The Role of Subbase Support in Concrete Pavement Sustainability

Transcription

1 The Role of Subbase Support in Concrete Pavement Sustainability TxDOT Project Alternatives to Asphalt Concrete Pavement Subbases for Concrete Pavement Youn su Jung Dan Zollinger Andrew Wimsatt Wednesday, Jan. 12, 2011

2 Jointed Pavement Slab Length Tandem Axle Slab Thickness Subgrade Tensile Stress Single Axle Subbase PCC Slab

3 CRC Pavement Transverse Cracks Single Axle Slab Thickness Maximum Tensile Stress CRC Slab Subbase Subgrade

4 Corner Failure

5 Adjacent Patch Deterioration

6 Keyway Failure

7 Drainage Swale

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10 Cracking on the dowel

11 Erosion: Mechanically and Hydraulically Induced s θ h z 0 - w 0 δ total v z Reinforcing steel v i

12 Load Transfer Efficiency 40 kn L UL d L = 1.8 mm d UL = 1.4 mm

13 Matrix Erosion Model V Z = SLAB VELOCITY V Z H = INITIAL VOID THICKNESS (t = 0) Z = SLAB DEFLECTION fi = fe 0 N i ρ ν a h = FINAL DIFLECTION (t = ) δ = THICKNESS AT ANY TIME y SLAB t 0 : ORIGINAL POSITION t t : FINAL POSITION Z h δ H x θ L SUBBASE Where, f i = Erosion depth (L) f 0 = Ultimate erosion depth (L) N i = Number of axle loads per load group contributing to erosion ρ = Calibration coefficient based on local performance v = Calibration coefficient represents the number of wheel loads (or time) for layer debonding to occur and erosion to initiate, 0 for lab test a = Inverse of the rate of void development 13

14 Subbase Erosion and Pavement Deterioration Process Joint sealing deterioration Slab Subbase Subgrade Patch Subbase Subgrade Good condition Newly patched Erosion by Wear Slab Subbase Subgrade Patch Subbase Subgrade Erosion by Wear Getting weak condition Next slab fail Voiding by Water Slab Subbase Subgrade Patch Subbase Subgrade Voiding by Water Poor condition Poor condition

15 Patched Area Deterioration No joint seal After 1 month Spalling & corner break

16 Maintenance Strategy As pavement condition degrades, Repair costs and time of repair go up Future renewal options become limited Preservative maintenance extend pavement life cost effectively Pavement condition Performance monitoring Preservative maintenance Functional CPR Structural CPR Remove and replace Pavement age

17 LTPP Faulting Data Sections State and Section ID AL 1_3028 CA 6_3013 CA 6_3017 CA 6_3019 CA 6_3021 CA 6_3024 CA 6_7456 NE 31_3018 OK 40_3018 SD 46_6600 AL 1_4007 AL 1_4084 AR 5_3073 AR 5_3074 AR 5_4021 LA 22_4001 NE 31_4019 Pavement Type JPCP JPCP JPCP JPCP JPCP JPCP JPCP JPCP JPCP JPCP JRCP JRCP JRCP JRCP JRCP JRCP JRCP

18 Estimated Average Faulting Depth 25 Estimated Average Faulting Depth 180 Faulting Depth, mm Average Wet days per Year Average Wet-days per Year, day AL 1_3028 CA 6_3013 CA 6_3017 CA 6_3019 CA 6_3021 CA 6_3024 CA 6_7456 NE 31_3018 OK 40_3018 SD 46_6600 JPCP AL 1_4007 AL 1_4084 AR 5_3073 AR 5_3074 AR 5_4021 JRCP LA 22_4001 NE 31_4019 Wet days in LTPP database is defined as the number of days for which precipitation was greater than 0.25 mm for year

