ASSESSMENT OF WATER AND TEMPERATURE SUSCEPTIBILITIES OF COLD RECYCLED BITUMINOUS EMULSION MIXTURES USING THE NAT IN THE ITSM MODE OF TESTING

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1 ASSESSMENT OF WATER AND TEMPERATURE SUSCEPTIBILITIES OF COLD RECYCLED BITUMINOUS EMULSION MIXTURES USING THE NAT IN THE ITSM MODE OF TESTING Authrs: O. L. Oke Lecturer - Ekiti State University - Civil Engineering Department, Faculty f Engineering, Ekiti State University, P.M.B. 5363, Ad Ekiti, Ekiti State, Nigeria seyike@htmail.cm T. Parry Assciate Prfessr University f Nttingham - Nttingham Transprtatin Engineering Centre, University f Nttingham, Nttingham, UK, NG7 2RD tny.parry@nttingham.ac.uk N. H. Thm Lecturer University f Nttingham - Nttingham Transprtatin Engineering Centre, University f Nttingham, Nttingham, UK, NG7 2RD nichlas.thm@nttingham.ac.uk

2 Oke, Parry and Thm ABSTRACT Energy efficiency, cst effectiveness and the need t minimise the impact f cnstructin activities n the envirnment are majr drivers respnsible fr cld recycled asphalt mixtures being cnsidered as alternatives t ht mixtures in rad wrks. Hwever such mixtures are still regarded in sme quarters as secnd class asphalt mainly because f durability prblems. The indirect tensile stiffness mdulus (ITSM) f such materials under the individual r cmbined effects f water and temperature is cnsidered a gd indicative prperty fr assessing durability. The wrk reprted herein invlved the assessment f five cld bituminus emulsin mixtures (s) fr ITSM under the effects f water and temperature. The five s were cnstituted such that the cntrl specimens cntained 100% virgin aggregate (VA), while the remaining fur cntained reclaimed asphalt pavements (RAP) with residual bitumen f varying penetratins f 5, 10, 15 and 20dmm. An aggregate gradatin cntaining RAP, 5mm granite dust and granite mineral filler in the prprtin 65:30:5 respectively was used fr the RAP s. Bitumen emulsin cntent f 6.5% and pre-wetting water cntent f 1.5% were applied while the s were manufactured in the gyratry cmpactr at temperatures f 20 Cand32C. The results f the water and temperature susceptibility tests indicated that irrespective f the type and the cnditin f curing and testing temperature fr ITSM, s prepared at 32 C cnsistently perfrmed better than thse prepared at 20 C even at an ITSM test temperature f 40 C, and verall, the RAP s perfrmed better than the VA. A trend which indicates that as the penetratin f residual bitumen in RAP s increases, perfrmance similarly increases was bserved. These results suggest that prblems assciated with durability culd be minimised when adequate quality cntrl measures based n labratry results are put in place and fllwed n site during prductin and the laying f such materials as rad pavement layer. Keywrds: RAPs, Cld Asphalt, Durability, ITSM INTRODUCTION It is nw a cmmn knwledge that cld recycled asphalts are sustainable materials fr rad wrks. It has been reprted that they are better ff than ht asphalts in terms f energy efficiency, cst effectiveness and in the degree f impact n the envirnment when used fr rad rehabilitatin wrks (Hakim and Fergussn, 2010; Thanaya, 2003; FHWA, 1997). Hwever such mixtures are still regarded in sme quarters as secnd class asphalt mainly because f durability prblems. Senen et al (2000) describe durability as the resistance f a material t changes caused by envirnmental expsure r the capacity f a material t keep its (riginal) prperties ver time. Durability f bituminus pavements is ften affected by envirnmental factrs (Needham, 1996). Carswell et al (2008) and Airey (2003) cmmented that durability f asphalt pavements is a majr issue and that it is a fairly cmplex prblem because it invlves a number f parameters, with binder ageing and misture damage cnsidered as prminent. Thugh presently, there is n universally accepted