Field Rutting Performance of Various Base/Subbase Materials under Two Types of Loading

Transcription

1 Field Rutting Performance of Various Base/Subbase Materials under Two Types of Loading Qiming Chen, Ph.D., P.E. (presenter) Murad Abu-Farsakh, Ph.D., P.E. Louisiana Transportation Research Center Apr. 28, 2010

2 Research Objective Investigate the performance of different base/subbase materials Identify the difference in pavement response to cyclic plate and rolling wheel loads

3 Research Approach Cyclic Plate Load Tests Rolling Wheel Load Tests

4 Testing Facilities Cyclic Plate Load Testing Facility

5 Load (kip) Cyclic Plate Load Tests at ALF Loading Shape Input pulse Measured Time (Sec)

6 Testing Facilities Rolling Wheel Load Testing Facility

7 Rolling Wheel Load Tests at ALF Loading X ZE Michelin dual tires 9,750 lb starting load; 12,050 lb after175,000 cycles (241,039 ESALs); 14,350 lb after 225,000 cycles (401,714 ESALs); 16,650 lb after 325,000 cycles (1,048,019 ESALs). Lateral wander normally distributed over a width of 30 in (15 in at each side of the pavement centerline) ESALS=N (Load/9000 lb) 4

8 Pavement Test Sections Pavement Sections Section 7 Section 6 13 ft (4 m) 30 ft (9 m) Section 1 Section 2 Section 5 13 ft (4 m) Section 3 Section 4 13 ft (4 m) ft (33 m) ft (33 m) HMA Base 8.5" Subbase Subgrade 2" 12" Cyclic plate load testing location Rolling wheel load testing location Section Base Subbase 1 BCS+LTS Raw BCS 2 BCS/Flyash +LTS Class C flyash (15% by volume) treated BCS 3 BCS/Slag + LTS 120 grade GGBFS (10% by volume) treated BCS 4 LS+LTS Crushed limestone Lime (10% by volume) treated soil 5 LS + CTS Crushed limestone Cement (8% by 6 100%RAP/FA+CTS FA treated 100% RAP volume) treated soil 7 50%RAP50%SC/FA+CTS FA treated 50%RAP and 50% soil cement blend

9 Testing Time Testing Time Section Rolling wheel load Cyclic plate load Test Start Test End Test Start Test End 1 BCS+LTS N/A N/A 11/ / BCS/Flyash +LTS 10/ / / / BCS/Slag + LTS 10/ / / / LS+LTS 01/ / / / LS + CTS 01/ / / / %RAP/FA+CTS 01/ / / / %RAP50%SC/FA+CTS 10/ / / /2009

10 Material Properties AC Layer (from Lab Tests) 19.0 mm superpave mixture Asphalt cement: PG76-22 Theoretical maximum specific gravity: Optimum asphalt content: 4.4% Resilient Modulus: 450 ksi

11 Material Properties Base Layer Material (from Lab Tests) BCS UCS (psi) 54.5 BCS /Flyash 60.5 (65.8) BCS /Slag (725.3) Crushed Limestone 100%RAP/FA 50%RAP50 %SC/FA N/A N/A N/A M r (psi) 80,061 89, ,196 40,030 30,023 32,294 e p (%) Optimum moisture content Maximum dry unit weight (lb/ft 3 ) USCS N/A N/A N/A GM GP GM AASHTO N/A N/A N/A A-1-a A-1-a A-1-a

12 Material Properties Subgrade and Subase Layer Materials (from Lab Tests) Subgrade Lime treated soil subbase Cement treated soil subbase UCS (psi) N/A N/A M r (psi) 5,656 20,595 62,366 e p (%) Optimum moisture content Maximum dry unit weight (lb/ft 3 ) 18.5 N/A N/A N/A N/A USCS CL N/A N/A AASHTO A-6 N/A N/A

13 In-Situ Testing of Mechanical Properties Equipment Dynaflect Dynatest 8002 model Falling Weight Deflectometer Dynamic Cone Penetrometer

14 In-Place Properties Test Results Section BCS + LTS BCS /Flyash + LTS BCS /Slag + LTS LS + LTS LS + CTS 100% RAP/FA+ CTS 50%RAP50 %SC/FA + CTS WL PL WL PL WL PL WL PL WL PL WL PL WL PL Dynamic Cone Penetrometer (DCP, mm/blow) Base N/A Subbase Subgrade DYNAFLECT SN N/A M r (ksi) N/A Falling Weight Deflectometer (FWD) D 0, mills N/A D 6, mills N/A D 7, mills N/A D 8, mills N/A

