national bureau of standards reportkh eh si £ 00m j-cmalnovo c\jvo ... panelno.6 100 84 84 63 83...

$: NATIONAL BUREAU OF STANDARDS REPORTkH Eh Si £ 00m J-CMAlnOvO C\JvO ... PanelNo.6 100 84 84 63 83 Average 98 83 80 72 82 FailurePattern^/ CA A AC EA AED AsphaltIII SofteningPoint,°F$
NATIONAL BUREAU OF STANDARDS REPORT

3616

LABORATORY STUDIES OF SEVERAL FACTORSAFFECTING THE BEHAVIOR OF SOME MINERALS

AS STABILIZERS FOR ASPHALT ROOFING

By

Sidney H. Greenfeld

<NBS>U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

U. S. DEPARTMENT OF COMMERCESinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDSA. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDSThe scope of activities of the National Bureau of Standards is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section is engaged in special-

ized research, development, and engineering in the field indicated by its title. A brief description

of the activities, arid of the resultant reports and publications, appears on the inside of the backcover of this report.

Electricity. Resistance and Reactance Measurements. Electrical Instruments. MagneticMeasurements. Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Optical Instruments. PhotographicTechnology. Length. Engineering Metrology.

Heat and Power. Temperature Measurements. Thermodynamics. Cryogenic Physics. Enginesand Lubrication. Engine Fuels. Cryogenic Engineering.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid

State Physics. Electron Physics. Atomic Physics. Neutron Measurements. Infrared Spectros-

copy. Nuclear Physics. Radioactivity. X-Ray. Betatron. Nucleonic Instrumentation. Radio-logical Equipment. Atomic Energy Commission Radiation Instruments Branch.

Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry.Inorganic Chemistry. Electrodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry.Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Fluid Mechanics. Engineering Mechanics. Massand Scale. Capacity, Density, and Fluid Meters. Combustion Control.

Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifica-

tions. Polymer Structure. Organic Plastics. Dental Research.

Metallurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion.

Mineral Products. Porcelain and Pottery. Glass. Refractories. Enameled Metals. Concreting

Materials. Constitution and Microstructure.

Building Technology. Structural Engineering. Fire Protection. Heating and Air Condition-

ing. Floor, Roof, and Wall Coverings. Codes and Specifications.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering.

Electronics. Engineering Electronics. Electron Tubes. Electronic Computers. Electronic

Instrumentation. Process Technology.

Radio Propagation. Upper Atmosphere Research. Ionospheric Research. Regular Propagation

Services. Frequency Utilization Research. Tropospheric Propagation Research. High FrequencyStandards. Microwave Standards.

^Office of Basic Instrumentation ®Office of Weights and Measures.

NATIONAL BUREAU OF STANDARDS REPORTNBS PROJECT NBS REPORT

1004-10-1017 August 16, 1954 3616

LABORATORY STUDIES OF SEVERAL FACTORSAFFECTING THE BEHAVIOR OF SOME MINERALS

AS STABILIZERS FOR ASPHALT ROOFING

By

Sidney H* GreenfeldResearch Associate

Asphalt Roofing Industry Bureau

Floor, Roof and Wall Coverings SectionBuilding Technology Division

Sponsored byAsphalt Roofing Industry Bureau

NBS

. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication,Approved for public release by the

or ln part ' IS prohlblted

unless permissior . XT . , T . „ Standards, WashingtonDirector of the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

25, D, C. Such p

cal ly prepared If

report has been specifi-

• report for its own use,

CONTENTS

9|c>(c^c^c3)c4o|c^:

