Astm stp 1412 2001

STP 1412 Aggregate Contribution to Hot Mix Asphalt (HMA)Performance Thomas D White, Sam R Johnson, and John J Yzenas, editors ASTM Stock Number: STP 1412 ASTM 100 Barr Harbor Drive PO Box C700 West Conshohocken, PA, 19428-2959 Printed in the U S A Copyright 2001 AMERICAN SOCIETY FOR TESTING AND MATERIALS, West Conshohocken, PA All rights reserved This material may not be reproduced or copied, in whole or in part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of the publisher Photocopy Rights Authorization to photocopy items for internal, personal, or educational classroom use, or the internal, personal, or educational classroom use of specific clients, is granted by the American Society for Testing and Materials (ASTM) provided that the appropriate fee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923; Tel" 978-750-8400; online: http:llwww.copyright.com/ Peer Review Policy Each paper published in this volume was evaluated by two peer reviewers and at least one editor The authors addressed all of the reviewers' comments to the satisfaction of both the technical editor(s) and the ASTM Committee on Publications To make technical information available as quickly as possible, the peer-reviewed papers in this publication were prepared "camera-ready" as submitted by the authors The quality of the papers in this publication reflects not only the obvious efforts of the authors and the technical editor(s), but also the work of the peer reviewers In keeping with longstanding publication practices, ASTM maintains the anonymity of the peer reviewers The ASTM Committee on Publications acknowledges with appreciation their dedication and contribution of time and effort on behalf of ASTM Printedin Bridgeport,NJ November2001 Foreword This publication, Aggregate Contribution to Hot Mix Asphalt (HMA) Performance, contains papers presented at the symposium of the same name held in Orlando, Florida, on December 5, 2000 The symposium was sponsored by ASTM Committee D04 on Road and Paving Materials The symposium co-chairmen were Thomas D White, Mississippi State University, Mississippi State, Mississippi, USA, Sam R Johnson, Martin Marietta Aggregates, Raleigh, North Carolina, USA, and John J Yzenas, Levy Co., Portage, Indiana, USA Contents Quantifying Contributions of Aggregate Characteristics to lIMA Performance Using PURWheel Laboratory Tracking Device -JAMESSTIADY,ADAMHAND, AND THOMAS WHITE Characterization of HMA Mixtures with the Asphalt Pavement Analyzer-LOUAY N MOHAMMAD, BAOSHAN HUANG, AND MEDAD CEA 16 Aggregate Contributions to the Performance of Hot Mix Asphalt at WesTrack-AMY L EPPS, ADAM J HAND, JON A EPPS, AND PETER E SEBAALY 30 Identification of Aggregate Role in Performance of Superpave Mixtures Employing Accelerated Testing F a c i l i t y - - J A M E S ST1AOY, KHALED GALAL, SAMY NOURELDIN, ADAM HAND, AND THOMAS WHITE Evaluation of Aggregate Contributions to Rutting Susceptibility of Asphalt Mixtures -LOUAYN MOHAMMAD, BAOSHAN HUANG, AND ZHENG ZHENG TAN 44 58 Evaluation of the Sensitivity of Repeated Simple Shear Test at Constant Height Based on Laboratory Rutting Characteristics of WesTrack Fine Mixes GAJANAN NATU, IRWIN GUADA, AND AKHTARHUSEIN A TAYEBALI Effects of Fine Aggregate Angularity on VMA and Rutting of Kansas HMA Mixtures -STEPHEN A CROSSAND ERICH M PURCELL Development of Tentative Guidelines for the Selection of Aggregate Gradations for Hot-Mix Asphalt -BJORNBIRGISSONANDBYRONE RUTH 72 95 110 Image Analysis Techniques to Determine Fine Aggregate Angularity-ARIF CHOWDHURY, JOE W B u T r o N , DOUGH WILSON, EYAD MASAD, AND BRIAN D PROWELL 128 Fine Aggregate Angularity: Conventional and Unconventional Approach ARIF CHOWDHURY AND JOE W BUTTON Determination of Aggregate Specific Gravity and Its Effect on HMA Mixture Performance JOHN E HADDOCK AND BRIAN D PROWELL 144 160 Effect of Restricted Zone on Permanent Deformation of Dense-Graded Superpave M i x t u r e s - - - P R I T H V I S KANDHAL AND L ALLEN COOLEY, JR 173 Polish Resistance of Tennessee Bituminous Surface Aggregates L K CROUCH, HEATHER J SAUTER, GREGORY M DUNCAN, W A GOODWIN 185 James Stiady, l Adam Hand,2 and Thomas White3 Quantifying Contributions of Aggregate Characteristics to HMA Performance Using PURWheel Laboratory Tracking Device Reference: Stiady, J., Hand, A., and White, T., "Quantifying Contributions of Aggregate Characteristics to HMA Performance Using PURWheel Laboratory Tracking Device," Aggregate Contribution to Hot Mix Asphalt (HMA) Performance, ASTMSTP 1412, T D White, S R Johnson, and J J Yzenas, Eds., American Society for Testing and Materials, West Conshohocken, PA, 2001 Abstract: The effects of nominal maximum aggregate size (NMS), coarse aggregate type, fine aggregate angularity (FAA), and gradation types on HMA rutting performance were evaluated using the Purdue Laboratory Wheel Track Device (PURWheel) Correlation between PURWheel and Indiana Department of Transportation/Purdue University (INDOT/Purdue) Accelerated Pavement Tests (APT) was used as an initial step to field pavement rutting performance evaluation Test results showed that PURWheel and APT are well correlated This is positive because the traffic loading and compaction method used in the prototype scale APT is essentially identical to field conditions The rutting performance of 9.5 and 19 mm mixtures and that of limestone and granite mixtures was not statistically different Analysis of the data revealed that adequate performance could be obtained with mixture gradations plotting above (ARZ), through (TRZ), and below (BRZ) the restricted zone FAA significantly impacted the rutting performance in PURWheel tests However, mixtures incorporating very high FAA values did not perform better than those incorporating typical (~ 45) FAA values Keywords: asphalt mixtures, nominal maximum aggregate size, coarse aggregate type, aggregate gradation, restricted zone, fine aggregate angularity, Superpave, rutting performance, laboratory wheel track device, PURWheel Introduction Nominal