Field Evaluation of Warm-Mix Asphalt TechnologiesShad Sargand, M.ASCE1; Munir D. Nazzal, M.ASCE2; Abdalla Al-Rawashdeh3; and David Powers4

Abstract: Warm mix asphalt (WMA) has received considerable attention in the past few years to reduce energy consumption and pollutantemissions during hot mix asphalt (HMA) production and placement. However, many concerns and questions are still unanswered regardingthe field performance and environmental benefits of WMA. In this study, WMAmixtures containing reclaimed asphalt pavement (RAP) wereevaluated in a field project in Ohio. The project included using Aspha-min, Sasobit, and Evotherm in three test sections. Furthermore, acontrol section was also produced so that a side-by-side comparison could be made between WMA and HMA mixtures. Temperature andemissions were monitored during the production and placement of the considered WMA and HMA mixtures. In addition, core samples wereobtained from the evaluated sections and tested in the laboratory. Roughness and rutting measurements were also conducted during the first46 months of service. The results of this study showed that the emissions were significantly reduced during the production and placement ofWMAmixtures as compared to the control HMAmixture. In addition, althoughWMAmixtures were compacted at much lower temperatures,they achieved higher in-place density than the control HMA mixture. The results of the laboratory tests conducted on core samples showedthat the WMA mixtures had higher indirect tensile strength (ITS) than the HMA mixture after 3 months of service. However, the HMAITS value increased more rapidly with time than that of the WMA. The moisture susceptibility test results demonstrated that the Sasobitand Evotherm mixtures exhibited acceptable resistance to moisture-induced damage. Finally, the collected performance data indicatedthat the WMA and HMA sections had similar International Roughness Index (IRI) values after 46 months of service. In addition, no meas-urable rutting was observed in any of the test sections. DOI: 10.1061/(ASCE)MT.1943-5533.0000434. © 2012 American Society of CivilEngineers.

CE Database subject headings: Evaluation; Emissions; Asphalts; Mixing.

Author keywords:Warm mix asphalt (WMA); Reclaimed asphalt pavement (RAP); Long-term performance; Field evaluation; Emissions.

Introduction

Warm mix asphalt (WMA) technologies have gained significantattention in the last few years as a means to reduce energy con-sumption and pollutant emissions during the production and place-ment of asphalt mixtures. This new group of technologies reducesthe viscosity of the asphalt binder by adding organic or chemicaladditives or introducing cool water into the heated molten asphaltunder controlled temperature and pressure conditions. The reduc-tion in viscosity allows the asphalt binder to adequately coat theaggregates during mixing, such that lower temperatures are neededduring the production of the asphalt mixtures. Various WMA tech-nologies have been proposed in the past few years. The FederalHighway Administration (FHWA) has initially identified six mainadditives/processes that may be used in the production of WMA(Button et al. 2007), which included Aspha-min, Sasobit, andEvothererm. However, currently more than 20 technologies aremarketed in the United States (Corrigan 2010).

Mixtures produced using various WMA technologies have beenevaluated in several laboratory studies during the past years(Bennert et al. 2010; Kristjansdottir et al. 2007; Kanitponget al. 2007; Wasiuddin et al. 2007; Hurley and Prowell 2005a, b;2006a, b). The results of those studies demonstrated that, ingeneral, the use of Aspha-Min, Sasobit, and Evotherm leads to im-proving the compactability of asphalt mixtures. The improvedcompaction was noted at temperatures as low as 88°C (190°F).In addition, Aspha-Min, Sasobit, and Evotherm were not foundto have any adverse effects on the resilient modulus of the evaluatedmixtures (Hurley and Prowell 2006a). However, WMA mixturesexhibited lower indirect tensile strengths (ITSs), which may beattributed to the decreased aging due to lower mixing and compac-tion temperatures. Finally, while Aspha-Min did not increase therutting potential of the evaluated mixtures, Sasobit and Evothermgenerally decreased it (Hurley and Prowell 2006b).

