EVALUATING THE IMPACT OF LIME ON PAVEMENT PERFORMANCE

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Technical Advisory Panel• Tim Aschenbrener, Colorado DOT• Hussain Bahia, University of Wisconsin, Madison• John Bukowski, Federal Highway Administration• James Eason, Georgia DOT• Jon Epps, Granite Construction• Milt Fletcher, S. Carolina DOT• Adam Hand, Granite Construction • Rita Leahy, Asphalt Pavement Association of California• Randy Mountcastle, Alabama DOT• Joe Peterson, California DOT • Dale Rand, Texas DOT• Dean Weitzel, Formerly, Nevada DOT• Randy West, National Center for Asphalt Technology• Tom Zehr, Illinois DOT

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Overall Objective

• Quantify expected changes in pavement life from adding lime to HMA.

• Extensive lab testing of multiple un-treated, liquid-treated, and lime-treated HMA mixtures.

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Overall Objective

• Evaluated 15 asphalt mixtures with the most widely accepted lab tests for the following modes of pavement failure:

Moisture damage

Permanent deformation

Fatigue cracking

Thermal cracking

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Overall Lab Experimental Plan

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Materials Sources

• A total of 5 material sources were evaluated.

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Mix Designs Summary

• All mixtures met the minimum TSR at 1% lime and 0.5% liquid.

• All mixtures met the minimum unconditioned TS at 77F.

• Moisture sensitivity:– Good: AL & IL– Fair: CA– Poor: SC & TX

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8

HMA

Base course

Subgrade soil

thermal tension

bending

shear

compression

Resistance to Moisture Damage

• Experimental Plan:– Measure unconditioned |E*| master curve (i.e. 0 F-T cycles).

– Subject samples to 70-80% saturation.

– Subject saturated samples to multiple freeze-thaw cycling wherein one F-T cycle consists of:

– freezing at 0F for 16 hours– followed by 24 hours thawing at 140 F– and 2 hours at 77F.

– Subject each sample to the required number of F-T cycles.

– Conduct E* testing after cycles: 1, 3, 6, 9, 12, & 15.

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Resistance to Moisture Damage

• Experimental Plan:– Sample preparation for unaged & aged mixes.

Asphalt Binder

Virgin Aggregate

Long-term oven aging:

5 days at 185F

Conditioning

Short-term oven aging:

4 hrs at 275F

0 F-T

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Loose Mix

Compacted spec.

Testing

Compacted spec.

Resistance to Moisture Damage

• |E*| master curve: Modulus of HMA at any combination of loading rate & temperature .

• |E*| on the unaged & aged mixes (simulate short & long-term behavior) & under multiple freeze-thaw cycling.

Time

Str

ess

Str

ain

Time

time shift = /

= 0sin(ωt)

= 0sin(ωt-)

0

0

|E*| = σ0/ε0

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Selecting the Critical F-T Cycles

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Selecting the Critical F-T Cycles

• The 6th F-T cycle is the critical: the point after which most of the mixtures hold a steady value of |E*|.

• Subject the permanent deformation, fatigue, & thermal cracking samples to 6 F-T cycles to represent their moisture conditioning stage.

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State Mix

Unaged E*, (ksi) at 104⁰F Aged E* (ksi) at 70⁰F

0 F-T 6 F-TRatio

E6FT/E0FT0 F-T 6 F-T

Ratio E6FT/E0FT

Alabama Un-treated 226 167 74% 1,123 806 72%

Liquid-treated 218 143 66% 1,113 813 73%

Lime-treated 261 205 79% 1,236 1,043 84%California Un-treated 292 144 49% 1,479 622 42%

Liquid-treated 407 207 51% 1,649 1,116 68%

Lime-treated 324 296 91% 1,683 1,717 102%Illinois Un-treated 235 154 66% 1,648 826 50%

Liquid-treated 362 203 56% 1,500 881 59%

Lime-treated 456 200 44% 1,614 1,328 82%South Carolina

Un-treated 243 56 23% 754 275 36%

Liquid-treated175 160

91% 749 560 75%

Lime-treated 197 248 126% 1,037 958 92%Texas Un-treated 253 99 39% 870 508 58%

Liquid-treated 207 149 72% 848 603 71%

Lime-treated 194 174 90% 852 843 99%

Resistance to Moisture DamageOverall Summary

• |E*| is significantly impacted by testing temperature & mixture aging condition.

