Mark Lindemann NDOR Geotechnical Engineer · Non-Nuclear Methods for HMA and Soil ... compaction of...
Transcript of Mark Lindemann NDOR Geotechnical Engineer · Non-Nuclear Methods for HMA and Soil ... compaction of...
Mark Lindemann NDOR Geotechnical Engineer
Background on previous field testing
Research – Non-nuclear field testing
Cost Savings of Going Non-Nuclear
Fundamentals of LWD
LWD Correlation
Field Implementation
Volumemeasure Test Method
Nuclear Density & Moisture Gauge (NDG)
Why fix what isn’t broken? Nuclear Gauges –
Regulations Licensing Storage and transport Training Costs add up Have 84 gauges needing replacement Possible Fines
Approximately $250,000/ year
Falls in Line with Every Day Counts Initiative
Innovative Technologies
University of Nebraska – Dr. Yong K. Cho Non-Nuclear Methods for HMA and Soil
Density Historical research Field Research: PQI (HMA) Compare to Nuclear Density Gauge Bulk Specific Gravity of Asphalt Cores
(AASHTO T166)
PQI (Pavement Quality Indicator)
Measures the change in electromagnetic field as current is sent through the material.
Calibrated with average of 5 core densities and average of 5 PQI densities.
Results: Both Nuclear and PQI provided results very
close to asphalt core values Nuclear gauge closer to asphalt core values
(+1.07 lb/ft3) PQI gauge values -1.89 lb/ft3 to asphalt core
values.
Nuclear Results: Average difference of 1.71 pcf compared to
standard for density. Average difference of 0.22% for moisture.
EDG Results: Average difference of 9.86 pcf compared to
standard for density Average difference of 1.66% for moisture.
M+DI (Moisture Density Indicator) Uses Time Domain Reflectometry to send
electromagnetic pulse through soil Requires correlation of several points from
Proctor tests Takes 15 to 20 minutes per test. Had trouble with device at beginning Removed from testing
Light-Weight Deflectometer (LWD)
Measures soil surface deflection
Provides Modulus, Deflection, Velocity
No moisture content results
LWD Results: Compared Pass/Fail results based on 95%
compaction of devices to standard (lab) Nuclear Gauge: 72% correlation LWD: 54% correlation Overall – best correlation of new devices Suggest better way to determine target value
(not density)
Widely Accepted QA/QC Method Indirect Parameter of Strength Small Variations – Result Large Variation in
Stiffness Compaction Lab vs. Compaction Field Costs/Regulations of Nuclear Results are Material dependent based on a
small sample compared to that in the field.
LWD Initial Costs: $8,257 Thermal Paper: $20/ Year Maintenance/ Calibration: $300
Net Present Worth of Costs (NPW)= Initial Costs + Yearly Costs (P/A, 15 yrs, 10%)
NPW of Nuclear Gauge= $10,873 + $2,155(P/A, 15yrs, 10%) = $27,264
NPW of LWD = $8,257 + $320(P/A, 15yrs, 10%) = $10,690
Dynamic non-destructive testing tool Measure layer/surface modulus (stiffness)
How it works Transient Load on Loading Plate Accelerometer within the device measures the
deflection of the ground due to the load Soil Modulus back-calculated based on deflection
and assumed Poisson’s ratio. Results taken as an immediate indication of the
materials strength (ability to support roadway) http://www.youtube.com/watch?v=6WGgosXlHss
Modulus Calculation:
Eo = f x (1-υ2) x σo x a / do Eo = Modulus f = Plate Rigidity factor (2) υ = Poisson’s Ratio (0.35) σo= Maximum contact stress a = Plate Radius do= Maximum deflection
Zorn Keros Dynatest Prima Loadman ELE