PageSUMMARY 1

1. INTRODUCTION 2

2 0 MINERAL MATERIALS 3

2.1 Materials Tested as Stabilizers 32.2 Asphalts 3

3. EQUIPMENT AND PROCEDURE 3

4. EXPOSURE SERIES 6

4.1 The Effect of the Softening Pointof the Asphalts on Their Dura-bility 6

4.2 The Effect of the Softening Point ofthe Base Asphalt on the Durabilityof Coatings Containing MineralAdditives 6

4.3 Selected Minerals ~ The Effect of SomeNatural Variations of Clay, Fly Ashand Silica on the Durability of Coat-ings 9

4.4 The Effect of the Degree of Mixing ofMinerals with Asphalt on the Dura-bility of Roof Coatings l4

4.5 The Effect of the Particle-Size Dis-tribution of the Mineral Matter onthe Durability of Coatings 17

4.6 The Effect of Particle Shape ofMinerals on the Durability ofCoatings 23

TABLES

Table No. Page

I. Properties of Minerals ^ - 5

II. Durability of Asphalt Products 7

III. Effect of the Softening Point ofthe Base Asphalt on the Durabilityof Coatings 8

IV. Properties of Clays, Fly Ashes, andSilicas 10-11

V. Durability Data 12-13

VI. Mixing Procedures in Asphalt III 16

VII. Particle Size Distribution Series3 5% Mineral Matter 18-20

VIII. Particle Size Distribution Series50% Mineral Matter in Asphalt II 22

IX. Fineness Factor 25

LABORATORY STUDIES OF SEVERAL FACTORS AFFECTINGTHE BEHAVIOR OF SOME MINERALS AS STABILIZERS

FOR ASPHALT ROOFING

by

Sidney H, Greenfeld

SUMMARY

The effects of a number of variables inherent in asphaltsand minerals available for use in asphalt roofings that werenot reported in "Laboratory Evaluation of Six SelectedCommercially Available Materials as Stabilizers for AsphaltRoofings" are covered in this report. The influence of soft-ening point of the asphalts; particle sLze distribution of themineral matter; particle shape of the mineral matter; naturalvariations in three of the minerals; and the thoroughness ofmixing on the durability of the coatings were measured. Thefollowing generalizations resulted:

(1) The durability of the three asphalts decreasedas their softening points increased,

(2) The greater durability of the lower softeningpoint asphalts was readily apparent with mineral con-centrations of 50% or greater,

(3) None of the three clays evaluated had anyappreciable effect on the durability,

(4) Fly ash samples could not be evaluated on thesame basis as other samples because the spark methodof determining failure could not be used.. The indica-tions are, however, based on visual determination offailure, that the effect of fly ash on durability isvariable, that sample being designated as "low carbon"being least beneficial,

(5) Of the four silicas- only the special silica,characterized by its relatively greater fineness,(and with Asphalt II, Ottawa Silica) increased thedurability of the asphalts,,

(6) Thorough mixing is necessary to obtain the mostuniform and optimum benefits from the use of mineralsas stabilizers*

(7) Commercial blue black slate, Niagara dolomiteand Lake Erie Silica were fractionated into a numberof particle size ranges and reconstituted into five

- 2 -

synthetic size distributions. The durabilities ofcoatings made from 35# of each of these with eachof the asphalts were in the following descendingorder

i

Classification with U. S. Standard Sieves

Passing 200 meshCommercial GradationPassing 325 meshEqual Size (approximately equal weights

on each sieve)Uniform Size (Passing 140 * Retained on

230 )

Passing 60 - Retained on 200 mesh

(8) Minerals with flat, plate-like particles(blue black slate, mica, and oyster shell) were most

. beneficial as stabilizers.

1. INTRODUCTION

During the planning of the mineral stabilizer researchprogram it was recognized that there were several variablesinvolved in stabilization of asphalts against degradation- .

that were not covered by the exposures of the main series*'to be made. Supplementary exposure series were planned todetermine whether any relationship could be establishedbetween some of these properties of the materials and dura-bility and between some processing variables and durability.The following series of exposures were made*

(1) The Effect of Softening Point on the Dura-bility of Asphalt.

(2) The Effect of the Softening Point of theBase Asphalts on the Durability of Coatings*Containing Mineral Additives.

Greenfeld. S. H.. "Laboratory Evaluation of Six SelectedCommercially Available Materials as Stabilizers forAsphalt Roofing"

,Sept. 23, 1953*

- 3 -

(3) Selected Minerals - The Effect of Some NaturalVariations of Clay, Fly Ash, and Silica on theDurability of Coatings

„

(b) The Effect of the Degree of Mixing of Mineralswith Asphalt on the Durability of Coatings,

(5) The Effect of the Particle-Size Distribution ofthe Mineral Matter on the Durability of Coatings.

(6) The Effect of the Particle Shape of the MineralMatter on the Durability of Coatings,

With the exception of the Selected-Materials andParticle-Shape Series, all of the properties studied areof the type that can be modified in the laboratory orplant

.

2, MINERAL MATERIALS

2.1 Materials Tested as Stabilizers

Because of the numerous materials tested as stabilizersand the limited number of tests performed on each, themineral materials will be described in connection with theseries of exposures with which each is connected. Table I

is a general tabulation of the properties of some of theseminerals

.

