Installation and Calibration of Moisture Probes Ben Worel Len Palek Minnesota Department of Transportation (MnROAD) More details contact Len for the full presentation & written documentation

MnROAD Moisture Probes (Experience With) ModelDescriptionDates Installed Gauges Installed ECDecagon-TE and 5TE2006, 2007, HD Heat Dissipation Sensor - Campbell Scientific CS MHConcrete Moisture MHConcrete Moisture - Sensirion SHT752010, MPWescor PST SF Psychrometer1997, MRELE EI Moisture Resistance Gauge1997, REWater Content Relectometer CS , 2006, TDFabricated or CS605 or CS610 or CS , 1999, 2000, 2004, 2007, WMIrrometer Watermark 200-X 1993, 1999, 2005, 2008,

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

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

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)

– 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

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)

Moisture Probe Calibration Functions

Sensor MnROAD Material Calibration Equation TEGeneric (2006)VWC= RAW SandVWC= RAW ClayVWC = RAW Select GranularVWC = RAW Class-3VWC = RAW Class-4VWC = RAW Class-5VWC = RAW Class-6VWC = RAW Class-7 (Reclaimed) 5TEGeneric (2008)VWC = RAW SandVWC = RAW ClayVWC = RAW Select GranularVWC = RAW Class-3VWC = RAW Class-4VWC = RAW Class-5VWC = RAW Class-6VWC = RAW Class-7 (Reclaimed HMA)VWC = TBD Next sensor types - Moisture Block (851) and CS616 (58) calibrations

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

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)

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

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)