Technical Questions

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The effect of maximum size of aggregate on concrete strength

Q. Does the nominal maximum size of the aggregate affect the strength at a given cementitious material content?

 

A. As the nominal maximum size of the aggregate is increased, the amount of water needed for the same workability is reduced. At the same cementitious material content, strength is therefore greater because the w/cm is lower. But in the high-strength range, over 40 MPa (5800 psi), higher compressive strengths are usually obtained at a given w/cm with smaller nominal maximum-size aggregate (ACI 363R, ACI 214.4R). Similarly, higher flexural strength is obtained at a given w/cm with smaller nominal maximum size aggregate. Data from compression tests of concrete containing very large aggregates, 100 mm (4 in.) and over, are conflicting because of limitations in the size of the test specimens and testing machines.

 

References: SP-1(02); E-1(16); ACI 221R-96; ACI 214R-11; ACI 213R-14; ACI 363R-10; ASTM C33

Topics in Concrete: Aggregate; Concrete Fundamentals; Materials

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