Field performance and constructability of WMA has also beeninvestigated through evaluating in-service as well as acceleratedloading test sections (Kvasnak et al. 2010; Jones 2010; Hurleyand Prowell 2008; Diefenderfer et al. 2008; Prowell et al. 2007;Daniel and Fowler 2006; Barthel et al. 2004). National centerfor asphalt technology (NCAT) conducted a study at its test trackto evaluate the field performance of WMA (Prowell et al. 2007).The results of this study indicated that both hot mix asphalt (HMA)and WMA field sections showed excellent rutting performanceafter the application of 515,333 equivalent single-axle loads(ESALs) over a 43-day period. One of the WMA sections was alsoevaluated for early opening to traffic and showed good rutting per-formance. Kvasnak et al. (2010) documented the production, con-structability, and 1-year performance of six field test sections thatwere produced as part of a demonstration project for WMA

1Russ Professor, Civil Engineering Dept., Ohio Univ., Athens, OH45701.

2Assistant Professor, Civil Engineering Dept., Ohio Univ., Athens, OH45701 (corresponding author). E-mail: nazzal@ohio.edu

3Graduate Research Assistant, Civil Engineering Dept., Ohio Univ.,Athens, OH 45701.

4Asphalt Materials Engineer, Ohio Dept. of Transportation, Columbus,OH 43223.

Note. This manuscript was submitted on February 2, 2011; approved onNovember 23, 2011; published online on November 25, 2011. Discussionperiod open until April 1, 2013; separate discussions must be submitted forindividual papers. This paper is part of the Journal of Materials in CivilEngineering, Vol. 24, No. 11, November 1, 2012. © ASCE, ISSN 0899-1561/2012/11-1343-1349/$25.00.

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technologies in Tennessee. Four sections with different WMA tech-nologies and two sections with HMA mixes were produced, tested,and evaluated. WMA and HMA mixtures used in those sectionswere also evaluated in the laboratory. The results of this studyshowed that the asphalt did not age to the same extent duringWMA production as it does during HMA production. In addition,Hamburg-loaded wheel tests indicated that all of the mixes exceptAdvera and Evotherm WMA mixes were moisture resistant.Dynamic modulus testing indicated that the two HMAs were stifferthan the four WMAs. Finally, 1-year field evaluations revealed as-phalt bleeding and raveling in the two HMA sections and the Ad-vera WMA section. Barthel et al. (2004) reported a study in whichtest sections were constructed with Aspha-Min WMAmixtures andconventional HMA mixtures in Europe. Visual inspection of theAspha-Min WMA test sections 3 years after construction indicatedsimilar performance to the control sections with conventional HMAmixtures.

In recent years, WMA technologies have been also utilized tofacilitate the use of reclaimed asphalt pavement (RAP) into new as-phalt mixtures to help in reducing their costs and environmental im-pacts. Laboratory studies were conducted to evaluate the effect ofWMA technologies on theworkability and performance of mixturescontaining RAP (Tao and Mallick 2009; Hodo et al. 2009). In gen-eral, those studies indicated that using WMA technologies mademixtures with RAP easier to compact than those with virgin asphaltbinder without any significant effect on the mechanical performanceof those mixtures. Field studies evaluating WMA mixtures con-taining RAP were also conducted recently (Wielinski et al. 2009;Austerman et al. 2009). Granite Construction constructed twoWMA paving projects from its Indio California facility (Wielinskiet al. 2009). WMA produced with the free water method were usedin both projects. The results of these projects indicated that WMAmixtures containing RAP could be produced and placed at lowertemperatures while yielding mix properties and field densities sim-ilar to those of conventional HMA. Furthermore, the initial fieldperformances of the WMA and HMA sections were similar.

Despite the number of research studies conducted in the past onthe use of WMA technologies, there are still concerns about thelong-term performance of WMA mixtures, especially for thosecontaining RAP material. However, it is believed that these poten-tial concerns could be mitigated as field trials progress.