2.2 Asphalts

The asphalts used were the same as those reported in"Laboratory Evaluation of Six Selected Commercially AvailableMaterials as Stabilizers for Asphalt Roofing", The asphaltproducts were blended to produce a base asphalt which, whenmixed with the desired mineral matter, resulted in coatingwith a softening point in the range of 217 to 227°F.

3, EQUIPMENT AND PROCEDURE

The equipment and procedures for making the exposurepanels and exposing and evaluating the coatings were asdescribed in the above-mentioned report.

TABLE

I.

PROPERTIES

OF

MINERALS

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Method described in "A Survey of Materials Availablefor Use as Mineral Stabilizers’*, A.R.I.B., Oct. 1952.

b/“Isopropyl Alcohol Displacement.

sJNitrogen Adsorption - B.E.T. Method.

d/A.S.T.M. Method D281-31, Using Primol D and Water.

e/Sedimentation in Isopropyl Alcohol.

f/Supplier’s Data for Typical Material.

*C Mineral Matter in Asphalt III (S.P. = 223°F).

- 6 -

EXPOSURE SERIES

4 0 1 The Effect of the Softening Point of theAsphalts on Their Durability

Coatings, 25 mils thick, were made from each of theasphalt products and exposed in the accelerated durabilitymachines to determine the effect of softening point onthe durability of the asphalts 0

The durabilities of these products are tabulated inTable II and shown graphically in Figure 1. The generaltrend is for the durability to decrease as the softeningpoint of the asphalt increases D It must be stated, however,that there was an occasional specimen that deviated fromthe general trend with an abnormally low or high durability.Some differences in durability were the result of exposinghalf of the panels in one machine (odd ones) and half inanother (even ones) 0 In most cases the agreement was good,but in two instances, there was considerable divergencebetween the results of the two exposures 0

4 q 2 The Effect of the Softening Point of the BaseAsphalt on the Durability of Coatings

Containing Mineral Additives

Table III and Figure 2 are comparisons of coatingsmade from a common base (Product C of Asphalt II) asphaltwith those made to a definite softening point range, em-ploying progressively softer asphalt as the quantity ofmineral additive was increasedo The coatings containingthe common base seemed to be slightly more durable in thelower mineral concentrations, but the difference was verysmall and of the same order of magnitude as the differencesfound in replicate panels exposed at the same time. Thus,variation in the softening point of coatings containingmineral additives seems to be less significant than inasphalt coatings without additive

s

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- 7 -

TABLE II. DURABILITY OF ASPHALT PRODUCTS

PRODUCT A B c D E

Asphalt I

Softening Point, °FPenetration at 25°C

192 205 215 224 2372b 21 19 17 15

Acc. Dur., DaysM/Panel No. 1 bb 37 29 29 28Panel No. 7 30 37 29 29 28Panel No. 2 52 38 36 36 28Panel No. 6 52 38 36 29 28Average 44 37 33 31 28

Failure Pattern—/ C C c C C

Asphalt IISoftening Point, °F 196 212 225 234 239Penetration at 25°C 25 20 17 17 15Acc. Dur., Dayss/

Panel No. 1 108 83 82 81 482/

Panel No. 7 83 83 69 61 81Panel No. 2 100 84 84 83 83Panel No. 6 100 84 84 63 83Average 98 83 80 72 82

Failure Pattern^/ CA A AC EA AED

Asphalt IIISoftening Point, °FPenetration at 25°C

195 195 208 235 23919 19 19 15 15

Acc. Dur., Days a/Panel No. 1 95 95 81 85 64Panel No. 7 86 95 81 85 57Panel No. 2 87 87 46 37Panel No. 6 87 87 ltl£/ 46 37Average . 89 91 81 66 48

Failure Pattern-^/ AC AC - 11 TPAi1 A

a/Odd numbered panels were in one machine; even in another,

Patterns are described in "Laboratory Evaluation of SixSelected Materials as Stabilizers in Asphalt Roofing".

^Jot counted in average.

- 8 -

TABLE III. EFFECT OF THE SOFTENING POINT OF THE BASEASPHALT ON THE DURABILITY OF COATINGS^/

CONCENTRATION OFMINERAL, $

PANEL.no.£/

COMMONSOFT. PT.°p

BASE MIX

BASE

DUR.DAYS

VARIABLESOFT. PT.° F o f

BASE MIX

BASE

DUR.DAYS

Asphalt II 1 225 225 82 228 228 747

ii it 69 it ii 742 it ii 84 it n 766 ii ii 84 ti it 76

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- 9 -

4.3 Selected Minerals - The Effect of Some NaturalVariations of Clay, Fly Ash and Silica on theDurability of Coatings (All coatings tested inthis series were 25 mils thick and contained

25% mineral matter.)

