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Advanced SealcoatingNPE, FEB 1, 2007, NASVILLE, TN
TOPIC HOW TO IMPROVE THE PERFORMANCE OF YOUR SEALER
Sealer CompositionMix DesignsCoverage Rates, Film
ThicknessOptimum Cure & Film Formation
Presented by Girish Dubey President, STAR, Inc.
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DESIGNED FORSEALCOATING PROFESSIONALSWHO WANT TOLEARN BEYOND THE
BASICS OF SEALCOATINGS.
TO MAKE EVERY JOB LOOK & PERFORM THE VERY BEST.
PERFORMANCE IS THE CENTERPIECE
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These facts are applicable to most water based coatings. All are
very critical. GOOD QUALITY SEALER- Meets specifications, and has
an established track record.RIGHT MIX DESIGN- Follow
recommendations (manufacturer or job specs.). APPLY @ RECOMMENDED
RATES- To deposit the right amount of sealer on the pavement. DRY
& CURE UNDER RIGHT AMBIENT CONDITIONS- temperature, humidity,
wind velocity.
PERFORMANCE THE CENTERPIECE
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SEALCOATING BASICSSEALCOATINGS ARE ;
WATER-BASED COATINGS,A STABLE DISPERSIONS OF;a. BINDER (RT-12 or
AC) is the backbone of the sealer and provides the protection to
the pavement against the elements.- weather, salt, water,
chemicals, etc.b. Clay and Fillers- Provide tensile strength,
toughness, body and stability.c. Water- is the medium in which tar,
clay fillers are dispersed. d. Emulsifiers, specialty chemicals-
help dispersion, provide stability and special properties.
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What Makes A Good SealerHow Can You Tell?1. Meets /or Exceeds
Specifications: (ASTM, FEDERAL, FAA, etc.). 2. Proven Performance:
Good Track Record.3. Dark, Chocolate Brown in Color- Indicating
Fine Dispersion of Tar or AC.
4. pH - 7-8 - Below 7 slightly acidic- May be unstable,- Over 8-
Alkaline- Prone to water sensitivity.
5. References, Comparative Evaluation
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What Makes A Good SealerHow Can You Tell?4. pH of the sealer,
7-8: Lower Ph-slightly Acidic may induce instability.Higher
pH-Alkaline- Prone to water sensitivity.5. References, Comparative
Test Data.
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TYPICAL SEALER COMPOSITION Undiluted (as manufactured)
Sheet1
SEALER COMPOSITION, %
BY WEIGHTBY VOLUME10.0733627251
BINDER3029.32.9126213592BINDER29.3
FILLER (CLAYS ETC.)198.90.8788159112FILLER (CLAYS ETC.)8.9
EMULSIFIER,ETC.11.30.1333333333EMULSIFIER,ETC.1.3
WATER5060.56.0024009604WATER60.5
TOTAL100100.09.9271715641
Sheet1
COMPONENTS BY WEIGHT, %
Sheet2
COMPONENTS BY VOLUME, %
Sheet3
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MIX DESIGNSAN OVERVIEW.
SEALCOATING IS NEVER APPLIED IN ITS CONCENTRATED FORM GENERALLY
MIXED WITH; 1. WATER- FOR FLUIDITY, WORKABILITY, 2. SILICA SAND-
TEXTURING, - TRACTION, - FILLING VOIDS (profile, minor surface
cracks),3. ADDITIVES (OPTIONAL)- PERFORMANCE BOOSTING (Flexibility,
Toughness, Resistance to salt, water, chemicals..),- Drying
Accelerator
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MIX DESIGNSAN OVERVIEW.STANDARD SYSTEM: A 2-coat system Mix
Design SEALCOATING (CONC) 100 GALWATER (30% BY VOL.) 30 GAL SILICA
SAND /aggregate 200-300 lb TOTAL 145 GAL. Application Rates, Gal
(conc.) Sealer/Sq. Yard: Ist. Coat- 0.10-0.12 IInd. Coat-0.08-0.10
TOTAL (2 COATS) : 0.18-0.20 GAL. /SQ. YARD.
