TENNESSEE DEPARTMENT OF TRANSPORTATION

Transcription

1 TENNESSEE DEPARTMENT OF TRANSPORTATION EVALUATION OF RUBBERIZED HOT MIX ASPHALT FOR USE ON TENNESSEE ROADWAYS INTERIM REPORT PREPARED BY: MARCH 2001

2 ACKNOWLEDGEMENTS The preparation of this report would not have been possible without the assistance of numerous individuals both within the paving industry and within the Tennessee Department of Transportation. We specifically wish to thank the following for their assistance: The Arizona Department of Transportation and the Georgia Department of Transportation for their insights and experiences with crumb rubber modified mixes and Open Graded Friction Course designs. Eubank Asphalt Paving and Sealing and Lehman-Roberts Company who constructed the projects in Region 3 and Region 4 and FNF Construction who supplied the crumb rubber for the mixes. Region 3 and Region 4 Materials and Tests Sections who supplied data regarding pavement depths and Mays ride values. The Field Operations Section of the Division of Materials and Tests, specifically Greg Duncan and Mike Doran, who provided background information and assisted in the collection of field data. Steven M. Hall, P.E. Danny L. Lane, A.S. i

3 TABLE OF CONTENTS Page # ACKNOWLEDGEMENTS TABLE OF CONTENTS i ii INTRODUCTION 1 SCOPE AND METHODOLOGY GENERAL 2 STRENGTH / DURABILITY 2 REDUCED VEHICLE SPRAY FROM WET PAVEMENT 3 COSTS 3 TEST RESULTS STRENGTH / DURABILITY 4 VEHICLE SPRAY 15 COST DATA 16 SUMMARY 18 APPENDIX 20 DICKSON COUNTY JOB MIX FORMULAS FOR GAP GRADED BINDER AND OGFC SHELBY COUNTY JOB MIX FORMULAS FOR GAP GRADED BINDER AND OGFC ii

4 INTRODUCTION The use of discarded tire rubber in asphalt pavements has been evaluated by numerous agencies throughout the United States. Specifically, in the last 10 years, this has been a significant issue with both the environmental and highway construction communities. In 1993, The Tennessee Department of Transportation placed three projects utilizing crumb rubber in anticipation of a proposed Federal mandate. Limited data is available on these projects and is therefore not included in this report. In 1998, TDOT placed two more crumb rubber projects which are the subject of this report. The two projects constructed in 1998, were both placed on U.S. 70 (SR 1), one in Shelby County (Contract # 5245) and the other in Dickson County (Contract #5220). Both projects included a gap graded crumb rubber modified binder mix and a crumb rubber modified open graded friction course (OGFC). The design of the gap graded binder mix was based on information received from the Arizona Department of Transportation regarding their experiences with the use of crumb rubber. Likewise, the Georgia Department of Transportation provided information and experience with the OGFC mix design. The Shelby County mixes were constructed with gravel while the Dickson County mixes were constructed with limestone. Approximately 20% by weight of crumb rubber was included in the mixes resulting in approximately 482 tons of crumb rubber being utilized on these two projects. This equates to approximately 80,300 tires. This study was proposed to answer several questions regarding the use of crumb rubber mixes in Tennessee. The strength or durability of asphalt pavements modified with crumb rubber along with it s ability to retard reflective cracking from underlying concrete pavement was of major interest to the Department. In addition, the ability of the open graded friction course to reduce vehicle spray from wet pavements is to be evaluated. Also of concern was the cost of crumb rubber modified mixes as compared to the cost of TDOT standard mixes. Of particular interest to the Department was the evaluation of all of the above concerns under real life traffic conditions instead of basing conclusions on laboratory results or accelerated loading. 1

