The Effect of Crumb Rubber Modifier (CRM) on the Performance Properties of Rubberized Binders in HMA pavements

Transcription

1 The Effect of Crum Ruer Modifier (CRM) on the Performnce Properties of Ruerized Binders in HMA pvements Soon-Je Lee* Ph.D. Grdute Student Deprtment of Civil Engineering Clemson University Clemson, SC Emil: Chndr K. Akisetty Ph.D. Grdute Student Deprtment of Civil Engineering Clemson University Clemson, SC Emil: Serji N. Amirkhnin Professor Deprtment of Civil Engineering Clemson University Clemson, SC Emil:

2 ABSTRACT The ppliction of crum ruer modifier (CRM) in sphlt mixtures is intended to improve the properties of inder y reducing the inder s inherent temperture susceptiility. During the interction with sphlt inder, the CRM prticles sor portion of the oils in sphlt inder nd the prticles swell; therefore, incresing the viscosity nd stiffness of the CRM inder. Still, the performnce properties of CRM inders in hot mix sphlt (HMA) pvement re considered to e uncler due to the vrious interction effects of CRM with sphlt inders, depending on the CRM percentge, source nd size. In this study, lortory investigtion ws conducted on the properties of CRM inders s function of CRM processing method nd percentges. A totl of twenty-four CRM inders (3 inder sources * 2 CRM processing methods * 4 CRM percentges) were produced nd rtificilly ged through n ccelerted ging process. Evlution of the CRM inders included the following testing procedures: Viscosity t high temperture, performnce properties t high nd intermedite tempertures, nd crcking properties t low temperture. The results from this study indicted tht the higher CRM percentges for CRM inders seemed to led to higher viscosity, etter rutting resistnce nd less chnce for low temperture crcking. In generl, the mient CRM ws found to e more effective on producing the CRM inders tht re more viscous nd less susceptile to rutting nd crcking. Keywords: HMA pvements, crum ruer modifier, rutting resistnce, low temperture crcking - 2 -

3 INTRODUCTION Bckground Crum ruer hs een mnufctured y two mjor methods: mient nd cryogenic grinding. Ech method cn produce crum ruer of similr prticle size, ut the primry difference etween them is the prticle surfce texture. Crum ruer prticles resulting from mient processing hve n irregulr shpe with rough texture due to the tering nd shredding ction of the ruer prticles in the crcker mills. The crum ruer prticles produced y the cryogenic method, on the other hnd, hve smooth surfces, which resemle shttered glss. This difference in prticle surfce texture results in the mient prticles hving higher surfce re thn the cryogenic crum ruer (1). The incresing usge of CRM in sphlt pvements requires etter understnding of its effects on the physicl, chemicl, nd performnce properties of CRM inders. Generlly, the ddition of CRM to sphlt inders is intended to improve some of inder s properties such s reducing the inherent temperture susceptiility of the inder. The improvement of the properties of CRM inders lrgely depends on the interction etween CRM nd sphlt inders where the CRM prticles swell in the inders to form viscous gel; resulting in n increse in the viscosity of the CRM inders (2-7). However, the properties of CRM inders t wide rnge of tempertures re considered to e somewht uncler due to the vrious interction effects of CRM with sphlt inders, lrgely depending on the chemistry of the sphlt inder (i.e., source of the inder) nd the CRM s well s the percentge, prticle size nd texture of the CRM nd the interction temperture nd time. Reserch Ojective nd Scope The min ojective of this reserch project ws to investigte the performnce properties of CRM inders due to CRM processing method nd percentge through selected - 3 -