The Ohio Department of Transportation (ODOT) constructedfield trials in 2006 to evaluate the constructability and performance

of three types of WMA mixtures containing RAP. Aspha-Min,Sasobit, and Evotherm WMA mixtures were used in three test sec-tions. In addition, a fourth section that had a conventional HMAmixture was also built and used as a control. The objective of thispaper is to utilize the data collected during the production, con-struction, and first 46 months of service of those field trials toevaluate the field performance and constructability of WMA mix-tures containing RAP and assess their potential environmentalbenefits.

Description of Field Project

The field test sections were part of a rehabilitation project on StateRoute 541 (SR 541) near Guernsey and Coshocton counties. Theselected roadway is a two-lane rural highway with an average dailytraffic of 2,150 vehicles. It was originally constructed in the early1960s using a 32 mm (1.25 in.) asphalt wearing course, a 44.4 mm(1.75 in.) asphalt intermediate course, and a 221 mm (9 in.) granu-lar base course. Two 38 mm (1.5 in.) overlays were added in 1985and 1994. The rehabilitation project in this study consisted of theplacement of an additional two-layer overlay. The first layer was a19 mm (0.75 in.) leveling course of a conventional HMA mixture.The second layer was a 32 mm (1.25 in.) wearing course placed infour sections: an HMA control section and three WMA test sec-tions. Evortherm, Sasobit, and Aspha-min were used in the WMAtest sections. Each of the four test sections was approximately4.82 km in length. A description of the wearing course mixturesused in the different test sections is provided subsequently.

Wearing Course Mixtures

The wearing course in all four sections consisted of a Marshall mix-ture with a 10 mm (3=8 in:) nominal maximum aggregate size(NMAS) designed to meet ODOT specifications for Item 448 formedium traffic roads (ODOT 2010). The same aggregate blend wasused in all mixtures evaluated, which included 15% RAP. All mix-tures were designed with a compactive effort of 50 blows on eachface. The optimum asphalt binder content for HMA and WMAmixtures was 6.1% (5.3% virgin binder and 0.8% from the RAP).The asphalt binder used was an styrene-butadiene-styrene (SBS)elastomeric polymer-modified performance grade (PG 70-22M)binder. Table 1 presents the job mix formula of the four wearing

Table 1. Summary of Properties of HMA and WMA Mixtures

Mixture designation Aspha-min Evotherm Sasobit HMA

Binder type PG70-22M PG70-22M PG70-22M PG70-22MBinder content (%) 6.1 6.1 6.1 6.1Design air void (%) 3.5 3.5 3.5 3.5WMA type Aspha-min Evotherm Sasobit NAAmount added 0.3% by weight of total mix 5.3% by weight of total mix 1.5% by weight of total binder NAAggregate blend 53% limestone (absorption: 1.31%, Gsb: 2.606) 32% natural sand (absorption: 1.53%, Gsb: 2.585) 15% RAP (5.1% AC,

limestone, and natural sand)

Seive size (mm) Gradation (% passing)

12.5 1009.5 924.75 512.36 381.18 280.6 180.3 70.15 40.075 2.8

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course mixtures evaluated. It also provides a summary of the dos-age and type of the WMA technology used for each of the threeWMA sections evaluated. The Evotherm emulsion was producedusing an SBS modified PG 70-22M binder similar to the controlmixture and was substituted for the liquid asphalt. The Evothermemulsion addition rate was adjusted such that the resulting asphaltresidue equaled the design asphalt content. Sasobit was added at arate of 1.5% by total weight of asphalt binder (including the binderin the RAP). Sasobit pellets were added directly to the mix. Aspha-min was added at 0.3% by total weight of mix. The Aspha-min wasadded to the mix at approximately the same point that the asphaltwas injected into the mixing drum.

The HMA and WMA mixtures were produced and deliveredfrom two different asphalt plants. Stack emissions tests wereconducted to measure the quantities of pollutants produced atthe plant for each of the mixtures evaluated.

