It’s that time of year. Cold weather is upon us! Many contractors continue to place concrete in late fall and through the winter. It is critical to protect concrete test cylinders on site, as they are used for acceptance of concrete for compressive strength purposes.

The following outline is a summary of requirements and not a comprehensive list.

• Tester must be currently certified – ACI Concrete Field Technician Grade I or DOT Certified
• Proper sampling – take and remix a representative sample (e.g. in wheelbarrow)
• Record concrete temperature – within 5 mins of sampling
• Record concrete slump – start test within 5 mins of sampling
• Record air content – start test within 5 mins of sampling
• Cast test cylinders – start molding within 15 mins of sampling and comply with all ASTM protocol
• Protect test specimens for initial storage period. For Standard-Cured specimens, which are used for Acceptance, cylinders must be:
  • Stored between 60 – 80°F before being transported to the lab within 24–48 hours – the contractor, working with the testing lab, is generally responsible for providing this initial curing environment
  • Record the initial curing temperatures – it is required to record the temperature using a max-min thermometer or thermocouples to ensure the initial curing temperature adjacent to the cylinders is between 60 to 80°F
  • Protected from moisture loss – typically covered with plastic caps or plastic bags
  • Insulated curing boxes/coolers should be utilized to maintain compliant initial curing temperature.
• Timely and proper transport to a lab where specimens will be placed in 100% humidity under controlled conditions for their final cure before testing

If test cylinders are not made, stored and transported properly, this will result in lower compressive strengths that are not representative of the concrete in place. It takes good planning, communication and inspection to ensure all the required specifications are followed.

We are all on the same side in wanting a successful project, and that includes ensuring the on-site testing is done correctly.