There are many instances where temperature measurements are required on a concrete construction jobsite. In most cases, the thermometer to be used is not specified. The one exception is the temperature test for fresh concrete where the thermometer must measure the temperature of the concrete to ± 1°F accuracy and must be inserted 3 inches into the concrete to take its internal temperature.
But there are many instances where measuring temperature with an infrared (IR) thermometer is appropriate and even recommended. Some of these are:
- Steel inserts, metal decks, reinforcement, and forms are to be less than 120°F.
- Monitoring the temperature under curing blankets to make sure it meets the curing requirements (especially at the edges of the blanket where there could be cold spots).
- For adhesive anchor installation, the concrete must be within a required temperature range.
- Concrete placed on the ground is not to be more than 30°F warmer than the ground.
- Water used for curing is not to be more than 20°F warmer than the concrete surface.
The list goes on. Once you start using an IR thermometer, you will find many other uses. These can be the trivial (making sure your coffee is warm enough) to complex evaluations, such as determining where there might be a hot spot in a motor.
We have become conditioned to IR thermometers during Covid. You’ve probably had your temperature checked with an IR thermometer before being admitted to an indoor location. Hopefully, the IR thermometer used had been calibrated and was designed for human use. Not all are for suitable for determining a person’s body temperature.
Recently I was on the internet looking for IR thermometers and found that my favorite, and the one that I have recommend, was discontinued. I liked this IR thermometer because it was small, fit conveniently in my pocket, and was accurate. But I had to start over and decide which thermometer I wanted to use.
The number of IR thermometers available can be overwhelming and the prices range from ten to several hundred dollars. Thus, you should develop your specification to narrow down the choices. Here is the specification I used:
- Can measure temperature in a range from at least -20°F to 300°F. Most will cover this range; some expensive ones will measure much higher temperatures or have higher ranges that you do not need for construction.
- Has an accuracy of ±4°F. Although the display gives the temperature to 0.1°F, the actual accuracy is ±4°F. Most IR thermometers are more accurate than ±4°F but not as accurate as a calibrated thermometer used to measure concrete temperature.
- Should require commonly available batteries that are easy to replace.
- Compact and easy to carry and store. Many IR thermometers look like starter pistols and have a holster. Others are compact and can be carried in your pocket. Either is OK and can be accurate. I prefer a compact model, even though the one with a holster reminds me of when I wanted to be a cowboy.
- Has a laser pointer. Although the laser has nothing to do with taking the temperature, it helps to define where you are measuring the temperature.
- If buying from the internet, read the reviews. Learn from the people who have had success and avoid those models with which people have had problems.
- Look on the internet for websites that have evaluated the various IR thermometers for accuracy, dependability, and durability.
- Consider IR thermometers in the mid-range of prices that are made by companies that specialize in making IR thermometers. From my experience, those are the most durable and accurate.
Once you have made the decision and purchased your IR thermometer, you now need to gain confidence in using it. I recommend that you do the ice cube test:
- Fill a cup with ice.
- Add cold water to just cover the ice.
- Wait two to three minutes.
- Push the ice aside and measure the temperature of the water with the IR thermometer about 3 to 4 inches above the water. Be sure to hold the IR thermometer perpendicular to the water surface.
- Repeat this five times.
Your IR thermometer is working properly if all the readings are 32°F ±4°F. If it fails this test, I recommend returning it to the supplier for a refund or replacement. I would repeat this test regularly to make sure your IR thermometer is providing reliable readings especially if you suspect that it may have been damaged or if any temperature readings appear to be questionable.
To successfully use your IR thermometer, here are some best practices to remember:
- IR thermometers measure only the surface temperature of an object, not the internal temperature.
- Although the temperature reading is given to 0.1°F, the accuracy is ±4°F.
- You must be relatively close to an object to measure its temperature; no further than 5 feet away.
- Keep the thermometer as close to perpendicular as possible.
- In cold weather, keep the IR thermometer warm before use. I keep mine in my pocket and only take it out when I need to take a reading.
- Do not take readings on shiny objects such as glass, mirrors, aluminum, or metal decks. If necessarily to take the temperature of these objects, put black tape on the object, wait a few minutes for the temperature to stabilize, then measure the temperature with the IR thermometer pointed at the black tape.
- Be careful with the laser since it can damage eyes. Make sure the laser beam does not hit anyone’s eye either directly or by reflecting off shiny surfaces.
- The IR thermometer is not a toy and should not be used by children without adult supervision.
There are many brands and types of IR thermometers. I personally like the mini one that fits into a pocket, although I have successfully used the starter pistol style.
I have written a detailed article on this topic and would be happy to send a copy to anyone wanting more details on using an IR thermometer for concrete construction. If interested, contact me at [email protected].