test fr assessing the durability f cld recycled asphalts, the stiffness respnses f such materials under the individual r cmbined effects f water and temperature culd serve as gd indicative tests fr assessing their durability. The Indirect Tensile Stiffness Mdulus (ITSM) test is the cmmn means f measuring this prperty f bituminus mixtures in the UK. In fact the ITSM test has been reprted as the mst frequently cnducted test in the Nttingham Asphalt Tester (Wu, 2009). Apart frm being inexpensive, the test is simple and can be quickly cnducted cmpared t ther traditinal means f testing the stiffness mdulus f bituminus mixtures. Brwn (1995) reprted that up t 100 specimens can be tested fr ITSM in a wrking day. Meanwhile, ascertaining temperature susceptibility f bituminus materials als gives a gd knwledge f such materials in service under extreme cnditins. Naturally bitumen is temperature susceptible i.e. becmes brittle at lw temperatures and gets increasingly less viscus and ready t flw at high temperatures. While lw temperatures make such materials susceptible t cracking they are prne t rutting at high temperatures. Under such ht cnditins t, xidative ageing is enhanced especially when the mixture is highly prus. This wrk examines the durability f the cld recycled asphalt mixtures in respect f water susceptibility, and their temperature susceptibility. SIIV Rma MMXII- 5 th Internatinal Cngress 2

3 Oke, Parry and Thm EXPERIMENTAL PROGRAMME This study required ascertaining the temperature and water susceptibilities f cld recycled asphalt mixtures by the stiffness test as indicative f the durability f the materials. Fr stiffness, the Indirect Tensile Stiffness Mdulus (ITSM) Test in line with BS DD 213: 1993 ITSM (Jacbsn, 2002) was fllwed using the Nttingham Asphalt Tester (NAT). The Cper Research Technlgy Gyratry Cmpactr was used fr the cmpactin f the materials. A detailed accunt f the prcedure fllwed fr the manufacturing f the specimens is reprted by Oke (2011). Fr the temperature susceptibility, the study examined the effects f material type, mixing and cmpactin temperature and cmpactive effrt n the stiffness prperties f the materials. Fur specimens were studied at each bservatin level. In rder t reduce variatins, the same sets f specimens were tested fr ITSM at each f the chsen testing temperatures f 20 C, 30 Cand40C. Fr the water susceptibility test, tw prtcls were used fr the test. The first invlved saking specimens in water at 20 C fr 24hrs fllwed by testing fr ITSM. The ITSM tests were cnducted at 20 C (mild cnditin) first and then at 30 C (severe cnditin) after specimens had been cnditined fr 2hrs at that temperature. Prir t saking, the specimens were tested dry at 20 C fr ITSM. The secnd prtcl similarly invlved saking specimens at 30 C fr 24hrs. These were fllwed by ITSM testing at 30 C (severe cnditin) first and then at 20 C (mild cnditin) after the specimens have been cnditined at that temperature fr 2hrs. Similarly, fur specimens were studied at each level f bservatin. It is wrth mentining that prir t saking, vacuum saturatin f all the specimens was carried ut at a pressure f 140mbar fr 10 minutes. Meanwhile, frm physical bservatin, the vacuum saturatin seemed nt t have affected the specimens since nne f the specimens bulged r cllapsed/disintegrated in the prcess. MATERIALS TESTED Five cld bituminus emulsin mixtures (s) were tested during this exercise as fllws: 1. VA - 100% virgin binder and aggregates 2. 5dmm - 65% RAP (recvered pen = 5dmm) 3. 10dmm - 65% RAP (recvered pen = 10dmm) 4. 15dmm - 65% RAP (recvered pen = 15dmm) 5. 