What nominal maximum sizes of aggregate are recommended?

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What nominal maximum sizes of aggregate are recommended?

Q. What nominal maximum sizes of aggregate are recommended?

 

A. The nominal maximum size of aggregate that may be used should not be larger than one-fifth the narrowest dimension between the sides of the form nor larger than three-fourths the minimum clear spacing between the reinforcing bars (ACI 211.1, ACI 318). In concrete slabs, the nominal maximum size should not be larger than one-third of the slab thickness (ACI 302.1R). Always use the largest nominal maximum size available and permissible. With the w/cm fixed, the larger the nominal maximum size of aggregates, the lower the cement content for a given consistency. Or, stated differently, for a given cement content, the larger the nominal maximum size of aggregate, the lower the water requirement. When strength requirements are high, however, smaller nominal maximum size aggregate will produce the highest strength for a given w/cm (ACI 363R, ACI 211.4R).

 

References: SP-1(02); ACI 211.1-91; ACI 318-14; ACI 302.1R-15; ACI 363R-10; ACI 211.4R-08

Topics in Concrete: 318 Building Code; Aggregate; Codes; Slab; Specifications

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