1. Installation and Calibration of Moisture Probes Ben Worel ben.worel@state.mn.us Len Palek leonard.e.palek@state.mn.us Minnesota Department of Transportation (MnROAD) More details contact Len for the full presentation & written documentation

2. MnROAD Moisture Probes (Experience With) ModelDescriptionDates Installed Gauges Installed ECDecagon-TE and 5TE2006, 2007, 2008227 HD Heat Dissipation Sensor - Campbell Scientific CS229200618 MHConcrete Moisture200430 MHConcrete Moisture - Sensirion SHT752010, 2011116 MPWescor PST-55-15-SF Psychrometer1997, 200030 MRELE EI23-7724 Moisture Resistance Gauge1997, 200039 REWater Content Relectometer CS6161999, 2006, 200858 TDFabricated or CS605 or CS610 or CS645 1993, 1999, 2000, 2004, 2007, 2008784 WMIrrometer Watermark 200-X 1993, 1999, 2005, 2008, 2011851

3. Installation of Moisture Probes at MnROAD 1.Bore Hole 2.Separate Materials 3.Install Sensors Flat installation 1” Sieve #4 Material - Lite Compaction 3” Material – Heavy Compaction May add water as needed Check void ratio – cup sampler

4. Installation of Moisture Probes at MnROAD Campbell CR1000 data logger and multiplexer Sensor Protection to Cabinet Cabinet Setup

5. Calibration Experience with Moisture Probes Calibration efforts prior to 2012 – 2006 calibrations for TE (manufacturer’s process) – 2009 generic calibration equations are found not useable – 2010 and 2011 experimented with small scale calibrations 2012 Calibration approach – Procedures developed by Starr and Paltineanu (2002) and refined by Decagon Devices (2010) – MnROAD Experience (Need calibration for each sensor and materials type)

6. – Soil drying containers – Scale or mass balance – Drying oven – Volumetric soil sampler – Calibration containers – Sensors (MnROAD started with Decagon TE and 5TE) – Data collection and storage system Moisture Probe Calibration Lab Equipment

7. Moisture Probe Calibration Procedure Sample Preparation – Air dry material - Sieve material with #4 (2-5mm) sieve Preliminary Calibration Procedure – Recording mass and volumes of calibration containers, volumetric samplers, and sensors with wire – Programming the data logger - Create spreadsheet templates Calibration Procedure 1.Start with air-dry material 2.Fill calibration containers with sensors (Compact in 5 lifts – 20% of Max Density) 3.Weigh containers to determine density 4.Record sensor output (1 hour of 1 minute intervals) 5.Sample volumetric moisture content 6.Record moisture content 7.Repeat procedure for next moisture content (6 Data Points Required)

8. Moisture Probe Calibration Functions

9. Sensor MnROAD Material Calibration Equation TEGeneric (2006)VWC= 0.00109 RAW - 0.629 SandVWC= 0.0009 RAW - 0.4929 ClayVWC = 0.0009 RAW - 0.4693 Select GranularVWC = 0.0011 RAW - 0.6615 Class-3VWC = 0.0009 RAW - 0.5149 Class-4VWC = 0.0008 RAW - 0.4120 Class-5VWC = 0.0007 RAW - 0.3524 Class-6VWC = 0.0011 RAW - 0.6787 Class-7 (Reclaimed) 5TEGeneric (2008)VWC = 0.00109 RAW - 0.629 SandVWC = 0.0004 RAW - 0.0780 ClayVWC = 0.0003 RAW - 0.0021 Select GranularVWC = 0.0005 RAW - 0.0908 Class-3VWC = 0.0004 RAW - 0.0481 Class-4VWC = 0.0004 RAW - 0.0520 Class-5VWC = 0.0003 RAW - 0.0239 Class-6VWC = 0.0006 RAW - 0.1438 Class-7 (Reclaimed HMA)VWC = TBD Next sensor types - Moisture Block (851) and CS616 (58) calibrations

10. With (top base) - ~.50 VMC With (bottom base) - ~.35 VMC Without (top base) - ~1.30 VMC Without (bottom base) - ~.80 VMC With Calibration With Generic Calibration Moisture Probe Generic and Calibration Functions Applied to MnROAD Data

11. Moisture Gauge - Installation Discussion Vertical (with forks) or Horizontal (without fork) Collect Raw data only (no factors) – apply later Use sieved material around sensor Sensor Lead Length effect (50’ vs 500’) Frequency of measurements (MnROAD 15 minutes) Excitation Voltage (MnROAD 12 volts) Data Collection Temperature Ranges (Cabinet Temps)

12. Role of material density and moisture measurements? – Differences – maybe soil sampler field? Does a generic calibration function work for other types of non-capacitance sensors used in pavement research? Does every sensor installed need a calibration? Discussion on the process (manufacture vs modified) – Manufacture use same volume of soil compacted in a calibration container – Modified working to get maximum density (minimize voids) Moisture Gauge – Calibration Discussion

13. Moisture Probe – Data Use Discussion Can moisture sensors detect bound and unbound water in fine-grained clay materials? Observe variation in the data (6 hour running average used) – why? Observed manufacture calibration factored data above 100% and negative data (why we did a calibration) Flat vs vertical (eliminate potential of condensation) Installation of sensor at a material interface Do the readings vary with temperature extreams Sensor Recommendations Capacitance sensors seem the best Moisture blocks have been improved (not fully tested)