4 Superpve inder tests. The CRM inders were produced in the lortory incorporting two CRM sources (mient nd cryogenic) nd four CRM percentges (5, 10, 15, nd ) into three se inders. The CRM inders were rtificilly ged using PAV (pressure ging vessel) procedure. The viscosity nd rutting properties for unged CRM inders, nd the crcking properties t intermedite nd low tempertures for ged CRM inders were evluted. Figure 1 shows flow chrt of the experimentl design used in this study. MATERIALS AND TEST PROGRAM Mterils Asphlt inders Three sphlt inders ll grded s PG 64-22; designted s A, B, nd C, from different crude sources were used in this study. Binder A ws from Venezueln crude source, inder B ws from Middle Estern source, nd inder C ws mixture of severl sources tht could not e identified y the supplier. Ech inder ws grded in ccordnce with AASHTO M320 to verify the performnce grde. Tle 1 summrizes the properties of the three se inders included in this study. Crum ruer modifier (CRM) The CRM used in this study ws otined from two sources. One source used the mient grinding method to process scrp pssenger tires into crum ruer nd the other used the cryogenic grinding process. One size of crum ruer ws otined from ech source: -40 mesh (0.425 mm), which is widely used to produce the CRM mixtures in South Crolin. The grdtion of ech crum ruer is shown in Figure 2. The surfce texture of ech CRM ws determined using scnning electron microscope (SEM) t mgnifiction level of 120x (Figure 3)

5 Preprtion nd ging of CRM inders The inder mixing used in this study ws the wet process, in which the CRM is dded to the se sphlt inder efore introducing it in the sphlt concrete mtrix. The CRM inders were mnufctured using two CRMs nd three se inders in the lortory t 177 C for 30 minutes y n open lde mixer t lending speed of 700 rpm (8). This mixing condition mtches the field prctices used in South Crolin to produce field mixtures. In totl, twenty-four CRM inders (3 inder sources * 2 CRM processing methods * 4 CRM percentges) nd three control inders were produced nd evluted during this study. The CRM nd control inders were then rtificilly ged through n ccelerted ging process (PAV ging for 20 hours t 100 C) (9). Superpve inder tests The properties of these CRM inders were evluted using selected Superpve inder test procedures including the viscosity test (AASHTO T 316), BBR (ending em rheometer) (AASHTO T 313), nd DSR (dynmic sher rheometer) (AASHTO T 315: with the plte gp djusted to 2 mm). The plte gp djustment ws used to eliminte the influence of ruer prticle size (10-12). Four duplicted smples were tested y the DSR, nd three duplicte smples were tested y the rottionl viscometer nd the BBR. The results were reported s the verge of these tests. A 10.5 g inder smple of CRM inders ws tested with numer 27 spindle in the rottionl viscometer t 135 C. The control inders were tested in ccordnce with the sme procedure except n 8.5 g smple ws used with numer 21 spindle. A different test configurtion ws used for the CRM inders to llow dditionl spce for ruer prticles etween the wll of the smple tue nd the smller dimeter numer 27 spindle (1). In the - 5 -

6 DSR, the unged inder ws tested using 25 mm prllel plte t 76 C nd the PAV-ged inder ws tested using n 8 mm prllel plte t 25 C. The BBR test ws conducted using ech sphlt em ( mm) t -12 C. RESULTS AND DISCUSSIONS Originl stte inder (no ging) Viscosity t high temperture The viscosity of sphlt inders t high tempertures is n importnt property s it reflects inder s ility to e pumped through n sphlt plnt, thoroughly cot the ggregte in hot mix sphlt (HMA) mixture, nd e plced nd compcted to form new pvement surfce (9). Figure 4 shows the viscosity results for the CRM inders tested in this reserch study. A generl trend ws found, s expected, indicting tht the higher CRM percentges led to the higher viscosity of the CRM inders, nd the mient CRM produced inders hving higher viscosity thn the cryogenic CRM. Additionlly, CRM inders produced with inder source A generlly hd higher viscosities thn those mde with inder sources B nd C. This is thought to e ttriuted to the initil higher viscosity of the se inder A. From n nlysis of the viscosity results shown in Tle 2, it is evident tht the CRM percentge hd mjor effect on the performnce of the CRM inders. In ddition, the processing method used to mnufcture CRM, mient vs. cryogenic, ws found to hve significnt effect. Superpve inder specifictions include mximum viscosity requirement (3 P s) for n unged inder mesured t 135 C (13). Bsed on this limit, ll CRM inders contining mient nd cryogenic CRM would e uncceptle