15 Test Results Cyclic Plate Load Test (Repeatability Check) ESALS=N (Load/9000 lb) 4

16 Permenant deformation (mm) Test Results Rolling Wheel Load Tests Section 2(BCS/flyash+LTS) Section 3(BCS/slag+LTS) Section 4(LS+LTS) Section 5(LS+CTS) Section 6(100%RAP/FA+CTS) Section 7(50%RAP50%SC/FA+CTS) ,000,000 2,000,000 3,000,000 4,000,000 5,000,000 ESALs

17 Cyclic Plate Load Tests Test Results

18 Test Results Equivalent Modulus of Elasticity E eq E 1 3 base h h base base E h h 1 3 subbase subbase subbase 3 (adopted in the reference manual of the NHI training course: Introduction to Mechanistic-Empirical Pavement Design) E eq E 1 3 base h base p( base) h i i base p( base) E h 1 3 subbase h i i subbase p( subbase) subbase p( subbase) 3 (Proposed) i p : postion factor a ratio of the Boussinesq stress influence factor at mid-point of each layer (I i ) to the sum of the influence factor of each layer (SI i ). Section BCS+ LTS BCS /Flyash +LTS BCS /Slag +LTS 100%RAP/F LS+LTS LS+CTS +CTS 50%RAP50 %SC/FA+CTS E eq (ksi) E eq (ksi) E eq (ksi) equivalent modulus of elasticity irrespective of the relative position; 2 equivalent modulus of elasticity for cyclic plate load test; 3 equivalent modulus of elasticity for rolling wheel load test.

19 Permenant deformation (mm) Permenant deformation (mm) Permenant deformation (mm) Test Results Cyclic Plate Load Tests vs. Rolling Wheel Load Tests Cyclic Plate Load Rolling Wheel Load Cyclic Plate Load Rolling Wheel Load 8 6 (BCS/Flyash+LTS) 8 6 BCS/Slag+LTS ,000,000 2,000,000 3,000,000 4,000,000 5,000,000 ESALs ,000,000 2,000,000 3,000,000 4,000,000 5,000,000 ESALs LS+LTS Cyclic Plate Load Rolling Wheel Load 0 0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000 ESALs

20 Permenant deformation (mm) Permenant deformation (mm) Permenant deformation (mm) Test Results Cyclic Plate Load Tests vs. Rolling Wheel Load Tests Cyclic Plate Load Rolling Wheel Load Cyclic Plate Load Rolling Wheel Load LS+CTS %RAP/FA+CTS ,000,000 2,000,000 3,000,000 4,000,000 5,000,000 ESALs 0 0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000 ESALs Cyclic Plate Load Rolling Wheel Load 50%RAP50%SC/FA+CTS ,000,000 2,000,000 3,000,000 4,000,000 5,000,000 ESALs

21 Ratio of rut depth Test Results Section BCS+ LTS BCS /Flyash +LTS BCS /Slag +LTS LS+LTS LS+CTS 100%RAP/F +CTS 50%RAP50 %SC/FA+CTS N/A N/A 3.5

22 Literature Data Literature Data (Brown and Brodrick, 1999)

23 Test Results Analysis Principal Stress Rotation v h v h Extension Compression v Extension v h h Time Time v=h q=v-h q=v-h in-situ stresses p=v+2h in-situ stresses p=v+2h

24 Test Results Analysis Lateral Wander Effect Donovan and Tutumluer (2008) - dramatic degradation of the unbound aggregate layer - more permanent deformation with future load applications - antishakedown effect Cyclic Plate Load: concentrated load consolidate and shakedown unbound/bound base layer to a steady state Rolling Wheel Load: lateral wander likely decrease the stability of unbound and weak bound granular base materials by inducing constant particle movement and rearrangement.

25 Test Results Analysis Lateral Wander Effect Shear Flow LS+LTS 50%RAP50%SC/FA+CTS

26 Aging Effect Test Results Analysis M CBR r MPa 292 / DCPI CBR 0.64 M r psi 96658/ DCPI Lime Treated Soil Cement Treated Soil

27 Conclusions The equivalent modulus of elasticity used to evaluate the performance of multi-layer systems needs account for the relative position of individual layers; Rolling wheel load is a much more damaging loading condition than the cyclic plate load: principal stress rotation, friction induced tangential forces, and lateral wander. 120 grade ground granulated blast furnace slag (GGBFS) stabilized BCS is a good candidate as an alternative to the conventional stone base; The cyclic plate load test can be used as a good performance indicator for evaluation of pavement structure; Age effect partially contributes to the differences between rolling wheel load tests and cyclic plate load tests that were performed at least 10 months after.

28 Questions