WY.HPP.4-1(5).Beartooth_Highway.Pavements.2008.pdf

Central Federal Lands Highway Division 12300 West Dakota Avenue Lakewood, CO 80228

Subject: WY HPP 4-1(4) Beartooth Rehabilitation Project – Pavement Recommendations

From: Mike Voth Pavement Discipline Leader Lakewood, CO

To: Bert McCauley Project Manager

Lakewood, CO

This project has potentially three different scopes / purposes as related to the pavement design and recommendations. (1) From Sta 50+770 to Sta 69+565 (11.75 miles) the intention is to complete a long-term performing pavement rehabilitation, and (2) from Sta 39+780 to 50+770 (6.9 miles) the intention is to complete patching, crack sealing, and a thin overlay to add short-term service life, and (3) from Sta 44+700 to 45+800 (0.7 miles) is bridge and roadway reconstruction. This last scope will not be addressed in this memo as pavement recommendations are to follow the guidance from a previous report (Report 98- 16).

Pavement recommendations from Sta 50+770 to Sta 69+565 are as follows:

▪ 50 mm HACP

▪ 150 mm FDR-Pulverize

▪ SN = 1.60

All of the pavement design inputs are included in an attachment. To summarize a couple of the key inputs: the design subgrade resilient modulus value used (MR) was 15,000 psi, and the amount of ESALs calculated for a 20-year period was about 110,000. This is based upon an AADT of 500 and 5% heavy vehicles. These traffic parameters were attained from engineering judgment as measured traffic data was not supplied. The required structural number (SN) is 1.65. The relatively high MR value is based on R-values that are all well above 60 and most above 70.

It should be noted that a pavement structural section with an SN slightly less than 1.65 is being recommended. This will result in a calculated service life of about 17 years. However, given the limited project funding and the desire to rehabilitate as much of the roadway as

Memorandum

Date: 8-29-08 possible, the CFT agreed that it was acceptable to go forward with a less than 20-year design in the base schedule and employ a technical standard design exception. To help mitigate the performance risk of this nominal structural section, an option will be included in the contract to add an additional 25 mm of HACP, pending availability of funds.

Because the recommended pavement design in the base schedule includes only a thin 50 mm HACP surface without any conservativeness, achieving 95% compaction of the pulverized material and assuring there is a stable platform to pave on will be very important. Areas of pulverized material that are not properly compacted or properly maintained under traffic will result in premature fatigue cracking in the HACP surface.

It should also be noted that the boring information in Materials Report 98-16 indicates the presences of cobbles and possibly even boulders within the depth of the pulverized layer. A project specific SCR for section 303 was developed to address this issue. Report 98-16 is included as an attachment.

Pavement recommendations for Sta 39+780 to Sta 50+770 are as follows:

▪ 38 mm HACP overlay

▪ Pre-overlay repair: Sawcut and remove pavement in areas of moderate and high severity fatigue cracking; and backfill with base and HACP (per section 428). An acceptable alternative to this patching would be to allow the distressed area to be pulverized and re-compacted (per section 303) prior to overlay.

▪ Pre-overlay repair: Seal transverse and longitudinal cracks less than 25 mm and greater than 3 mm with a hot pour elastic sealant (AASHTO M 324, Type II);

recommended that working cracks (i.e. thermal cracks) be routed. Fill cracks greater than 25 mm with a 404 or 417 type asphalt material.

The scope of the above recommendations is to preserve and add additional service life to the roadway at a minimal cost. Per the PDDM, no structural design is required when completing a preservation treatment. A chip seal would be an acceptable alternative to the thin overlay.

However, given the very short construction season, cool summer temperatures of the project location, and the fact that HACP is already included in the project, it was anticipated that an HACP overlay would be most appropriate and cost effective.

Pavement Material Recommendations:

● HACP can be 401 Superpave or 402 Marshall. The grading should use a 12.5 mm nominal maximum size aggregate. Pavement roughness should be Type IV for segments, Sta 50+770 to Sta 69+565 and Sta 39+780 to Sta 50+770. The unit weight can be estimated at 2325 kg/m3. The 50 mm and 38 mm depth HACP will be placed in 1 lift.

•Hydrated lime (Type III), at 1% of the unit weight of the HACP, will be the antistrip additive.

•The asphalt binder grade per the LTPPBind software program at 95% or greater reliability should be a PG 58-34. WFLHD’s current reconstruction project on Beartooth is using a PG 58-34 graded binder. However, the scope of this project includes a thin overlay on a distressed pavement and a pavement rehabilitation on a segment that’s closed to traffic and covered with snow (insulated) during the cold winter months. As a result it is recommended to use a PG 58-28 graded binder. This is one of the common grades used in the area, and it will be cost effective. The CFT can decide to use a “higher” grade, but this most likely will result in higher costs that would be difficult to justify.