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MIX DESIGNS
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Hazards in Altering the Mix DesignsFollow the recommended mix
designsChanging the mix design may cause performance problems 1.
WATER:A. EXCESSIVE- - Thinner Dry Film Thickness (D.F.T.) - Poor
Durability, - Premature failure.Important ADJUST APPLICATION RATE
TO MAINTAIN DRY FILM THICKNESS.B. NOT ENOUGH WATER- - Poor Flow,
uneven appearance - The sealer may not wet out the surface properly
for good adhesion.- Tracking is possible.
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Hazards in Altering the Mix Designs
The coverage rate will have to be adjusted to account for the
higher amounts of water to maintain the same Dry Film Thickness
(DFT)
COMPONENTS.%
SEALER COMPOSITION, %
BY WEIGHTBY VOLUME10.0733627251
BINDER3029.32.9126213592BINDER29.3
FILLER (CLAYS ETC.)198.90.8788159112FILLER (CLAYS ETC.)8.9
EMULSIFIER,ETC.11.30.1333333333EMULSIFIER,ETC.1.3
WATER5060.56.0024009604WATER60.5
TOTAL100100.09.9271715641
COMPONENTS.%
COMPONENTS BY WEIGHT, %
Sheet2
COMPONENTS BY VOLUME, %
Sheet3
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATERDILUTION RATE, %DFTWFT
SEALER10060.52512.840.43.15625
WATER2525.03012.8423.28125
ADDITIVE10.63512.843.63.40625
5012.845.23.53125
TOTAL12686.16012.851.64.03125
SEALER, % BY VOLUME79%
% WATER68.3%
SOLIDS, % VOLUME31.7%
APPLICATION RATE OF THE MIXTURE0.23GAL/SQ.YD
39.7SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS40.4
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER3030.0DILUTION RATE, %DFTWFT
ADDITIVE10.62514.345
3013.745
TOTAL13191.13513.245
SEALER, % BY VOLUME76%5012.745
% WATER69.5%6011.245
SOLIDS, % VOLUME30.5%
APPLICATION RATE OF THE MIXTURE0.24GAL/SQ.YD
38.2SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS42.0
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER3535.0
ADDITIVE10.6
TOTAL13696.1
SEALER, % BY VOLUME74%
% WATER70.7%
SOLIDS, % VOLUME29.3%
APPLICATION RATE OF THE MIXTURE0.24GAL/SQ.YD
36.8SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS43.6
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER4040.0
ADDITIVE10.6
TOTAL141101.1
SEALER, % BY VOLUME71%
% WATER71.7%
SOLIDS, % VOLUME28.3%
APPLICATION RATE OF THE MIXTURE0.25GAL/SQ.YD
35.5SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS45.2
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER5050.0
ADDITIVE10.6
TOTAL151111.1
SEALER, % BY VOLUME66%
% WATER73.6%
SOLIDS, % VOLUME26.4%
APPLICATION RATE OF THE MIXTURE0.27GAL/SQ.YD
33.1SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS48.4
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER6060.0
ADDITIVE10.6
TOTAL161121.1
SEALER, % BY VOLUME62%
% WATER75.2%
SOLIDS, % VOLUME24.8%
APPLICATION RATE OF THE MIXTURE0.29GAL/SQ.YD
31.1SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS51.6
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER8080.0
ADDITIVE10.6
TOTAL181141.1
SEALER, % BY VOLUME55%
% WATER78.0%
SOLIDS, % VOLUME22.0%
APPLICATION RATE OF THE MIXTURE0.33GAL/SQ.YD
27.6SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS58.1
DRY FILM THICKNESS (DFT), MILS12.8
Sheet3
DFT
WFT
% WATER OF DILUTION
MILS, DFT
MAINTAIN DFT-REDUCE COVERAGE
DFT
WFT
% WATER OF DILUTION
MILS, DFT
DFT WILL DECREASWE WITH DILUTION
Chart1
14.345
13.745
13.245
12.745
11.245