• After multiple F-T cycling:– The lime-treated mixes of all 5 sources hold their |E*| properties

significantly better.– The un-treated CA mixture at the unaged stage could not be tested

after 10 F-T cycles– The liquid-treated IL mixture at the unaged stage could not be tested

after 10 F-T cycles – The un-treated SC mixture at the aged stage could not be tested after

6 F-T cycles

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Resistance to Permanent Deformation

• Repeated Load triaxial test (RLT)

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30 psi

d = 45 psi

Before After

Permanent Deformation Model

• Model used to characterize the permanent deformation behavior of the HMA mixtures (Table 6):

– p: accumulated permanent strain at N-loads (in/in) – r : resilient strain of the HMA layer (in/in)– N: number of load repetitions– T: pavement temperature (F)– ai: regression constants

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321

aa

r

p NTa

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Illinois Mixtures – Good moisture sensitivity Texas Mixtures – Poor moisture sensitivity

Resistance to Fatigue Cracking

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100

1,000

10,000

1,000 10,000 100,000 1,000,000Cycles to Failure

Str

ain

(m

icro

ns)

Construction Variability

Repeated haversine load on long-term oven aged mixes at a frequency of 10 Hz & a temperature of 70F.

Fatigue Cracking Model

• Model used to characterize the fatigue behavior of the HMA mixtures (Table 7):

– Nf: number of repetitions to fatigue cracking– t: tensile strain at the top or bottom of HMA (in/in)– E: modulus of the HMA mix (psi)– k’s: laboratory regression coefficients

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32

111

kk

tf EkN

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Alabama Mixture – Good moisture sensitivity California Mixtures – Medium moisture sensitivity

Resistance to Thermal Cracking

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TSRST - Load applied to maintain the 2”2”10” beam at a constant height.

• Fracture temperature: temperature at which HMA mix crack due to thermal stresses.

• Fracture stress: magnitude of the stress caused by thermal contraction of the HMA mix.

Constant

Height

Temp Drop at 10C/hr

Resistance to Thermal Cracking Overall Summary

• Majority of un-treated, liquid-treated, & lime-treated mixes have similar fracture temperatures at both 0 & 6 F-T cycles.

• Exceptions:• California & South Carolina source: liquid-treated mix have colder

fracture temperature than lime-treated mix at the conditioned stage.

• Illinois source: lime-treated mix have colder fracture temperature than liquid-treated mix at the unconditioned stage.

• Lime-treated mixtures: significantly higher fracture stresses.

• HMA pavements with lime-treated mixtures would experience fewer cracks/mile.

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MEPDG Design Inputs

• Traffic• Climate• Foundation• Materials

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Field Projects

• Alabama: US31 and SR7• California: PLA80 and PLA28• Illinois: Chicago• South Carolina: SC12 and SC161• Texas: FM396 and SH30

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• Flexible Pavement Performance Indicators:

Permanent Deformation in HMAAND

Bottom-up Fatigue Cracking

MEPDG Design InputsPerformance Prediction

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State Location Condition HMA Mixture

Structural Design Control DistressHMA (in) Base (in)

Alabama US31un-damaged(0F-T)

un-treated 8.50 11.0 Ruttingliquid-treated 13.0 11.0 Ruttinglime-treated 6.0 11.0 Neither

moisture-damaged(6F-T)

un-treated 7.5 11.0 Ruttingliquid-treated 11.0 11.0 Fatiguelime-treated 6.5 11.0 Rutting

SR7un-damaged(0F-T)

un-treated 7.0 9.0 Ruttingliquid-treated -- 9.0 No-Designlime-treated 6.0 9.0 Neither

moisture-damaged(6F-T)

un-treated 6.0 9.0 Neitherliquid-treated 10.5 9.0 Ruttinglime-treated 6.0 9.0 Rutting

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State Location HMA Mixture

Structural DesignHMA (in) Base (in)

Alabama US31un-treated 8.5 11.0liquid-treated 13.0 11.0lime-treated 6.5 11.0

SR7un-treated 7.0 9.0liquid-treated 10.5 9.0lime-treated 6.0 9.0

California PLA28un-treated 9.5 8.0liquid-treated 8.0 8.0lime-treated 6.0 8.0

Illinois Chicagoun-treated 8.5 10.0liquid-treated 10.75 10.0lime-treated 6.0 10.0