7 Performnce properties t high temperture In generl, the higher G*/sin vlues indicte tht the inders will e less susceptile to permnent deformtion t high pvement tempertures (9). The rutting resistnce prmeter, the G*/sin, of the control nd CRM inders ws mesured t 76 C nd the results re shown in Figure 5. Generlly, the G*/sin did follow the sme trend for ll of the comintions tested. For ll three inder sources, there is n increse in G*/sin with n increse in CRM percentges. The sttisticl results indicte tht there were sttisticlly significnt differences in the G*/sin of CRM inders s function of CRM percentges (Tle 3). The differences etween the CRM inders produced with mient nd cryogenic CRM were lso sttisticlly significnt t the level, with n exception of inder source B. This finding is consistent with the surfce texture of two CRMs (Figure 3). Amient CRM intercts with sphlt inder more esily nd quickly thn cryogenic CRM, s the former hs much higher surfce re due to its porous surfce texture (14). Therefore, the CRM inders with mient CRM will result in more sorption of the light prts of the sphlt inder, leding to etter rutting properties (higher G*/sin vlues). Similr to viscosity results, the CRM inders produced from inder source A showed significntly greter G*/sin vlues thn those produced from inder sources B nd C. It should e mentioned tht the se inders hd different G*/sin vlues. The G*/sin of se inder A t 76 C ws 38% nd 42% higher thn those of se inders B nd C, respectively (Figure 5). Long-term ged inder (PAV ging) Ftigue crcking properties t intermedite temperture - 7 -

8 The Superpve inder specifiction hs mximum vlue of 5,000 kp for G*sin, nd low vlues of G*sin re considered desirle ttriutes from the stndpoint of resistnce to ftigue crcking (9). After PAV ging, the ftigue resistnce prmeters, G*sin vlues, of the control nd CRM inders were mesured using the DSR t 25 C nd the results re illustrted in Figure 6. In generl, the higher CRM percentges seemed to led to the lower G*sin of the CRM inders, ut this trend ws not consistent. From Duncn s multiple rnge test (Tle 4), the sttisticl differences of G*sin s function of CRM percentges vried depending on the inder source nd the CRM percentge used. Additionlly, the difference etween mient nd cryogenic CRM ws found to hve n insignificnt effect, t the level, on G*sin of the CRM inders produced from inder sources A nd B. With respect to the effect of inder source on G*sin of CRM inders, the CRM inders produced with inder source A were considered to e the most resistnt to ftigue crcking. This is lso thought to e ttriuted to the lower G*sin of the se inder A. It should e noted tht the vrince of G*sin vlues (t 25 C) otined from four duplicted smples ws much greter thn tht of G*/sin vlues (t 76 C), nd this my e relted to the difference of the smple mount used t two DSR tests (for unged nd PAV ged CRM inders), especilly in the CRM inders with high CRM percentges. Also, the CRM prticles remining in the inder might e nother reson of the greter vrince of G* sin t 25 C. Crcking properties t low temperture To prevent therml crcking, creep stiffness hs mximum limit of 300 MP, nd the decrese in stiffness leds to smller tensile stresses in the sphlt inder nd less chnce for low temperture crcking (9). From the BBR tests t -12 C, the shrinkge resistnce - 8 -

