Evaluation of NDTE Technologies for Airport Pavement Maintenance and Acceptance Activities

Transcription

1 Evaluation of NDTE Technologies for Airport Pavement Maintenance and Acceptance Activities I. L. Al-Qadi, J. S. Popovics S. Alzate, S. Lahouar, Z. Leng, and J. Baek

2 Outline Project scope and objectives Current work: (i) improved layer thickness estimation (ii) development of field testing protocols for surface wave methods (SASW and MASW) (iii) Quantify thickness accuracy of GPR, investigate low frequency antenna or study the feasibility of HMA density prediction Discussion of future work directions

3 Objectives To determine the effectiveness and practicality of new and existing NDTE technologies for maintenance, evaluation, quality control and acceptance of airport pavements To evaluate and recommend appropriate NDTE technologies to the FAA based on field evaluation results

4 Overall Scope of Work Year 2 Year 1 Identify current NDTE needs for airport pavements and facilities Review and summarize existing and new NDTE technologies New research State-of-the-art report Identify promising NDTE technology (technical and practical suitability) Year 3 Field testing and analysis of promising NDTE technology Final report

5 Mechanical Wave Methods: e.g. PSPA Ultrasonic Body Waves (UBV Time Response), Ultrasonic Surface Waves (USW One sided Velocity-Stiffness) and Impact-Echo (Thickness). 1 IMPACTOR 2 RECEIVERS LUNCH BOX WITH A ACQUISITION SYSTEM.

6 Surface Wave Modified Impact Echo (For Layer Thickness Estimation) d Traditional IE: f = βv P /(2 d) β = 0.96 FFT f Surface wave modified IE: f = βv R /(2 d) β = 1.66 to 1.83* * Depending on concrete type

7 Surface Wave Velocity Measurement Surface wave velocity measurements are much more consistent and accurate than 1-sided P- wave measurements in concrete P-wave arrival: first leading edge Surface wave arrival: zero crossing after first sharp peak

8 Testing Trial At Atrel Full scale concrete slabs atop a variety of bases were tested. Both mature and earlyage concrete were considered. Traditional impact echo (IE), P-wave modified IE (MIE) and surface wave modified IE (SWA) methods were applied Afterwards cores were drawn from the tested locations, and slab depth verified directly.

9 THICKNESS RESULTS (early age) ERROR (mm) DAY SLAB 1 SLAB 2 SLAB 3 SLAB 4 IE MIE SWA IE MIE SWA IE MIE SWA IE MIE SWA ACTUAL THICKNESS

10 Development of Field Testing Protocols for Surface Wave Methods 0.04 Surface wave modified impact-echo Amplitude Near sensor Far sensor Time (s) Impact-echo mode SASW Phase velocity (m/s) MASW Δt Δt Frequency (khz)

11 Other Methods: Digital Imaging Technology Automated digital imaging system consists of image acquisition and distress image processing After Huang et al. 2006

12 Video Crack Survey A high resolution digital video camera: 4m x 3m Highway speed up to 30MPH (limited by our device) 3m 4m Starting Low Medium High L L Visual survey L L L (unsealed) L L L m Video survey m IL130 northbound (STA to STA )

13 Video Crack Survey Crack detection 165 out of 195 (84.2%) transverse cracks Shift in severity distribution 60 Control Visual survey 60 Control Video survey # of cracks IL4.95mm # of cracks IL4.95mm 0 0 S SL L LM M MH H S SL L LM M MH H Crack severity Crack severity

14 Other Methods: Laser Profiling Pavement surface information can be determined by the movement of reflected beam spot on the detector It provides rapid, continuous, and highly accurate measurement of profile, microtexture, macrotexture, and grooving condition (see poster) Laser Beam Detector Lens Pavement Surface