Construction of Wearing Course

The wearing course layer in the four test sections was constructedusing the same method and equipment. The contractor used therolling pattern that is typically used for HMA mixtures with similargradation. In general, the rolling pattern included first performingfive compaction passes using a static three-wheel roller, followedby a single pass of a vibratory wheel roller, and completed by afinishing compaction pass using a tandem finish roller. An infraredcamera was used to record temperatures during the compaction ofthe wearing course layer of the four test sections. Industrial hygienetesting was also performed to monitor emissions during the pavingoperation of the four test sections. Samples were collected using sixlow-volume air-sampling pumps attached to the paver. In addition,two sampling pumps were also mounted on tripods to monitorbackground air conditions as shown in Fig. 1. Collected sampleswere analyzed by an accredited laboratory using National Instituteof Safety and Health (NIOSH) Method 5042 for total particulatesand benzene soluble matter. Finally, in-place density measurementswere obtained by the contractor using a nuclear density gauge di-rectly after construction of the wearing course layer of each testsection.

Description of Testing Program

The testing program in this study included obtaining core samplesat different test points along the wheel path in each of the evaluatedtest sections after 3, 27, and 46 months of service. Indirect tensilestrength tests were conducted on the collected samples. The tests

were conducted at a temperature of 25°C (77°F). Moisture suscep-tibility tests were also conducted in accordance with AASHTOT283 on core samples obtained after 46 months of service. Theconditioned samples were vacuum saturated so that the internalvoids were between 70 and 80% filled with water and were sub-jected to one laboratory freeze—thaw cycle.

Light falling weight deflectometer (LFWD) tests were per-formed after 46 months of service to characterize the in situ proper-ties of WMA and HMA mixtures. The LFWD is a portable devicethat is designed for estimating the elastic modulus of pavement ma-terials. The Prima 100 LFWD was used in this study. This deviceconsists of a 10 kg (22 lb) drop weight that falls freely onto a load-ing plate that has a 150 mm (5.9 in.) diameter, producing a loadpulse. During any test operation, the Prima 100 device measuresboth the applied force and center deflection, utilizing a velocitytransducer. The measured load and deflection are used to computethe LFWD elastic modulus (ELFWD).

Finally, rutting and roughness measurements as well as visualinspection of the test sections were conducted after 3, 27, and46 months of service. The roughness measurements were takenusing a noncontact inertial profiler on each section, applying a0.16 km segment length. The roadway was dry when taking thosemeasurements. The FHWA pavement Profile Viewing and Analysis(ProVAL) software was used to analyze the collected profiles andobtain the International Roughness Index (IRI) for each segment.

Results and Analysis

Results of Emission Tests during Production

The quantity of different pollutants released during the productionof each of the evaluated mixtures was measured by using stackemissions tests. The pollutants considered during those tests in-cluded sulfur dioxide (SO2), nitric oxides (NOx), carbon monoxide(CO), and volatile organic compounds (VOCs). Table 2 presents asummary of the stack emissions test results. In this table, negativepercent change values indicate a reduction in emissions comparedwith conventional HMA production, whereas positive values re-present an increase. Aspha-min and Sasobit WMA mixtures showsubstantial reductions in various pollutants, ranging from 83.3% forSO2 to 21.2% for NOx. The reduction in emissions represents asignificant cost savings because 30 to 50% of the overhead costsat an asphalt plant can be attributed to emission controls (Hampton2003). The results in Table 2 also indicate that the use of theEvotherm yielded a negligible 1.92% decrease in NOx and asubstantial increase in the other emittants. In particular, over2.5 times as much volatile organic compounds are released in the

Fig. 1. Pictures of the paving operation on SR 541 showing ambient air sampling equipment

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Evotherm process compared with conventional HMA. The increasein Evotherm emissions may be attributed to an increase in the fuelusage needed to convert the water in the Evotherm to steam.Emissions reduction has been reported in other WMA projects us-ing Evotherm. However, the Evotherm was produced at lower tem-peratures in those projects.

