How to non-destructively test the water content of concrete slabs?
There are various methods available forConcrete Moisture Test. two common methodsNon-destructive electronic impedance meterandIn-Situ Relative Humidity (RH) ProbesThis article will discuss the existing electronic impedance meter;How they work, and how Defelsko worksPosiTest CMM Concrete HygrometerA simple, durable and accurate way to measure the moisture content of concrete slabsASTM F2659 standard.
What is a Concrete Hygrometer? How do they work?
Nondestructive Concrete Hygrometer(or Electronic Impedance Meter) Measures the moisture content of concrete using the principle of concrete electrical impedance, which is related to the moisture content of concrete.An alternating electric field flows from the device's transmit sensor pins across the substrate and is captured by the receive electrodes.Impedance is measured, as the moisture content increases, the impedance reading increases.Using a concrete standard with known moisture levels, the meter can be calibrated to read concrete moisture units.
The Concrete Moisture Tester provides instant results without the need to drill into the concrete (i.e. with an in situ RH probe).However, impedance can also be affected by changes in the composition of the concrete or by reinforcement close to the surface.These meters measure moisture near the surface of the concrete, ¾" of the top of the concrete slab.A non-destructive concrete Moisture Meter is a convenient comparative instrument for identifying areas of relatively high humidity within a slab.They work well with in situ RH probes such asPosiTector coordinate measuring machine.
How to Measure Concrete Moisture Content with PosiTest CMM
thisposition coordinate measuring machineA fast, non-destructive impedance meter is an excellent choice for inspectors to quickly assess the moisture condition of concrete slabs.Featuring a simple four-button interface, innovative measurement modes, and 3 measurement scales, taking a moisture content measurement is easy.
• Continuous measurement modeis the default mode and continuously updates the display with the current measured value.
• Hold max modeDisplays and holds maximum reading until memory button is pressed to save, or power button is pressed to abort.
• Innovativekeep max and save modeAutomatically saves readings to memory without the need for any buttons*
*existkeep max and save modeIdeal for use withTelescopic expander accessories, which attaches to a sturdy tripod built into the meter.Quickly measure and record the moisture content of large areas of concrete without bending or kneeling.
4Verify Operation: Includes a check standard to verify the operation and accuracy of the meter.Simply place the check standard on a flat, non-conductive surface and press down on the gauge firmly until the pins are compressed.If the displayed reading is within the range written on the check standard, the instrument is working properly.
5Make sure that the measured surface is wellposition coordinate measuring machineFree from dirt, dust and other contaminants.thisPosiTest CMM Concrete HygrometerThe pin needs to be in direct contact with the concrete surface to get an accurate reading.
6Place the hygrometer on the concrete surface and press down to fully compress the sensor pin.The sensor needle is designed for precise measurements on smooth, rough or uneven concrete surfaces.The humidity measurement reading will remain displayed until the gauge is lifted from the concrete surface, depending onmeasurement methodpicked out.
How to Test the Moisture Content of Concrete Slabs According to ASTM F2659
The outline and procedures in ASTM F2659 guide the user in performing relative humidity testing with an electrical impedance meter.It defines the appropriate environmental conditions and describes the preparatory tasks to be done before performing the measurements.
This section will outline the general procedures on how to followASTM F2659 standard- "Standard Guide for the Initial Evaluation of the Relative Humidity Conditions of Concrete, Gypsum Cement, and Other Floors and Mortars Using a Nondestructive Electronic Moisture Meter".Standards need to be reviewed prior to measurement to ensure full understanding and compliance.
ASTM F2659 test preparation
1. Before testing the moisture content, the concrete floor is required to be at the working temperature for at least 48 hours. The air space above the concrete slab also needs to be at operating temperature and the relative humidity should be at the level expected under normal use. If these conditions are not feasible, the test shall be conducted at 75°F±10°F (24°C±5°C) and 50±10% relative humidity *
2. The concrete surface of the selected test site shall be free from liquid, dirt, paint, floor, adhesive or other contaminants.
*See PosiTest DPM dew point meter for environmental monitoring.
How to Test Concrete Moisture Using the ASTM F2659 CMM
Before starting, make sureposition coordinate measuring machinepower up and set to desiredmeasurement methodOptimize work.
1. Determine the test location- ASTM F2659 specifies a minimum of 8 tests for the first 1000 feet(100 metres2) at least 5 additional test locations for each additional 1000 feet(100 metres2).
It is recommended that inspectors test locations across the slab to get a better idea of the moisture conditions within.Look for an area with high humidity that is out of direct sunlight or other heat sources.Include the area in the middle of the concrete slab and near each exterior wall.
2. Measurement-
A. According to the ASTM F2659 standard, record the relative humidity, air temperature and dew point above the test location.
Record the concrete surface temperature within 8 in (200 mm) of each test location.PosiTector DPM Dew Point MeterIt is an accurate and reliable instrument that meets this requirement.
usePositron DPMTake surface and ambient air readings according to ASTM F2659
B. At each test location, use a concrete hygrometer to make 3-5 measurements within 1 foot2(929 cm2)area.Report the maximum reading for each location.Use PosiTest CMMkeep maxorHold Max and saveMake this task quick and easy.
Take 3-5 desired readings at each test location using Hold Max or Hold Max and Save modes
Note:Chlorides, carbonates, rebar, and other materials can affect the accuracy of concrete Moisture Meter readings.Note when these or similar materials are used.NDT equipment is better used in conjunction with in situ RH probes such asPosiTector coordinate measuring machineTo ensure the accuracy of concrete slab moisture determination.
*usekeep maxorHold Max and savepattern withTelescopic expander accessoriesMake measuring faster without bending or kneeling.
3. Report-When an exam is complete, use the built-in USB port and included cable to download, view and print readings stored in a professional PDF reportPosiSoft Desktop.
ASTM F2659 requires reporting of the following data:
• Location of the test area on the concrete slab
• Highest moisture reading at each test location
• Relative humidity, ambient air and dew point temperature above each test location
• Additional information related to location, inspector, and other observations should also be recorded.Refer to ASTM F2659 for complete instructions.
Example of a Concrete Moisture Inspection Report CreatedPosiSoft Desktop
if other defalsco instrumentsPosiTector CMM is an in-situ concrete RH probe,PosiTector DPM Dew Point Meter,orPosiTector 200 Concrete Coating Thickness GaugeUsed in the same job, measurement data can easily be compiled into a report.Fully customized reports can also be created to match existing paper forms or layouts.
in conclusion
newPosiTest CMM Concrete HygrometerA simple, durable and accurate way to measure the moisture content of concrete and screeds.With an easy-to-use interface, fast measurement speed, memory and reporting solutions, all backed by DeFelsko's renowned quality, customer service and exceptional two-year warrantyposition coordinate measuring machineExcellent choice for measuring concrete moisture according to ASTM F2659.
