Keeping tabs on concrete temperature throughout the setting process is crucial to ensure the concrete's strength and quality once complete. Temperatures that are too high or too low can have a negative impact on the concrete's mix design, and they can ultimately cause a project to fail because it doesn't meet ASTM, AASHTO or other specifications. Luckily, it's quite easy to keep tabs on concrete temperature with a simple lab grade thermometer. Before you choose the first thermometer you come across, however, you should keep a few important considerations in mind.

Different Types of Thermometers and Their Uses

Modern technology has given us several different types of thermometers that have their own unique strengths and features. Most will fall into one of the following categories.

Liquid-in-Glass Thermometers

This category represents the classic image that probably pops into your head when you hear the term "thermometer." Liquid-in-glass (LiG) thermometers consist of either mercury, red alcohol or another liquid substance sealed in glass with volumetric measurements printed on the casing. Based on the laws of thermal expansion, the liquid within the glass will expand or contract depending on how hot or cold the substance is, providing a fairly high level of accuracy. Mercury thermometers in particular are hailed for their ability to measure extreme temperature ranges.

But, are mercury thermometers accurate? Yes; mercury has certain thermal expansion properties that can make these thermometers more accurate for temperature readings than other LiG materials. The bigger issue is that mercury is hazardous and, therefore, prohibited in certain municipalities. Mercury thermometers are also no longer calibrated by the National Institute of Standards and Technology (NIST), although the ASTM still requires their use in certain testing situations that require a 7C or 7F thermometer (no other LiG materials can be used as accurately for this purpose). Always be sure to check your locale's regulations before using a mercury thermometer for your application, or simply use other accurate LiG thermometers to be safe.

Bimetallic/Bimetal Thermometers

These thermometers are often used to measure the temperature of food and beverages. They are mechanical, using two metal strips (often steel and copper or brass) that bend at different rates when exposed to heat to move a dial along a scale. They're a durable and fairly accurate solution, often displaying readings at an accuracy of ±1%. They are also safe, durable and inexpensive. However, certain environments can throw off the calibration of bimetal thermometers, making them less accurate and consistent than LiG thermometers, so they may not be the best choice for concrete testing purposes.

Digital Thermometers

Digital or electronic thermometers are some of the most technologically advanced options available, using electronic circuitry and microchips to provide quick, accurate results. They can include many features depending on how complex they are, including automatic calibration, data logging, maximum/minimum temperature recording and timestamping. Given these advanced features, they can be much more expensive than a traditional LiG or bimetallic thermometer.

Another advantage of digital thermometers is that they do not contain any toxic or hazardous materials, making them safe for any use. They also provide results faster and, in certain cases, do not require calibration via boiling or ice bath to provide accurate readings.

Infrared Thermometers

Another advanced style, infrared thermometers measure temperature by converting infrared energy into an electrical signal that provides a temperature readout on the device's display, all without making actual contact with the substance being measured. They can measure a broad range of temperatures, as well. However, infrared thermometers do not have a very high degree of accuracy and are generally used for repeatability purposes instead.

Digital Thermometers vs. Mercury Thermometers

One of the biggest debates about lab grade thermometers is whether digital or mercury is more accurate for concrete testing (or any temperature measuring) purposes. Consider these factors that distinguish digital and mercury thermometers:

Other Factors to Consider When Choosing a Lab Grade Thermometer

Aside from accuracy of results, there are varying levels of convenience and features that different thermometers can provide to make your job quicker and easier. Take these factors into account when choosing your lab grade thermometer as well:

5 Best Lab Grade Thermometer Options from Certified MTP