Results of Emission Tests during Construction

Table 3 presents the results of the industrial hygiene tests that wereperformed during the paving operation of the four test sections. Thethree WMA mixtures resulted in significant reduction in emissions.The total particulate matter was reduced by at least 67% whenWMA mixtures were used as compared with the HMA mixture.In addition, the use of WMA resulted in 72 to 81% reduction inbenzene soluble matter (BSM). The BSM represents the fractionof the total particulates that could be caused by asphalt fume ex-posure. Thus, any reduction in the BSM indicates a decrease in thereleased asphalt fumes. This suggests that WMA would help inreducing health risks and problems of paving workers that are as-sociated with the asphalt fumes released during the paving phase.

Compaction Temperature Measurements

The maximum temperatures were obtained from all the infraredpictures taken during the compaction of the wearing course layerof each test section. Table 4 presents the average maximum com-paction temperature of the different WMA and HMA mixtures

evaluated in this study. The average maximum compaction temper-ature of the WMAmixtures was at least 13°C (55°F) lower than thatof the HMA mixture.

ANOVAwas conducted by using the statistical analysis softwareto compare the maximum compaction temperatures for the consid-eredWMA and HMAmixtures. The results of the ANOVA analysisshowed that, at the 95% confidence level, the type of mixture usedhad a significant effect on the compaction temperature. Table 4presents the results of the grouping of those mixtures that was de-termined using the post-ANOVA least-square mean (LSM) analy-ses. In this table, the groups are listed in descending order with theletter A assigned to the highest mean followed by the other lettersin appropriate order. A double letter designation, such as B=C,indicates that in the analysis the difference in the average was notclear cut and that the average was close to either group. The WMAmixtures had significantly lower maximum compaction tempera-tures than the HMA mixture. In addition, while the Evotherm mix-ture had significantly lower temperature than that of the Sasobitmixture, the Aspha-min compaction temperature was statisticallysimilar to the other two types of WMA mixtures.

Field Density Measurements

Fig. 2 presents the average relative density obtained for the testsections. Although the WMA mixtures were produced and com-pacted at lower temperatures, they achieved higher densities thanthe control HMA mixture. Furthermore, Evotherm and Sasobit hadthe highest and lowest density, respectively, among the consideredWMA mixtures. The control HMA mixture had higher variabilityin the in-place density than the WMA mixtures, as indicated by theerror bar in Fig. 2. The results of the in-place density suggests thatthe WMA mixtures would require less compaction effort to achievethe same density as a control HMA mixture, and hence, lower en-ergy and fuel consumption will be needed during construction.

Laboratory Test Results

Fig. 3 presents the average indirect tensile strength values obtainedfrom ITS tests that were conducted on core samples obtained fromthe WMA and HMA sections after 3, 27, and 46 months of service.After 3 months of service, the WMA mixtures had higher ITS val-ues than the HMA control mixture. Furthermore, the Aspha-minmixture had the highest ITS value. The ITS value increased withtime for all mixtures. However, the HMA mixture demonstrated agreater rate of increase than the WMA mixtures, such that it exhib-ited the highest ITS value after 46 months of service. The Aspha-min mixture possessed the lowest ITS value after 46 months.

Table 3. Results of Emissions Tests at Construction Site

MixtureTPM

(mg=m3)Change fromHMA (%)

BSM(mg=m3)

Change fromHMA (%)

Control HMA 1.25 — 1.05 —Evotherm 0.29 76.8 0.29 72.4Aspha-min 0.41 67.2 0.2 81.0Sasobit 0.33 73.6 0.21 80.0

Note: TPM = total particulate matter, BSM = benzene soluble matter.