maximum aggregate size (NMS), coarse aggregate type, fine aggregate angularity (FAA), and gradation type impact mixture characteristics, such as voids in Materials/Geotech Engineer, Kleinfelder Inc., 5015 Shoreham Place, San Diego, CA 92122 Quality Systems Engineer, Granite Construction Incorporated, 1900 Glendale Avenue, Sparks, NV 89431 Professor & Head, Civil Engineering Department, Mississippi State University, Civil Engineering Department, P.O Box 9546, Mississippi State, MS 39762 Copyright9 by ASTMInternational www.astm.org 2_ AGGREGATE CONTRIBUTION TO HOT MIX ASPHALT (HMA) PERFORMANCE mineral aggregate (VMA), voids filled with asphalt (VFA), dust proportion, and film thickness The impact of aggregate and mixture characteristics on HMA rutting performance may not be the same For example, the VMA of 9.5 mm mixtures is higher than that of 19 mm mixtures However the performance of the 9.5 mm mixtures is not necessarily different than that of the 19 mm mixtures because the factors that critically impact mixture characteristics may not be critical for performance Twenty-one Superpave mixtures were designed using two NMS mixtures (9.5 and 19 mm), two coarse aggregates (limestone and granite), three fine aggregates (granite, limestone, and natural sand), and three gradation types (ARZ, TRZ, and BRZ) The granite, limestone, and natural sand fine aggregates had FAA values of 50, 44, and 39, respectively A single, neat PG64-22 binder was employed for all mixtures Mixture rutting performance was evaluated using the PURWheel shown in Figure Figure - Purdue Laboratory Wheel Track Device (PURWheel) STIADY ET AL ON PURWHEEL The PURWheel was designed to apply a moving wheel load to compacted slabs for the study of HMA rutting and stripping Of the commercially available laboratory wheel track testing devices it is most similar to the Hamburg device In addition to features associated with a Hamburg device, the PURWheel was designed to accommodate different wheel types, transverse wheel wander, constant wheel speed, larger test specimens, the ability to measure rutting over the entire length of test specimens, and testing under hot/dry as well as hot/wet conditions It is complimented with a linear compactor designed and built specifically for PURWheel test slab preparation Although PURWheel simulates the effect of moving wheel loads, there are other factors that may impact field mixture performance evaluation, such as mixture properties, compaction method, and mixture preparation technique Therefore, it is necessary to determine whether PURWheel test results evaluate consistently field pavement rutting performance The correlation between INDOT/Purdue APT and PURWheel test results would be the initial step in field pavement rutting performance evaluation because the traffic loading and compaction method in the APT are essentially identical to field conditions The correlation between the two tests is reliable because the environment conditions, such as temperature, contact pressure, and wheel velocity can be controlled consistently A comparison between load and geometry parameters of PURWheel and APT test conditions is presented in Figure 203 mm (8 i ~ ] 40 kN (9 I kips) 1.5 Id~ (334.1 lb.) Gross contact l pressure = 620 kPa (90 psi.) ~ ~ ( i n ) 51 mm 76.2 mm\ t ) )j' / 620 kPa(90 102 mm I (4 in.) 292 mm 1.5 m (5 ft.) (11.5 in.) PURWheei INDOT/Purdue APT ] Figure - Comparison between Load and Geometry Parameters of PURWheel and APT AGGREGATECONTRIBUTION TO HOT MIX ASPHALT (HMA) PERFORMANCE Test Methods Mixture designs were conducted in accordance with AASHTO MP2, Specification for Superpave VolumetricMix Design The coarse and fine aggregates were subjected to full characterization using Superpave protocols The asphalt binder was tested according to AASHTO PP6, Practicefor Grading or Verifying the Performance Grade of an Asphalt Binder, to ensure that it met the desired grade A Pine Superpave Gyratory Compactor (SGC) was used to compact all specimens The Ninitial, Ndesign, and Nmaximura employed were 8, 96, and 152 gyrations, respectively This was the compaetive effort specified in Superpave for a traffic level of 3-10 million Equivalent Single Axle Loads (ESAL) and an average design high air temperature of less than 39~ at the time the research was conducted All mixtures tested in the PURWheel are presented in Table Previous results suggested that mixture preparation and compaction method impact correlation between PURWheel and APT tests [1] In order to take into account the effects of mixture preparation and compaction methods, comparison was conducted based on three different specimen types, i.e., field mixed-field compacted (FMFC), field mixed-laboratory compacted (FMLC), and laboratory mixed-laboratory compacted to observed field properties (LMLCF) specimens A test temperature of 50~ was used to test FMFC, FMLC, and LMLCF specimens in order to correspond with APT tests FMFC specimens were obtained by cutting slabs directly from APT test sections prior to traffic loading They were trimmed to the appropriate PURWheel test specimen size FMLC specimens were slabs made from loose mix sampled behind the paver and compacted using the Purdue linear compactor These mixtures were identical to those placed in APT test sections, except that the mixtures were stored at room temperature, reheated prior to compaction, and compacted using Purdue linear compactor instead of field rollers LMLCF specimens were slabs made of laboratory prepared mixture compacted using the Purdue linear compactor The specimens were prepared at the asphalt content, gradation, and density observed in the corresponding APT test sections Once the comparison was established, effects of mixture properties could be evaluated further using laboratory mixed-laboratory compacted samples at design conditions (LMLCD) The PURWheel test results of the LMLCD specimens were also correlated with triaxial tests to provide the information of the mixture strength Details of the triaxial test can be found in