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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 coarse aggregate used in the concrete would pass the 1 in. (25.0 mm) sieve and some would be retained on the 3/4 in. (19.0 mm) sieve, such as a Size Number 57 stone per ASTM C33.1 The contractor, however, has interpreted this provision simply to mean that all of the coarse aggregate must pass a 1 in. (25.0 mm) sieve. Therefore, they believe that the pea gravel (Size Number 7) coarse aggregate they submitted should be approved. They want to use this mixture so the concrete can be pumped using a masonry grout pump they own rather than having to rent a concrete pump for the small quantity required. I can see how my specification could be interpreted both ways, but many of the boiler plate specifications I've reviewed or referred to contain very similar language. For this small project, specifying ASTM size number wasn't a good option because much of the locally available coarse aggregate doesn't quite meet the ASTM gradation requirements. What is the proper way to specify the aggregate I want in such a case?
A. The ACI Web site has a free online dictionary, titled "ACI Concrete Terminology,"2 that defines...