• A prime coat should be applied on the pulverized material prior to paving on the segment from Sta 50+770 to Sta 69+565. Bid item 41101-0000 should be used and the material should be a formulated to penetrate the surface at least 6 mm or it must be worked into the surface. The quantity can be estimated at 1.5 L/ m2. A bid item for blotter material, 41105- 0000, should also be included (at 8 kg/ m2).

● A tack coat, bid item 41201-1000 should be included for the segment from Sta 39+780 to Sta 50+770. For estimating quantities use an application rate of 0.45 L/m2. The emulsion type can be CSS-1, SS-1, CSS-1h, or SS-1h.

• Crack cleaning, sealing, and routing should be completed as discussed in the pavement recommendations above. An estimated linear quantity measured from a field visit should be used for plan quantities.

Attachments cc:

Tech Services files Acquisitions Bill Hakala, COE

1993 AASHTO Pavement Design

DARWin Pavement Design and Analysis System

A Proprietary AASHTOWare Computer Software Product

Flexible Structural Design Module

- 1000 ADT when route is open (closed half the year - used 500 ADT)

- Assume 5% heavy vehicles (using an RV as typical heavy vehicle)

Flexible Structural Design

18-kip ESALs Over Initial Performance Period 109,575 Initial Serviceability 4.2 Terminal Serviceability 2 Reliability Level 75 % Overall Standard Deviation 0.49 Roadbed Soil Resilient Modulus 15,000 psi Stage Construction 1

Calculated Design Structural Number 1.65 in

Simple ESAL Calculation

Performance Period (years) 20 Two-Way Traffic (ADT) 500 Number of Lanes in Design Direction 1 Percent of All Trucks in Design Lane 100 % Percent Trucks in Design Direction 60 % Percent Heavy Trucks (of ADT) FHWA Class 5 or Greater 5 % Average Initial Truck Factor (ESALs/truck) 1 Annual Truck Factor Growth Rate 0 % Annual Truck Volume Growth Rate 0 % Growth Compound

Total Calculated Cumulative ESALs 109,575

Specified Layer Design

Layer

Material Description

Struct Coef.

(Ai)

Drain Coef.

(Mi)

Thickness (Di)(in)

Width

(ft)

Calculated

SN (in)

1 HACP 0.44 1 2 - 0.88

2 FDR-Pulverize 0.12 1 6 - 0.72

Total - - - 8.00 - 1.60

1993 AASHTO Pavement Design

DARWin Pavement Design and Analysis System

A Proprietary AASHTOWare Computer Software Product

Flexible Structural Design Module

Calculate ESALs (perf life) on the as recommended section

Flexible Structural Design

Structural Number 1.6 in Initial Serviceability 4.2 Terminal Serviceability 2 Reliability Level 75 % Overall Standard Deviation 0.49 Roadbed Soil Resilient Modulus 15,000 psi Stage Construction 1

18-kip ESALs Over Initial Performance Period 91,479

Beartooth BindReport-5Closest.txt

Five Closest Weather Stations For Latitude/Longitude= 45.084/109.972 Report Date: 7/21/2008 (LTPPBind V3.0 Alpha)

Three Closest WS Report Title

General A=8 km B=24 km C=38 km D=43 km E=52 km Station ID MT1995 MT5961 WY9025 MT6190 MT3378 County/District park stillwater yellowstone national stillwater park Weather Station cooke city 2 w mystic lake tower falls nye 2 gardiner Elevation, m 2113 1858 1774 1362 1494 Latitude, Longitude 45.02 ,109.97 45.23 ,109.75 44.92 ,110.42 45.43 ,109.8 45.03 ,110.68 Last Year Data Available 1997 1997 1997 1997 1997

Air Temperature Mean ( Std, N ) Mean ( Std, N ) Mean ( Std, N ) Mean ( Std, N ) Mean ( Std, N ) High Temperature 26.7 (13,26) 27.5 (13,35) 29.8 (16,26) 31.3 (22,16) 33 (15,29) Low Temperature -35.2 (36,23) -29.3 (40,35) -36.8 (42,28) -32.1 (45,16) -29.1 (35,31) Low Temperature Drop 29.5 (30,23) 27.8 (42,35) 32.2 (36,28) 32.4 (44,16) 27.4 (32,31) Degree-Days > 10C 1439 (183,26) 1648 (170,35) 1960 (219,26) 2261 (227,16) 2494 (231,29)

PG High Low Rel. High Low Rel. High Low Rel. High Low Rel. High Low Rel.

Pavement Temperature, C 41.4 -26.3 43.7 -22.1 47.0 -27.4 49.9 -24.2 52.1 -21.9 50% Reliability PG 46-28 (98,70) 46-28 (94,95) 52-28 (98,57) 52-28 (88,84) 58-22 (98,52) >50% Reliability PG 46-34 (98,98) 52-28 (98,95) 52-34 (98,96) 52-34 (88,98) 58-28 (98,97) = 52-34 (98,98) 52-40 (98,98) 58-34 (98,98) 58-34 (98,98)