Reference The LMLCD specimens were tested at 60~ in order to correspond with triaxial test temperature LMLCD specimens were slabs that were made of laboratory prepared mixtures compacted using the Purdue linear compactor The mixtures were blended in accordance with mixture design gradation, mixed at specific asphalt content levels, and compacted to their corresponding mixture design densities FMFC specimens were tested in two replicates Each FMFC specimen corresponded to an APT test section FMLC, LMLCF, and LMLCD specimens were tested in four replicates The four replicates make a set of specimens compacted to one target density The target density was either the APT test section density (FMLC and LMLCF specimens) or the design density (LMLCD specimens) In PURWheel tests a pneumatic tire was used with a gross contact pressure of 620 kPa and tire pressure of 793 kPa The wheel traversed test specimens at 0.33 m/s (0.74 STIADY ET AL ON PURWHEEL mph) without transverse wander Tests were terminated after the application of 20 000 wheel passes or when rut depths reached 20.0 mm, which ever occurred first This rut depth is downward deformation relative to the original sample surface, i.e the uplift is not measured automatically The rut depth is measured with an electronic transducer with accuracy of 0.03 mm Two slabs were tested simultaneously All tests were conducted in the dry state Typical specimen dimensions were 292 mm (11.5 in) wide by 311 mm (12.3 in) long Slab thicknesses of 38 and 51 mm (1.5 and in) were used for 9.5 and 19 nun NMS mixtures, respectively Table - Summary of Mixtures Tested in PURWheel Nominal Maximum Size Fine Aggregate Type and FAA Gradation Type 9.5 mm (with respect to the Restricted Zone) 19 mm Coarse Aggregate Type Limestone Granite M M Above X Below X Above Limestone FAA=44 Through Below X Y X X X Through Below gr f.~ ~-d ,-d X X X X Y X X X Y Above Granite FAA=50 Granite o M Natural Sand FAA =39 Limestone X X Y X X X X Y X X X X X Y X X X ~ X Y X X X X X FMFC= field mixed-field compacted specimen, FMLC=field mixed-laboratory compacted specimen, LMLCF=laboratory mixed-laboratory compacted specimen at observed field properties, LMLCD=mixture design and laboratory mixed-laboratory compacted specimen at design condition, X= four test replicates, Y = two test replicates L K Crouch,l Heather J Sauter,2 Gregory M Duncan,3W K Goodwin4 Polish Resistance of Tennessee Bituminous Surface Aggregates Reference: Crouch, L K., Sauter, H J., Duncan, G M., and Goodwin, W A., "Polish Resistance of Tennessee Bituminous Surface Aggregates," Aggregate Contributionto Hot Mix Asphalt (HMA) Performance, ASTMSTP 1412, T D White, S IL Johnson, and J J Yzenas, Eds., American Society for Testing and Materials, West Conshohocken, PA, 2001 Abstract: In 1992, the Tennessee Department of Transportation (TDOT) initiated a project to pair aggregate performance with pavement functional needs so that all Tennessee aggregate sources could be used efficiently.The principal result of the project was a new pro-evaluation procedure for aggregate polish resistance called the Tennessee Terminal Textural Condition Method (T3CM) The TaCM uses an up-scaled version ofthe AASHTO T 304 device to monitor an aggregate's abilityto retain angularity and texture through a simulated aging process In the fourth phase of the study, twenty-three coarse aggregates, sampled at the cold feed stockpile, are subjected to T3CM, T3CMwith sand aging X-ray diffraction,British Pendulum, Loss-on-Ignition, and chemical percent silicatechniques By comparing skid performance versus traffic(ADT, passes, and ESALs) with laboratory test results, aggregate performance and aggregate source variabilitymay be categorized for effectiveuse Ptelinm~ results indicate that the correlation between T3CM and skid performance (R2 = 0.74) isfar superiorto the correlationsbetween ASTIVl C 25 percent silica(R = 0.38),percem silicaby X-ray diffraction(R2 = 0.36),and BPN (g = 0.0004) with skidperformance Keywords: polishresistance, coarse aggregate, skid resistance, void content, mica-otexture, particle shape, percent silica, x-ray ~ o n 1Professor, Civil and Environmental Engineering Department, Tennessee Technological University, P.O Box 5015, Cookeville, TN 38505 2C_n'aduatePh.D Candidate, Civil Engineering Department, Tennessee Technological University, P.O Box 5015, Cookeville, TN 38505 3Transportation Manager L Materials & Test Division, Tennessee Department of Transportation, 6601 Centennial Blvd., Nashville, TN 37209 *Professor Emeritus, Civil Engineering Department, Tennessee Technological University, P.O Box 31515, Knoxville, TN 37930-1515 185 Copyright* 2001 by ASTM International www.astm.org 186 AGGREGATE CONTRIBUTION TO HOT MIX ASPHALT (HMA) PERFORMANCE Introduction Aggregates should be pre-evaluated before being placed on roadway surfaces to ensure safety of the motoring public, as well as for economic reasons, If unsatisfactory materials can be eliminated, savings in accident costs, maintenance and reconstruction will result However, there is ambiguity in the term '~umatisfactory" An aggregate, which is satisfactory for most average daily traffic (ADT) levels, may be unsatisfactory for high ADT interstate applicatiom In eliminating"unsafiffactory" materials, caution is often considered prudent and subsequently some materials, which could provide adequate performance in many ADT applications, are eliminated from consideration because these materials will not meet specifications for high ADT levels The state of Tennessee has an abundance of carbonate aggregates especially in middle and east Tcnncssoe However, in the past, Tennessee also had significant sources of highly polishresistant bituminous surface aggregates such as slag in these same areas Cauticaas specifications defining what is an "approved" surface aggregate source posed no problem when a large supply of highty polish-resistant aggregates was available However, when the supply of these excellent aggregates declined, the cost of producing safe