The three types of materials investigated in this series(described in Table IV) are representative of the wide varietyof each type available. Despite the fact that the threeclays tested varied from a disordered kaolinite (FloridaClay) to a mullite, there was little difference in theireffects on the durability of any of the asphalts (Table Vand Figure 3). Because of the flocculated nature of theFlorida and Bradbury clays, the reported size distributionsare probably not accurate. These clays were not dispersedreadily in the asphalts. However, even in the Kyanite, whichwas mixed easily with the asphalts, there was no appreciableimprovement in durability. In general, therefore, all threeclays produced no decrease in the durability of asphalts IIand III and only a small decrease in asphalt I.

Fly ash contains some components which are conductorsof electricity; therefore, the high voltage probe couldnot be used to determine failures in coatings containingfly ash. Therefore, all end-point determinations on coatingscontaining fly ash were made by visual inspection.

Because fly ash is a by-product of the combustion ofcoal, its composition, both physical and chemical, varieswith the source of the coal, the way it is burned, and theefficiency of the combustion. Therefore, its effect on

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the durability of asphalt roofing varies considerably.The three samples of fly ash tested varied from one producedunder very efficient combustion conditions (2% loss on ig-nition) to one with almost 18$ loss on ignition. All threematerials were very finely divided and had appreciable amountsof water-soluble material present

5only two had small amounts

of free alkali. Because failure was determined visually onthese coatings

,their durability cannot be compared directly

with the unstabilized asphalts or the other coatings in whichfailure was measured by means of a high voltage probe. (Wherecomparisons between the two methods for determining failureare possible, visible inspection always results in a somewhatlonger coating life.) Therefore, only comparisons among thefly ash specimens can legitimately be made. The materialdesignated as Low Carbon Fly Ash contributes the least tothe durability of the coatings.

Two of the samples of silica tested were in their naturalform while the other two (Ottawa and Special) had been pro-cessed through a grinding and sieving operation. Further,the Special Silica had been used to polish plate glass andin addition to- the small particles of glass present, thecorners and edges of the particles were rounded. With theexception of this material* which was appreciably soluble inwater, the silicas were rather coarse and inert.

None of the silicas affected the durability of asphaltboth of the processed silicas and Lake Erie Silica in-

creased the durability of asphalt II5and only the Special

Silica appreciably increased the durability of asphalt III.The efficacy of the Special Silica is probably due to itsfine degree of subdivision, 82% being minus M+ microns(325-mesh sieve).

4A The Effect of the Degree of Mixing of Mineralswith Asphalt on the Durability of Roof Coatings

The effect of the thoroughness with which the mineralmatter was mixed with the asphalt on the durability of thecoating was investigated. Three mineral additives wereuseds 1) Blue black slate, representing a material whichmixes readily and easily with asphalt

5 2) Niagara

DURABILITY,

DAYS

FIGURE 3

EFFECTS OF SELECTED MATERIALS ON DURABILITY

35% MINERAL MATTER25 MILS THICK

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FLY ASH

- 15 -

dolomite, representing a material which is incorporatedwith asphalt with moderate difficulty; and 3) FloridaClay, representing a material extremely difficult to mixwith asphalt. These materials were mixed in concentrationsof 35, 50, and 60% with asphalt III by three different pro-cedures:

1) Prolonged Hand Mixing - The melt was stirredcontinually for about one hour until allbubbling and foaming ceased.

2) Continuous Mechanical Mixing - The mixture wasstirred for 30 minutes with a high-speed lab-oratory stirrer after the mineral matter wasadded to the molten asphalt.

3) Brief Hand Mixing - Panels were made as soon asthe mineral matter was folded into the asphalt.Only enough stirring was used to keep the min-eral matter suspended.

The three minerals are described in Table I. Table VIand Figure 4 cover the results of the accelerated durabilitytests on these coatings. The data in Figures 4 and 5 areplotted on a ratio basis, i.e., the durability of the coatingdivided by the durability of the corresponding asphalt withoutmineral additives. In this way, it is possible to see at aglance the magnitude of the change in durability produced bythe additive, and the effects of the additive are reduced toa comparable basis. It can be seen that with blue black slate,the mineral which mixes readily with asphalt, there was littledifference in the durability of the panel made by the threeprocedures. The same was true of the coatings containing dolo-mite, except that there was a little more spread among thethree procedures. However, with clay, the material that isdifficult to mix with asphalt, the only procedure that yieldedcoatings as durable as the unstabilized asphalt was the pro-longed hand mixing, i.e., thorough mixing. Despite the factthat the average durability was not appreciably changed by thedegree of mixing in most cases, the data show that with boththe 30-minute mechanical mixing and with the brief hand mixing,the spread in durability of replicate panels exposed in differ-ent machines was greater than with prolonged hand mixing.Therefore, it must be recommended strongly that thorough mixingbe employed to obtain the most uniform and optimum benefitsfrom a mineral additive.