9 prmeters, stiffness nd m-vlue, of the control nd CRM inders were clculted, nd the results re shown in Figure 7. The stiffness of CRM inders did tend to decrese s the CRM percentges incresed from to, regrdless of the inder source nd CRM processing methods. In ddition, the CRM inders produced with mient CRM generlly showed the lower stiffness vlues thn those with cryogenic CRM, nd the difference ws sttisticlly significnt t the level (Tle 5). It is importnt to note tht the CRM inders with mient CRM hd etter resistnce on low temperture crcking, s well s permnent deformtion t high temperture. The CRM inders produced from inder source A showed lower stiffness vlues thn those produced from inder sources B nd C. However, the stiffness difference within inder sources ws found to e smller s the CRM percentges incresed (Figure 7 ()). The finding indictes tht the effect of inder source on the CRM inder t low temperture my lessen s the CRM percentges increses. Figure 6 () depicts the chnge in the m-vlue s function of the CRM percentge. As shown in this figure nd Tle 6, the effect of CRM percentge on the m-vlue ws not significnt t the level. Similrly, the processing method employed to mnufcture CRM hd n insignificnt effect, with the exception of inder source B. These findings were consistent with the previous reserch (3). SUMMARY AND CONCLUSIONS To investigte the performnce properties of CRM inders s function of CRM processing method nd percentge, twenty four CRM inders were produced in the lortory, using two CRM sources, four CRM percentges nd three se inders (PG 64-22). The CRM inders were rtificilly ged through n ccelerted ging process. A series of selected - 9 -

10 Superpve inder tests were conducted using rottionl viscometer, DSR, nd BBR to evlute the viscosity nd rutting properties t high temperture nd the crcking properties t intermedite nd low tempertures. From these test results, the following conclusions were drwn for the mterils used in this study: 1) The higher CRM percentges used to produce CRM inders, s expected, led to n increse in the viscosity t 135 C, which is relted to the increse in the CRM mss through inder sorption. The mient CRM resulted in higher viscosity vlues thn the cryogenic CRM t the sme percentge usge, nd this is ttriuted to the incresed surfce re nd irregulr shpe of the mient CRM. 2) The rutting properties of CRM inders improved s the CRM percentge incresed. The mient CRM ws found to e more effective on producing the CRM inders tht re less susceptile to rutting t high pvement tempertures. 3) In generl, the higher CRM percentges seemed to led to etter ftigue crcking properties of the CRM inders, ut the difference etween mient nd cryogenic CRM ws not found to hve significnt effect on the G*sin of the CRM inders t the level. 4) The higher CRM percentge resulted in the lower stiffness of CRM inders, nd the CRM inders produced with mient CRM showed etter resistnce on low temperture crcking thn those with cryogenic CRM. The inder source influence on the CRM inder properties t low temperture ws not s significnt s the CRM percentge incresed. 5) The CRM percentges nd the processing methods (mient vs. cryogenic) used to mnufcture CRM were not found to hve sttisticlly significnt effects on chnge in the m-vlue

11 6) It is recommended to conduct nother study to evlute the effect of CRM prticle size using the sme test comintions. Also, further study with mny other inder nd CRM sources is needed to generlize these findings. ACKNOWLEDGEMENT This study ws supported y the Asphlt Ruer Technology Service (ARTS) t Civil Engineering Deprtment, Clemson University, Clemson, South Crolin, USA. The uthors wish to cknowledge nd thnk South Crolin's Deprtment of Helth nd Environmentl Control (DHEC) for their finncil support of this project. REFERENCES 1. Putmn, B.J. (2005) Quntifiction of the Effects of Crum Ruer in CRM Binders, Disserttion in prtil fulfillment of the requirements for Ph.D in Civil Eng., Clemson University, Clemson, SC. 2. Airey, G.D., Rhmn, M.M. nd Collop, A.C. (2003) Asorption of Bitumen into Crum Ruer Using the Bsket Dringe Method, The Interntionl Journl of Pvement Engineering, Vol. 4(2), pp Bhi, H.U. nd Dvis, R. (1994) Effect of Crum Ruer Modifiers (CRM) on Performnce relted Properties of Asphlt Binders, Journl of the Assocition of Asphlt Pving Technologists 63, pp Green, E.L. nd Tolonen, W.J. (1977) The Chemicl nd Physicl Properties of Asphlt- Ruer Mixtures, Report ADOT-RS-14 (162), Arizon Deprtment of Trnsporttion. 5. Heitzmn, M. (1992) Design nd Construction of Asphlt Pving Mterils with Crum Ruer Modifier, Trnsporttion Reserch Record: Journl of the Trnsporttion Reserch Bord, No. 1339, pp Kim, S., Loh, S.W., Zhi, H. nd Bhi, H. (2001) Advnced Chrcteriztion of Crum Ruer-Modified Asphlts, Using Protocols Developed for Complex Binder, Trnsporttion Reserch Record: Journl of the Trnsporttion Reserch Bord, No. 1767, pp

