hesion, resistance to heat, UV,

chemi-cals, and freeze/thaw(FIT)cycling.

Mechanical Propertlps-Tensile

Strength andPercent Elongation

Membranes must endure stresses imposed by traffic without damage. Mechanical properties must remain satisfactory at all temperatures likely to be encountered in the parking ga-rage. Mechanical properties are usu-ally determined by measuring changes in tensile strength and elon-gation of free film and composite specimens.Results are expressed as a percent of the controlｶ｡ｬｵ･ＮＧｾ

Intercoat Adhesion and Adhesion to the Concrete Substrate

Good intercoat adhesion and ad-hesion to the substrate is a primary requirement that should be satisfied under normal, humid, or other spe-cific conditions to which the deck will be sUbjected. Adhesive strength of the concrete coating was evaluated us-ing a tensile bond test. Bond strengths varied with the type of concrete due to the macro structural effects of the

concrete surface on adhesion.1_,4,7

Ingeneral, lower values were ob-tained with air entrained concrete. Concretes made with water:cement (W / C) ratios exceeding 0.55 may pro-duce varied results, depending on the difference in viscosity of the mem-branes. Lower viscosity materials penetrate the pores of the concrete and provide mechanical interlocking. This increases bond strength. Lower values obtained with air entrained concrete was probably due to a fatty acid film on the surface of the cement and aggregate particles. Most air en-training admixtures are fatty acid

based. Thefilmthey produce on mor-tar and aggregate reduces adhesion of the membrane to such substrates.'

Water Vapor and Chloride Ion Permeability

The whole system (including seals curbs and joints) should be im-pervious to water and chloride ions . under all anticipated conditions. Applying the waterproofing mem-brane reduces water vapor per-meance of the concrete. However, the degree to which permeance is re-duced depends on the type of coat-ing and concrete substrate.

Waterproofing properties are usually determined through perme-ability tests conducted on composite samples consisting of the

waterproof-ing and wear coat. Tests were ｣ｯｮｾ

ducted on samples in which the coating was applied to air entrained and non-air entrained concrete at two different W/ C ratios. These tests de-termined the effect of concrete sur-face characteristics on coating film

formation, and hence moisture vapor transmission. The result (expressed as percentage permeance) was ob-tained by comparing the test values to the control value-that produced from uncoated concrete samples. Re-duced percentage permeance values were obtained for samples made with air-entrained concrete as well as those with the higher W/C ratio.' Reduced percent permeance values observed in the air entrained and higher W/ C ratio specimens was due to thicker resinous coats formed on the more porous surface of such concretes."'"

The efficiency of the coating in reducing chloride ion permeability was measured by the chloride per-meability test AASHTO T-831, based on the total electric charge passed. Most results obtained from this test showed the coating significantly re-duced chloride ion permeability into the concrete substrate. Some coatings applied to air-entrained and higher W/C ratio concrete substrates gave higher permeability values (Table1).

COATINGS & LININGS

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PDM2 PDM3 PDM4 PDM5 PDM6

FIGURE 3

Resistance to heat aging: weight changes after 28 days' exposure to 1DO°C.

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Resistance to heat aging: retention of elongation after 28 days' exposure to 100°C.

120 100

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80 Cl c

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₆₀ .c 0 1f'. 40 20 0 PDM1 PDM2 PDM3 PDM4 PDM5 PDM6 FIGURES

Resistance to UV radiation: retention of elongation of free film specimens.

Exposure to motor oil produced small reductions in tensile strength, while elongation capacity decreased in a number of membranes. Membranes immersed in ethylene glycol showed significant tensile strength reduction. ASTM C-957 has no requirements for elongation capacity, but requires a

70% retention of tensile strength. Some of the membranes did not meet theseｲ･ｱｵｩｲ･ｭ･ｮｴｳＮＲＬＵｾ

Abrasion Resistance

Wear characteristics are usually determined with a Taber Abrader'. Results are presented in terms of the

wear index, defined as the mass in grams of material worn away by the action of a rotating wheel after 1,000 cycles. Membranes with the lowest

wear index were the most wear

resis-tant (Figure 6).'·6 Some membranes were readily worn away, raising con-cern about their performance in

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COATINGS & LININGS

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,40 FIGURE 2

Effects of cold temperatures on elongation characteristics of different types of coatings.