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- 17 -

4.5 The Effect of the Particle-SizeDistribution of the Mineral Matteron the Durability of Coatings

Because the particle-size distribution is one of theattributes of mineral matter which may seriously affect itsperformance, its effects on durability were evaluated inall three asphalts. Three minerals, blue black slate,Niagara dolomite and Lake Erie silica, were sieved intoeight fractions and reconstituted into five differentsynthetic size distributions, as follows

s

1) +200 Mesh - Coarse material retained on a No. 200U. S. Standard Sieve.

2) -200 Mesh - Material passing a No. 200 U. S.Standard Sieve.

3) 4325 Mesh - Material passing a No. 325 U. S.Standard Sieve.

4) Uniform Size - Material passing a No. l4o but re-tained on a No. 230 U. S. StandardSieve.

5) Equal Size - Approximately equal weights retainedon a square-root of two series ofU.S. Standard Sieves.

The geometry of irregular particles being separated by meansof sieves with square openings introduced some deviationsfrom the distributions desired.

Exposure panels (25 mils thick) were made from coatingscontaining 35 per cent of materials containing each of thesedistributions. The particle-size distributions are recordedalong with the accelerated durability data in Table VII.Average durability figures are shown graphically in Figure 5°

- 18 -

TABLE VII. PARTICLE SIZE DISTRIBUTION SERIES*

BLUE BLACK SLATE

ASPHALT None Kf|U- + 200 -200 -325-146+ 230

EqualSize

Asphalt I

Panel No. 1, Dur., Days 52 61 5§ 58 75 53 52" "7, Dur., Days 52 -- 58 58 75 59 52" "2, Dur., Days 34 75 65 72 80 55 54" "6, Dur., Days 34 65 72 80 42 54

Average 43 68 62 65 77 52 53Durability Ratio 1 1.58 1.44 1.51 1.79 1.21 1.23Crack Pattern C BG B G G BC CSoftening Point, °F 219 222 226 220 222 227 230Base Soft. Point, °FBase Pen. at 77°F

219 210 220 207 207 212 21418 21 18 21 21 20 20

Asphalt II

Panel No. 1, Dur., Days 74 146 131 161 149 140 122" " 7, Dur., Days 74 --- 131 161 128 133 129" "2, Dur., Days 76 158 131 147 --- 182 152" "6, Dur., Days 76 --- 138 161 191 168 153

Average 75 152 133 157 156 158 143Durability Ratio 1 2.01 1.77 2.09 2.08 2.11 1.91Crack Pattern AC C A A A A ASoftening Point, °F 228 222 225 227 224 225 220Base Soft. Point, °FBase Pen. at 77°F

228 211 217 215 211 21

7

21517 22 19 19 22 19 19

Asphalt IIIPanel No. 1, Dur., Days 66 188 122 185 177 145 153

51 "7, Dur., Days 69 --- 122 171 163 138 13311 "2, Dur., Days 81 159 120 198 161 !34 149" 11

6, Dur., Days 81 -=- 100 173 154 134 129Average 75 174 116 182 164 137 l4l

Durability Ratio 1 2.32 1. 56 2.43 2.19 1.83 1.88Crack Pattern F A A AH A A ASoftening Point, °FBase Soft. Point, °FBase Pen. at 77°F

227 218 226 221 227 223 223227 205 221 205 207 205 20914 20 17 20 20 20 20

%> Passing U. S. 6080

100120170200230

. 3^ _

99.899.397.996.291.386.983.1

,76 -y.

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99.194.785.074.135.25.71.0

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100.0100.0100.099«999.999.395.485^5 100.0

100.0100.094.792.472.940.213.54.1

100.098.795.190.266.654.542.821.7

35% Mineral Additive Exposed in Films 2 5 mils thick on Aluminum*,

FIGURE

5

EFFECT

OF

PARTICLE

SIZE

DISTRIBUTION

ON

DURABILITY I-_i<XQ_<S)

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E.S.

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E.S.