ASTM E 2835-11 for LWD without Load Cell ASTM E2583-07 for LWD with Load Cell Plate Size Drop Height Falling Weight Type and location of Sensors Significant variability between manufacturers Seating Load (3 Drops) Testing Load (3 Additional Drops)
MnDot Research – Beginning 1997 NCHRP – 382 & 456 Colorado DOT Vermont DOT US Army Corps of Engineers UK – Fleming, Frost, and Lambert Virginia Transportation Research Council Kansas DOT Louisiana Transportation Research Center
Several LWD models with variety of differences
Steel spring buffer and accelerometer in plate Critical to use same device with same plate
diameter, drop height, and falling mass Hand-held recording instrument
SD card memory Graphical and numerical results Printout of results GPS capability
Normal Result For unbound materials
Rebound Common for Bound materials If rebound is >20% Of Peak Re-seat and retest
Variable May be poor Compaction
Recipe for Good Compaction Know Soil Type Moisture Control Limit Lift Thickness Compaction Testing Stiffness/ Strength of materials
Target = Minimum Modulus or Maximum Deflection Based on Material Type Moisture Content
May Require A Test Strip
Side by Side LWD Tests & Nuke Tests
Bag Samples for Lab
Determine NGI & Moisture
Compare Deflection vs % Compaction for each Soil Type (NGI)
PI= 20 LL = 45 % Ret.= 50
Chart 1 = 3.5
Chart 2 = 3.5
NGI = 7
Modulus in Laboratory is complicated, expensive, and time consuming. Test methods have continually changed over the
years NDOR – Resilient Modulus Research based on
Nebraska Soil Types (NGI) Correlate well with FWD Do not correlate with LWD
Resilient Modulus Correlation to NGI
Deflection is easy to understand
Two Specifications
1. Provide Target Value for each NGI
2. Perform Test Strip / Calibration Area
Maximum Deflection based on Nebraska Group Index (PI, LL, #200)
First – Make sure moisture is within Spec.
Refer to Chart for Deflection Requirements
1.2
Target Value = Max Deflection 1.2 mm For Equivalent to 95% Compaction
Nebraska Group Index
Concrete Upper 3' Concrete Below 3' Asphalt Upper 3' Asphalt Below 3'
Max Deflection (mm)
Max Deflection (mm)
Max Deflection (mm)
Max Deflection (mm)
-2 0.5 0.5 0.5 0.5
-1 0.5 0.5 0.5 0.5
0 0.5 0.5 0.5 0.5
1 1 1.5 0.5 1.5
2 1 1.5 0.5 1.5
3 2 3 1 3
4 2 3 1 3
5 2 3 1 3
6 2 3 1 3
7 1.5 3 0.75 3
8 1.5 3 0.75 3
9 1.5 3 0.75 3
10 2 4 1 4
11 2 4 1 4
12 2 4 1 4
13 2 4 1 4
14 3 5 2 5
15 3 5 2 5
16 3 5 2 5
17 4 6 3 6
18 4 6 3 6
19 5 8 4 8
20 5 8 4 8
21 5 8 4 8
22 6 9 5 9
23 6 9 5 9
24 6 9 5 9
NGI = 7 Under Concrete Top 3’
NGI = 7 Under Asphalt Below 3’
Deflection Data for Soil Type not available
Perform a Test Strip/ Calibration Area First Test Moisture Size of Test Strip – 200’ Length x Width of
Embankment, Two-8” Lifts 3 LWD Tests/ Roller Pass – Random Locations
Continue LWD/ Roller Pass Testing Target Deflection Value Obtained when: Moisture Content Acceptable Range (based on PL or
Standard Proctor) Average of Deflection Tests for three consecutive
passes does not change significantly with each additional pass (when change is < 10%)
Obtain Rep. Sample from test strip for further lab testing
Passing Test = < 1.1 x Target Value
Re-Evaluate when:
More than 20% of test measurements are less than 0.8 x TV
Failing results consistently occur even though adequate compaction observed.
Perform new Test Strip
Finalize and Implement Specifications
Eliminate all Nuclear Gauges
Build NGI Chart
Find a reliable field moisture testing device
QUESTIONS?