5 SCOPE AND METHODOLOGY GENERAL The scope of this research effort is to evaluate the two projects placed during the 1998 paving season for a period of five years. In general, strength, durability, the reduction in vehicle spray from wet pavement and bid costs of the mixes are to be evaluated. Both projects were constructed over an existing asphalt pavement underlain by an older concrete pavement. Reflective cracking was present at all concrete joints prior to placing the crumb rubber mixes. Figure 1 shows the typical pavement depths for both the Shelby and Dickson County projects. A ¼ mile test section was randomly established for each project. The Shelby County test section runs from Log Mile to while the Dickson County section is from Log Mile 3.25 to 3.5. C.R. OGFC AVG. DEPTH = 1 C.R. OGFC AVG. DEPTH = 1 CRUMB RUBBER BINDER AVG. DEPTH = 2 CRUMB RUBBER BINDER AVG. DEPTH = 2 EXISTING ASPHALT AVG. DEPTH = 11 1/8 EXISTING CONCRETE EXISTING ASPHALT AVG. DEPTH = 8 ½ EXISTING CONCRETE SHELBY COUNTY DICKSON COUNTY FIGURE 1 STRENGTH / DURABILITY Strength and durability will be evaluated based on the change in pavement smoothness as measured by the Department s Mays Ride Meter, the change in skid number measured with the Department s Wet Skid Trailer and the change in rutting measured by straightedge and caliper. Rut measurements will be taken in the four wheel paths of the 2-lane roadways at distances of 0, 264, 528, 792, 1056 and 1320 feet within the ¼ mile test sections (see photograph on page 3). 2

6 In addition, all cracks, if any, will be mapped as determined from visual inspection. It is generally accepted in Tennessee that reflective cracking propagates through standard TDOT asphalt pavements at a rate of approximately 1 per year. Any other visual pavement defects will also be noted. REDUCED VEHICLE SPRAY FROM WET PAVEMENT Reduced vehicle spray will be evaluated solely by visual inspection during and after rain events. COSTS The actual bid costs of the mixes will be compared to average unit prices paid for TDOT standard mix designs placed during the 1998 paving season. TYPICAL OF RUT MEASUREMENTS 3

7 TEST RESULTS STRENGTH / DURABILITY The following data is from the Shelby County test section located between Log Miles and This 2-lane section has an Daily Traffic of 4230, with 5% trucks. Shelby County Mays Meter Readings (inches per mile) (< 35 inches per mile required at project acceptance) East Bound West Bound Initial Value Value After 29 Months inches per mile East Bound West Bound Initial Value Value After 29 Months 4

8 Shelby County Wet Skid Data East Bound West Bound Initial Value No Data No Data Value After 29 Months East Bound West Bound Initial Value Value After 29 Months 5

9 NOT TO SCALE County _Shelby Location Station 0.00' to 264' State Route_1, US 70 Project or Contract No Eastbound and Westbound Lanes Crumb Rubber Section 264 WESTBOUND 24 EASTBOUND Length: 24' Width: 5-15 mm N O R T H Culvert 198 centerline Length: 18' Width: 5-15 mm 132 Length: 22' Width: 5-15 mm Length: 22' Width: 5-15 mm 66 Length: 11' Width: 5-10 mm 0.0 A B C D Rut Measurements A B C D (inches) Avg:.141 6

10 NOT TO SCALE County _Shelby Location Station 264' to 528' State Route_1, US 70 Project or Contract No Eastbound and Westbound Lanes Crumb Rubber Section N O R T H WESTBOUND EASTBOUND Length: 30' Width: 5-20 mm Length: 8' Width: 5 mm centerline Length: 24' Width: 5-20 mm 330 Length: 24' Width: 5-20 mm 264 A B C D Rut Measurements A B C D (inches) Avg:.154 7

11 NOT TO SCALE County _Shelby Location Station 528' to 792' State Route_1, US 70 Eastbound and Westbound Lanes Project or Contract No Crumb Rubber Section 792 N O R T H WESTBOUND 24 EASTBOUND Length: 30' Width:5-10 mm Length: 6' Width:5 mm 726 centerline Length: 15' Width:5 mm Length: 22' Width:5 mm Pop Out 660 Length: 24' Width:5-10 mm Length: 30' Width: 5 mm 594 Length: 24' Width:5-15 mm Length: 26' Width:5-10 mm 528 A B C D Rut Measurements A B C D (inches) Avg: Length: 6' Width:5-10 mm Length: 3' Width: 5-10 mm

12 NOT TO SCALE County _Shelby Location Station 792' to 1056' State Route_1, US 70 Project or Contract No Eastbound and Westbound Lanes Crumb Rubber Section WESTBOUND EASTBOUND N O R T H Length: 30' Width: mm centerline Longitudinal * Continued into the next section Length: 375' Width: 5-8 mm 858 Length: 16' Width: 5 mm Length: 36' Width: mm 792 A B C D Rut Measurements A B C D (inches) Avg:.183 9