12 7. Znzotto, L. nd Kennepohl, G. (1996) Development of Ruer nd Asphlt Binders y Depolymeriztion nd Devulcniztion of Scrp Tires in Asphlt, Trnsporttion Reserch Record: Journl of the Trnsporttion Reserch Bord, No. 1530, pp Shen, J., Amirkhnin, S., Lee, S.-J. nd Putmn, B.J. (2006), Recycling of Lortory- Prepred RAP Mixtures Contining Crum Ruer Modified Binders in HMA, Trnsporttion Reserch Record: Journl of the Trnsporttion Reserch Bord, No. 1962,, pp The Asphlt Institute (2003), Performnce Grded Asphlt Binder Specifiction nd Testing, SP-1, The Asphlt Institute, Lexington, KY. 10. Airey, G., Singleton, T.M nd Collop, A. (2002), Properties of Polymer Modified Bitumen fter Ruer-Bitumen Interction, Journl of Mteril in Civil Engineering, ASCE, 14(4), pp McGennis, R.B. (1995), Evlution of Physicl Properties of Fine Crum Ruer Modified Asphlt Binders, Trnsporttion Reserch Record: Journl of the Trnsporttion Reserch Bord, No. 1488, pp Shen, J., Amirkhnin, S., nd Lee, S.-J. (2005), Effects of Rejuventing Agents on Recycled Aged Ruer Modified Binders, The Interntionl Journl of Pvement Engineering, Vol. 6, No. 4, pp Stndrd Specifictions for Trnsporttion Mterils nd Methods of Smpling nd Testing, 22nd Edition, (2002), Americn Assocition of Stte Highwy nd Trnsporttion Officils, Wshington D.C. 14. Shen, J. nd Amirkhnin, S. (2005), The Influence of Crum Ruer Modifier (CRM) Microstructures on The High Temperture Properties of CRM Binders, The Interntionl Journl of Pvement Engineering, Vol. 6, No. 4, pp

13 List of Tles TABLE 1 Properties of three se inders (PG 64-22) TABLE 2 Results of ANOVA y Duncn s multiple rnge test to determine differences etween viscosity results of CRM inders within ech inder source ( =0.05). TABLE 3 Results of ANOVA y Duncn s multiple rnge test to determine differences etween G*/sin results of CRM inders within ech inder source ( =0.05). TABLE 4 Results of ANOVA y Duncn s multiple rnge test to determine differences etween G*sin results of ged CRM inders within ech inder source ( =0.05). TABLE 5 Results of ANOVA y Duncn s multiple rnge test to determine differences etween stiffness results of ged CRM inders within ech inder source ( =0.05). TABLE 6 Results of ANOVA y Duncn s multiple rnge test to determine differences etween m-vlue results of ged CRM inders within ech inder source ( =0.05)

14 List of Figures FIGURE 1 Flow chrt of experimentl design procedures FIGURE 2 Grdtions of two CRMs FIGURE 3 SEM microgrphs t 120x mgnifiction of () mient CRM (-40 mesh) nd () cryogenic CRM (-40 mesh) FIGURE 4 Viscosity test results of unged CRM inders (t 135 C) FIGURE 5 DSR test results of unged CRM inders (t 76 C) FIGURE 6 DSR test results of ged CRM inders (t 25 C) FIGURE 7 BBR test results of ged CRM inders: () stiffness; () m-vlue

15 TABLE 1 Properties of three se inders (PG 64-22) Aging sttes Unged inder Test properties Binder sources A B C Rottionl 135 o C (P-s) o C (kp) RTFO ged residue 64 o C (kp) RTFO + PAV ged residue 25 o C (kp) o C (MP) o C