DFT
WFT
% WATER OF DILUTION
MILS, FILM THICKNESS
DECREASE IN DFT AT CONSTANT WFT
Sheet1
DILUTION RATE, %DFTWFT
2514.345
3013.745
3513.245
5012.745
6011.245
Sheet1
DFT
WFT
% WATER OF DILUTION
MILS, FILM THICKNESS
DECREASE IN DFT AT CONSTANT WFT
Sheet2
Sheet3
MBD0057DE41.xls
COMPONENTS.%
SEALER COMPOSITION, %
BY WEIGHTBY VOLUME10.0733627251
BINDER3029.32.9126213592BINDER29.3
FILLER (CLAYS ETC.)198.90.8788159112FILLER (CLAYS ETC.)8.9
EMULSIFIER,ETC.11.30.1333333333EMULSIFIER,ETC.1.3
WATER5060.56.0024009604WATER60.5
TOTAL100100.09.9271715641
COMPONENTS.%
0
0
0
0
COMPONENTS BY WEIGHT, %
Sheet2
0
0
0
0
COMPONENTS BY VOLUME, %
Sheet3
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATERDILUTION RATE, %DFTWFT
SEALER10060.52512.840.43.15625
WATER2525.03012.8423.28125
ADDITIVE10.63512.843.63.40625
5012.845.23.53125
TOTAL12686.16012.851.64.03125
SEALER, % BY VOLUME79%
% WATER68.3%
SOLIDS, % VOLUME31.7%
APPLICATION RATE OF THE MIXTURE0.23GAL/SQ.YD
39.7SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS40.4
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER3030.0DILUTION RATE, %DFTWFT
ADDITIVE10.62514.345
3013.745
TOTAL13191.13513.245
SEALER, % BY VOLUME76%5012.745
% WATER69.5%6011.245
SOLIDS, % VOLUME30.5%
APPLICATION RATE OF THE MIXTURE0.24GAL/SQ.YD
38.2SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS42.0
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER3535.0
ADDITIVE10.6
TOTAL13696.1
SEALER, % BY VOLUME74%
% WATER70.7%
SOLIDS, % VOLUME29.3%
APPLICATION RATE OF THE MIXTURE0.24GAL/SQ.YD
36.8SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS43.6
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER4040.0
ADDITIVE10.6
TOTAL141101.1
SEALER, % BY VOLUME71%
% WATER71.7%
SOLIDS, % VOLUME28.3%
APPLICATION RATE OF THE MIXTURE0.25GAL/SQ.YD
35.5SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS45.2
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER5050.0
ADDITIVE10.6
TOTAL151111.1
SEALER, % BY VOLUME66%
% WATER73.6%
SOLIDS, % VOLUME26.4%
APPLICATION RATE OF THE MIXTURE0.27GAL/SQ.YD
33.1SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS48.4
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER6060.0
ADDITIVE10.6
TOTAL161121.1
SEALER, % BY VOLUME62%
% WATER75.2%
SOLIDS, % VOLUME24.8%
APPLICATION RATE OF THE MIXTURE0.29GAL/SQ.YD
31.1SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS51.6
DRY FILM THICKNESS (DFT), MILS12.8
MIX DESIGNS
EFFECT OF WATER ADDITION ON DFT.
GALLONSWATER
SEALER10060.5
WATER8080.0
ADDITIVE10.6
TOTAL181141.1
SEALER, % BY VOLUME55%
% WATER78.0%
SOLIDS, % VOLUME22.0%
APPLICATION RATE OF THE MIXTURE0.33GAL/SQ.YD
27.6SQ.FT/GALLON
WET FILM THICKNESS (WFT), MILS58.1
DRY FILM THICKNESS (DFT), MILS12.8
Sheet3
00
00
00
00
00
DFT
WFT
% WATER OF DILUTION
MILS, DFT
MAINTAIN DFT-REDUCE COVERAGE
00
00
00
00
00
DFT
WFT
% WATER OF DILUTION
MILS, DFT
DFT WILL DECREASWE WITH DILUTION
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Hazards in Altering the Mix Designs 2. SAND/ AGGREGATEEXCESSIVE
(OVER 5,6 LB)-POOR FLEXIBILITY, BRITTLENSSPOOR ADHESION TO
PAVEMENTPOOR ANCHORING,SAND ROLL OUTPREMATURE FAILURENONE OR VERY
LITTLE (
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Hazards in Altering the Mix Designs 3. ADDITIVES
- VERY SELECTIVE. - FOLLOW MANUFACTURERS RECOMMENDATIONS. - MAY
NOT BE COMPATIBLE WTH THE SEALER.
