Concrete Curing

Curing Conditions with WEDGE

Construction sites must maintain the right conditions once concrete has been poured to maximize the resulting concrete strength and minimize the curing time. This is especially a challenge throughout North America where temperatures can reach extremes and fluctuate quickly.

The Basics

Newly poured concrete must be maintained at the temperature recommended by the mix supplier and/or structural engineer to ensure optimum curing conditions. Maintaining this target temperature is a matter of mitigating temperature extremes:

Curing Concrete in Cold Temperatures

At a minimum, concrete should be cured at temperatures above 7.2 degrees Celsius (45 degrees Fahrenheit). Below this temperature, concrete’s chemical reaction completely stops – which can result in costly delays and rework.

If temperatures are allowed to go below zero degrees Celsius (32 degrees Fahrenheit) before concrete has cured to at least 500 psi, the cement paste will not be able to resist the stresses applied by expansive, freezing pore water. This results in concrete curing with as little as 50% of its intended ultimate strength. This will almost certainly result in rework costs – sometimes requiring removal and replacement of entire slabs.

Curing Concrete in Hot Temperatures

On the other hand, when concrete is allowed to get too warm, particularly above 30 degrees Celsius (86 degrees Fahrenheit) during the curing process it will also not reach its maximum strength over a 28-day period. Large differences in core and surface temperature can result in thermal cracking, particularly for mass pours.

Applying more heat than is required for curing purposes can be costly in terms of fuel consumption. Additionally, unevenly applied heat can result in concrete defects such as scaling and cracking which, in many cases, will require refinishing costs.

Controlling Temperature

In order to maintain moderate temperatures that maximize concrete strength, construction companies have ways in which they can control the curing environment. These include the following:

  • Using industrial-grade heaters
  • Setting up fans to even temperature throughout areas
  • Using temporary hoarding (e.g. tarps)
  • Using periodic wet-downs or water spray
  • Covering curing concrete with insulating material or blankets
  • Setting up curing ponds

Monitoring, Data Logging, Alerting

Regardless of the environmental control setup, conditions can change. This means that it is vital to have real-time monitoring of temperature so that adjustments can be made to maintain quality and maximize concrete strength.

It’s also valuable to have a record of past temperatures for quality records and to provide recourse in case of a dispute resolution scenario. Additionally, concrete temperature data logging may be required – particularly for infrastructure projects.

Construction sites can utilize a monitoring system that measures and records temperatures in the surrounding air, as well as right inside curing concrete. With numerous sensors installed on a site, and an easy-to-read dashboard showing real-time temperature and humidity levels, a construction site superintendent knows when and where any problems are arising while there is still time to do something about it.

Alerts are put in place, so you are notified on a mobile phone if exceed thresholds. Getting such an alert in time to rectify the situation can save a construction project hundreds of thousands of dollars, let alone keeping the project on-time without needing to redo phases if things were to go awry.

As an experienced company providing services and expertise for construction sites in Canada, WesternOne (now United Rentals) identified the need to monitor temperatures and humidity levels on industrial-grade concrete pours. Thus, in 2017, the company invested in developing a smart technology for worksites called WEDGE. It’s a fully-integrated, reliable remote monitoring service providing accessible data 24/7 from the worksite, to your smartphone, tablet or computer. WEDGE excels in applications for curing concrete in harsh conditions.

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