Field-Cured vs. Standard-Cured Cylinders

Concrete cylinder Break test
Concrete cylinder Break test

How Curing Methods Affect High-Strength Concrete

ASTM C31 is the standard that defines two different concrete curing conditions, standard curing and field curing. It is the standard that dictates the procedures for making and curing test cylinders and can become a problem when an engineer or purchaser argues that field-cured test cylinders must be the basis of acceptance for a project.

Safely Pour Concrete Under Any Weather Conditions

The leading concrete sensor for real-time temperature and strength monitoring

ASTM C31 section 10.1 defines standard curing as a condition that “involves subjecting the specimens to standard temperature and humidity conditions.” According to ASTM C511, these test specimens are generally stored in curing tanks or rooms at 23.0 ± 2°C and at a relative humidity (RH) greater than 95%. The results from standard-cured concrete break tests are primarily used for quality control and concrete acceptance.

ASTM C31 section 10.2 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 field-cured concrete break tests are predominantly used for determining whether a structure is ready for formwork removal and other critical construction operations such as opening roads to traffic.

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

While it is assumed 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 and have a very low water-cementitious materials ratio (w/c).

Curious About Easily Monitoring Your Concrete? Learn more here!

field cured cylindersCylinders, 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, high-strength concrete mixtures have much different hydration characteristics than more conventional concrete mixtures and tend to self-desiccate, meaning 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 as standard-cured cylinders are supplied with the necessary moisture during the curing process, but field-cured specimens, as well as the structural elements, might not be, causing self-desiccation and discrepancies between standard- and field-cured cylinders.

Another possible factor to explain the difference in strength for both tested specimens is moisture loss through the surface of the cylinders. 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 which 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!

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

As per section 4.2 of ASTM C31/C31M specimens must be standard cured in order to be used for acceptance testing for specified strength. Field-cured specimens are fabricated for comparison purposes with the standard-cured specimen test results and to let the user know when to remove formwork, etc.

One possible way to eliminate discrepancies between testing methods and to ensure the most accurate field data would be to use the maturity method to determine 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 has been updated for accuracy and comprehensiveness.

One Response

  1. I would like to see the ASTM C31 be more specific about the term initial curing and how it effects both standard and field cured specimens. I have dealt with QC QA people who think that from the moment a test cylinder is taken it is okay to just put in a box and let the temperature go over 110 degrees F. If you can keep a field cured cylinder protected for the first 48 hours before it is moved to point of placement, why would you not take advantage of this to insure the quality of your testing?
    It always surprises me that the language used in ASHTO & ASTM can be interpreted different ways depending on your point of view.

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Articles

Use These Tech Tools for More Efficient Cold Weather Concreting

Let’s dive into our sensors in detail.   Safely Pour Concrete Under Any Weather Conditions The leading concrete sensor for real-time temperature and strength monitoring Learn More SmartRock Sensors:    SmartRock is a wireless concrete sensor designed for temperature and strength monitoring with the ability to record real-time temperature data for every 15-minute interval for 2 months and comes with remote-monitoring capabilities. It is fast, simple, designed rugged and waterproof, and can be activated and installed hassle-free. The sensor contains two points of temperature measurements located in the sensor cable and body, and comes with an extended temperature cable and probe for mass…

Everything You Need to Know About Pouring Concrete in Winter

Winter is coming! Worried about the cold weather concreting that comes with it in the construction industry? We’ve got it covered with Giatec’s SmartRock sensors.  Keep reading to learn more.  Safely Pour Concrete Under Any Weather Conditions The leading concrete sensor for real-time temperature and strength monitoring Learn More The temperature is dropping, the days start to get shorter, and frost covers the ground. While it may be exciting to imagine a festive winter season, that is not what comes to mind when working in the construction industry. Especially, when you have a project to complete, a schedule to maintain, and a desired concrete temperature and…

Giatec’s Unique Concrete Knowledge Resources

The Giatec Scientific website is a treasure trove of concrete knowledge, ranging from blogs and case studies to podcasts and videos! Find a few of our exclusive resources below: Safely Pour Concrete Under Any Weather Conditions The leading concrete sensor for real-time temperature and strength monitoring Learn More Giatec’s Concrete Terminology Search Bar Need a one-stop destination for searching definitions for a plethora of terms related to concrete knowledge? Make sure to check out our concrete terminology search bar! To search for a term related to…

We use cookies to provide you with a better experience, analyze site traffic and assist in our marketing efforts. By continuing to use this website, you consent to the use of cookies in accordance with our Privacy Policy Page.