20dmm - 65% RAP (recvered pen = 20dmm) The s listed in 2 t 5 were cnstituted in the rati 65:30:5 fr RAP, fine aggregate (5mm) and filler respectively and the RAP was made in the labratry (Oke et al, 2010) frm aged 20mm Dense Bitumen Macadam (DBM) with 4.25% binder cntent. The VA was similarly cnstituted except that the RAP was replaced with virgin aggregate and the gradatin used was 20mmDBM (TRRL and DFID, 2002). Granite aggregates were used thrughut. The chice f aggregate and RAP ageing was made t reflect cnditins in Nigeria which was the subject f a wider study f which this wrk frmed part. Tests were cnducted at 20, 30 and 40 C. The pre-wetting water cntent was 1.5% by aggregate mass and 6.5% f catinic bitumen emulsin (with water/bitumen rati f 2:3) was used in all the mixtures. The penetratin and sftening pint f the residual bitumen in the emulsin were determined as 48dmm and 51.4 C respectively. Mixing and cmpactin temperatures f 20 Cand32C were maintained thrughut t simulate typical lw and high ambient temperatures in the trpics. All the specimens were cmpacted in the gyratry cmpactr using 100 and 200 gyratins, 600kPa pressure and a 1.25 angle f gyratin. The materials were either cnditined t intermediate life (40 C ver 72hrs) r fully cured (60 C ver 96hrs) cnditins fllwing extrusin after 24hrs in the muld. Fr each cnditin, fur specimens were tested and the quted values are averages f the fur. TEST RESULTS Table 1 details a summary f the ITSM results alng with the respective average air vid cntents f the specimens fr the temperature susceptibility f the cld recycled asphalts. Tables 2 and 3 detail the summary f ITSM results alng with the respective average air vid cntents f the specimens fr Prtcls 1 and 2 fr the water susceptibility test. SIIV Rma MMXII- 5 th Internatinal Cngress 3

4 Oke, Parry and Thm Cnditin I.L. (32,100) I.L. (20,100) I.L. (32, 200) I.L. (20,200) F.C. (32,100) F.C. (20,100) F.C. (32, 200) F.C. (20,200) Table 1 Summary f ITSM Results fr Temperature Susceptibility f s 5dmm 15dmm 20dmm Testing Cnditin VA 10dmm C (MPa) C (MPa) C (MPa) Ave. Air vids (%) C (MPa) C (MPa) C (MPa) Ave. Air vids (%) C (MPa) C (MPa) C (MPa) Ave. Air vids (%) C (MPa) C (MPa) C (MPa) Ave. Air vids (%) C (MPa) C (MPa) C (MPa) Ave. Air vids (%) C (MPa) C (MPa) C (MPa) Ave. Air vids (%) C (MPa) C (MPa) C (MPa) Ave. Air vids (%) C (MPa) C (MPa) C (MPa) Ave. Air vids (%) Nte: F.C. = Fully Cured; I.L. = Intermediate Life Numbers in parenthesis = mixing and cmpactin temperature in C, number f gyratins. DISCUSSION ON TEMPERATURE SUSCEPTIBILITY OF s Frm Table 1, the relevant results fr intermediate life f curing shw that the ITSM respnses fr the s were generally belw 2500MPa irrespective f testing temperature. This bservatin is nt unexpected as the s are still evlving at this pint. The s did nt fllw a distinct trend at intermediate life when cmpared t thse that had SIIV Rma MMXII- 5 th Internatinal Cngress 4

5 Oke, Parry and Thm Table 2 ITSM Results f Water Susceptibility f s fr Prtcl 1 VA 5dmm 10dmm 15dmm 20dmm Cnditin Testing Cnditin At 20 CDry I.L. (32,100) I.L. (32,200) F.C. (32,100) F.C.(32,200) At 20 Ct20 C Wet At 20 Ct30 C Wet Air vids (%) At 20 CDry At 20 Ct20 C Wet At 20 Ct30 C Wet Air vids (%) At 20 CDry At 20 Ct20 C Wet At 20 Ct30 C Wet Air vids (%) At 20 CDry At 20 Ct20 C Wet At 20 Ct30 C Wet Air vids (%) Table 3 ITSM Results f Water Susceptibility f s fr Prtcl 2 VA 5dmm 10dmm 15dmm Cnditin Testing Cnditin I.L. (32,100) I.L. (32,200) F.C. (32,100) F.C.(32,200) 20dmm At 20 CDry At 30 CDry Ct30 C Wet Ct20 C Wet Air vids (%) At 20 CDry At 30 CDry Ct30 C Wet Ct20 C Wet Air vids (%) At 20 CDry At 30 CDry Ct30 C Wet Ct20 C Wet Air vids (%) At 20 CDry At 30 CDry Ct30 C Wet Ct20 C Wet Air vids (%) Nte: F.C. = Fully Cured; I.L. = Intermediate Life Numbers in parenthesis = mixing and cmpactin temperature, number f gyratins SIIV Rma MMXII- 5 th Internatinal Cngress 5

