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Warm Mix for a Cold Climate Update on Colorado DOT’s 2007 WMA Project on I-70 2009 Rocky Mountain Asphalt Conference and Equipment Show.

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Presentation on theme: "Warm Mix for a Cold Climate Update on Colorado DOT’s 2007 WMA Project on I-70 2009 Rocky Mountain Asphalt Conference and Equipment Show."— Presentation transcript:

1 Warm Mix for a Cold Climate Update on Colorado DOT’s 2007 WMA Project on I-70 2009 Rocky Mountain Asphalt Conference and Equipment Show

2 Colorado DOT 2007 WMA Project Summary Asphalt Mixture Details WMA Specification Summary Construction Highlights WMA Performance Monitoring Conclusions

3 CDOT WMA Project Summary Project Location: I-70, 70 miles west of Denver Mountain terrain – elev. 8,800’ to 11,100’

4 CDOT WMA Project Summary West Portal of Eisenhower-Johnson Memorial Tunnel on I-70 WMA Job started here and continued down to Town of Silverthorne

5 CDOT WMA Project Summary Climate 35”+ annual precipitation over 200” annual snowfall 150 - 200 freeze/thaw cycles per year Cool summer conditions (construction) July – at lowest elevation on the project Winds avg. 8-21mph

6 CDOT WMA Project Summary Traffic 30,000 AADT, 10% trucks, 4.85M ESALS (10-yr.) Extreme winter conditions (truck chain area) Winter 2007/8 Stats: - Snowed 65 of 76 days between 12/1 & 2/14 - 128 chain-days total for 2007/8

7 WMA Specification Summary SAME mix design for WMA and for HMA 3 additives – Advera-WMA, Sasobit, Evotherm ~1000 tons each, ~1 mile for each section Control mix placed each night prior to WMA section Three lanes each direction, WMA in middle lane WMA sections placed nearly adjacent to each other to ensure similar site conditions

8 Project Mixture Details Project scope of work: Mill surface distress 2.5” and fill with 2.5” HMA Thick existing pav’t (12”+ HMA over R75 fill) Superpave dense graded mix specified - ½-inch nominal max (CDOT SX-mix) - PG58-28 binder - 75 gyration design - Volumetric Acceptance for pay (Voids, VMA, AC, mat density, joint density)

9 Project Mixture Details Contractor’s mixture design with CDOT approval Project called for standard mix design with no WMA additives during design - Fine graded mix design by Everist Materials aggregates from crushed river rock - Production targets established: Voids = 3.6% (+/-1.2% tolerance) VMA = 16.8% (+/-1.2% tolerance) %AC = 6.3% (+/-0.3% tolerance) Average bid prices $66/ton WMA, $48 HMA (~38%+)

10 Construction Highlights WMA produced and tested at 250 °F HMA produced and tested at 280 °F Same roller configuration used WMA Density per Spec (92%-96%) and WMA Volumetric pay factors “set to 1” and after discussions at pre-pave meetings

11 Advera-WMA feed system - Similar to Sasobit feed system - blown in like SMA fibers

12 Advera-WMA and Sasobit blown in here Evotherm injected into AC feed line here

13 Advera-WMA Sasobit

14 Same haul, placement and compaction equipment used for WMA as for HMA sections WMA ~240°F behind the paver – no fumes

15 Construction Highlights - Field Data Mix Type Field PropertyControl 7-24-07 Advera WMA Control 7-26-07 SasobitControl 8-13-07 Evotherm Low Air Temp. (°F) 54 50 36 Mix Delivery Temp. (°F) * 280+260* 280+235* 280+243 Mix Temp At Screed (°F) *243*230*235 Mat Density (% Max. Theoret.) 93.893.3 95.7 (single data point) 93.293.794.7 All values are averages of multiple tests except as noted * Per Specifications - minimum delivery temp for control HMA was 280 °F (actual temp not recorded) Target plant production temp for WMA mix was 250 degrees for all sections Spec 92-96%

16 Construction Highlights – Lab Data Mix Type Lab Property Control 7-24-07 Advera WMA Control 7-26-07 SasobitControl 8-13-07 Evotherm Results are from the CDOT QA lab – QC results were comparable AC (%) 6.236.386.416.326.046.38 Voids (%) 3.11.83.02.43.62.2 VMA (%) 16.515.716.515.916.315.8 Stability 363435363534 NOTE: Samples compacted immediately at temps on previous slide Design 6.3% 3.6% 16.8% 39

17 Interpreting Hamburg Data NOTE: CDOT does not typically run Hamburg on 75 Gyration mixtures Failure due to plastic flow is typical below the 100 gyration level Failure if more than 4mm in 10,000 cycles

18 Construction Highlights – TSR and Hamburg Data Mix Type Lab PropertyControl 7-24-07 Advera WMA Control 7-26-07 SasobitControl 8-13-07 Evotherm TSR Results are from the CDOT QA lab. 80% min. for design, 70% min for production Hamburg Results from CDOT Euro Lab. Max rut 4mm in 10,000 cycles for production TSR (%)10083*971119480 Hamburg (mm rut) 9.09.516.010.0 13.5 Hamburg (cycles) 9,7005,1007,6509,4009,6507,750 Hamburg Stripping Inflection (cycles) 7,8003,3005,0005,7008,4006,200 * Average of other control mix tested on the job. - TSR samples compacted immediately at temps previously stated - Hamburg samples cooled and shipped to Denver where they were all reheated for compaction to standard temperature (280 degrees)

19 M320 Continuous Performance Grade M320, Table 2 Performance Grade Additive Rate, by wt of binder Base 59.9 – 30.3 58 – 28 Sasobit 64.2 – 29.2 64 – 22 1.5% Aspha-Min 61.1 – 30.9 58 – 28 Advera 60.7 – 30.4 58 - 28 4.33% Evotherm No Data Obtained Due to Schedule FHWA Mobile Asphalt Mixture Testing Laboratory and TFHRC Data

20 Dynamic Modulus E* Master Curve (from Asphalt Mix Performance Tester)

21 I-70 Flow Number, Fn, from AMPT 689 kPa (100 psi) – Deviator Stress 69 kPa (10 psi) – Confining Pressure

22 WMA Performance Monitoring NCAT under contract for WMA project support - field data collection during construction - long term tracking (3+ years) - interim and final reporting First condition evaluation was in October, 2008

23 WMA Performance Monitoring Results from First Annual Evaluation Rutting less than 5mm in all sections Transverse cracking is occurring but is relatively sparse and is occurring similarly in both control and WMA sections (3 to 4 cracks per mile) Some transverse cracks stop or are shorter in the WMA sections. Weathering, raveling and other distresses were rare with workmanship problems likely the cause Excellent performance in all sections at this time

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26 Conclusions WMA decreased voids in lab compaction WMA field compaction comparable at lower temps TSR Lower, but passing, in two of three WMA sections Hamburg data may be inconclusive – will rely on actual field moisture performance for these test sections Early WMA performance equal to HMA on the job: - no rutting, moisture damage or early distresses Due to harsh site conditions, we anticipate useful performance data within 3 years Confident that WMA facilitates cold temp. placement Will use more WMA in this corridor if performance is comparable to HMA

27 Questions, Please Anticipating Warmth in the future


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