15 GPR: How Does It Work? Transceiver Control Unit Antenna DMI Layer 1 Layer 2

16 GPR Antennae Ground-coupled: the antenna is in contact with the ground surface Air-coupled: the antenna is 0.5m above surface Monostatic: one antenna used as Tx and Rx Bistatic: one antenna is used for Tx and another one for Rx

17 Typical GPR Response (scan) Amplitude A 0 HMA Base Subgrade t 1 A 1 t 2 A 2 HMA Base Subgrade Time (ns)

18 Typical Raw GPR Data HMA Base Subgrade HMA Base Subgrade

19 Dielectric Constant Estimation i r i i ct d, 2 ε = ,, = = = p n n i p i i p p n n i p i i p n- r n r A A A A γ A A A A A A γ A A ε ε Thickness of i th layer: HMA Base Subgrade t 1, d 1 t 2, d 2 A 0 A 1 A 2 ε r,1 ε r,2 ε r,3 2 1, + = o p o p r A A A A ε 1,, 1,, = i r i r i r i r i ε ε ε ε γ Layer 1: where: Layer n:

20 CMP Technique Common midpoint (CMP) technique (or commondepth point, CDP) is used as follows: HMA ε r1 T t 2 x T/R t 1 P ν : EM velocity in the layer R vt1 = 2h h ε r = c 2 vt v ( 2 2 t t ) 2 2 = x 2 = 2 2 x 2 h + c εr 1 = t 2 2 x 2 t 2 1

21 Modified Common Midpoint Technique: Snell s law of refraction: air ε r0 =1 HMA ε r1 T x 0 x θ 1 i T/R t 1 θ t t 2 P R h 0 h 1 ε sin θ = ε 0 1 r Using the figure: v = i 2h tan + x = x 0 θ i tan θ t = t 2 2 x x 1 = 2h t 2 1 r x vt 1 sin 0 1 θ t (1) (2) (3) (4)

22 Dielectric Constant Estimation Algorithm: 1. Measure the reflection times t 1 and t 2 2. Calculate the transmission angle θ t using: 3. Find the angle θ i by solving numerically sin θ t 2 2 2h 0 tanθi + c t2 t1 = x0 sin θi 4. Solve for ε r1 using: ε r 1 sin θ = sin θ 5. HMA thickness found using t 1 and ε r1 h = ct ε r1 i t 2 tan θ t = 2 2 t t t Modified CMP Setup

23 GPR Data Analysis Raw GPR Data Layer Interface/ Distress Separation Preprocessing Layer Interface Detection Dielectric Properties Estimation Layer Thicknesses

24 GPR Depth Resolution Amplitude Surface Reflection WS/BM-25.0 Reflection WS BM-25.0 OGDL Base BM-25.0/OGDL Reflection Time (ns) Amplitude OGDL/Base Reflection Base/Subgrade Reflection Surface Reflection Reflection Overlap Time (ns) Synthesized Signal HMA/Base Reflection Base/Subgrade Reflection Measured Signal

25 Detected Layer Interfaces Layer 1 Layer 2 Raw GPR Data Layer 3 Layer 3 Layer 2 Detected Time Delays Layer 1

26 Examples at ATREL Full Depth Asphalt Pavement Concrete Pavement Composite Pavement

27 Full Depth Pavement Layout Section A Section B Section D Section F SMA 2in DG Surface 2in Poly. Binder 2.25in Poly. Binder 2.25in Poly. Binder 2.25in Poly. Binder 2.25in DG Surface 2in Standard Binder 3.5in Standard Binder 3.5in Poly. Binder 2.25in Standard Binder 2.5in Standard Binder 2.5in Poly. Binder 2.25in DG Surface 2in Rich Bottom Binder 4in Standard Binder 4in Standard Binder 3.5in Standard Binder 4in Lime Modified Subgrade 12in Lime Modified Subgrade 12in Lime Modified Subgrade 12in Lime Modified Subgrade 12in Thermocouple Strain gauge