6 Oke, Parry and Thm been fully cured. Als the effect f mixing and cmpactin temperature is nt as clear as bserved fr the fully cured cnditin. ITSM respnses tested at 20 C fr fully cured s mixed and cmpacted at 32 C were generally abve 2500MPa (with the exceptin f the 5dmm) irrespective f the cmpactive effrt applied. Hwever, the respnses drpped t arund 1500MPa fr ITSM tests cnducted at 30 C and further dwn t arund 650MPa fr tests cnducted at 40 C n the same specimens. The 5dmm shwed the least gd perfrmance fr the three test temperatures. The results cnfirm the superirity f s prepared at 32 Ccmparedtthsef20C. Irrespective f the type, the cnditin f curing and testing temperature fr ITSM, s prepared at 32 C cnsistently perfrmed better than thse prepared at 20 C even at ITSM test temperature f 40 C. Overall, the results indicate that all the materials prepared at 32 C, 100 gyratins have least lss in ITSM which suggests just enugh cmpactive effrt alng with apprpriate temperature fr preparatin f s. Mre imprtantly, the VA as bserved here indicates that it has the highest temperature susceptibility. DISCUSSION ON WATER SUSCEPTIBILITY OF s A clse inspectin f the Tables 2 and 3 indicate that the VA has the prest perfrmance fr the severe cnditins irrespective f the preparatin methd thugh with an exceptin t materials prepared at 32 C, 200 gyratins in Prtcl 1, where it indicates a slightly better ITSM respnse than the 5dmm. Fr Prtcl 2 which simulated the recvery f the s after experiencing a severe cnditin, the ITSM respnses indicated a pr recvery in stiffness fr the VA cmpared t the thers except fr materials prepared at 32 C, 100 gyratins where it perfrmed reasnably well thugh nly a little better than the 5dmm. Fr the tw prtcls, materials prepared using the higher cmpactive effrt clearly perfrmed better than thse with less cmpactive effrt except fr the intermediate life in Prtcl. Althugh the tw prtcls have prved useful by clearly ranking the s, Prtcl 2 appeals mre as it als simulates and assesses perfrmance after the recvery prcess f the s which is very imprtant fr perfrmance in service. Hwever in rder t ascertain this, percentage in lss fr each individual was further investigated. The percentage lss was relative t the ITSM respnse at 20 C (dry). Tables 4 and 5 detail the percentage lsses in ITSM f the s as a result f the cmbined damaging effects f water and temperature. The table fr Prtcl 1 indicates a clear and lgical trend fr all the s. Fr all the cnditins investigated here, the VA clearly indicate the wrst perfrmance recrding the highest lsses bth fr the severe and mild cnditins. In fact fr the mild cnditins, values as high as 52% lss were bserved fr VA, while the 5dmm which is next in rank recrded a little abve 30% lss fr the same cnditins. Fr the higher cmpactive effrt, the 20mm cnsistently recrded the least lss i.e. the best perfrmance fr the severe cnditin f testing irrespective f the curing cnditin applied n the s. Materials prepared at 32 C and 200 gyratins (fully cured) were clearly ranked fr bth the mild and severe cnditins f testing in a lgical rder starting with VA up the range t the 20dmm, the 15dmm cntrary t lgic recrded the verall best perfrmance. The results indicated that s prepared at this level have the best resistance under severe cnditins. The Figures 1 t 4 fr Prtcl 2 detail respnses fr bth temperature susceptibility and water damaging effects n the s. This has been purpsely dne in rder t ascertain the effectiveness f the temperature susceptibility test at being able t rank the materials. It is bvius frm the figures that measurements fr the temperature susceptibility did nt fllw a clear rder cmpared t the water damaging test. Althugh the trend fr the severe cnditin here were nt cmpletely cnsistent with the bservatins made fr s prepared at 32 C, 200 gyratins, verall again, the VA indicated the wrst perfrmance fr bth the severe and mild cnditins (recvery path) with the 15dmm still having the best perfrmance. Fr the recvery prcess in Prtcl 2, the VA achieved a significant imprvement fr materials prepared at 32 C, 100 gyratins just as the RAP s. The recvery path fr ther cnditins was generally pr fr the VA while it was rather impressive fr the RAP s. The pr perfrmance f the VA culd have SIIV Rma MMXII- 5 th Internatinal Cngress 6

