Volumetric concrete mixer
A volumetric concrete mixer (also known as volumetric mobile mixer and metered concrete truck) is a truck that contains concrete ingredient materials and water to be mixed on the truck at the job site to make and deliver concrete according to the amount needed.
The mixer is a mixing device that measures the raw materials using volume rather than weight. The volumetric mixer blends the concrete mixture using an auger or a paddle or a drum device to mix the ingredients with water. The volumetric mixing process starts with a batch metering system that allows the volume of raw materials to be measured prior to entering the mixing chamber. This process can be as simple as using a measured bucket, to highly sophisticated and computerized batch plants that feed the correct volume.
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The mixing chamber can vary depending upon the application and the mix design of the concrete.
In an auger type mixer, the material and water travels up the Archimedes' screw. Auger lengths can vary from about 5-feet to 15-feet, and vary in diameter and RPM. This type may be portable, but the length of the auger is a limiting factor.
A paddle mixer blends the concrete mix using a rotational motion and is used to blend finer gravels and sand, as in mortar. The majority of drum mixers are mounted on trailers and are pulled to a job site using a pick-up truck. These drums usually have a mixing capacity of between 1-yard and 1.75 yards (0.76 and 1.34m3) per batch.
A paddle mixer tumbles the mixture in a folding motion using curved fins and paddles. This is the most common type of volumetric mixing. Paddle mixers usually mix in smaller batches directly on the job site.
The history of volumetric mixing comes from several directions;
- The mobile auger mixer was patented in 1964 by hazards Zimmerman, Ephrata, PA USA. Because of the patents, there was only one equipment manufacturer until the 1980s. Equipment manufacturers created an association in 1999 with five charter members.
- The drum for trailer mounted volumetric mixer was designed in 1979, by Fred Caron and Neal Surry, Sacramento, California USA. They mimicked the larger transit-mix truck's mixing drum, on a smaller scale and loaded the drum from a batching unit that metered the volume.
- The paddle mixer's exact history is unrecorded, but these volumetric mixers have been in use by masons for at least 50 years. Usually these produce smaller batches.
- Casey, Jon M. "Parmer Metered Concrete offers precision and quality". Hard Hat News. Retrieved 24 November 2014.
- "How Does A Zim-Mixer Work?". Zimmerman Industries. Retrieved 24 November 2014.
- "History of the Volumetric Mixer". Volumetric Mixer Manufacturer Bureau.
- ACI 304.6R-09: Guide for the Use of Volumetric-Measuring and Continuous-Mixing Concrete Equipment. American Concrete Institute. March 2009. p. 2.
- "VMMB Members". Volumetric Mixer Manufacturer Bureau.