19 Relationship between Faulting and Number of Wet days 20 Estimated Average Faulting Depth 25 Estimated Average Faulting Depth 18 Faulting Depth, mm y = 0.124x R 2 = Faulting Depth, mm y = 0.192x R 2 = Average Annual Wet Days, day JPCP Sections Average Annual Wet Days, day JRCP Sections Average faulting depth is estimated at the 100 million ESAL repetitions based on LTPP faulting data

20 h 1 E 1 h e E e h σ 1 2 E 2 k k σ e

21 SS Ba sin Area = δ ( ) δ1+ δ δ j 1 + δ j 2* δ 0

22 Falling Weight Deflectometer (cont.) LTE Testing Measure of independent action LTE = d d U L 100 Where, LTE = Load transfer effectiveness, percent du = Deflection on the unloaded side of the joint or crack, mils dl = Deflection at the loaded side of the joint or crack, mils d U d L LTE < 70% Retrofit load transfer

23 Falling Weight Deflectometer (cont.) Deflection Testing AREA = 6(D 0 + 2D1 + 2D2 + D 0 D 3 ) Where, AREA = FWD deflection parameter, in. D0 = Deflection at the loading position, mils D1 = Deflection at 12 in. from the loading position, mils D2 = Deflection at 24 in. from the loading position, mils D3 = Deflection at 36 in. from the loading position, mils Basin area < 25 Check base/subgrade support Reference: Ioannides, A. M. Dimensional Analysis in NDT Rigid Pavement Evaluation, Journal of Transportation Engineering, Vol. 116, No. 1, July 1990, pp

24 Slab Action: l - Value

25 Equivalent Thickness h 3 e p h e-p lm k b E c = 4 m 12 ν k ( ) 1 2 b Ec Equivalent Thickness Measured Value Back-calculated Based on Cores

26 US 75 (Sherman District) Good joint seal condition Severe joint seal damage Good Performing Section Good joint seal condition Newly Patched Section Poorly Performing Section Moderate joint seal damage Old Patched Section Built in 1983 ADT: 42, JCP 6 Flex base Subgrade Sever shoulder joint seal damage Flex base weakening

27 US 75 DCP, Core Base Voiding Penetration depth (in.) Blow number Good condition Bad condition Newly patched Elastic Modulus (ksi) Old patch 0 5 Depth Base (10-16 ) Subgrade (16 - ) Base (10-16") Subgrade (16" - ) Good condition Good condition 16.3 ksi 13.9 ksi Poor condition Poor condition 24.4 ksi 12.6 ksi Newly patched Newly patched 32.8 ksi 12.1 ksi Old patch Old patch 37.1 ksi 11.6 ksi Good Poor Penetration ratio Elastic Modulus New Patch Old Patch

28 US 81/287 (Wise County) Joint seal damage 8 CRCP 4 AC base 6 Lime treated subgrade Joint seal damage Section 1 Wide cracks Subgrade Section 1&2, Built in 1971 ADT: 23,000 (23% truck) AC base and lime treated subgrade erosion Section 2 12 CRCP 2 AC base 2 AC subbase Good joint seal condition Section 3 6 Lime treated subgrade Subgrade Section 3, Built in 1985 ADT: 23,000 (23% truck) Debonded AC subbase erosion

29 US 81/287 DCP, Core -3 Blow number Penetration through subgrade (in.) Section 1 Section 2 Section 3 Debonded AC base Debonded AC base Debonded AC base Debonded AC subbase Elastic Modulus (ksi) Section 1 Section 2 Section 3 AC base bottom AC base bottom AC base bottom AC base bottom AC subbase top Section 1 Section 2 Section 3

30 US 287 (Vernon District) Good performing area No crack Good joint sealing condition Good performing area Poor performing area Poor performing area Sever joint and crack sealant deterioration Wide shoulder joint opening ( > ½ in.) Base erosion under crack Joint & crack sealant deterioration

31 US 287 FWD, DCP, Core LTE Effective thickness, he (in.) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Loading ID hc he Deflection Deflection (mils) Penetration (mm) Blow number Hole Hole Hole Subbase Modulus (ksi) DCP penetration and Subbase Modulus Drop location ID 0