7 Oke, Parry and Thm been partly as a result f its high air vid cntent, while the lwer air vids f the RAP s culd have been partly respnsible fr their better perfrmance. Mre imprtantly, it is believed that the residual bitumen in the severely aged Table 4 Results f Percentage Lss in ITSM due t Water Susceptibility fr Prtcl 1 Cnditin I.L. (32 C, 100) I.L. (32 C,200) F.C. (32 C,100) F.C. (32 C,200) Percentage Lss Descriptin t 20 C Wet t 30 C Wet t 20 C Wet t 30 C Wet t 20 C Wet t 30 C Wet t 20 C Wet t 30 C Wet VA 5dmm 10dmm 15dmm 20dmm Cnditin I.L. (32 C, 100) I.L. (32 C,200) F.C. (32 C,100) F.C. (32 C,200) Table 5 Results f Percentage Lss in ITSM due t Water Susceptibility fr Prtcl 2 Percentage Lss VA 5dmm 10dmm 15dmm 20dmm Descriptin (%) t 30 CDry t 30 C Wet t 30 C-20 CWet t 30 CDry t 30 C Wet t 30 C-20 CWet t 30 CDry t 30 C Wet t 30 C-20 CWet t 30 CDry t 30 C Wet t 30 C-20 CWet Nte: F.C. = Fully Cured; I.L. = Intermediate Life Numbers in parenthesis = mixing and cmpactin temperature, number f gyratins SIIV Rma MMXII- 5 th Internatinal Cngress 7

8 Oke, Parry and Thm (%) VA 5dmm 10dmm 15dmm 20dmm Percentage Lss in ITSM frm 20 C Dry t 30 C Dry Percentage Lss in ITSM frm 20 C Dry t 30 CWet Stiffness (32 C, 100,40 C,72hrs) Percentage Lss in ITSM frm 20 C Dry t 30 C -20 CWet Figure 1 Water Susceptibility f s at Intermediate Life Cnditin Mixed and Cmpacted at 32 C, 100 gyratins (Prtcl 2) (%) VA 5dmm 10dmm 15dmm 20dmm Percentage Lss in ITSM frm 20 C Dry t 30 C Dry Percentage Lss in ITSM frm 20 C Dry t 30 CWet Stiffness (32 C,200,40 C,72hrs) Percentage Lss in ITSM frm 20 C Dry t 30 C -20 CWet Figure 2 Water Susceptibility f s at Intermediate Life Cnditin Mixed and Cmpacted at 32 C, 200 gyratins (Prtcl 2) (%) VA 90 5dmm 10dmm 15dmm 20dmm Percentage Lss in ITSM frm 20 C Dry t 30 C Dry Percentage Lss in ITSM frm 20 C Dry t 30 CWet Stiffness (32 C,100,60 C,96hrs) Percentage Lss in ITSM frm 20 C Dry t 30 C -20 CWet SIIV Rma MMXII- 5 th Internatinal Cngress 8

9 Oke, Parry and Thm Figure 3 Water Susceptibility f s at Fully Cured Cnditin Mixed and Cmpacted at 32 C, 100 gyratins (Prtcl 2) VA 5dmm 10dmm 15dmm 20dmm Percentage Lss in Percentage Lss in Percentage Lss in ITSM frm 20 C Dry t ITSM frm 20 C Dry t ITSM frm 20 C Dry t 30 C Dry 30 CWet 30 C -20 CWet (%) Stiffness (32 C,200,60 C,96hrs) Figure 4 Water Susceptibility f s at Fully Cured Cnditin Mixed and Cmpacted at 32 C, 200 gyratins (Prtcl 2) RAPs that cnstitute the RAP s culd pssibly have been rejuvenated thus prviding a larger vlume f active binder. This must have been respnsible fr the impressive perfrmance bserved fr these RAP s in the recvery prcess and generally in being able t reasnably cntain the water damaging effects when cmpared t the VA. Cmparing the results btained here with the results f the temperature susceptibility tests, it is hwever likely that thse materials prepared at 20 C might nt have been able t cntain the water damaging effects as thse prepared at 32 C did. While this is an interesting area fr future investigatins, the tw water susceptibility prtcls as cnducted here have been able t rank the s cmpared t the temperature susceptibility tests. CONCLUSION ITSM respnses tested at 20 C fr fully cured s mixed and cmpacted at 32 C were generally abve 2500MPa (with the exceptin f the 5dmm) irrespective f the cmpactive effrt applied. The respnses drpped t arund 1500MPa fr ITSM tests cnducted at 30 C and further dwn t arund 650MPa fr test cnducted at 40 C n the same specimens. Irrespective f the type, the cnditin f curing and testing temperature fr ITSM, s prepared at 32 C cnsistently perfrmed