16 TABLE 2 Results of ANOVA y Duncn s multiple rnge test to determine differences etween viscosity results of CRM inders within ech inder source ( =0.05). Binder source CRM content Duncn grouping CRM grind Duncn grouping A 1 c d e Amient B 1 c d e Amient C 1 c d e Amient * Viscosity results of CRM inders with the sme letter, within ech inder source, re not significntly different

17 TABLE 3 Results of ANOVA y Duncn s multiple rnge test to determine differences etween G*/sin results of CRM inders within ech inder source ( =0.05). Binder source CRM content Duncn grouping CRM grind Duncn grouping A 1 c d e Amient B 1 c d e Amient C 1 c d e Amient G*/sin results of CRM inders with the sme letter, within ech inder source, re not significntly different

18 TABLE 4 Results of ANOVA y Duncn s multiple rnge test to determine differences etween G*sin results of ged CRM inders within ech inder source ( =0.05). Binder source CRM content Duncn grouping CRM grind Duncn grouping A 1 B c A c A c Amient B 1 B c c A c Amient C 1 c d Amient G* sin results of CRM inders with the sme letter, within ech inder source, re not significntly different

19 TABLE 5 Results of ANOVA y Duncn s multiple rnge test to determine differences etween stiffness results of ged CRM inders within ech inder source ( =0.05). Binder source CRM content Duncn grouping CRM grind Duncn grouping A 1 c d d Amient B 1 c d e Amient C 1 c d e Amient Stiffness results of CRM inders with the sme letter, within ech inder source, re not significntly different

20 TABLE 6 Results of ANOVA y Duncn s multiple rnge test to determine differences etween m-vlue results of ged CRM inders within ech inder source ( =0.05). Binder source CRM content Duncn grouping CRM grind Duncn grouping A 1 c Amient B 1 Amient C 1 Amient M-vlue results of CRM inders with the sme letter, within ech inder source, re not significntly different

21 PG Asphlt Binder Binder Source A (A) Binder Source B (B) Binder Source C (C) Sme testing procedure s (B) Crum Ruer Modifier (CRM) Sme testing procedure s (B) Amient Ground () Ground () Sme s testing procedure () CRM Binder (y wt. of inder) (1) CRM Binder (y wt. of inder) (2) CRM Binder (y wt. of inder) (3) 1 CRM Binder (y wt. of inder) (4) CRM Binder (y wt. of inder) (5) Sme testing procedure s (3) Sme testing procedure s (3) Sme testing procedure s (3) Sme testing procedure s (3) Rottionl Viscometer (n = 3) DSR (n = 4) Artificil Long-term Aging (PAV ging) DSR (n = 4) BBR (n = 3) FIGURE 1 Flow chrt of experimentl design procedures

22 Amient CRM CRM Percent Pssing (%) Sieve Sizes (mm) FIGURE 2 Grdtions of two CRMs

23 () FIGURE 3 SEM microgrphs t 120x mgnifiction of () mient CRM (-40 mesh) nd () cryogenic CRM (-40 mesh) ()

24 10 A Am. A Cry. 8 B Am. B Cry. Viscosity (P- s) 6 4 C Am. C Cry Percentge of CRM (%) FIGURE 4 Viscosity test results of unged CRM inders (t 135 C)

25 7 6 A Am. B Am. A Cry. B Cry. G*/sin (kp) C Am. C Cry Percentge of CRM (%) FIGURE 5 DSR test results of unged CRM inders (t 76 C)

26 G* sin (kp) A Am. A Cry. 400 B Am. B Cry. C Am. C Cry Percentge of CRM (%) FIGURE 6 DSR test results of ged CRM inders (t 25 C)

27 250 A Am. A Cry. 200 B Am. C Am. B Cry. C Cry. Stiffness (MP) Percentge of CRM (%) () m-vlue A Am. A Cry. 0.1 B Am. B Cry. C Am. C Cry Percentge of CRM (%) () FIGURE 7 BBR test results of ged CRM inders: () stiffness; () m-vlue