bituminous pavement surfaces increased With only a small number of approved aggregate sources, two problems began to occur First, as demand increased, the aggregate price increased Second, transporting aggregates ~om approved sources to distant areas increased pavement costs In 1992, the Tennessee Department of Transportation (TDOT) initiated a project to pair aggregate performance with the pavement functional needs (based on ADT) so that all Tennessee aggregate sources could be used efficiently Objectives This project was undertaken to achieve the following objectives: Ascertain what laboratory methods are currently available to pro-evaluate aggregate polish.resistance for bituminous surfaces Determine the relative effectiveness of the methods through a literature review If no suitable methods are found, attempt to develop a test to characterize an aggreg=e's ability to retain microtextum over time The test must be inexpensive, repeatable, and not operator sensitive Perform a p r ' ~ evaluation of the new method Make rccorftnesdations for implementation of project findings Objectives and were accomplished in Phase of the project [1, 2] In sammary, information on laboratory test methods for charaot~ng aggregate polish resistance cunemly available or beingdeveloped was obtained A survey was made of State Departments of TranspormOonthroughoutthe country, along with associatod industry and ~c~demia Only three standardiz_,~t laboratory tests were commonly used by respondents, the percent insoluble residue (ASTM D 3042), petrographic analysis (ASTM C 295), and British polishing wheel / British pendulum (AASHTO T 278 & T 279) Objectives 3, and were part ofPhase of the project The Tennessee Textural Retention Method (TTRM) was developed and evaluated [.3,4] The TTRM was found to be repeatable, not operator sensitive, and inexpensive However, the TTRM did not reveal an aggregate's terminal texture CROUCH ET AL ON TENNESSEEBITUMINOUSSURFACEAGGREGATES 187 Background and LiteratureReview There are many factors affecting skid resistance The three primary factors influencing skid resistance performance ofhituminous roadways are pavement distress, macrotextm'e, and microtexlure The pavement distress modes of rutting and bleeding greatly decrease skid resistance [5] Surface rutting allows water to pond in the ruts Bleeding drowns aggregate microtexture thus decreasing skid resistance due to loss of tire-pavement interaction Macrotexture is the result of the size, shape, and arrangement of aggregate particles in the mix For a pavement that is not rutted or excessively bleeding, macrotexture controls water film thickness on the roadway surface [6] Macrotexture relieves the water pressure, which is built up in the forward portion of the tire-pavement interface, thus allowing a large portion of the tire area to remain in contact with the pavement surface [7] Macrotexture is a measure of the general coarseness of the pavement Macrotexture also controls seasonal variations seen in the Skid Number (SN) readings taken in the field [8] Microtexture is the fine texture ofthe aggregate that makes it smooth or rough to the touch Microtexture provides the adhesion component of skid resistance [ 7] Goodwin [9] and Cn'amling[10] found that, while accumulating field skid resistance research data, the coarse aggregate in bituminous mixtures was more influential in determining skid resistance than other mix constituents Nitta, Saito and Isozaki [1I] agreed, indicating that mixture component changes such as asphalt content, type of fine aggregate and coarse aggregate grading are less important than coarse aggregate type Based on field experience, a highly skid-resistant surface course will reach a terminal skid number during the pavement service life Research in New Jersey on bituminous pavement, showed cyclic skid resistance values with a constant mean value, hereaRer referred to as the terminal skid number This may be expected after approximately two million vehicle passes [12] After a pavement has reached its terminal skid number, the pavement's skid resistance is primarily affected by cyclic seasonal effects [12] Several researchers including Kandhal et al [13], Nitta et al [11], and Skerritt [14] agree that aggregates will reach an ultimate polishing value or terminal textural condition This behavior is similar to that in the field (measured with the locked-wheel trailer, AASHTO T 242) as the pavement is exposed to more traffic repetitions An aggregate's terminal textural condition is the minimum surface roughness and particle angularity achieved when the aggregate is subject to polishing and wear For bituminous surface courses which are not rutted or significantly bleeding the terminal textural condition of the coarse aggregate particles is the controlling factor in determining the terminal skid number Therefore, adequate characterization of an aggregate's terminal textural condition is essential in determining its contribution to the skid resistance of the bituminous surface course Dirringer used the British Polishing Wheel and British Pendulum to achieve a terminal aggregate texture in the laboratory [12] The specimens were polished far beyond the standard nine-hour period Unfommately, Kulakowski, Henry and Lin [15] found considerable variation in the British Pendulum results The cause of the variation was considered to he the complex, cumbersome and ineffective calibration procedures Therefore, a new method for evaluating aggregate terminal textural condition was needed To summarize, the lit~ture review suggests any new pre-evaluation method for bituminous surface aggregates should: Concentrate on the termin~ textural condition of coarse aggregates 188 AGGREGATECONTRIBUTIONTO HOT MIX ASPHALT (HMA) PERFORMANCE Be repe~ .table Be operator insensitive Summary of the Tennessee Terminal Textural Condition Method ('I~ Genera~ The T3CMVoids Device is based on a modiilcafionof the National AggregaIe Association's Uncompacted Voids Apparatus for Fine Aggregate (AASHTO T 304) The moditication consists of a larger reservoir to hold the aggregate and a larger funnel through which the aggregate flows to fallthe reservoir The reservoir used in the moditivd appara~ is a 2832-mL AASHTO T19 mold The funnel was chosen to have approximatelythe same shape of the standard funnel yet have a volume equal to twice that of the modified cytinddcel reservoir The |ea~ufinderof the apparatus was increased in size proportional to the new reservoir See Figure for details 87ram, 130ram !.