EXCESSIVE (OVER 5 %):- WASTE OF MONEY- MAY ADVERSELY AFFECT
PROPERTIES
NOT ENOUGH (LESS THAN 1 %):- INEFFECTIVE- MARGINAL PERFORMANCE
IMPROVEMENT,- MOSTLY FOR NAMESAKE.
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COVERAGE RATES AREA COVERED BY A GALLON OF (undiluted)
SEALER
EXPRESSED IN 2 WAYS; 1. Gallons of sealer per square yard
(gal./sq. yard) .Most commonly used. or2. Square feet area covered
by one gallon of undiluted sealer.
A typical Coverage Rate for a two (2) coat application is-
0.18-0.20 gal (undiluted)sealer/sq. yard 1st Coat- 0.10-0.12
gal./sq. yd.2nd Coat-0.08-0.10 gal./sq. yd.
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CRITICAL FACTORS FOR SEALER PERORMANCECOVERAGE RATE Sealer must
be applied at the recommended coverage rate. It is assured by
measuring:-WET FILM THICKNESS (W.F.T.) & -Calculating DRY FILM
THICKNESS (D.F.T.)
2. CURE CONDITIONS: Must be right.TEMPERATURE (ground and
surface) HUMIDITY OR RELATIVE HUMIDITY(R.H.)- Capacity of air to
hold water @ ambient temperature.WIND VELOCITY
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COVERAGE RATE CONFIRMATION-SEALER FILM THICKNESS STEP 1DETERMINE
THE WET FILM THICKNESS (W.F.T.)Two methods: Calculate- Apply sealer
on a known area (sq. feet) and divide gallons used, to get coverage
in sq. ft./gallon. W.F.T. (IN MILS) = 1604/COVERAGE IN
SQ.FT.GALLON.Discussed later.. Use a wet film thickness gauge
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COVERAGE RATE CONFIRMATION-SEALER FILM THICKNESS
STEP-2
Determine the solids % by Volume
2. Calculate % solids by volumeWater (% by Vol.) = 101.2/155.9 =
65% Solids (% by Vol.) = 100% - 65% = 35%
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Determine the wet film thickness Wet Film Thickness is expressed
in mils 1 MIL= 1/1000 inch.
IF THE ;
a. COVERAGE IS KNOWN IN SQ. Ft./GAL. DIVIDE INTO 1604
(CONSTANT)
For example for 50 sq. ft/gal.,W.F.T. = 1604/50 = 32 MILS.
1604 = one gallon of coating covers 1604 sq. ft. in one (1) mil
film thickness.
b. COVERAGE KNOWN IN GAL./SQ. YARD. MULTIPLY WITH 178.2
(CONSTANT)
For example 0.18 Gal./Sq. YardW.F.T. = 178.2 X 0.18 = 32
mils.COVERAGE RATE CONFIRMATION-SEALER FILM THICKNESS
Step-3
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STEP 4
Calculate Dry Film Thickness (D.F.T.)
SIMPLEMULTIPLY WET FILM THICKNESS (W.F.T.) WITH SOLIDS %
BYVOLUME)D.F.T = W.F.T. x % solids by vol.
EXAMPLED.F.T. = 32 mils x 0.35 = 11.2 mils.
COVERAGE RATE CONFIRMATION-SEALER FILM THICKNESS
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DRYING & CURING of SEALCOATINGSDRYING- EARLY STAGES
CURING-FINAL FILM SET UP SEALCOATINGS CURE THROUGH:
RELEASE OF WATER , THROUGH EVAPORATION
FILM SHRINKS IN VOLUME
PARTICLES OF THE BINDER AND FILLER ARE FORCED TO COALESCE
BINDER PARTICLES SOFTEN, FUSE AND ENVELOPE CLAY/FILLER
PARTICLES.
