Concrete Curing

The curing and strength development of concrete is a complex chemical hydration process that begins the moment water contacts the cement ingredients. Successful sampling, curing, and strength testing of concrete depends on following the rules imposed by the process itself.

Early-age (green) concrete is very sensitive to disturbances and temperature variations. As a result, curing of the samples is carried out in two stages:

  • Initial curing for the first day or two occurs on the job site. Immediately after molding, the fresh concrete samples are placed in a protected environment where they gain enough strength to allow them to be transported to a testing laboratory.
  • Once in the lab, the samples are removed from the molds and begin the longer-term phase of final curing.

Initial, or Field Curing

It’s just another day at the office. Or in this case, the job site, and the concrete strength specimens you’ve just made have started their initial curing. The ASTM C31 and AASHTO T23 Practices for Making and Curing Concrete Test Specimens in the Field are clear on what is needed for this period of fewer than 48 hours when the samples reach the final set and start their strength development:

  • Moisture loss must be prevented.
  • Ambient temperature must be maintained between 16°C and 27°C for most concrete types.

While not as clearly stated in the practice, it is also known that impact, vibration, or other disturbances at this stage directly affect the strength development of concrete, so the samples must also be protected from physical forces.

Concrete curing boxes/cube moulds are built to meet the demands of initial curing and enhance the efficiency of your field operations with portability and convenience. Options are available for heating, heating, and cooling, or sample temperature and moisture control by immersion in circulating water. The units are easily transported between projects or stored at the lab between uses.

Final, Laboratory Curing

At the end of the initial curing period in the field, the specimens are ready to be transported back to the testing laboratory. There, they begin a final curing phase until they reach an age of 7 days, 28 days, or more before they are tested for compressive or flexural strength. But how do you store them so that they will cure properly and continue to gain strength until they are tested? This can all be very challenging.

Adequate protection of concrete samples from vibration, jolting, and temperature extremes during transportation is critical and could affect strength test results if overlooked. Gilson’s Field Curing Chest and Cylinder Transport Racks safeguard samples for reliable test results.

Accurate strength tests for concrete, grout, and masonry specimens in the form of cylinders, beams, or cubes begin with proper curing as required in their respective ASTM and AASHTO standards, yet one of the most common errors found in CCRL (Cement and Concrete Reference Laboratory) audits is the inability to maintain specified curing temperatures and moisture levels in the laboratory. Improper curing conditions directly inhibit optimal strength development of concrete strength specimens.

Moisture Rooms or Concrete Curing Tanks are two acceptable and widely used methods for curing samples for concrete strength tests. Specific requirements for each are outlined in ASTM C511 and AASHTO M201 standard specifications.


Bath dimensions: 1.1m x 0.95m x 690mm


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