+230

+230

+230

- 19 -

TABLE VII, PARTICLE SIZE DISTRIBUTION* ( C ONT g D

)

ASPHALTRegu-lar

NIAGARA

+200 -200

DOLOMITE~l4o

-325 +230EqualSize

Asphalt I

Panel No. 1, Dur., Days 45 ^3 43 38 36 35II II

yII II 36 38 36 35

II II p II II

« 59 42 5° 37 36 35II II II II 42 42 37 36 35

Average 52 43 43 37 36 35Durability Ratio 1.21 1.00 1.00 0.86 0.84 0.81Crack Pattern C B c BC C CSoftening Point, °F 220 226 221 218 223 224Base Soft. Point, °FBase Pen. at 77° F

209 219 211 207 212 21421 18 20 21 20 20

Asphalt IIPanel No. 1, Dur., Days 98 87 88 99 91 99

it ii

yii ti -- 80 88 87 84 99

it li p *it il 103 89 114 93 83 85

it ii£,

ii II 103 104 93 90 78Average 101 90 99 93

>

87 91Durability Ratio 1.35 1.20 1.32 1.24 1.16 1.21Crack Pattern A AC AE A A ASoftening Point, °F 225 223 226 219 223 223Base Soft. Point, °FBase Pen. at 77°F

217 214 219 214 2l4 22119 19 18 19 19 18

Asphalt IIIPanel No. 1, Dur., Days 122 112 !34 109 95 87

ii ii

yii ii 112 134 102 95 87

tl ft O *!! II

9 108 108 128 116 98 noii ii £ ii ii 94 110 116 98 76

Average 115 107 127 111 97 90Durability Ratio 1.53 1.43 1.69 1.48 1.29 1.20Crack Pattern A A A A A ASoftening Point, °F 221 226 220 223 222 223Base Soft. Point, °FBase Pen. at 77°F

204 219 215 206 210 21420 18 19 20 20 19

%o Passing U.S. 6080

100120

99-999°999o699.3

99.698.695.891.1

100.0100.0100.0100.0 100.0

100.097.994.5

170 96.6 61.4 99.9 93.0 79.8200

<j3 .4 20.5 99.9 74.1 70.0230

fc?41.2 50.0

325 §Lo 100.0 9.5 19 ol*35% Mineral Additive Exposed in Films 2 5 Mils Thick on Aluminium

20 -

TABLE VII. PARTICLE SIZE DISTRIBUTION SERIES* (C ONT 'D)

LAKE ERIE SILICA

ASPHALT Regu-lar + 200 -200 -325

-l40+230

EqualSize

Asphalt I

Panel No. 1, Dur., Days 33 28 49 41 29 37u ii

yii n —

.

28 49 4l 36 30ft ft 9* »! II 4l 42 35 26 29 30ii ii ^ u ii — 35 35 40 29 30

Average 37 33 42 37 31 32Durability Ratio 0.86 0.77 0.98 0.86 0.72 0.75

Crack Pattern C BC Cr\O C c

Softening Point, °F --- 222 226 227 223 225Base Soft. Point, °FBase Pen. at 77°

F

213 212 210 208 213 21320 20 21 21 20 20

Asphalt IIPanel No. 1, Dur., Days 91 68 132 112 93 120

ii ii

yii ii -- 68 132 112 93 109

U II p *II II 117 84 118 112 93 101

II II£>

II II --- 98 132 112 93 101Average 104 80 128 112 93^ 107

Durability Ratio 1.39 1.07 1.71 1.49 1.24 1.43Crack Pattern AC AC A A A ASoftening Point, °F 217 219 223 227 225 226Base Soft. Point, °F 207 214 215 217 215 216Base Pen. at 77°F 23 19 19 19 19 19

Asphalt IIIPanel No. 1, Dur., Days 80 93 122 108 95 100

ii "7 n it -= 93 122 108 87 100it it p *

ii it 72 81 143 123 105 103ii ii £ it it — 81 136 123 105 103

Average 76 87 129 115 93 102Durability Ratio 1.01 1.08 1.72 1.53 1.31 1.36Crack Pattern A A A A A ASoftening Point, °F 226 222 223 224 226 219Base Soft. Point, °FBase Pen. at 77°F

206 215 210 207 216 21020 19 20 20 19 20

% Passing U. S. 6080

100120

99.998.280.853.7

100.099.392.7

.76.9

100.0100.099.999.9 100.0

100.097.993.1

170 15.3 26.5 99.7 *+3.7 71.2200 8.1 7.7 98.2 18.8 56.5230 5.4 1.8 85.7 7.3 46.722? 3A_ 1.1 52.5 100.0 1.2 28.2

*35$ Mineral Additive Exposed in Films ;25 Mils Thick on Aluminum.