\ /H / n , b-q 47mm 315ram ooo L [ Figure 1-Schematic g CM ~ e d VoidsContentapparatus ModifiedAdSHTO T 304 GROUCH ET AL ON TENNESSEE BITUMINOUSSURFACE AGGREGATES 189 To conduct an uncompacted void content test, the funnel opening is blocked to pemfit filling of the funnel ~ i r ARer filling the aggregate is allowed to flow through the funnel opening, fr~f~Uing intothe r nmamm The tneas~ ist[~ struckoffwith a beveled steal straightedge and the retained aggregate is wdghed That wright, along with the aggregate's specific gravity and volume of the cylindrical mea,mre, is used to calculate the void content The equation for U is given as (AASHTO T 304): u = {V-(F/C)}/v • where: U = uncompacted voids, in the material, in percent; V = volume of the cylindrical m e , ml; F = net mass ofaggregate in meamre (gross minus the mass ofthe empty mmsure), grams; and G = bulk dry specific 8rarity of the aggregate In the evaluation,flve 12-kilogram samples of each aggregate are sieved to the proper size range and oven dried Each sample is tested for initial uncompacted void content using the modified AASHTO T 304 apparatus After initial testing a sample is subjected to 500 revolutions in the Los Angeles Abrasion Machine (AASHTO T96) using no steel spheres The combined actions of abrasion and grinding in the rotating steel drum change the particle shape and surface texture The sample is then resieved to the initial grading The samples are aged 500 revolutions at a time and sieved until all specimens reach 8000 revolutions Prior to 8000 revolutions, the n t a n ~ of samples may be reduced dependin_~on the aggregate degradation without wasting any material No individual sample is allowed to exceed 12-1dlograms When each sample has been aged and sieved for 8000 revolutions, all samples are combined and mixed If the combined sample exceeds 24-kilograms, it is reduc~l to 24-1dlogramsby wasting The combined sample is split into two 12-kilogram samples The two samples at 8000 revolutions are tested using the modified AASHTO T 304 device Three tests were conducted on each sample for a total of six tests Following testing, the samples are continually aged, sieved, and tested every 500 revolutions until each sample is aged 14000 revolutions When each sample reaches 14 000 revolutions, the two samples are combined and mixed If the combined sample exceeds 12-kilograms, it is reduced to 12-kilograms by wasting The sample is then tested six times with the modified AASHTO T 304 device Following the testing procedure, the sample is continually aged, sieved, and tested every 500 revolutions until TTC is achieved ortbe sample is r162 The testing protocol is summarized in Table 190 AGGREGATECONTRIBUTIONTO HOT MIX ASPHALT(HMA) PERFORMANCE Table - TestingProtocol 100% Passing (sieve) 100% Retained (sieve) Sample Size kg (lbs) Number of Samples of Aggregate Number of Spheres Test Frequency (number of revolutions) Number of Testing Cycles De,de , i Parameters 9.5 mm (3/8") 6.3 mm (1/4") 12 (26.5) Initially @ 8000 revolutions @ 14 000 revolutions 500 (after 8000 revolutions) As need to reach TTC Modified AASHTO T 304 Good bituminous sur~ce aggregates achieve a terminal textural condition That is, after a certain amount of aging (abrasion and wear), the aggregate's angularity and surface texture begin to regenerate and no longer decline (Figure 2a and Figure 2b {close-up}) Specifically,an aggregate is considered to have reached a TIC if the linearlyregressed slope of the last seven points has a-0.00003 or greater slope This value was determined experimentally and could be adjusted should more data become available [17] The limiting slope was chosen for two reasons First, the vast majority of TDOT proven-performing limestones had a slope greater than this value Second, it allowed for some oscillation about the terminal textural condition similar to the oscillation of field skid numbers For ~ t e s in a terminal textural condition, the Tennessee Terminal Textural Condition Rating is equal to the average of the last seven average per~nt uncompacted air voids tests Ocr~ooally, the slope of the curve will temporarily increase above -0.00003 before the aggregate is truly in a terminal condition To avoid erroneous results, testing should be continued until TTC has been achieved four consecutive times before rq~orting a TTC for any aggregate The final TTC reported is the mean of the four TTC values Not all aggregates have a TTC Poor performing bituminous surface aggregates continue to polish and not achieve a TIC Rationale Many Tennessee limestones are composed of a combination of hard and soft materials These materials have ditfvrenfialpolishingrates under traffic Softer materials in the aggregate particles at the pavement surface polish faster than the harder component, which regenerates the particle surface texture The central question in allowingthe use of such particles is what is the minimumamount of harder materials in the particles necessary to achieve an acceptable regenerative texture In the past, chemical and mineralogicalmethods have been used in attempt to answer this question However, neither chemicalnor mineralogicalmethods reveal anything about the distribution of hard constituents in the aggregate particles The T~CM attempts to determine regenerative texture physically,by establishinga TTC for an aggregate CROUCH ET AL ON TENNESSEE BITUMINOUS SURFACE AGGREGATES Percent Uncompacted Voids vs Revolutions 5O 42 20o0 40o0 6ooo 8o0o 10ooo 120oo 140o0 le0oo 180o0 2oooo Number of R e v o l u t i o n s