Coating Thickness Measurement on Concrete
Concrete is a widely used construction material, often coated for both aesthetic and protective purposes. However, measuring the thickness of coatings on concrete can be challenging due to its porous nature and varying surface textures. These factors, while aiding in coating adhesion, can cause inconsistencies in measurement accuracy.
Coatings on masonry substrates serve several critical functions, such as improving appearance, providing durability, resisting abrasion, and protecting against environmental factors like moisture, salt, chemicals, and UV light. Common concrete coatings include latex paints, acrylics, epoxies, urethanes, and polyester resins.
To ensure sufficient protection and control coating costs, accurate measurement of coating thickness is essential. Non-destructive testing methods, such as ultrasonic measurement, have become the preferred approach, as they eliminate the need for repairs post-inspection, saving both time and resources for contractors and inspectors.
In this article, we will explore the challenges of measuring coating thickness on concrete, the importance of accurate measurements, and the tools and methods available for effective testing.
PosiTector 200 Ultrasonic Coating Thickness Gauge
DeFelsko’s PosiTector 200 Ultrasonic Coating Thickness Gauge is perfect for non-destructive measurement of coating thickness on concrete. This eliminates the need for repairs after the inspection and saves time for both contractors and inspectors.
PosiTector 200C
The PosiTector 200C is ideal for measuring coatings on concrete, with a range from 50 to 3,800 µm (2 to 150 mils). It requires minimal calibration adjustment for most applications, making it a reliable tool for measuring coating thickness on a wide range of concrete surfaces. Figure 1 shows a cross-sectional view of a representative 125 to 375 µm (5 to 15 mil) coating on large aggregate concrete, which is well-suited for the PosiTector 200C.
Figure 1. Coating on rough, large aggregate concrete
PosiTector 200B
The PosiTector 200B Ultrasonic Coating Thickness Gauge measures coatings from 13 to 1,000 µm (0.5 to 40 mils). Although not specifically designed for concrete, it can still provide accurate results on hard, thin coatings over smooth surfaces after a simple calibration. Figure 2 represents an application where the PosiTector 200 B may be preferred.
Figure 2. Thin coating on smooth, cement surface
Measuring Coating Thickness on Rough or Uneven Surfaces
When measuring coating thickness on smooth but uneven, or rough and porous concrete surfaces, it is expected that the measurement values will vary. Under magnification, areas where the coating has flowed into pores or crevices may appear as outliers during measurements.
Figure 3. Thick, soft coating on concrete
For example, as shown in Figure 3, a bump in the substrate at point "A" results in a significantly different thickness compared to the nearby point "B." It is important for the user to compare the measurement results with the specification or expected coating thickness. Some results may need to be excluded from the calculation.
Figure 4: Coating on rough, lightweight concrete
For surfaces like the one shown in Figure 4, which has both a rough substrate and a rough coating, it may be necessary to take multiple measurements in small areas, calculate the average readings, and compare them against the coating thickness specification. Destructive testing on the sample in Figure 4 revealed a 1 to 3 mm (40 to 115 mil) variation within a ¼” diameter area.
How to Measure Coatings on Concrete with the PosiTector 200
Ultrasonic measurement works by sending ultrasonic vibrations into the coating using a probe (transducer) with the help of a couplant applied to the surface. Every PosiTector 200 comes with a 4 oz bottle of water-based glycol gel. Alternatively, a drop of water can be used as a couplant on smooth, horizontal surfaces.
Once the couplant is applied to the surface of the coated area, place the probe flat on the surface. Pressing down on the probe will initiate a measurement. When you hear a double beep, lift the probe to hold the last measurement on the LCD screen. A second reading can be taken at the same spot by continuing to press the probe down on the surface. Once finished, wipe the probe and surface clean with a tissue or soft cloth.
Using the PosiTector 200's Graphic Mode
The PosiTector 200 (Advanced models only) can display a graphical representation of the ultrasonic pulse as it passes through the coating system. This feature allows the user to better understand what the gauge "sees" beneath the surface of the coating.
The Best Ultrasonic Coating Thickness Gauge for Concrete and Masonry Substrates
DeFelsko’s PosiTector 200 ultrasonic coating thickness gauge is ideal for measuring paint thickness on various non-metal substrates. Two models are well-suited for masonry coatings:
- PosiTector 200 C1: The economical and most common solution for measuring total coating system thickness.
- PosiTector 200 C3: Capable of measuring both total coating thickness and up to three individual layer thicknesses in a multi-layer system. It also features a graphic readout for detailed analysis of the coating system.
Each PosiTector 200 comes complete with the following:
- PosiTector gauge body
- 200 C probe
- Couplant (ultrasonic gel)
- Plastic shims or block
- Protective rubber holster
- Wrist strap
- 3 AAA alkaline batteries
- Instructions
- Protective lens shield
- Convenient carrying case
- Long Form Certificate of Calibration traceable to NIST or PTB
- USB cable
- PosiSoft software
- Two-year warranty
DeFelsko Distributor in Singapore
LFC PTE LTD is the authorized distributor of DeFelsko products in Singapore. Our expert team can assist you in selecting the appropriate replica tape solutions for your surface profile measurement.
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