The Basic Standard – ASTM C 33

Bay Area aggregate producers put forth substantial effort to test and certify their aggregates in accordance with the requirements of several standards and many test methods.  Specifying that concrete aggregates conform to ASTM C 33 will result in aggregates with material properties that conform to certain limits when tested in accordance with the following test methods:

Although the test for alkali-silica reactivity of aggregates (ASTM C 289) is in the nonmandatory Appendix to ASTM C33, the text of the standard contains a requirement that both fine and coarse aggregates for use in concrete to be exposed to wetting, humid atmosphere, or moist ground shall not contain aggregates that are deleteriously reactive with the alkalies in the cement.  Reactive aggregates can be used with low-alkali cement or with concrete made with admixtures such as fly ash.  Although no Bay Area aggregates are known to be deleterious, Caltrans, for example, requires that all concrete contain a minimum amount of fly ash.

It is not generally understood that the limits for deleterious substances and physical properties in ASTM C 33 vary according to the use of the concrete (location in structure) and the “weathering region” in which the structure is located.  Figure 1 in ASTM C 33 indicates that the entire Bay Area is in the negligible weathering region, while portions of the mountains and deserts are in the moderate to severe weathering region.  To be complete, a concrete specification should identify the weathering region.

Recycled concrete is referenced in ASTM C 33 as an acceptable coarse aggregate, subject to the requirements of the standard, but caution is advised in its use for structural concrete, due to porosity and the wide variability of the quality of the material.

ASTM C 33 does not limit the salt content of aggregates.  However, water soluble chloride ions in the reinforced concrete itself are limited by the Uniform Building Code and ACI 318 as a function of the exposure, and whether or not the concrete is prestressed.  Although dredged sands, such as the local Angel Island Washed Sand produced by Hanson Aggregates, are generally washed to remove chlorides, significant chlorides can remain.  Since the mix water, admixtures, and cementitious materials can also contribute chlorides, it may be wise to specify that the concrete supplier certify that the chloride content of the concrete itself remains within the ACI 318 limits.

It should be noted that, while the grading ranges of ASTM C 33 are quite wide, and the cleanness and physical property requirements are not particularly strict, concrete made with aggregates conforming to ASTM C 33 can generally be expected to perform adequately in most cases.  If it is desired to control other specific aggregate characteristics, such as aggregate particle shape or texture, the project specification must be augmented.

• Producers:  
•   Hanson
•    CEMEX
•    Syar
•    Vulcan
•    Graniterock
•    West Coast Aggregates
•    Granite Construction