Date: April 1, 2010

Strengths reported to be low due to incorrectly tested concrete can be costly to every-one. They can result in job delays as well as additional expenses for extra testing, which never should have to be done in the first place if everything was done properly. This is why it is crucial to ensure that cylinders are made and tested correctly.

The only allowable methods for testing fresh plastic concrete are the American Society for Testing Materials (A.S.T.M.) Standards, and more and more we see a lack of com-pliance with these standards. Here are a few things to look out for to ensure that cylind-ers are made, cured, stored, transported and tested properly:

• At minimum, the inspectors should be ACI Grade I certified.
• Sampling concrete from a truck mixer can only be done by obtaining the sample at two or more regularly spaced intervals during discharge of the middle portion of the load and then compositing them into one sample.
• Cylinders are made by filling in three layers of equal volume and rodding each layer 25 times. After each layer is rodded, tap the sides 10 to 15 times to close any holes left by rodding.
• Cylinders are then to be covered and placed in a protected environment within 15 minutes and not moved for 24 hours +/- 8 hrs.
• They are to be kept within a temperature range of between 60 to 80 degrees F.

There is no other acceptable method. Yet in spite of this, we see cylinders moved long after they should be, left all over job-sites, exposed to the hot and cold weather, and left near vibrating machines and equipment.

It is everyone’s responsibility to demand qualified personnel and strict compliance with A.S.T.M. Standards: we need to set the standard and call these problems to everyone’s attention when they occur.

Other news articles from April 2010

• NRMCA Green-Star Status Granted to Chaney Enterprises
• Bringing the Comfort of Home to the Outdoors
• Customers Learn How to Save Time and Money with Flowable Fill and Self-Consolidating Concrete
• Lite-Deck® provides permanent insulation while reducing jobsite labor.
• Old Man Winter Hits Maryland Hard