Table 4. Average Maximum Compaction Temperature of Wearing CourseMixtures

MixtureEstimate of maximumtemperature [°C (°F)] Letter group

Control HMA 159 (319) ASasobit 134 (273) BAspha-min 127 (260) BCEvotherm 122 (251) C Fig. 2. Field relative densities of WMA and HMA mixtures

Table 2. Results of Stack Emissions Tests at Asphalt Plant

Emittant

Mixture

Control HMA Evotherm Aspha-min Sasobit

SO2 kg=h (lb=h) 0.11 (0.24) 0.17 (0.37) 0.02 (0.04) 0.02 (0.04)Change from HMA — 54.20% −83.30% −83.30%NOx kg=h (lb=h) 2.4 (5.2) 2.3 (5.1) 1.6 (3.6) 1.87 (4.1)Change from HMA — −1.92% −30.80% −21.20%CO kg=h (lb=h) 28.6 (63.1) 22.8 (50.3) 11 (24) 10.5 (23.2)Change from HMA — −20.30% −62.00% −63.20%VOC kg=h (lb=h) 3.5 (7.8) 9.2 (20.2) 1.3 (2.9) 1.7 (3.8)Change from HMA — 159.00% −62.80% −51.30%Note: SO2 is sulfur dioxide, NOx are nitrogen oxides, CO is carbonmonoxide, and VOC are volatile organic compounds.

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In general, higher ITS values are desirable because they corre-spond to a strong and durable mixture. However, the greater ITSincrease rate with time may indicate that higher binder aging oc-curred (Kandhal and Chakraborty 1996; Liang and Lee 1996). Toinvestigate that, the ratio between ITS obtained after 46 months ofservice to that obtained after 3 months was computed. Fig. 4presents the ratio computed for the WMA and HMA mixtures.The WMA mixtures had lower ITS ratios than the HMA mixture.The Aspha-min mixture exhibited the lowest ratio, which was ap-proximately 23% lower than that of the HMA mixture. This indi-cates that the extent of binder aging was greater in the HMAmixture than that in the WMA mixtures.

The results of the indirect tensile strength tests that were con-ducted on conditioned samples were used to compute the ratio ofthe original tensile strength that is retained after the moisture andfreeze—thaw conditioning, commonly known as the tensile strengthratio (TSR). Only one sample of the control HMA mixture wasavailable for conditioning and was used to compute the TSR for thatmixture. Fig. 5 presents the computed TSR for the considered mix-tures. The Aspha-min and control HMA mixtures did not meet theTSR requirement of 0.7 specified by the Ohio Department of Trans-portation. Furthermore, the Evotherm had the highest TSR of 0.8,followed by the Sasobit mixtures. The results of the moisture sus-ceptibility laboratory tests that were conducted by NCAT on sam-ples fabricated from loose mixture obtained during the constructionof the evaluated test sections yielded similar results, such that theEvotherm and Aspha-min mixtures had the greatest and least resis-tance to moisture damage, respectively (Hurley et al. 2009).

LFWD Test Results

The average value of the LFWD modulus and the standarddeviation of the tested sections are presented in Fig. 6. Although

the Asph-min and Evotherm sections had higher LFWD modulithan the control HMA section, the Sasobit section showed a slightlylower LFWD modulus. Furthermore, the Aspha-min section hadthe highest LFWD modulus value, which was 30% higher thanthe control HMA section. ANOVA and post-ANOVA analyseswere conducted to compare the LFWD modulus of the differentWMA and HMA sections. Table 5 shows the results of this analy-sis. The Aspha-min and Evotherm sections had significantly higherLFWD moduli than the control HMA section. In addition, theLFWD modulus of the Sasobit section was statistically indistin-guishable from that of the control section.

Results of Pavement Performance Evaluation

The results of the roughness measurement were used to obtain theIRI value for every 0.16 km segment. IRI simulates a standard ve-hicle traveling down the roadway and is equal to the total antici-pated vertical movement of this vehicle accumulated over thelength of the section. Fig. 7 presents the average IRI values for eachtest section, which were taken after 3, 27, and 46 months of service.The WMA sections had similar IRI values to that of the HMA sec-tion after 3 months of service, with a slightly lower value for the

Fig. 4. Indirect tensile strength ratio of evaluated mixtures

Table 5. Results of Statistical Analysis of LFWD Test

Mixture Estimate of ELFWD [MPa (ksi)] Letter group

Aspha-min 696.4 (101) AEvotherm 558.5 (81) BSasobit 420.6 (61) CControl HMA 462 (67) C