better than thse prepared at 20 C even at an ITSM test temperature f 40 C. The materials prepared at 32 C, 100 gyratins have least lss in ITSM due t high temperature which implies just enugh cmpactive effrt alng with apprpriate temperature fr preparatin f s. VA as bserved here shws the highest temperature susceptibility. The RAP s perfrmed better than the VA in water susceptibility. In Prtcl 2 where recvery was mnitred after the s were subjected t severe cnditins, the VA perfrmed prly cmpared t the ther s. The pr perfrmance f the VA culd have been partly caused by its high air vid cntent, while the lwer air vids f the ther s culd have been partly respnsible fr their better perfrmance. Mre imprtantly, it is believed that the residual bitumen in the severely aged RAPs that cnstitute the RAP s is pssibly being rejuvenated thus causing the RAP s t have larger vlume f active binder. Furthermre, the perfrmance culd similarly be linked t the pssible changes in the vlumetrics f the RAP s as a result f the sftening f the residual bitumen in the RAP and nt necessarily rejuvenatin. SIIV Rma MMXII- 5 th Internatinal Cngress 9

10 Oke, Parry and Thm A trend which indicates that as the penetratin f residual bitumen in RAP s increases, perfrmance similarly increases was bserved. ACKNOWLEDGEMENT: Dr. Oke is grateful t the Ekiti State University, Ad-Ekiti, Nigeria and the University f Nttingham, Nttingham, UK fr a PhD schlarship. This wrk received supprt frm Nynas Bitumen, UK, Cliffe Hill Quarry, UK, Lngcliffe Quarries UK and Cper Research Technlgy, UK. REFERENCES Airey, G.D. (2003). State f the Art Reprt n Ageing Test Methds fr Bituminus Pavement Materials. The Internatinal Jurnal f Pavement Engineering, Vl. 4 (3) September, pp Brwn, S.F. (1995). Practical test Prcedures fr Mechanical prperties f Bituminus Materials. Prc. Instn. Civ. Engrs Transp., 1998, 111, Nv, ICE, Carswell, J., Ellis, S. J. and Hewitt, A. (2008). Design and Specificatin fr Sustainable Maintenance f Rads using Cld Recycling Techniques. Review f the Grwth and Develpment f Recycling in Pavement Cnstructin, Wrld Rad Assciatin (PIARC), Cedex, pp FHWA (1997). Pavement Recycling Guidelines fr State and Lcal Gvernments. Participant s Reference Bk, Federal Highway Administratin, USA, (Accessed: 20/11/2007). Hakim, B. and Fergussn, C., (2010). Sustainable Pavement Cnstructin at the Isle f Man Airprt, Asphalt Prfessinal, The Jurnal f the Institute f Asphalt Technlgy, N. 46, Nvember 2010, The Institute f Asphalt Technlgy, Surrey.. Jacbsn, T., (2002). Cld Recycling f Asphalt Pavement Mix In Plant, Swedish Natinal Rad and Transprt Research Institute, Linkping. Needham, D. (1996). Develpments in bitumen emulsin mixtures fr rads. PhD Thesis, University f Nttingham Oke, O.L., Parry, T., Thm, N. H. and Airey, G. D., (2010)., Labratry Ageing Prtcls fr Asphalt Recycling in Ht Climates, Prceedings f Special Technical Sessins, Secnd Internatinal Cnference n Sustainable Materials and Technlgies,Ancna. Oke, O. L., (2010). A Study n the Develpment f Guidelines fr the Prductin f Bitumen Emulsin Stabilised Raps fr Rads in the Trpics, PhD Thesis, University f Nttingham, UK. Senen, H., Sandman, B. and Nilssn, A. (2000). Rhelgical and Chemical Evaluatin f the Ageing f SBS Mdified Bitumen as Used in Rfing, 11th Internatinal Cngress Prceedings, Internatinal Waterprfing Assciatin, Nttingham. Thanaya, I. N. A. (2003). Imprving The Perfrmance f Cld Bituminus Emulsin Mixtures (s) Incrprating Waste Materials. PhD Thesis, Schl f Civil Engineering, the University f Leeds, Leeds. TRRL and DFID (2002). Overseas Rad Nte 19: A guide t the design f ht mix asphalt in trpical and subtrpical cuntries, TRL, Crwthrne,. Wu, J. (2009) The Influence f Mineral Aggregates and Binder Vlumetrics n Bitumen Ageing. PhD Thesis, University f Nttingham. SIIV Rma MMXII- 5 th Internatinal Cngress 10