13 NOT TO SCALE County _Shelby Location Station 1056' to 1320' State Route_1, US 70 Project or Contract No Eastbound and Westbound Lanes Crumb Rubber Section WESTBOUND EASTBOUND NO RUT DATA TAKEN DUE TO INTERSECTION N O R T H Length: 24' Width: 3-5 mm 1254 v centerline Length: 24' Width: 15 mm 264' 1188 Length: 18' Width: 5 mm 1122 Length: 30' Width: 5 mm Length: 24' Width: 3-15 mm 1056 A B C D Rut Measurements A B C D (inches) Avg: Longitudinal * Continued from last section Length: 375' Width: 5-8 mm

14 The following data is from the Dickson County test section located between Log Miles 3.25 and 3.5. This 2-lane section has an Daily Traffic of 8000, with 7% trucks. Dickson County Mays Meter Readings (inches per mile) (< 40 inches per mile required at project acceptance) East Bound West Bound Initial Value Value After 29 Months inches per mile Initial Value Value After 29 Months 0 East Bound West Bound 11

15 Dickson County Wet Skid Data East Bound West Bound Initial Value Value After 29 Months Initial Value Value After 29 Months 0 East Bound West Bound 12

16 NOT TO SCALE County _Dickson Location Station 0.00' to 1320' State Route_1, US 70 Project or Contract No Eastbound and Westbound Lanes Crumb Rubber Section EASTBOUND 24 WESTBOUND 1320' Rut Measurements Avg:.093 N O R T H 1056' Length 6' Width 5mm Rut Measurements Avg:.095 centerline 792' Rut Measurements Avg: ' Rut Measurements Avg: ' Rut Measurements Avg: Rut Measurements Avg:.069 Rut Measurements A B C D (inches) 13

17 The cracking and rutting data shown on the previous page indicate only one crack in the Dickson County test site. It should be noted however that evidence of possible future reflective cracking is present and can be seen after rain events. This evidence is in the form of dark spots transverse to the traffic lanes at regular intervals where it appears water is being held in the pavement structure. The following photograph is a typical representation of these areas in the pavement. 14

18 VEHICLE SPRAY The reduction in vehicle spray during rain events was evaluated solely on a visual basis. This was reviewed on several trips to the project sites, and spray during and after rain events appears to be less from the OGFC than from traditional TDOT surface mixes for light to moderate rainfalls. However, during heavy rainfalls no significant reduction in vehicle spray was noticed. The following two photographs shown below illustrate these occurrences. OGFC DICKSON CO. SR 1 (US 70) OGFC OGFC SHELBY CO. SR 1 (US 70) STANDARD MIX 15

19 COST DATA The cost data which follows is obtained from the actual bid prices for the crumb rubber mixes. These values are compared to costs obtained from the Department s Unit Price book for projects let to contract during the 1998 paving season. Please note that the Shelby County project is located in Region 4, and the Dickson County project is located in Region 3. Also, these projects were let to contract as metric jobs, therefore, all costs are in dollars per metric ton. SURFACE MIX 1998 PAVING SEASON AVERAGE UNIT PRICES $/TONNE C.R. OGFC AC SUPERPAVE AC (PG76-22) PG76-22 AC OGFC AGGREGATE SUPERPAVE AGGREGATE GRADING D AGGREGATE NO DATA REG REG 4 $/TONNE REGION 3 REGION 4 C.R. OGFC AC SUPERPAV... PG76-22 AC OGFC AGG... SUPERPAV... GRADING D... 16

20 BINDER MIX 1998 PAVING SEASON AVERAGE UNIT PRICES $/TONNE C.R. GAP GRADED SUPERPAVE BINDER B-M2 (PG76-22) MIX 307-S (PG76-22) NO DATA REGION REGION 4 $/TONNE REGION 3 REGION 4 C.R. GAP G... SUPERPAVE... B-M2 (PG76-22) 17