21

The durability was a function of both the asphalt andthe mineral additive. However, the results will be dis-cussed primarily in terms of the minerals. While the finerdistributions of blue black slate increased the durabilitymore than the coarse ones in asphalts I and III, in asphaltII the durability was independent of the size distribution.The coatings made with silica, however, indicated that thefiner distributions yielded the more durable coatings.

The indecisive nature of the above results led to theconclusion that the quantity of mineral matter present wasinsufficient for the effect of particle-size distributionsto be observed in coatings 25 mils thick. Accordingly, thetwo extreme size ranges, +200 and -200, were formulated ata concentration of 5

0

%> in asphalt II and exposed in films13 and 25 mils thick. The results are presented in TableVIII and Figure 5®

The effects of size distribution were clearly evidentwith 50% mineral matter in coatings 13 mils thick. Forexample, +200 blue black slate lasted only b2%> as long asthe asphalt alone, but the coating with the -200 blue blackslate was three times as durable, making it produce overseven times the durability of the +200 material. At 25 mils,the same trend, though not so extreme, was maintained, the-200 mesh material producing a coating twice as durable asthe +200 mesh. With dolomite, there was a factor of abouttwo in both cases, but in the thin film it shifted the dura-bility from below to above that of the asphalt alone. Inthe case of silica, however, the increase in durability pro-duced by going to the finer size was small.

In summary, the -200 mesh fraction of blue black slate,Niagara dolomite, and Lake Erie silica seem to be mosteffective in increasing the durability of asphalt roof coat-ings in concentrations of 35 and 50 percent. The materialretained on the 200 mesh sieve is the least effective, whilethe regular (commercial), -325 ?

equal size, and uniform size(_llf0 +230) follow in descending order, with little differ-ence between adjacent distributions.

- 22 -

TABLE VIII „ PARTICLE-SIZE DISTRIBUTION SERIES

50% MINERAL MATTER IN ASPHALT II*

MINERALBLUE BLACK

SLATENIAGARADOLOMITE

LAKE ERIESILICA

Size RangeSoftening Pt.,°F13 Mils Thick

No. 1, Dur.,Days

No. 7, Dur

.

9Days

No. 2, Dur.9Days

No. Dur.,Days

Ave . 9Dur.

9Days

Durability RatioCrack Pattern

25 Mils ThickNo. 1, Dur.

9Lays

No. 7, Dur.,Days

No. 2, Dur.,Days

No. 65Dur.

,Lays

Ave

,

B9Dur.

9Days

Durability RatioCrack Pattern

+ 200 -200 + 200220 ; 226 219

23 178 5b23 178 6123 167 5323 160 4823 171 5b

0.42 3*10 0.98A A A

120 225 110135 230 110145 223 102120 233 102129 228 106

1.72 3.04 1.4lA EG A

-200 + 200 -200217. 219 223

10b 64 8090 50 8693 5° 71

102 43 6497 52 75

1.76 0.94 1.36A A A

144 134 129139 120 129137 98 113143 98 113Ibl 112 121

1.88 1.49 1.61E A A

*Durability of Asphalt II; 13 Mils - 55 Days25 Mils - 75 Days

- 23 -

4„6 The Effect of Particle Shape of Mineralson the Durability of Coatings

Because particle shape was the one property of theminerals studied in the Principal Seriesi/ of exposures thatseemed to be related to the efficacy of their stabilizingaction, some quantitative method of expressing particle shapewas sought. A relation between a bulk density and the truedensity of the minerals seemed worth considering for thispurpose . Franz Popel,^/ in 1929 ?

proposed a relation of thistype

,which he called "fineness factor", and defined as

^_ density - compacted wt„ = d-b

compacted wt. b

where the compacted weight is an empirical bulk density deter-mined under any set of conditions that would yield reproducibleresults o

Rather than a compacted weight, the bulk density used wasobtained by fluffing the mineral matter by letting it flowslowly through a column of one-inch inside diameter, 21 incheslong. Baffles set at an angle of *+5° were placed 12 and 16inches from the top of the column and the column was con-stricted to a diameter of 3/b inch at the bottom. Thecolumn discharged into a 100-ml, weighed and calibrated,graduated cylinder from a point 1/b inch above the cylinder.In practice the mineral matter was poured slowly into thecolumn until it just overflowed the receiver. The excesswas struck off level with the top of the receiver and thereceiver and contents weighed. The weight of the mineral

1/"Laboratory Evaluation of Six Commercially Available Min-erals as Stabilizers for Asphalt Coatings", S. H. Greenfeld.