28 Sect. Full Depth Pavement Ground-coupled Antennae D Length (m) 20 Machine support pad Depth (mm) B A 1.5 GHZ HMA Surface HMA Bottom 900 MHz HMA Surface HMA Bottom

29 Sect. A B Full Depth Pavement Air-coupled Antennae Length (m) Machine 20 Machine 20 support support Depth (mm) pad 250 pad 150 D F HMA Surface 2 GHZ HMA Bottom A B D F

30 Full Depth Pavement Thickness Measured Thickness by GPR Designed Thickness HMA Thickness (mm) Section A Section B Section D Section F

31 Concrete Pavement Ground-coupled Antennae Sect. A B C D E Length (m) PCC Thickness (in) GHZ Better Resolution PCC Bottom NOT Clear PCC Surface 900 MHZ Better Penetration Depth Clear

32 Composite Pavement East Section 1 Section 2 Section 3 Section 4 West Joint location Dowel bars 500ft Various HMA 6in PCC 12in granular subbase

33 Composite Pavement Air-coupled Antennae Sect Length (ft) Overlay (in) 4.0, GHz 4in HMA overlay 6in PCC HMA surface HMA bottom 2.0 GHz

34 Overlay Thickness 6.0 Overlay thickness (in) Cores Section 1 Section 2 Section 3 Section Distance (ft)

35 Joint Characterization 1.5GHz ground-coupled antenna (1scan/1in) HMA surface Instrumentations HMA bottom PCC bottom Saw-cut joint 12.5ft Dowel joints Dowel bar (18in.) Dowel bars

36 GPR Survey (Reflective Cracking) Using a ground-coupled antenna ISAC identification/ accurate width measurement (0.9m) 0.9m New overlay ISAC Old overlay Multiple strong reflections from a dowel bar Weak reflection from PCC and HMA overlay

37 Dielectric Constant Relation to Volumetric Properties HMA Composed of the following: Air-voids Aggregate Asphalt binder Moisture

38 Dielectric Constant Relation to Volumetric Properties Complex Refractive Index Model mixture theory: ε = V ε + V ε + V ε + V HMA air air agg V air : fractional volume of air, ε air = 1 V agg : fractional volume of aggregate, ε agg = 3-9 V b : fractional volume of asphalt, ε b = 3-4 V w : fractional volume of water, ε w = 81 agg b b w ε w ε = V ε + V ε + V HMA air air agg agg b ε b

39 Dielectric Constant Relation to Density Assume ε agg, ε b, and ε w constants for a given site: ε = f V, V, V, V ) HMA ( air agg b w ε HMA = f ( Air Voids,GS, AC, MC) ε HMA D HMA : Density of HMA = f ( DHMA )

40 Future Work on GPR

41 Feasibility of Dielectric Estimation Using A New Modified CMP Technique Dielectric measurement using bistatic air-coupled antennae: x 02 T R x 01 T R x 2 h 2 x 1 h 1 θ i2 θ i1 θ t1 t 1 θ t 2 t 2 d 1

42 CMP Technique with two Air-Coupled Antennas: Example t 0 t 1 t

43 Experimental Procedure for HMA Density Prediction Test Various Pavements Having Different HMA JMF: Air Voids Aggregate AC Estimate ε HMA from GPR measurements Measure Density from cores Correlate Density to ε HMA

44 Investigate the Feasibility of the New 500MHz Antenna for Deeper Penetration

45 Surface Image/ GPR Visual survey (2006) m m Video survey (2006) GPR survey (2006) 0 30m PCC patch PCC patch HMA patch HMA patch Visual survey (2003) before overlay PCC patch PCC patch PCC patch HMA patch m m

46 Summary of Future Work Implement surface wave method procedures (surface wave modified IE, SASW and MASW) in self-developed testing package Modify procedures for improved estimation of top-layer moduli Determine the accuracy of GPR predicted pavement layer thickness Investigate the feasibility of GPR application for HMA density prediction Other NDTE focus directions?