I* p'~ Ao=m~ J Fisurr 2a Percent Utcomtxtcted Voids vs Number of Revolutions - Percent U n c o m p a c t e d V o i d s vs Revolutions A 4,3,2m • 43.16 ~ 43.12q 43.08 ~ 43,1N 12000 12500 13000 13500 14000 14500 1500O Number of Revolutions , Pr0~ ~ r e ~ e ~ tJn~rtyR~mmd slo~ - - - MtnlmumAccepmbleSlope Figure 2b - Close-up of Percent ~ t e d Voids vs Number of Revolutions 191 192 AGGREGATECONTRIBUTIONTO HOT MIX ASPHALT (HMA) PERFORMANCE T3CM Development The results of Phase of the TDOT study, as well as several small projects have shown the T3CM to be a logistical success Ease of performance, repeatability, reduced cost (compared to the British PolishingWheel and Pendulum) and operator insensitivity are advantages indicating that this test may be an ideal addition to normal aggregate pre-qualification tests However, the T3CM was new and an insufficient number of complete data sets were available to correlate TTC with terminal skid numbers in the field To address this situation, the TDOT Materials and Tests Division sponsored a fourth phase of the T3CM study Planfor Phase of the ~CM S~My In Phase 4, twenty-three bituminous surface projects wcar selected for evaluation The projects selected included both test strips and in-service bituminous retraces Further, several projects contain aggregates fi'om the same source The coarse aggregates used in the projects were sampled at the lIMA cold feed stockpile rather than the aggregate source to ensure that the exact a~,~regates placed in the bituminous surface course were tested The aggregates were subjected to three physical tests: T3CM, T3CM with sand aging and British polishing wheel/British pendulum (AASHTO T 278 & T 279); as well as three chemical/mineralogical tests: Percent silica ASTM C 25, Percent silica by X-ray diffraction, and Loss-on-ignition (LOI) Further, the bituminous surface courses containing these aggregates are being monitored for pavement distress and skid resistance Skid resistance data is being obtained by TDOT personnel using locked-wheel trailer skid tests (AASHTO T 242) By comparing the skid performance versus trd~C (ADT, passes, and ESALs) with laboratory test results, aggregate performance and aggregate source variability may be categorized for effective use With all Tennessee bituminous surface aggregates correctly categorized, TDOT personnel can make informed decisions about the most economical aggregate to meet the pavement's functional requirements As a result, the department win save money and extend the supply of approved bituminous surface aggregates while maintaining a high level of skid resistance to ensure the motoring public's safety TestProcedures Loss-on-ignition values were obtained by determining the percent weight loss when a 600gram sample of the aggregate is subjected to 950 degrees C for eight hours in a muffle furnace T3CM with sand aging is simply the standard T3CM with kilograms of high-silica river sand passing the No 30 sieve and retained on the No 50 sieve added to the sample during aging to enhance abrasion TDOT personnel evaluated the British Pendulum Number after nine hours of polishing (BPN 9) and pe~'cent silica by ASTM C25 ofthe selected aggregates Tennessee Tcch researchers arc conducting p e r c ~ silica by X-ray ~ o n , LOI, T3CM, and T3CM with sand aging procedures CROUCH ET AL ON TENNESSEE BITUMINOUS SURFACE AGGREGATES 193 Repeatability Testing In Phase 3, a limitedprw.e&aal repeatabilityanalysiswas conducted on a large sample of Aggregate The sample was obtained from a local pavnnent contractor The samplewas sieved to the appropriate gra_&.~3_"n, thoroughly mixed and divided into six large containers Eighteen 12-kilogramsampleswere weighed out using 2-kilogramsfi'om each large container The three students working on the project were instructed to independentlyconduct three terminal textural condition tests each A total of twelve specificgravity and absorption tests and two LOI tests were also conducted on the same material The remits are shown in Table [16] A similarrepeatabilityanalysiswith four students each conductingtwo terminaltextural condition tests each is plarmed for Phase The new repeatabilityanalysiswill be used to measure the effect of procedural and TTC determinationchanges adopted in Phase The Phase repeatabilityis currently underway and results are not yet available Table - Phase PreliminaryRepeatabifityResults [16] i i ,, i i i ] Operator[ Test , 1-1 1-2 1-3 2.1 2-2 2-3 3-1 3-2 3-3 Ovorall J , t , i, i TTC 44.32 44.21 44.35 44.25 44.06 44.38 44.21 43.96 44.36 i i ii i i i ' std r AveraSr i eon coy 44.29 0.07 0.17 44.23 0.16 0.36 44.18 44.23 0.20 0.14 O.46 0.32 i i, i J i i Pre~ntation of RJ~ults to Date Sampling for Phase of the project began in the spring of 1998 Phase is scheduled to conclude 12/31/01 The results available to date for aggregates with three or more samples are shown in Table No T3CM results with sand aging or LOI data is currently available The SN 40 values are the latest values provided by TDOT for the surface courses and should not necessarily be considered terminal skid numbers Vehicle passes refers to the number of passes (automobiles and trucks) in the design lane for the surface course projects when the latest skid numbers were obtained Analysis of Remits Varial#li9, Variability of six multiple sample aggregates was determined by using coe~cient of variation (COV) The COV for each aggregate by each laboratory method for which results are 194 AGGREGATECONTRIBUTIONTO HOT MIX ASPHALT (HMA) PERFORMANCE currently available are shown in Table In addition, the method mean COV and aggregate mean COV are also shown in Table 4, Table - Results to Date Aggregate San~le Number ' Number Trc Silica %' ASTM C 25 Siiica % X-ray BPN 19.84 15.48 18.60 18.80 19,44 12.72 14.68 12,56 46.56 46.44 23.86 ~' 21.69 21.48 2L93 21.06 16.51 58.19 55.70 19 35 31 53.12 45.40 42.96 43.12 47.28 45,60 36.36 36.60 36.64 34.60 61.46 58.39 51.65 49.39 57.92 57.63 41.42 46.75 46.51 43.82 32 38 29 26 32 34 30 31 SN'~0 'Vehicle Passes , i ' 1 I 42.71 42.97 43.03 43.18 43.22 2 3 3 4 5 6 3 3 43.03 43.35 43.37 43.40 43.40 43.67 43.89 43.21 44.29 44.37 43.80 43.54 44.59 44.63 44.71 44.77 ii i 35 38 35 40 46 4.31 1.80 4.31 2.65 1.64 49.8 10.33 44 51 8.71 41 2.16 55 3.89 23 22 22 32 i i I Table - Variability of Aggregates and Laboratory Test Methods ' TCM Number Method Mean 0.47 0.44 0.54 1.47 1.24 0.16 0.72 Sili ASTM C 25 9.35 8.86 7.85 3.11 13.65 3.24 7.68 , , , si& Bi'N'9 X-ray 4.93 , ,, 4.94 8.81 18.05 3.56 8.06 ,, ,, 3.14 10.35 6.37 20.15 6.25 2.24 8.08 Mean 4.47 6.55 4.93 8.39 9.80 2.30 , The method showing the least variability in all aggregates is the T3CM This can partly be attributed to the magnitude of TrC values compared to the magnitude of the values of other CROUCH ET AL ON TENNESSEEBITUMINOUSSURFACEAGGREGATES 195 methods However, ifthe method mean of the TsCM was doublexlitwould stillbe lessthan the othermethod means Aggregate has the lowestaggregatemean C O Y indicatingthat,judged by allavailabled~t~,ithas the most consistentlaboratory-measuredproperties Correlation with Pavement Performance The T3CM only measures the aggrcgate's terminal texture, however, a multitude of other factors affect the SN 40 value Rese~ch 6me was dedicated to correlating the effect of agSresate polish resistance to field perfonnan~, There was insu~dent time to thoroughly evaluate ait other factors Although the laboratory data was incom_pleteand the skid numbers for the various surface course projects were not necessarily terminal values, an attempt was made to correlate laboratory properties with the currently avai!~le skid numbers The best correlation between laboratory properties and skid numbers was R2 = 0.74 for the TsCM A plot of skid number vs TaCM is shown in Figure The poorest correlation between laboratory properties and skid numbers, with R2 = 0.0004, was BPN ASTM C 25 Percent Silica and percent silica by X-ray ~ o n were int(~mediate with R of 0.38 and 0.36 respectively Based on this prelimin~ a~t~ there is no discemable relationship between BPN and surface ag~'cgate skid p e r f o ~ The correlation between ASTM C 25 Percent Silica and percem silica by X-ray Diffraction and surface aggregate skid performance is very weak if it exists In the 1970s, AASHTO realized that ASTM C 25 percem silica is a good indicator of aggregates, which are likely to be highly polish susceptible However, the method should not be used as a principle means of predicting aggregate polish resistance [ 7] Further, percent silica by X-ray diffraction measures the same thing with only a slightly better correlation with surface aggregate skid performance Finally, LOI is simply an improved percent silica test, easier to perform and more repea table However, the method provides the same infomaafion as percentsilica.In Phase 3, neitherLOI or percentsilicatestwere indicatorsof aggregate heterogeneity, when the asgre~ates had a few particles high in silic~ Field performance records from other states indicated that aggregates with this level of heterogeneity performed unsatisfactorily in most HMA surface applications T3CM was able to correctly identify this heterogeneous condition 60 50 y = 9.6032x - 373.55 Ra ffi 0.7404 i 4O E ~.3o-It 10 O 42.5 , 43 43.5 44 TTC Value Figure - Skid Number vs TTC 44.5 4,5 196 AGGREGATECONTRIBUTION TO HOT MIX ASPHALT (HMA) PERFORMANCE Pre-evaluation of PotentialNew SurfaceAggregate Sources TsCM has provided an additionalbenefit to TDOT during it's development and continuing validation T3CM has served as a reliable method for pre-evaluating potential new mn'fa~ aggregates for consideration by the department In recent years the T~CMhas been used to evaluate 12 new aggregate sources, nine in Tennessee and one each in Kentucky, North Carolina, and Adcansas Eight of these were recommended to TDOT for test strip evaluation at various ADT levels Four of the eight have been evaluated on test strips and approved by the TDOT Materials and Tests Division for surface course use One ofthe eight is currently being evaluated with a test strip and the remainingthree are under considerationby the TDOT Materials and Tests Division Ease of Perfornumce The resultsofthisstudyhave shown the T3CM to be a logistical~ Compared to the BritishTest involvingthe polishingwheel and pendulum, the T~CM has an initialmedal cost of approximately$200 (assuming the lab isalreadyequipped with the L.A Abrasion and SievingDevices),while the BritishTest has an initialcost of approximately$25,000 [18].The T3CM requireslessoperatorskilland experiencethan the BritishWheel and BritishPen~dmn Unfortunately,the T~CM islaborimemive A typicalT3CM takesapproximately47 hours of laborto complete ifone L.A Abrasion deviceisused The time isreduced to approximately30 hours iftwo L.A Abrasion devicesare available.However, the T~CM's largersample size helpsinsurerepeatability.Ease of performance, repeatability,and substantiallylower equipment costS are advantages indicatingthat this test may be an ideal addition to presently used methods for pre-evaluatingHMA surface aggregates Recommendations In sunmmry,the T3CM appears to be a conservative, reliable surface aggregate prequalificationmethod T3CM measures what is really impol~nt in selectingbiluminous mrfa~ aggregate, the aggregate's terminal textural condition Further, T3CM's abilityto identify agglegates which will perform well in limited ADT applicationshas the potential to reduce the cost of surface aggregate to TDOT while maintaininga high levd of safety for the motoring public The research team therefore recommended that the ~ C M be used as a pre-evaluation procedure for aggregate sources In addition, the T3CM should be used as a verificationtest for random aggregate lots Current TDOT specifications(shown in Table 5) make use ofthe T3CM The research team recommends that Type and Type have a minimumTIC of 43.5 A recommendationfor the minimumTTC of TDOT Type aggregate will require additional data The recommendation is expected near the end of Phase CROUCH ET AL ON TENNESSEE BITUMINOUS