32 FM 364 (Beaumont District) 10 JCP 6 cement stabilized base Subgrade Transverse cracks near joint Built in 1985 ADT: 21,000 (2.5% truck) Transverse cracks near joint (no crack sealing) Cement treated base erosion under crack

33 FM 364 DCP, Core Debonded CSB 0 Blow number Penetration (mm) Section 1 Section 2 Modulus (ksi) Hole 1 Hole 2 DCP result of subgrade PCC bottom (debonded) Base bottom

34 IH 635 (Dallas District) FDR patch spalling FDR patch FDR patch spalling Widened longitudinal joint Longitudinal crack Patch spalling Built in CRCP 4 cement stabilized base Subgrade ADT: 200,000 (12% truck) Spalling on cracks and patches Widened longitudinal joint No sever erosion

35 IH 635 FWD, GPR 100% 90% 80% 70% 60% LTE 50% 40% 30% 20% 10% 0% Drop location ID Low DC value 7~ Effective thickness (in.) hc Effective thickness Deflection Deflection (mils) Drop location ID 0 GPR along Edge Side Wheel Path

36 IH 635 DCP, Core Penetration (mm) Blow number Modulus (ksi) # 1 # 2 # Hole number # 4 # 5 # 6

37 Erosion Factors: Moisture Traffic Erodible Subbase Layer

38 Functions of Subbase? 1) Provide a stable construction platform 2) Prevent erosion of the pavement support 3) Reduce early bonding stress 4) Provide uniform slab support 5) Facilitate drainage 6) Provide increased slab support

39 Is this surface type a good idea?

40 What distress types do present design methods address?? Tandem Axle Slab Length Single Axle Slab Thickness Subgrade Tensile Stress Subbase PCC Slab

41 MEPDG Fatigue Cracking Faulting (Jointed) Punchouts (CRC) Roughness Spalling

42 Erosion in Design Procedures MEPDG design method Included to faulting model by 5 classes of erodibility based on percent of stabilizer and compressive strength FAULTMAX FAULTMAX i 0 m = FAULTMAX 0 + C7 j= 1 = C δ 12 curling Log(1 + C DE 5 j 5.0 Log( 1+ C5 EROD 5.0 P ) Log( 200 EROD ) C 6 WetDays ) P s C 6 Where, FAULTMAXi FAULTMAX0 EROD DEi C12 Ci FR δcurling Ps P200 WetDays = maximum mean transverse joint faulting for month i, in = initial maximum mean transverse joint faulting, in = base/subbase erodibility factor = differential deformation energy accumulated during month i = C1 + C2 * FR0.25 = calibration constants = base freezing index defined as percentage of time the top base temperature is below freezing (32 F) temperature = maximum mean monthly slab corner upward deflection PCC due to temperature curling and moisture warping = overburden on subgrade, lb = percent subgrade material passing #200 sieve = average annual number of wet days (greater than 0.1 in rainfall) 42

43 Erosion in Design Procedures PCA Design Method Empirical erosion model based on outdated highly erodible subbase type in the AASHO Road Test log N = ( C P Percent erosion damage = ) 100 Where, N = allowable number of load repetitions based on a PSI of 3.0 C 1 = adjustment factor (1 for untreated subbase, 0.9 for stabilized subbase) P = rate of work or power = p hk m i= 1 C 2 N n i i p = pressure on the foundation under the slab corner in psi, p = kw k = modulus of subgrade reaction in psi/in w = corner deflection in in h = thickness of slab in in m = total number of load groups C 2 = 0.06 for pavement without concrete shoulder, 0.94 for pavements with tied concrete shoulder n i = predicted number of repetitions for ith load group = allowable number of repetitions for ith load group N i 43

