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Basics of
Cylinder Breaks
Concrete cylinder breaks are an accepted/standard testing method used to confirm that the concrete being used at the job site meets the specified PSI (pounds per square inch). The standard used for this testing procedure is ASTM C 31 entitled "Standard Practice for Making and Curing Concrete Test Specimens in the Field".
Here are the basics of how it works. The concrete is placed into the cylinder molds. The molds need to be on a level, rigid surface, free of vibration. Concrete is put into the molds in three equal layers, and a steel rod is jabbed into each layer of concrete 25 times (rodding) to consolidate the concrete in the mold. The outside of the  mold is also tapped with a mallet to remove any air bubbles. Most molds used today are single-use plastic, much more convenient than the old steel molds. The top of the concrete cylinder is then struck off cleanly with the rod, and the cylinder is capped and marked. The cylinders are immediately placed where they are going to stay until the concrete sets up. This phase is called initial curing, the cylinders can stay in this location for up to 48 hours, but must be kept at a temperature between 60° and 80° F and in a moist environment. There are several ideas on ways to achieve this moist environment, including boxes, plastic bags, and simply capping the plastic cylinder mold. To control temperature, it is suggested using ventilation, ice (when the weather's hot), or thermostatically controlled boxes. Curing boxes are by far the best way to store cylinders onsite. Keeping cylinders out of the sun, or away from radiant heaters on a winter site, is top priority in proper curing.
The cylinders can be transported to the test lab no sooner than eight hours after final set. They should be padded, not allowed to freeze, and kept moist during transport, which cannot take longer than four hours. When the cylinders arrive at the lab, the molds are removed, and the cylinders are stored submerged in a water tank or in a room with 100% humidity-final curing. The temperature has to be kept at 73±3° F. Finally, the cylinders are taken out of the water tanks, capped with a very high strength sulfur compound, and tested. Testing always means that they are broken, most commonly in direct compression. So then we know the strength of the concrete, which is hopefully greater than the specified strength.
One of the benefits of being a Zim-Mixer owner, is that our knowledgeable customer support staff is here to assist you with any questions or concerns you may have in regards to cylinder breaks, mix designs or any issues dealing with concrete or cement.
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Volumetric Mixers and Cylinder Breaks
Cylinder break tests are a useful tool for volumetric mixer owners. Test cylinders are taken to determine if a particular batch of concrete attains the required strength specified. When the cylinders are taken, other information is recorded. This includes the entrained air content, if any, and the unit weight which is used to determine theoretical yield. As the concrete producer, the volumetric mixer owner is entitled to a copy of any test report resulting from the material produced. Owners should always request a copy when tests are taken.
The information can tell you a number of things. If you are producing air entrained concrete, the tests can show if the admixture delivery system is working correctly. If the required air content is not met, a check of the admixture system can be done to verify the delivery rate.
If the required strength is not attained, it may indicate that one or more of the material delivery mechanisms is out of calibration. A clogged cement chute, for example, will lead to low test results. Either sand or stone delivered out of the required amount can also impact results. Spot checking the delivery of any of these ingredients can be done easily with a Zim-Mixer due to the patented delivery system. If a material is found to be out of calibration, it can be reset to deliver the required amount.
Another item that can be found is if your mix design is using more cement than needed. If test results are consistently high, an adjustment can be made to the cement content to reduce the cost of production.
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| Well Done by the ZI Welding Team
In our continued effort to produce the best volumetric mixers in the industry, Zimmerman Industries proudly announces that our  entire welding team has been recertified in structural welding per American Welding Society D.1.1. This certification is an important part of our welding education program authorized by Zimmerman Industries through the years. Our welding team takes great pride in producing superior welds and quality equipment. Welder certification is based on specially designed tests to determine a welder's skill and ability to deposit sound welds. The extent of certification is described by a number of variables, which include the specific welding process, type of deposited metal, thickness, joint design, position, backing, and others .
Congratulations to the Zimmerman welding team!
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Zimmerman Industries will be closed
Monday, Sept. 4th
for Labor Day
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Concrete Fact
Almost two thousand years after it was built, the Pantheon's dome is still the world's largest unreinforced concrete dome. The height to the oculus and the diameter of the interior circle are the same, 142 ft.
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| Upcoming Events |
World of Concrete
Las Vegas, NV
January 23 - 26, 2018
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