CONTINUOUS SEALER FILM IS FORMED.
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DRYING & CURING OF SEALCOATINGS
WE WILL DISCUSS
1. CURE MECHANISM
2. FACTORS AFFECTING CURE
TEMPERATURE- (SURAFCE & AMBIENT) RELATIVE HUMIDITY (%
R.H.)
WIND VELOCITY
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DRYING & CURING OF SEALCOATINGS1. Cure Mechanism:
Sealcoatings are water-based Water represents the largest
portion of mix design (65%) They dry/ cure by releasing water. As
water evaporates, the film shrinks in volume (to 35% remaining as
dry film)
Binder (tar/asphalt) and clay/filler particles are forced in
closer proximity
Binder particles touch each other and start fusing, thus
enveloping clay/filler particles and bonding to the pavement
Continuous film results-Free of voids
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DRYING & CURING OF SEALCOATINGSCURE MECHANISM:Volume
Shrinkage in Film
Sealer Solids onlyWATER
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DRYING & CURING OF SEALCOATINGS
CURE MECHANISM:Sealer wet film: Is multi-layered (composite)
layer of many thin films
Each layer dries individually from top to bottom,
The release of water becomes more difficult as each layer dries
Bottom layer takes longer to cure
The sealer may appear fully dry on the surface but the bottom
layers may still be soft.
Allow sufficient drying.
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DRYING & CURING OF SEALCOATINGS CURE MECHANISM:
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2. CURE CONDITIONSFactors Affecting Drying
TEMPERATURE (ambient & surface)
Min. 500 F and rising is preferredA. Lower temperatures :
POOR FILM FORMATION. BINDER PARTICLES DO NOT SOFTEN PROPERLY TO
FUSE AND FORM A CONTINOUS FILMIt may result in: POOR PERFORMANCE.
SEALER PROPERTIES ARE LOST, SELDOM RECOVER.GRAY COLOR ON INITIAL
DRYING.
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Factors Affecting Drying (cont..)
B. Higher Temperatures: Over 90o F
WATER FLASHES OFF- IMMOBILIZING THE BINDER PARTICLES IN THE
FILM. IT MAY RESULT INTO:
TRACKINGPINHOLINGSAND BALLINGDRYING IN THE WINDROWPOOR &
STREAKY APPEARANCE
HumidityCapacity of the surrounding air to hold water Low
Humidity: Very favorable for drying and cure. Will speed up
drying.
High Humidity- Slow cure. Need more drying time.
WIND VELOCITY Will carry volatiles away.
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HumidityWater Vapor in the Air Additional Notes
Relative Humidity (R.H.) : Capacity (%) of air to hold water
vapor at a particular temperature.- Low R.H.- MEANS THE AIR HAS
ROOM TO ABSORB MORE WATER VAPOR. 30% MEANS 30% of the capacity used
up- 70% remaining.Good for sealer drying.- High R.H.- MEANS THE AIR
HAS VERY LITTLE ROOM ABSORB MORE WATER VAPOR. 80% MEANS 80% of the
capacity used up- 20% remaining.Poor for sealer drying.Air is like
a blotting paper.- It will keep absorbing water as long as it is
not saturated. The capacity of the Air to hold water vapor will
change with temperature.Higher temperature Higher the capacity .
Air will expand.
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CAPACITY OF AIR TO HOLD WATER VAPOR @ SATURATION VS.
TEMPERATURE
-
EVAPORATION RATE @ VARIOUS R.H. and TEMPERATURE
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DRYING & CURING of SEALCOATINGSFavorable Conditions:
Moderate Temperatures Low humidity Moderate wind velocity
Unfavorable Conditions: Low Temperatures High humidity Stagnant
wind
GENERAL
Allow each coat to dry sufficiently, prior to applying the
subsequent coating.
Take light vehicular traffic (application equipment - e.g. spray
rig) scuffing and tearing.
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ADDITIVES1. WHAT ARE ADDITIVES? DEFINITION TYPES
2. WHAT THEY DO & HOW THEY IMPROVE THE SEALER PERFORMANCE?
FAA QUALIFYING TESTS
3. WHAT THEY DO NOT DO?COMPENSATE FOR POOR PERFORMANCE, IF
EXCESSIVE WATER OR SAND IS USED.
