Unit weight can be very important in multiple story buildings: if you use full weight concrete on the second floor of a building and lightweight concrete on the first floor, your building is likely to collapse under the weight. The procedure for unit weight can also help you calculate other important parameters for a batch of concrete, such as yield, gravimetric air content, and theoretical density for the entire batch. To get the unit weight of a sample of concrete, you must get the weight of a full container of concrete, subtract the weight of the empty container, and divide that by the volume of the container. The scale must be able to display a reading for the measure even when it is full to the brim with concrete. Tamping Rod if slump is greater than 1 inch, you can rod the concrete — use the same tamping rod you would use for 6x12 cylinders. The rod must also have a hemispherical tip.

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More C Yield is defined as the volume of concrete produced from a mixture of known quantities of the component materials. The test method shall use the following apparatuses: balance or scale; tamping rod, which is a round straight steel rod having the tamping end rounded to a hemispherical tip; internal vibrator which may have rigid of flexible shafts, preferably powered by electric motors; measure, which is a cylindrical container made of steel or other suitable metal specified herein; strike-off plate; mallet; and scoop of a size large enough so each amount of concrete obtained from the sampling receptacle is representative and small enough so it is not spilled during placement in the measure.

This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date. Scope 1. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other.

Combining values from the two systems may result in non-conformance with the standard. These notes and footnotes excluding those in tables shall not be considered as requirements of this test method. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure.


ASTM C138: Unit Weight, Yield, and Gravimetric Air Content of Concrete



ASTM C138/C138M


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