S. Carolina SC12un-treated * 12.0liquid-treated 13.75 12.0lime-treated 13.0 12.0

SC161un-treated 15.5 10.0liquid-treated 12.75 10.0lime-treated 12.0 10.0

Texas FM396un-treated 13.75 11.0liquid-treated 9.25 11.0lime-treated 7.0 11.0

SH30un-treated 13.5 9.0liquid-treated 9.75 9.0lime-treated 7.25 9.0

Cost Figures• Based on $/yd2-in:

- un-treated: $5.12 ($65.0/ton of HMA)- liquid-treated: $5.16 ($65.5/ton of HMA)- lime-treated: $5.39 ($68.4/to of HMA)

No additional cost for LiquidLime additional cost: 3 x material cost

$3.75/ton of HMA

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State Location HMA Mixture HMA Thickness (in)Total Cost of HMA

($ / lane-mile)Percent Saving

Alabama US31(4.6106 ESALs, 1438 ADTT)

un-treated 8.50 306,381 --

liquid-treated 13.00 472,243 -54%

lime-treated 6.50 246,646 19%

SR7(2.8106 ESALs, 910 ADTT)

un-treated 7.00 252,314 --

liquid-treated 10.501381,427 -51

lime-treated 6.00 227,674 10%

California PLA28(1.6106 ESALs, 360 ADTT)

un-treated 9.50 342,426 --

liquid-treated 8.00 290,611 15%

lime-treated 6.00 227,674 34%

Illinois Chicago(3.7106 ESALs, 1050 ADTT)

un-treated 8.50 306,381 --

liquid-treated 10.75 390,509 -27%

lime-treated 6.00 227,674 26%

S. Carolina SC12(9.6106 ESALs, 2170 ADTT)

un-treated 16.002576,717 --

liquid-treated 13.75 499,488 13%

lime-treated 13.00 493,293 14%

SC161(7.1106 ESALs, 2360 ADTT)

un-treated 15.50 558,694 --

liquid-treated 12.75 463,162 17%

lime-treated 12.00 455,347 18%

Texas FM396(7.8106 ESALs, 872 ADTT)

un-treated 13.75 495,616 --

liquid-treated 9.25 336,019 32%

lime-treated 7.00 265,619 46%

SH30(3.3106 ESALs, 824 ADTT)

un-treated 13.50 486,605 --

liquid-treated 9.75 354,182 27%

lime-treated 7.25 275,106 43%

Percent Reduction in HMA Thickness

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Percent Cost Savings

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FINDINGS

• Five Aggregate sources – Moisture Sensitivity– AL and IL: Low– CA: Moderate– SC and TX: High

• Both Lime and Liquid Improved the moisture sensitivity based on TSR

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FINDINGS FOR NEW DESIGNS• For low moisture sensitive mixtures: AL & IL

– Adding lime resulted in savings: 10-25%– Adding liquid resulted in additional cost: 25-50%

• For moderate moisture sensitive mixtures: CA– Adding lime resulted in savings: 35%– Adding liquid resulted in savings: 15%

• For high moisture sensitive mixtures: SC & TX– Adding lime resulted in savings: 14-43%– Adding liquid resulted in savings: 13-32%

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Stresses in Overlaid Pavements

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HMA Overlay

Base course

Subgrade soil

thermal tension bending

shear

compression

Old HMA

Overlay Designs

• Account for reflective cracking in addition to rutting, fatigue, and Thermal cracking

• The measured E* and fatigue resistance properties of the mixtures were used

• The Rubber Pavement Association model was used to establish 10-years designs

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Percent Cost Savings

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FINDINGS FOR OVERLAYS• For low moisture sensitive mixtures: AL

– Adding lime resulted in savings: 47-55%– Adding liquid resulted in additional cost: 30-44%

• For high moisture sensitive mixtures: SC & TX– Adding lime resulted in savings: 47-68%– Adding liquid resulted in savings: 14-50%

• For CA and IL projects: no-designs for un-treated mix

– Adding lime resulted in 22-48% savings over the use of liquid

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