44 Erosion in Design Procedures AASHTO design method loss of support factors affecting to the modulus of subgrade reaction subjective range of modulus Typical Ranges of LS Factors for Various Types of Materials Type of Material Loss of Support Cement-treated granular base (E = 1x10 6 to 2x10 6 psi) 0.0 to 1.0 Cement aggregate mixtures (E = 500,000 to 1x10 6 psi) 0.0 to 1.0 Asphalt-treated bases (E = 350,000 to 1x10 6 psi) 0.0 to 1.0 Bituminous-stabilized mixture (E = 40,000 to 300,000 psi) 0.0 to 1.0 Lime-stabilized materials (E = 20,000 to 70,000 psi) 1.0 to 3.0 Unbound granular materials (E = 15,000 to 45,000 psi) 1.0 to 3.0 Fine-grained or natural subgrade materials (E = 3,000 to 40,000 psi) 2.0 to 3.0 Correction of Effective Modulus of Subgrade Reaction due to Loss of Support 44

45 Maintenance Strategy As pavement condition degrades, Repair costs and time of repair go up Future renewal options become limited Preservative maintenance extend pavement life cost effectively Pavement condition Performance monitoring Preservative maintenance Functional CPR Structural CPR Remove and replace Pavement age

46 Erosion Test of Cement Treated Samples Deviatoric stress, σ 1 σ n τ Concrete Confining stress, σ 3 Base Base Sample Cement treated flexbase 30% recycled asphalt 50% recycled asphalt Crushed recycled concrete

47 Erosion Test Results Weight loss (g) % RAP 50% RAP CTB RC Weight loss (g) % RAP 50% RAP CTB RC Shear stress (psi) Weight Loss vs. Shear Stress Levels Loading Repetition Weight Loss vs. Load Repetitions

48 Hamburg Wheel-tracking Test Sample Diameter = 6 in. Layer Profile 1 in. Jointed Concrete 1.85 in. 1 in. Subbase Layer 3/8 in. Artificial Subgrade (Rubber Pad ) 60 ppm Load Frequency 25 C Water temperature 158 lb 5,000 or 10,000 Load Repetition Conc. Conc. Subbase Subgrade (Pad) 1 in. 1 in. ¼~ 3/8 in. Deflection Measurement by 11 Spots along Wheel Load 48

49 Hamburg Wheel-tracking Test 49

50 Matrix Erosion Model Fitting to HWTD Test Results 6.0 Erosion at Joint Loaction 6.0 Erosion at Joint Loaction Erosion Depth (mm) Number of Load Flex-0 Flex-2 Flex-4 Flex-6 Erosion Depth (mm) Number of Load RC-0 RC-2 RC-4 RC-6 Erosion Depth (mm) Erosion at Joint Loaction Number of Load RAP-0 RAP-2 RAP-4 RAP-6 Erosion rate (mm/million) % cement Erosion Rate at Joint Location Flex RC RAP 50

51 Hamburg Wheel-tracking Test Result Erosion Rate (mm/million) Flex RC RAP Cement Content (%) 51

52 Subbase Erosion Prediction Model Erosion Ratio Partial bond Unbond Interfacial Bond Deterioration Matrix Erosion Number of ESAL Fatigue Fracture Stage Erosion Stage 52

53 Matrix Erosion Model V Z = SLAB VELOCITY V Z H = INITIAL VOID THICKNESS (t = 0) Z = SLAB DEFLECTION fi = fe 0 N i ρ ν a h = FINAL DIFLECTION (t = ) δ = THICKNESS AT ANY TIME y SLAB t 0 : ORIGINAL POSITION t t : FINAL POSITION Z h δ H x θ L SUBBASE Where, f i = Erosion depth (L) f 0 = Ultimate erosion depth (L) N i = Number of axle loads per load group contributing to erosion ρ = Calibration coefficient based on local performance v = Calibration coefficient represents the number of wheel loads (or time) for layer debonding to occur and erosion to initiate, 0 for lab test a = Inverse of the rate of void development 53