Fig. 3. Indirect tensile strength of evaluated mixtures

Fig. 5. Tensile strength ratio of evaluated mixtures

Fig. 6. LFWD test results

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Evotherm section. Furthermore, although the Sasobit and Aspha-min sections exhibited lower IRI values than the HMA section after46 months of service, the Evotherm had a slightly higher value. TheEvotherm section had the lowest initial IRI value. ANOVA analysiswas conducted to evaluate the effect of the mixture type on the IRIvalue that was obtained after 46 months of service. The results ofthe ANOVA analysis showed that, at the 95% confidence level, themixture type did not have a significant effect on the obtained IRIvalues. This suggests that the IRI values of the WMA sections arestatistically similar to that of the HMA section.

Fig. 7 shows that the IRI values of the different sections is wellbelow 2.71 m=km (172 in:=mi), which is the terminal value recom-mended by the FHWA and used in the mechanistic empirical pave-ment design (MEPDG). To estimate the time at which this IRIterminal value is expected to be reached for each section, and hencepavement rehabilitation will be required, regression analyses wereconducted on the obtained data for each section. The results of thisanalysis showed that linear models best predict the variation of theIRI with time. The developed regression models were used to pre-dict the number of months at which an IRI value of 2.71 m=km(172 in:=mi) is reached for the WMA and HMA sections. Fig. 8presents the predicted service life for each of the evaluated sections.The Aspha-min section has better longevity than the HMA section.On the other hand, the Evotherm and Sasobit sections will requirerehabilitation sooner than the HMA section. More IRI data needs tobe collected in the future to validate the prediction of the developedlinear regression models.

The rutting measurement that was conducted after 46 months ofservice showed no measurable signs of rutting in any of the WMAand HMA test sections. In addition, visual inspections of those sec-tions did not indicate any problems. ODOT’s regular inspectiongave a score of 99 for the four tests sections, with no structuraldeductions.

Conclusions

This paper documents the production, construction, laboratory test-ing, and 46 months of evaluation of WMA field test sections. Onthe basis of the results of this study, the following conclusions canbe drawn:• The maximum compaction temperatures of the WMA mixtures

were at least 13°C (55°F) less than that of the HMA mixture.• Although the WMA mixtures were produced and compacted at

lower temperatures than the HMAmixture, they achieved higherin-place densities.

• Emissions during the production of the Aspha-min and Sasobitmixtures were reduced by at least 50% for volatile organic com-pounds, 60% for carbon monoxide, 20% for nitrogen oxides,and 83% for sulfur dioxide when compared with those of thecontrol HMA mixture.

• The BSMmeasured during the paving operation was reduced by72 to 81% when WMA mixtures were used, suggesting that theuse of WMA results in a decrease in the asphalt fumes releasedduring paving.

• WMA mixtures had higher ITS values than the HMA mixtureafter 3 months of service. However, the HMA exhibited thehighest ITS value after 46 months.

• The ITS test results indicted that higher binder aging with timeoccurred in the HMA mixture than that in the WMA mixtures.

• The Evotherm and Sasobit mixtures demonstrated acceptablemoisture damage resistance as measured by the TSR value.

• The Aspha-min and Evotherm sections had significantly higherLFWD moduli than the control HMA section. However, theLFWD modulus of the Sasobit section was similar to that ofthe HMA.

The IRI values of WMA sections were statistically similar to that ofthe control HMA section after 46 months of service. In addition, nomeasurable signs of rutting were observed in any of the four testsections.

Acknowledgments

This research was supported by the Ohio Department of Transpor-tation (ODOT) and the Federal Highway Administration. Theauthors would like to express thanks to ODOT personnel thathelped in this research study, particularly Roger Green. We thankDan Radanovish of ODOT for taking the IRI measurements. Theauthors would also acknowledge the contributions of ORITEResearch Engineer Issam Khoury and undergraduate studentsBen Jordan and Dan Rhine.

References

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