(25.0 mm) sieve. [...] they believe that the pea gravel (Size Number 7) coarse aggregate they submitted should be approved. (12.5 mm) nominal maximum size material. Because your specification required a "maximum aggregate size of 1 in. nominal," the contractor cannot claim that the Size Number 7 coarse aggregate meets the specification.
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, http://termin
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