Durability of the Coatings

The materials should not show any detrimental heat or photochemi- / cal aging effects, such as an increase in brittleness. They should be unaf-fected by

FIT

cycles and a variety of chemicals encountered in the park-ing garage environment. Durability depends on the interaction of the ma-terial with degradative factors, in-cluding temperatures in excess of lOO.oC, UV radiation, cyclic movement

at low temperature, abrasion, ｡ｵｴｯｾ

motive chemicals, and FIT cycling. Degradation caused by these factors was assessed by determining the change in the following critical coat· ing properties:

• cold temperature crack-bridging

character,

• heat aging,

• resistance toUVradiation,

• chemical resistance (to automotive fluids),

• abrasion resistance, and

• FITresistance.

The manner in which critical properties are affected by the degradative factors encountered in the parking environment is described by a discussion of results obtained from the previously mentioned study. In the discussion, test results were compared to values obtained from specimens not exposed to degradative

conditions.3_..5-8

Cold Temperature Crack-Bridging Character

The membrane should bridge cracks not exceeding 3 rnm without tearing. This capability (which should be retained at temperatures down to

-26°C) is usually evaluated by deter· mining the elongation capacity of free·ffim samples at various tempera-tures. Low temperature behavior of most waterproofing coatings, mea-sured by crack bridging and low tem-perature elongation, appeared to be poor (Figure 2). The elongation ca-pacity of most membranes was dras-tically affected at temperatures at which crack-bridging character was determined. This indicated that cracks which develop in the concrete after the coatings is installed, tend to reflect through those coatings with insufficient low-temperature elonga-tion capacity."'"

Heat Aging

Characteristics

Heat aging characteristics are important because most exterior decks of parking garages attain high surface temperatures. Car tires, de-pending on the distance traveled, can further increase the temperature in excess of 100°C. High temperatures can drastically alter properties by a change in molecular structure or a loss of volatile components.

Exposure to 100'C produced a drastic reduction in elongation capac-ity, particularly in some coatings. The dramatic loss of elongation capabil-ity of membranes can be related to the large weight loss-possibly vola-tile components, such as plasticizers (Figures 3 and 4). Loss of plasticizer decreased the flexibility of the mate-rial, reducing it's capacity to accom-modate low temperature move-ment.'''' Some membranes melted at the test temperature.

Resistance to UV Radiation

Polymeric materials exposed to sustained UV radiation (as in ex-posed roof decks) may undergo photochemical aging due to the in-. creased cross-linkingin-. Such degra-dation was accelerated in black coatings because of the increased ab-sorption of light, which raised the temperature of the coating. As the

material's temperature rose,

in-creased thermal energy caused bond cleavage and breakdown of the

poly-mer structure.2

The effects of UV degradation were determined on both the free film and composite samples, so the shield-ing effect of the wearshield-ing course, and the rate of deterioration of the water-proofing coating with no protection (as in situations where the wearing coat is pried off), could be deter-mined. Results for free film coupons, showed exposure to UV caused a re-duction in elqngation capacity of a number of coatings (Figure 5). In the composite systems, a significant re-duction in the adverse effects due to UV was observed. A shielding effect due to the wearing coat, was

evi-dent.3,5,8-9

Resistance to Automotive Chemicals

Automobiles drip antifreeze,

bat-tery acid, motor oil, and water on

parking decks. Resistance to those chemicals was determined by im-mersing cured free ffim coupons in motor oil, ethylene glycol, and water.

After a period of immersion,

reten-tion of both tensile strength and elon-gation capacity were determined.

.,"

COATINGS & LININGS

FIGURE 6

Abrasion resistance: wear index of free film specimens with H·1 0 wheels.

POMS

It

is important to

determine the F/T

durability of the

membrane/concrete

interface to ensure

integrity of the system.

type and thickness to suit in-service conditions; limitations imposed by weather conditions; surface finish of

the concrete required; exclusion of

materials (such as curing membrane)

ｴｨｾｴ interfere with adhesion; installa-tion by applicator certified by mem-brane manufacturer; and test area for appraisal.'"

Quality Control

Performance of the final product depends on material properties and on the care excised during installa-tion. Good oI;l-site control is neces-sary. Samples obtained for acceptance tests should be retained for compari-son to material delivered during the course of the installation. This also will be useful for repair. Membrane thickness should be monitored dur-ing application usdur-ing a wet mill thick-ness gauge. Samples should be

obtained from noncritical areas to

verify that dry-film thicknesses are being met. During application, cou-pons for testing of tensile strength and elongation should be obtained by spraying on boards. Values ob-tained from these tests indicate the efficiency ofthe mixing and spraying process as well as the consistency of the product being installed."',9

MP/Oclober 1996 POM3

Material Specification for Intended Job

Selection of a material for a par-ticular job should be based on a match of the material's field performance to the specific service conditions of the parking garage environment.

Crite-ria for selection must include:7 -9

• degree of structural movement, • extent of traffic loading

(commer-cial vs residential),

• designed live load capacity, height and weight restrictions, and • for exposed decks, resistance to

heat andUVradiation.

