The Effects of Temperature on Concrete Curing

The effects of temperature early in the life of concrete can strongly influence long-term stability.
In general, concrete temperature peaks at 48 hours and remains constant for seven days. The larger the concrete structure, the more heat it will likely generate. Differential temperature, air temperature and concrete mix temperature are all important factors. Monitoring the temperature of concrete during the curing process is a critical factor in making sure the product sets to its full strength and knowing when it is safe to build on.

Curing is the hardening of cement over time; it can take three weeks or longer. As cement mixes with water, a chemical reaction known as hydration occurs during which heat is generated:

• Heat gets trapped and cannot escape quickly
• The core continues to heat while surface cools.

Large temperature differentials can form between the core and surface of the concrete structure. These temperature differentials can lead to thermal cracks, which in turn can cause:

• Increased permeability for easy penetration of water and air
• Reduced durability and structural integrity.

Generally, concrete temperature should be maintained above 10°C for adequate strength. Uniform temperatures need to be maintained – a challenge with weather extremes.

High Concrete Temperature Issues

• Increased water demand; and therefore cost
• Increased chance of shrinkage – leading to cracking
• Decreased concrete strength after 28 days
• Increased potential for corrosion of reinforcements

Hot weather can speed up the curing process and lead to short-term strength gains, but excessive heat ultimately leads to weaker concrete.

Low Concrete Temperature Issues

• Water freezes in concrete capillaries at -2°C; this can lead to cracks as the water expands when freezing.
• Up to a 50% strength reduction if concrete freezes before reaching 500 psi.

The Need for Concrete Temperature Monitoring During the Curing Process

Concrete temperature monitoring is critical to ensure the long-term strength and stability of concrete structures. Monitoring is necessary to verify:

• Temperature differentials did not go beyond safe limits
• Concrete did not cool more than 2.8°C per hour during the first 24 hours
• The core temperatures at various stages, in order to determine any necessary temperature control strategies to put in place
• Temperature consistency was maintained during the curing process.

Curing concrete in cold weather is costly: the real costs are not just in the rental equipment but in the fuel and labour to operate the heating systems. Accurate temperature monitoring during curing helps to minimise fuel usage.

Huge cost benefits can be realised if build can be brought forward by several days because you know the concrete is sufficiently cured.

Concrete temperature monitoring with a data logger fitted with thermocouple probes

Data Loggers And Thermocouple Temperature Sensors (Probes)

Data loggers with thermocouple temperature sensors fitted are used to accurately monitor and record concrete temperature throughout the curing process. Type K thermocouple probes are embedded within the concrete so that the actual core temperature of the mixture is logged, rather than just the ambient air temperature.

Our remote monitoring solutions enable conditions to be logged 24/7 and monitored off-site – particularly useful for remote or hazardous locations, whilst still providing on-site engineers with the information they need to make quick decisions regarding any necessary temperature control strategies. For more information on our remote monitoring systems, simply fill out our contact form, or call our friendly team on +44 (0)1243 558270.

Alternatively, for an out-of-the-box solution suitable for local deployments, see the Tempcon Concrete Temperature Monitoring Kit.

Some of the benefits of Thermocouple Data Loggers:

• A cost-effective and simple way to take in-situ measurements in concrete as it cures
• Enable around-the-clock measurement and reporting of temperature at critical locations
• Accept a wide range of thermocouple probes
• Can be configured and installed in minutes
• Display readout of current temperatures, visual alarms, etc
• Are offered in single and multi-channel form factors.

Thermocouple Logger Deployment

• Temperature sensor sample rates range from every 10 minutes to once per hour (concrete pours in cold weather typically require more frequent sampling).
• The concrete temperature monitoring period usually lasts several days.
• For multi-channel logger applications, thermocouple sensors are often placed at the bottom, middle and top of the concrete structure, with an additional channel for ambient air temperature.

What Gets Measured Gets Managed

The implications of knowing (or not knowing) whether concrete is curing correctly can be huge: the cost savings of not delaying building unnecessarily, long-term structural integrity and having temperature records for insurance purposes. Being alerted to cure temperatures outside safe parameters enables you to take corrective action while you have the chance.

The Choice of Construction Industry Professionals

Since 1980, Tempcon have been a leading choice for professional-grade sensors, thermometers, monitoring and data logging equipment. Their concrete temperature monitoring equipment is used by nationwide concrete construction firms, including Breedon Group, Mackley and Roadbridge; and on major infrastructure projects including the Aberdeen Western Peripheral Route.

More than just a reseller, the company provides expert advice to assist its customers; plus, thermocouple temperature probe manufacture, repair and temperature calibration services.