Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.

Definition of concrete, hydraulic cement, mortar, and grout

Q. What are concrete, hydraulic cement, mortar, and grout?


A. Concrete is a composite material that consists of a mixture of hydraulic cement, aggregates, and water, with or without admixtures, fibers, or other cementitious materials.

Hydraulic cement is cement that sets and hardens by chemical reaction with water (hydration) and is capable of doing so under water (ACI 225R). The hydration reactions result in the formation of a hard solid mass. The most widely used hydraulic cement is portland cement. Other kinds of hydraulic cement include blended cements and ground granulated blast-furnace slag (ACI 233R). Pozzolans, both natural (ACI 232.1R) and artificial (fly ash, ACI 232.2R, and silica fume, ACI 234R) are often used as a cementitious ingredient of concrete.

Mortar is a mixture of cement paste and fine aggregate; in fresh concrete, the material occupying the interstices among particles of coarse aggregate; in masonry construction, joint mortar may contain masonry cement, or may contain hydraulic cement with lime (and possibly other admixtures) to afford greater plasticity and workability than are attainable with standard portland cement mortar.

Grout is a mixture of cementitious materials and water, or other binding medium, with fine aggregate.


References: SP-1(02); CT-23; ACI 225R-19; ACI 233R-03; ACI 232.1R-12; ACI 232.2R-03; ACI 234R-06; E-1(16); E3-13

Topics in Concrete: Concrete Fundamentals; Grout; Materials

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