Maximum Size versus Nominal Maximum Size by ProQuest


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									  Maximum Size versus
 Nominal Maximum Size
Q.     The specification I prepared for a project calls for
       “Maximum coarse aggregate size to be 1 in. nominal.”
I intended this provision to mean that almost all of the
                                                                identical definitions for these two terms and also includes
                                                                the following discussion for the term “nominal maximum
                                                                size (of aggregate)”:
coarse aggregate used in the concrete would pass the 1 in.            DISCUSSION—Specifications on aggregates usually
(25.0 mm) sieve and some would be retained on the 3/4 in.             stipulate a sieve opening through which all of the
(19.0 mm) sieve, such as a Size Number 57 stone per ASTM              aggregate may, but need not, pass so that a stated
C33.1 The contractor, however, has interpreted this provision         maximum proportion of the aggregate may be
simply to mean that all of the coarse aggregate must pass a           retained on that sieve. A sieve opening so designated
1 in. (25.0 mm) sieve. Therefore, they believe that the pea           is the nominal maximum size of the aggregate.
gravel (Size Number 7) coarse aggregate they submitted              It’s not surprising that these terms are often confused,
should be approved. They want to use this mixture so the        as the definitions differ by only one word.
concrete can be pumped using a masonry grout pump they              To illustrate the difference between these two terms,
own rather than having to rent a concrete pump for the          the aggregate gradation requirements from ASTM C33 for
small quantity required. I can see how my specification         Size Number 57, 67, and 7 coarse aggregates are shown in
could be interpreted both ways, but many of the boiler plate    Table 1. For Size Number 57 aggregate, the smallest sieve
specifications I’ve reviewed or referred to contain very        size through which 100% is required to pass is the 1-1/2 in.
similar language. For this small project, specifying ASTM       (37.5 mm) sieve. The maximum size for Size Number 57
size number wasn’t a good option because much of the            aggregate is therefore 1-1/2 in. (37.5 mm). The smallest
locally available coarse aggregate doesn’t quite meet the       sieve size through which 100% is permitted to pass is less
ASTM gradation requirements. What is the proper way to          apparent because 95 to 100% is permitted to pass the
specify the aggregate I want in such a case?                    1 in. (25.0 mm) sieve, but there’s no requirement for the
                                                                amount permitted to pass the next smaller 3/4 in. (19.0 mm)

A.    The ACI Web site has a free online dictionary, titled
      “ACI Concrete Terminology,”2 that defines terms
common to the concrete industry. It is available at
                                                                sieve. Because 100% is allowed to pass the 3/4 in. (19.0 mm)
                                                                sieve, it could be argued that this aggregate’s nominal
                                                                maximum size is 3/4 in. (19.0 mm). In these situations,
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