21 SUMMARY Two projects utilizing crumb rubber were constructed in 1998, on SR 1 (U.S. 70). Contract 5245 was constructed in Shelby County and Contract 5220 was constructed in Dickson County. Both projects included a gap graded crumb rubber modified binder mix and a crumb rubber modified open graded friction course (OGFC). The Shelby County mixes were constructed with gravel while the Dickson County mixes were constructed with limestone. Both the Dickson and Shelby County projects have increased Mays Meter readings (average of 6.5 to 8.5 points increase) indicating a less smooth ride than was present shortly after construction. However, this is to be expected and both projects would still be considered acceptable from a smoothness standpoint. Skid values have dropped an average of 9 points on the Dickson County project but still remain well above what would be considered minimum for this type roadway. No initial skid values were collected for the Shelby County project. Reflective cracking was present throughout the entire test section on the Shelby County project. Transverse reflective cracking is present at approximately 25% of the old concrete joints. Low severity cracks accounted for 47% of the total, moderate severity cracks accounted for 41% and 12% of the cracks were of high severity. Also, there was one longitudinal reflective crack of low severity that was 375 in length. In the Dickson County test section, only one 6 long transverse reflective crack of low severity was present. It should be noted however that evidence of possible future reflective cracking is present and can be seen after rain events. This evidence is in the form of dark spots transverse to the traffic lanes at regular intervals where it appears water is being held in the pavement structure. Vehicle spray during and after rain events appears to be less from the OGFC than from traditional TDOT surface mixes for light to moderate rainfalls. However, during heavy rainfalls no significant reduction in vehicle spray was noticed. Cost data was obtained from the actual bid prices for the crumb rubber mixes. These values were compared to costs obtained from the 18

22 Department s Unit Price book for projects let to contract during the 1998 paving season. Crumb rubber modified asphalt cement averaged 1.5 times the cost of PG76-22 AC used in TDOT Superpave surface mixes and 1.7 times the cost of PG76-22 used in TDOT traditional surface mixes. OGFC aggregate was 1.4 times the cost of both Superpave and Grading D surface aggregate. The cost of the crumb rubber modified Gap Graded mix averaged 1.8 times that of 307S Superpave binder mix modified with PG76-22 AC and 2.1 times the cost of TDOT s traditional B-M2 mix modified with PG76-22 AC. However, it should be noted that data was presented at the 2000 Arkansas Recycler s Coalition meeting showing that with increased use, the price of asphalt rubber material begins to compare to conventional high performance liquid asphalt materials. 19

23 APPENDIX 20

24 STATE OF TENNESSEE ASPHALT JOB MIX FORMULA Date: 8/11/98 Project Ref. No. STP-EN-1(84) County Dickson Region 3 Proj. No Layer Binder Contract No Type Gap Graded - Fine Sec. No. SP 904CR Article Contractor Eubank Paving Subcontrac tor St. Route 1 Total Mix including Bitumen Date of Letting 5/1/98 Material Size Range or Type Producer and Address % Used Soft 5/8" 5/8"- Pan Burns Stone, Dickson, TN Hard #10's 3/8"-Pan Burns Stone, Dickson, 9.20 TN Hard Block 3/8"-Pan Burns Stone, Dickson, 's TN Soft #10's 3/8"-Pan Burns Stone, Dickson, TN Crumb 14 Mesh Polytek, Pheonix, AZ (17.5% by total 0.00 Rubber wt) Asphalt PG Marathon Petroleum, Nashville, TN 8.00 Cement Anti-Strip Dosage Rate: % Fractured Faces on +4 Material: % Glassy Particles on +4 Material PERCENT MINERAL AGGREGATE AGGREGATE ANALYSIS TOTAL PERCENT PASSING Screen Ttl. Passing Requested Soft 5/8" Hard #10's Hard Block 10's Soft #10's Calculated Design Range Percent Percent Percent Percent Percent Percent Mix Temp % AC 8.0 NCAT Furnace Corr. Factor: Compaction Temp: Loss On Ignition: Mixing Temp: Theoretical Maximum Density: (Washed Gradations) AC in RAP: " /2" " /4" /2" /8" # # # # # # #