SURFACE AGGREGATES 197 Table - Current TDOTSpecificatiomfor Polish Resistanceof B#uminous Surface Aggregates T~pel " T.ype2* i'.Typr ' Type4* Traffic use All roads All roads 15,000ADT max 7,500 ADT max 10% Silicon Dioxide 40% rain 30% 200 rain (AS~Vl C25) 30 rain 25 rain 22 rain BPN (AASHTO 30 rain T-278, T-279) T3CM (TTU Method) 42.5 rain Caldum Carbonate 32% max Test Section (ADT) ,, 10,000 10,000 10,000 * Before approved forum, all sources mu~ show satisfactory field'performance ~ e r a 2-year period (SN of 40 minimum) Conclusions On the basis of the limited laboratory 0ata and skid ~ av_ajlableand the pre"lm3inmy analysis done, the following conclusions can be drawn: The T~CM appears to be able to better discern the performance of Tennessee bituminous surface aggregates than the British Pendulum and British Wheel Method, ASTM C 25 Percent Silica, or X-ray Diffraction percent silica Correlation coefficients indicating the strength of relation between laboratory test methods and field skid performance of bitun'anous surface aggegates showed T3CM to be vastly superior to the other methods The T3CM has identified several promising aggregate sources Some of these new sources are in areas where approved bituminous surface aggregate sources are scarce Acknowledgments The authors wish to gratefully acknowledge the support of the Tennessee Department of Transportation and the Federal Highway Administration We also wish to thank the many aggregateproducersin Tennessee,Kentucky, North Carolin~,and Arkansas whose cooperationmade the projectpossible In addition,the authorswould liketo thank Mr Ri~ard Maxwell for hispatienceand sldll in fabrication, maintenance, and repair of the equipment We would also like to thank Patty Buchatman, Jason Laxson, Neal Whitten, Jake Williams, Leslie Parker, John Gravely, Johrl Davis, Brandon I-fill, John Dudley, Bart Saucier, Veto Prentice, Keith Honeycutt, Todd Walker, Jamey Dotson, Adam Ledsinger, Ban Romano, Kevin Cagle, and Nicky Wells for theirhelp in the laboratory The opinions,findings,and conclusionsexpressedhere are thoseof the authorsand not necessarilythose of the Tennessee Department of Tnmsportation orthe FederalI-fighway Administration 198 AGGREGATECONTRIBUTION TO HOT MIX ASPHALT (HMA) PERFORMANCE References [1] Crouch, L K., Gothard, J., Head, G., and Goodwin, W., "Evaluation of Textural Retention of Pavement Surface Aggregates," In TraraportationResearch Record 1486, TRB National Research Council,Washington,D.C., 1995 [2] Gothard, J., "Evaluationof Aggregate Polish-Resistanceby the TTU Textural Retention Method," Master of Sdence Thesis, Tennessee TechnologicalUniversity,Cookeville, TN, 38505, May 1994 [3] Shirley,G., "Pre-Evaluationof PolishingResistanceof AggregatesforTennessee Bituminous Surface Courses," Master of ScienceThesis, Tennessee Technological University,Cookevillr TN, 38505, December 1995 [4] Crouch, L., Shirley,G., Head, G., and Goodwin, W., "Aggregate Polishing ResistancePre-Evaluation," In T r ~ o n Research Record 1530, TRB National Research Record 1530, TRB National Research Council,Washington,D.C., 1996 [5] Highway Research Board Special Report 113: StandardNome~lature and Definitions for Pavement-Componentsand Defideneies, Highway Research Board, National Research Council,Washington,D.C., 1970, p6 [6] Yager, T and Bdalmama,F., "Macrotoxture and Drainage Management on a Variety of Concrete and Asphalt Surfaces,"Pavement Surface Characteristicsand Materials, ASTMS1P 763, C.M Hayden, Ed., American Society for Testing and Materials, Philadelphia, 1982, pp 16-30 [7] GuidelinesFor Skid Resistant Pavement Design, The AmericanAssociationof State Highway and Transportation Officials,Washington,D.C., 1976 [8] HIU,B, and Henry, J., "Surface Materials and Properties Related to SeasonalVariations in Skid Resistance,"Pavement Surface Characteristicsand Materials, ASTM STP 763, C.M Haydert,Ed., American Society for Testing and Materials, Philadelphia, 1982, pp 45.60 [9] Goodwin, W., "Eva/uafion of Pavement Aggregates For Non-Skid Qualities, " Presented at the Twelfth Annual Symposiumon Geology as Appliedto Highway Engineering,Universityof Tennessee,KnoxvilleTennessee,February I0-I I, 1961 [10] Grmnli~ W., "Effect o f ~ e 1Wmeralogyon PolishingRate and Skid Resistance in Pennsylvania,"In Highway Research Report 341, HRB, National Research Council, Washington,D.C., 1970, pp 18-2I [11] Nitta, N., Saito, K., Isozaki, S., "Evaluatingthe PolishingProperties of Aggregates and BituminousPavement Surfac~ by Means of the Penn State Reciprocating CROUCH ET AL ON TENNESSEE BITUMINOUS SURFACE AGGREGATES 199 Polishin8 Machine," Surface Characteristics of Roadways: International Resew'ch and Tedmologies, ASTMSTP 1031, W.E MeTerand J Rdchart, Eds., American Societyfor Testing and Materials,Philadelphia, 1990, pp 113-126 [121 Diringer, K., A~_,~grcgatesand Skid Resistance,Rr No FHWA/NJ8%008-7110, March 1990 [131 Kandlud,P., P Frazier, Jr and Bishara, E., "Evaluationof AlabamaLimestone Aggregatesfor AsphaltWearing Courses," In T ~ o n ResearchRecord 1418, TRB, NationalResearch Counoil,Washington,DC., 1993, pp 12-21 04] Skerritt, W., "Aggregate Type and TrafficVoltane as controllingFactors in BituminousPavtment Friction,"In Transportation Rese~ch Report 1418, TRB, National Research Council,Washington,D.C., 1993, pp 22-29 [15] Kulakowski,B., Henry, J and Lin, C., "A Closed-LoopCalibration Procedure for a British PendulumTester," Surface Charactemtic,s of Roadways: Intermtional Research and Technologies, ASTMS1P 1031, W.E Meyer and J Reiche~ Eds., Amcdcan Societyfor Testing and Materials, Philaddphia,PA, 1990, pp 103-112 [16] Tucker, C., Aggregate TerminalTextural Con~fio~ M~ter o f s d ~ TennesseeTerminalTechnologicalUniversity,Cookeville,'IN, 38505, May 1997 [17] Burgess, J., EvaluatingBituminousSurfaceAggregateswith the T3CM Master of Sdencr Thesis, TennesseeTechnologicalUniversity,CookcviUe,TN, 38505, May 1998 [18] CATALOGCE-95 C~on GilsonLaboratoryEquipmentCatalog Construction Materials Testing Gilson Company,Inc 1995