Specifications should define the membrane type and quality of the installed system. It should include All membrane systems improve

the FIT durability of air entrained

concretes. For nona,ir entrained con-cretes, only some coatings improve

theFIT durability of the concrete

sub-strate, indicating water ingress can

occur due to pinhole and blister

for-mation. POM2 POM1 0.1JI)4 1.323 0.041 1.047 ｏＮｉｊｉＩｾ 0.006 0.003 0.006 -o.(JiIJl -0.028 -0.013 -0.017 O.Of 0.628 0.019 1.371 -o.Of2 0.017 -0.018 -0.031 12.121 I') 12.712

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%Length Change ｾｾＭＭＺＭＭＺＺＭ［ＺＺＭＭＭＭＭ］ＭＭＭＢＭＭＭＭＭＺＺＺＭ］ＭＭＭ w/c=0.45 w/c

=

0.55

Air Enlf,loed Nonalr Entrained Air Entrained Nonalr Entrained

TABLE 2

Letlgth Change After 100 FreezefThaw Cycles('Vo)

1.4 1.2 1 0.8 0.6 0.4 0.2

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IAlSample. completely dolflriorated.

28

FIT Res/stance

Many parking I\arages inCanada and the U.S. have cxposed decks dam-age due toFIT. cyding is of

particu-lar concern. Damag(Ito the membrane

can result if water Sl1turates concretel

membraneｩｮｴ･ｲｦｭｾＴＮＡＬ Subsequent

ex-posure to freezinl\ conditions will cause the membrane to flake off.Itis important to detcrmine the FIT

du-rability of the membranelconcrete in-terface to ensurc integrity of the system. FIT dunlbility ,:"as

deter-mined by the perel'ntage mcrease or decrease in length<If coated concrete prisms observed ,1Iter 100 cycles of

freezing and thawing (Table 2). It

was generally acccpted that increases over0.1%in length represented the onset of fracturing in mortar

speci-mens.3,6

tain locations of the parking garage (such as the isles) where they will be subjected to constilnt abrasive stres.ses from braking wliides and spmmng

car tires.

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3. Transportation Research Board, Waterproof Membranes for Protection of Concrete Bridge Decks, laboratory phase (Project 12-11), Na-tional Cooperative Highway Research Program (NCHRP) report no. 165, National Research Council, Washington, D.C, 1976.

4. D.C. Monroe, "Reflective Cracking and Cold, Uquid-Applied Elastomeric Deck Coating and Membrane Systems: Practical Considerations from Field Observations," in: Building Deck Waterproofing, ASTM STP 1084,00, L.E. Gish, 1990, pp. 121-131.

5. Evaluation of Elastomeric Membrane Sys-tems used in Parking Garage Protection, Insti-tute for Research in Construction, National Research Council of Canada, client report A-2032, March 1992.

"6. R.M. Evans, "Test Methods Used'in ASTM Specifications for Liquid-Applied Elastomeric Membranes for Waterproofing Concrete/' in: Building Deck Waterproofing, ASTM STP 1084, ed. L.E. Gish, 1990, pp.107-118.

7. J.M. Hunnicut, "Parking Deck Deteriora-tion-The Reasons Why/' Concreteｃｯｮｳｴｲｵ｣ｾ

tion,21 (9),1976, pp. 441-448.

8. N.G. Jacobson Jr., "A Case Study of Parking Deck Deterioration Methods," Parking, Win-ter, 1982, pp. 47-57.

9. N.P. Mailvaganam, "Elastomeric Parking Deck Membranes," Concrete International: De-sign & Construction, 8 (0) 1986, pp. 51-58.

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Concluding Remarks

Elastomeric membranes restrict the ingress of moisture and chloride ions into the concrete deck. A num-ber of the systems were vulnerabie to deterioration when subjected to most of the degradative agents encoun-tered in the parking garage environ-ment. Poor installation aggravates inherent problems by producing de-fects which affect waterproofing char-acteristics. In view of the limitations

of certain membranes, selection

should be based on a serious consid-eration of the location and in-service

conditions, rather than basingit on

cost.

References

1.American Concrete Institute, "A Guide to the Use of Waterproofing, Dampproofing,ｐｲｯｾ

tective and Decorative Barrier Systems for Con-crete;' report ACI -515.1R-79, in: Manual of Concrete Practice, part 5, Detroit, MI, 1984. 2. N.P. Mailvaganam,ed., Repair and Protec-tion of Concrete Structures,eRePress, Florida, pp. 182-185,January1992, Report CR 6145.3, February 1992.

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