25 STATE OF TENNESSEE ASPHALT JOB MIX FORMULA Date: 8/11/98 Project Ref. No. STP-EN-1(84) County Dickson Region 3 Proj. No Layer Surface Contract No Type Open Graded Sec. No. SP 904CR Article Contractor Eubank Paving Subcontrac tor St. Route 1 Total Mix including Bitumen Date of Letting 5/1/98 Material Size Range or Type Producer and Address % Used OGFC Rock 1/2"- Pan Burns Stone, Dickson, TN Hard Block 3/8"-Pan Burns Stone, Dickson, TN Soft Block 3/8"-Pan Burns Stone, Dickson, TN Crumb Rubber (17.5%) 14 Mesh Polytek, Pheonix, AZ (by total wt of 0.00 binder) Asphalt PG Marathon Petroleum, Memphis, TN 8.50 Cement Anti-Strip Dosage Rate: % Fractured Faces on +4 % Glassy Particles on +4 Material: Material PERCENT MINERAL AGGREGATE AGGREGATE ANALYSIS TOTAL PERCENT PA SSING Screen Ttl. Passing Requested OGFC Rock Hard Block Soft Block Calculated Design Range Percent Percent Percent Percent Percent Percent Mix Temp % AC 8.5 NCAT Furnace Corr. Factor: Compaction Temp: Loss On Ignition: Mixing Temp: Theoretical Maximum Density: (Washed Gradations) AC in RAP: " /2" " /4" /2" /8" # # # # # # #

26 STATE OF TENNESSEE ASPHALT JOB MIX FORMULA Date: 8/1/98 Project Ref. No. SP County Shelby Region 4 Proj. No Layer Binder Contract No Type Gap Graded Sec. No. SP 904CR Article Contractor Lehman-Roberts Co. Subcontrac tor St. Route 1 Total Mix including Bitumen Date of Letting 5/1/98 Material Size Range or Type Producer and Address % Used D Rock 5/8"- Pan Memphis Stone & Gravel pit#558 LS #8's 1/2"-Pan Vulcan Materials pit#457 Coarse 3/8"-Pan Memphis Stone & Sand Gravel pit#409 Crumb Rubber Asphalt Cement Anti-Strip Mesh Polytek, Pheonix, AZ (17.5% by total 0.00 wt) PG Marathon Petroleum, Memphis, TN 8.00 Dosage Rate: % Fractured Faces on +4 % Glassy Particles on +4 Material: Material 100 PERCENT MINERAL AGGREGATE AGGREGATE ANALYSIS TOTAL PERCENT PASSING Screen Ttl. Passing Requested D Rock LS #8's Calculated Design Range Percent Percent Percent Percent Percent Percent Mix Temp % AC 8.0 NCAT Furnace Corr. Factor: Compaction Temp: Loss On Ignition: Mixing Temp: Theoretical Maximum Density: (Washed Gradations) AC in RAP: " /2" " /4" /2" /8" # # # # # # #

27 STATE OF TENNESSEE ASPHALT JOB MIX FORMULA Date: 8/1/98 Project Ref. No. SP County Shelby Region 4 Proj. No Layer Surface Contract No Type Open Graded Sec. No. SP 904CR Article Contractor Lehman-Roberts Co. Subcontrac tor St. Route 1 Total Mix including Bitumen Date of Letting 5/1/98 Material Size Range or Type Producer and Address % Used 1/2" Crushed 1/2"- Pan Memphis Stone & Gravel pit#409 Grit Sand 1/2"-Pan Memphis Stone & Gravel pit#558 Crumb Rubber (17.5%) 14 Mesh Polytek, Pheonix, AZ (by total wt of 0.00 binder) Asphalt PG Marathon Petroleum, Memphis, TN 9.00 Cement Anti-Strip Dosage Rate: % Fractured Faces on +4 Material: % Glassy Particles on +4 Material PERCENT MINERAL AGGREGATE AGGREGATE ANALYSIS TOTAL PERCENT PASSING Screen Ttl. Passing Requested 1/2" Crushed Grit Sand Calculated Design Range Percent Percent Percent Percent Percent Percent Mix Temp % AC 9.0 NCAT Furnace Corr. Factor: Compaction Temp: Loss On Ignition: Mixing Temp: Theoretical Maximum Density: (Washed Gradations) AC in RAP: " /2" " /4" /2" /8" # # # # # # #