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DEFINITIONSADDTIVES ARE THE
Materials Added to Sealcoatings to ACCOMPLISH
SPECIFICOBJECTIVESADDITIVES
-
ADDITIVESOBJECTIVESIMPROVED PROPERTIES:Flexibility and
elongationToughnessWater resistanceResistance to chemicals,
de-icing salts, oils, fats, grease etc..FAST DRYING:Even under
not-so-ideal weather conditions. UNIFORM DRY COLOR:Under shade or
shine.THICKENING:To accommodate large amounts of water.SAND OR
AGGREGATE SUSPENSION: No streaking, NO SAND BALLING.
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ADDITIVESfor PERFORMANCE BOOSTING
Have been used for the last 30-35 years.
Extensively used since mid-70s FAA specified
A/B (Acrylonitrile/butadiene) rubber latex for coal tar based
sealers.
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PERFORMANCE BOOSTING RUBBERIZING ADDITIVES FOR SEALCOATINGS
1. REDUCE TEMPERATURE SUSCEPTIBILITY; Reduce Tack and flow in
summer & brittleness in winter months.
2. INCREASE TOUGHNESS;Greater resistance to abrasion, scour and
wear. Better retention of aggregates.
3. INCREASE FLEXIBILITY AND ADHESION;Better anchoring of
aggregates.
OTHER BENEFITS
THICKENING Due to pH alteration of the coating system.FAST
DRYING Even under not-so-ideal weather conditions.
UNIFORM DRIED COLOR
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RUBBERIZING ADDITIVESHOW DO THEY WORKRubberizing additives are
water emulsion of polymer molecules.
Polymers (selected) have;Large chain length, heavily branched,
Excellent resistance to chemicals, salts, water, weathering,
etc.
When mixed with the sealer:Polymer chains in sealcoating
materials, 1. Form a flexible and tough network of polymer
molecules,2. Hold binder (tar, asphalt), fillers and aggregate
uniformly.
-
AS THE SEALCOATING DRIES
Polymer network tightens within the film, it forces water out at
a uniform rate, producing uniform dry color. Polymer fuses onto the
tar (asphalt) particles thus improving;
ELXIBILITY, TOUGHNESSFUEL & CHEMICAL RESISTANCESAND
SUSPESION AND ANCHORINGFAST DRYING.
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THE POLYMER FOR THE ADDITIVEMUST BE RESISTANT TO:
WEATHERINGGASOLINE, OILS, FATSSALTSPETROCHEMICALSOTHER
CHEMICALS..
WEAKNESS IN THE POLYMER (ADDITIVE) WILL INTRODUCE WEAK LINKS IN
THE SEALER AND MAY CAUSE PREMATURE FAILURE.
-
Majority of the POLYMERIC ADDITIVES:
Produce Thickening, Speed up Drying Time, Produce Uniform Dry
Color, Help to Suspend aggregates.
But they differ in their abilities to;
Reinforce the properties like, Flexibility, Toughness,
Temperature Susceptibility etc.
Improve resistance to Chemicals, oils, fats, grease, de-icing
salts, aromatic fuels etc.
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ADDITIVESThe Right Additive Used in Right Proportion
will;Reinforce the properties,Improve the overall performance
BUT WILL NOTMix design deficiencies caused by the excessive
amounts of ;
Water- thinner dry films Sand/Aggregate- May not supply enough
binder to satisfy the demand of the excessive amounts of aggregates
used in the mix.
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ADDITIVES: CONCLUSIONS
1.Acrylonitrile/Butadiene polymers (NBR TYPE) have the best
overall properties. - They reinforce and boost the properties of
asphalt and coal-tar based sealers.- better resistance to oils and
other petrochemicals than Styrene/Butadiene polymers. Rest of the
properties are similar.
2.Polyvinyl Acetate/acrylic co-polymers (PVAs) are not
recommended due to poor water and alkali resistance. Introduce weak
spots in the film when attacked by water. Useful only as thickeners
and for speeding up drying.