54 Aquiring a and ρ from HWTD Test f f ln(-ln(f i / f 0 )) i = e ρ N i y = x y = x a y = x y = x ln f f i 0 ln ln( Flex-0 Flex-2 Flex-4 Flex Load Repitition, ln(n i ) a ρ = N i f f i 0 ) = a ln ρ a ln N b In figure, -a is the slope, m a ln ρ Therefore, a = m ρ = e b a m is the intercept, b i 54

55 Erosion Prediction Model Calibration Interfacial bond deterioration stage need to be calibrated using field performance data Matrix erosion stage need to be calibrated using lab test data Erosion Ratio Lab Calibration Number of ESAL Field Calibration 55

56 h 1 E 1 h e E e h σ 1 2 E 2 k k σ e

57 Unbonded Layers e 1 2 h = h +n h No separation during bending w (x,y) = w (x,y) = w (x,y) 1 2 e m (x,y) = m (x,y) + m (x,y) e 1 2 D =D +D e 1 2 e e m = 1+ D m 2 e 1 D1 b D σ = 1+ m 2 e 2 1 he D1 E h =E h +E h h 1 E1h 1 + E2h 2 =σ h e Eh 1 1 h E h h =σ σ = σ σ =σ n 2 h E h e e e he 1

58 Bonded Layers E 2 3 h1 E2 h2 he = h 1+ h 2+12 x- h 1+ h1-x+ h 2 E 1 2 E 1 2 E =E e x= σ=σ Eh h 2 2 E h +E h 1 e E2h2 h ( ) 2 h -x h 1 e

59 W Dual L Tandem D o Tridem τ = 0 or f unbonded or bonded Tied or Extended Shoulder

60 Partially Bonded System he u h = ( 1 x) + ( x) h 2 e p e b µ x= e (x = degree of bond; µ = coeff. of friction) σe Notes on h e-p: Transformed Section 2 Eh 12( 1 ν ) k 1) ; h h ; derived from basin area 3) σ A 3 4 c e p e = e-p = e = e e 12 1 k Ec 2 ( ν ) 2 e e e e e 2 he e-p m sp 2)s = a+ b + c ; σ = = σ s P h τ ; σ = ; τ = µ + σ ; σ = load induced pressure e u c e u f e u 2 f v v h e u 12 ( h y ) ( h ) 2 e u p 2 e u 4) and σe p= σ e = σe 1 he p he p h e-u y p σ σ e-p e-u h e-p

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63 x µ = Where Friction Model sp e 2 σ e = ; (for FWD plate loading) 2 s e = a + b e + c e he P = Applied FWD load (F) a, b, c = , , and (for FWD plate loading) h c = Concrete slab thickness (L) = Load induced vertical pressure (FL -2 ) ( 0.7 psi) σ v A e p h e u µ h = = h h σ e b e u e u 2h σe he hc + σ v 12 e u p e 1 B ln(-ln(x)) Where ln(mu) A = e 3 X B 2 B = ( 0.039y ) y µ = Ln(μ)

64 Friction Model Parameters Base Type Thick HMAC (>3.5 in) over flexible base Cement Stabilized (CS) Cement Aggregate Mixture (CAM) Permeable AC Soil Cement (SC) Thin HMAC (<1.5 in) over stabilized-base Base Modulus (ksi) Temperature Dependant Stabilization Content Dependant Stabilization Content Dependant Density and Temperature Dependant Stabilization Content Dependant Temperature Dependant Bonded μ (μ b ) Base Type Friction Factor (X) Lime Rock (LR) Granular Base (GB)

65 Summary 1. Estimate erodibility using lab test data 2. Relate faulting data to # wet days a. Related to presence of interfacial water 3. Estimate condition of the seal a. Visually assess debonding b. Moisture content vs. time c. Related to infiltration rate 4. Need to know the condition of the joint a. Inter-layer friction b. Rate of infiltration 65

66 Thank you Questions? 66