EVALUATING THE IMPACT OF LIME ON PAVEMENT PERFORMANCE 1

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 2

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. 3

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 4

Overall Lab Experimental Plan 5

Materials Sources A total of 5 material sources were evaluated. 6

Mix Designs Summary All mixtures met the minimum TSR at 1% lime and 0.5% liquid. All mixtures met the minimum unconditioned TS at 77  F. Moisture sensitivity: – Good: AL & IL – Fair: CA – Poor: SC & TX 7

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 0  F for 16 hours – followed by 24 hours thawing at 140  F – and 2 hours at 77  F. – Subject each sample to the required number of F-T cycles. – Conduct E* testing after cycles: 1, 3, 6, 9, 12, & 15. 9

Resistance to Moisture Damage Experimental Plan: – Sample preparation for unaged & aged mixes. Asphalt Binder Virgin Aggregate Long-term oven aging: 5 days at 185  F Conditioning Short-term oven aging: 4 hrs at 275  F 0 F-T 10 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 Stress Strain Time time shift =  /   =  0 sin(ωt)  =  0 sin(ωt-  ) 00 00 |E*| = σ 0 /ε 0 11

Selecting the Critical F-T Cycles 12

Selecting the Critical F-T Cycles The 6 th 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. 13

14 StateMix Unaged E *, (ksi) at 104 ⁰ FAged E * (ksi) at 70 ⁰ F 0 F-T6 F-T Ratio E 6FT /E 0FT 0 F-T6 F-T Ratio E 6FT /E 0F T Alabama Un-treated %1, % Liquid-treated %1, % Lime-treated %1,2361,04384% California Un-treated %1, % Liquid-treated %1,6491,11668% Lime-treated % 1,6831, % Illinois Un-treated %1, % Liquid-treated %1, % Lime-treated %1,6141,32882% South Carolina Un-treated % % Liquid-treated % % Lime-treated %1, % Texas Un-treated % % Liquid-treated % % Lime-treated % %

Resistance to Moisture Damage Overall 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 15

Resistance to Permanent Deformation Repeated Load triaxial test (RLT) 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) – a i : regression constants 17

18 Illinois Mixtures – Good moisture sensitivityTexas Mixtures – Poor moisture sensitivity

Resistance to Fatigue Cracking 19 Repeated haversine load on long-term oven aged mixes at a frequency of 10 Hz & a temperature of 70  F.

Fatigue Cracking Model Model used to characterize the fatigue behavior of the HMA mixtures (Table 7): – N f : 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 20

21 Alabama Mixture – Good moisture sensitivityCalifornia Mixtures – Medium moisture sensitivity

Resistance to Thermal Cracking 22 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 10  C/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. 23

MEPDG Design Inputs Traffic Climate Foundation Materials 24

Field Projects Alabama: US31 and SR7 California: PLA80 and PLA28 Illinois: Chicago South Carolina: SC12 and SC161 Texas: FM396 and SH30 25

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Flexible Pavement Performance Indicators: Permanent Deformation in HMA AND Bottom-up Fatigue Cracking MEPDG Design Inputs Performance Prediction 27

28 StateLocationConditionHMA Mixture Structural DesignControl Distress HMA (in)Base (in) AlabamaUS31 un-damaged (0F-T) un-treated Rutting liquid-treated Rutting lime-treated Neither moisture- damaged (6F-T) un-treated Rutting liquid-treated11.0 Fatigue lime-treated Rutting SR7 un-damaged (0F-T) un-treated7.09.0Rutting liquid-treated--9.0No-Design lime-treated6.09.0Neither moisture- damaged (6F-T) un-treated6.09.0Neither liquid-treated Rutting lime-treated6.09.0Rutting

29 StateLocationHMA Mixture Structural Design HMA (in)Base (in) AlabamaUS31 un-treated liquid-treated lime-treated SR7 un-treated liquid-treated lime-treated CaliforniaPLA28 un-treated liquid-treated8.0 lime-treated IllinoisChicago un-treated liquid-treated lime-treated S. CarolinaSC12 un-treated*12.0 liquid-treated lime-treated SC161 un-treated liquid-treated lime-treated TexasFM396 un-treated liquid-treated lime-treated SH30 un-treated liquid-treated lime-treated

Cost Figures Based on $/yd 2 -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 Liquid Lime additional cost: 3 x material cost $3.75/ton of HMA 30

31 StateLocationHMA MixtureHMA Thickness (in) Total Cost of HMA ($ / lane-mile) Percent Saving Alabama US31 (4.6  10 6 ESALs, 1438 ADTT) un-treated ,381-- liquid-treated ,243-54% lime-treated ,64619% SR7 (2.8  10 6 ESALs, 910 ADTT) un-treated ,314-- liquid-treated , lime-treated ,67410% California PLA28 (1.6  10 6 ESALs, 360 ADTT) un-treated ,426-- liquid-treated ,61115% lime-treated ,67434% Illinois Chicago (3.7  10 6 ESALs, 1050 ADTT) un-treated ,381-- liquid-treated ,509-27% lime-treated ,67426% S. Carolina SC12 (9.6  10 6 ESALs, 2170 ADTT) un-treated ,717-- liquid-treated ,48813% lime-treated ,29314% SC161 (7.1  10 6 ESALs, 2360 ADTT) un-treated ,694-- liquid-treated ,16217% lime-treated ,34718% Texas FM396 (7.8  10 6 ESALs, 872 ADTT) un-treated ,616-- liquid-treated ,01932% lime-treated ,61946% SH30 (3.3  10 6 ESALs, 824 ADTT) un-treated ,605-- liquid-treated ,18227% lime-treated ,106 43%

Percent Reduction in HMA Thickness 32

Percent Cost Savings 33

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 34

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% 35

Stresses in Overlaid Pavements 36 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 37

Percent Cost Savings 38

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 39