Field-Cured vs. Standard-Cured Cylinders: How They Affect Concrete Performance

Why Your Field-Cured Concrete Test Cylinders Break Lower Than Standard-Cured Ones

If your field-cured concrete test cylinders consistently break 25-35% below your standard-cured ones, you are not alone. The gap is not always a quality problem. ASTM C31 governs the curing condition, and that condition drives how engineers measure, dispute, and ultimately accept concrete field performance on the job. Understanding which result represents your in-place concrete, and which one the contract actually requires, is the difference between a defensible pour and a costly delay.

ASTM C31 defines two different curing conditions for test cylinders: standard curing and field curing. The standard dictates how to make and cure each type. The problem starts when an engineer or purchaser argues that field-cured results must be the basis of acceptance, when ASTM C31 says otherwise.

ASTM C31 section 10.1 defines standard curing as a condition that “involves subjecting the specimens to standard temperature and humidity conditions.” ASTM C511 directs labs to store these specimens in curing tanks or rooms at 23.0 ± 2°C and at a relative humidity (RH) greater than 95%. Engineers use the results from standard-cured concrete break tests primarily for quality control and concrete acceptance, where they provide an accurate baseline concrete strength measurement. They also ensure an adequate concrete strength measurement.

Section 10.2 of the same standard defines field curing as a condition that “involves subjecting the specimens to the temperature and humidity that the actual structure experiences.” These test specimens are stored alongside the structural element in question to ensure similar relative humidity and ambient temperatures. The strength results from concrete field performance tests predominantly serve to determine whether a structure is ready for formwork removal. This also includes other critical operations, such as opening roads to traffic.

Discrepancies in Concrete Field Performance

In many cases, engineers have encountered discrepancies between the two testing methods. For example, let’s look at testing high-strength field-cured and standard-cured specimens for quality assurance. Say a technician found that the field-cured specimens of a high concrete strength measurement were consistently breaking at 25-35% lower strengths than the standard-cured cylinders.

Assuming that the technician had been using testing procedures that were appropriate for the type of high-strength concrete they were using, typical high-strength concrete mixtures will include one or more supplementary cementitious materials. Additionally, they have a very low water-cementitious materials ratio (w/c).

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Hydration

Cylinders, as well as the structural elements produced with high-strength concrete, generally need additional moisture during the curing process for continued hydration of the cementitious materials. That being said, mixtures with a high concrete strength measurement have much different hydration characteristics than more conventional concrete mixtures. They tend to self-desiccate, meaning that they starve the cement paste from future hydration as they use all available water for the hydration process. This is where we might run into problems. Standard-cured cylinders are supplied with the necessary moisture during the curing process. However, field-cured specimens, as well as the structural elements, might not be. As a result, it can cause self-desiccation and discrepancies between standard- and field-cured cylinders.

Moisture Loss

Another possible factor to explain the difference in strength for both tested specimens is moisture loss through the surface of the cylinders. When testing concrete field performance, if the field-cured cylinders are not provided with enough moisture during the curing process as mentioned above, they could develop initial moisture gradients as the exterior surfaces would dry faster and diminish in size as compared to the internal portion of the specimen. The shrinking caused during the curing process would lead to tension and micro-cracking at the surface. This would, in turn, negatively impact the measured compressive strength and long-term durability of the structural element.

Interested in Learning Why Curing Conditions for Test Cylinders is Important? Read Here!

High-Strength Concrete

Testing concrete field performance the traditional field curing methods may be more appropriate for conventional concrete with moderate w/c. However, they may not be suitable for high-strength concrete. This is because the hydration attributes of high-strength concrete are much different. High-strength concrete also has a higher demand for moisture during the curing stages. This is, among other things, necessary for proper cement paste hydration.

ASTM C31/C31M section 4.2 is explicit on which test governs what. Standard-cured concrete test cylinders are required for acceptance testing against specified strength. Field-cured specimens exist for a different purpose: to estimate in-place strength for decisions about formwork removal, opening to traffic, or post-tensioning.

There is a possible way to eliminate discrepancies and variations in concrete strength measurements between testing methods while ensuring the most accurate field data. This would be to use the maturity method to determine the in-place strength of concrete. Smart sensors can be used to measure and report more efficiently than concrete break tests.

Source:

“Field- versus Standard-Cured Cylinders Made from High-Strength Concrete.” Concrete International, Aug. 2017, p. 64.

**Editor’s Note: This post was originally published in March 2017 and was updated for accuracy and comprehensiveness in June 2026.