2/Franz Popel, Der Moderne Asphalstrassenbau (Strassenbau-Verlag Martin Boerner, Halle 1929)

.

- 2b -

matter divided by its volume is termed the "fluffed bulkdensity" or simply, the "fluff density", A correlationof fineness factor based on this bulk density is pre-sented in Figure 6, The individual points are tabulatedin Table IX,

It is readily seen that for each asphalt this factorcorrelated well with durability. The only materials thatdeviate considerably from the curves are oyster shell andmica, both being materials characterized by flat, plate-like particles. Since the deviations are in the directionof greater durability than indicated by the lines, the linesmay be taken as conservative indications of durability.

Despite the rather good correlations indicated byFigure 6, it must be emphasized that these data were ob-tained for specific materials under very specific testconditions and that the results may vary under other con-ditions. The fact that a different line is plotted (fpr

each asphalt emphasizes the importance of the asphaltitself in respect to durability.

TABLE

IX.

FINENESS

FACTOR

25

• *H

-P ® H 0•H [x, 0 -Pi—1 Pi—I H•H O CD Cd M

-P £cd -H aP to S mP Co CQ cd\3^QUnm m

O CM J- roUNOMNHvD UnnO nO CN-vDO CO C'- OnUn i—I

C\1 i—1 i—I i—|On [>~O

O'—li—1'—li—I'—li—

I

1—I i—I'—I i—

I

i—

I

\

o O- C\J 00 mvO ONporOH CO vO o UnO U\UN ON CM H On ON POO ON00 ONoO I—li—li—li—li—I i—li—I 1—

I

CM UNOO UnUnnO rO O- CM CM rOCO rO [N.

C^nO OHJ-J-J- pOnO IfNJr POj- rOUn i—

I

0 chCD

CD P

0 P> I JrQd o p|•H cd

Ep (L

CN-poOCN-POCMHrHOOOi>-lrNCMH090 e« 0«9000009ON pT) pp) CMCMCMCMCMCMHr—lr—IrHi—

I

CoCh P>Ch -H ONCO PO CM OO CM J" PO ON po ONHp3 co pi CM

n

0 O- CN- [N-nO OnOnOnOpOOCMpOr—I f] •• o......®ooo®pC| (D OOOOOOOOOr—IrHi—lr—I 1—

I

Q

I

to I

cd Oa p

oP H0 a-PtO-P•H &pq to

0 Hp 0 i—

I

0 0p p pP H O° P .

0 O CT1 P0 0 cd

P> PhPP £[0 p w -p

i—1 0CP pq 0 p

ca-p oP H H0 ^ P P>

i—I >*H 0P^Ch o 0O O 0 H Pi•H O P p OOH PH O<4 pq H p 0

II II II

CP COC pq H

-p•H H J” _d" CO CO CM O-. l>-J- NOi [N-CO0 p O ON On\D UnnO 00 CO OnOO nO nO OO nO0 .•«.o..esoaaas0 pO CM CM CM CM CM CM CM CM CM PO CM CM CMQ

0 -—

\

i—I i—

I

O 0 0•H P« P-P 0 0p h h0 C/} >CP

cpcPCPCPpq&qcococpcoi-iMcopqPin fx, <q pq pq pq ip, pq pq pq

0p0PpooP0H 0P P

0 p O0 O 0-p pc; p0 0

i—

l

0 pq 1—

1

O' toi—

1

o 0 cd CP >N o0 •H <q O o M P

1—

1

pq i—

1

• o 11

o •H -p O 00 CO CO H >SI—

1

i—1 CO o 1—

1

i—

1

0 O -PP pq CO 1—

1

o o pq Q 0 o •H 1—

1

H 00 pq P Q q pq -P cd Q CO (p pq CPP 0 • O •H —

1

•H 0 o -p o o O UNO to P o O •II li li

s o o CO 0 0 o O CM o 0 0 O w•H CM pq >> Ph • CM rO CM •H o CM • CP pqs 1 pq o CO hi 1 1 4- w + hi fp pq CP

FIGURE

6

DURABILITY

VS.

FINENESS

FACTOR

I

3

I

(3T0A0 06- IS) SAVG ‘AllH8Vdna

FINENESS

FACTOR

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