Glossary - Design and Control of Concrete Mixtures - page 329

Entrained air —spherical microscopic air bubbles—
usually 10 µm to 1000 µm in diameter—intentionally
incorporated into concrete to provide freezing and
thawing resistance and/or improve workability.
Epoxy resin —class of organic chemical bonding
systems used in the preparation of special coatings or
adhesives for concrete or masonry or as binders in
epoxy-resin mortars and concretes.
Ettringite —needle like crystalline compound
produced by the reaction of C 3 A, gypsum, and water
within a portland cement concrete.
Expansion joint —a separation provided between ad-
joining parts of a structure to allow movement.

G
Grading —size distribution of aggregate particles,
determined by separation with standard screen sieves.
Grout —mixture of cementitious material with or with-
out aggregate or admixtures to which sufficient water
is added to produce a pouring or pumping consistency
without segregation of the constituent materials.

H
Hardened concrete —concrete that is in a solid state
and has developed a certain strength.
High-density concrete (heavyweight concrete) —
concrete of very high density; normally designed by
the use of heavyweight aggregates.
High-strength concrete —concrete with a design
strength of at least 70 MPa (10,000 psi).
Honeycomb —term that describes the failure of mortar
to completely surround coarse aggregates in concrete,
leaving empty spaces (voids) between them.
Hydrated lime —dry powder obtained by treating
quicklime with sufficient water to satisfy its chemical
affinity for water; consists essentially of calcium
hydroxide or a mixture of calcium hydroxide and
magnesium oxide or magnesium hydroxide, or both.
Hydration —in concrete, mortar, grout, and plaster, the
chemical reaction between hydraulic cement and water
in which new compounds with strength-producing
properties are formed.
Hydraulic cement —cement that sets and hardens by
chemical reaction with water, and is capable of doing
so under water. (See also Portland cement. )

F
Ferrocement —one or more layers of steel or wire rein-
forcement encased in portland cement mortar creating
a thin-section composite material.
Fibers —thread or thread like material ranging from
0.05 to 4 mm (0.002 to 0.16 in.) in diameter and from 10
to 150 mm (0.5 to 6 in.) in length and made of steel,
glass, synthetic (plastic), carbon, or natural materials.
Fiber concrete —concrete containing randomly oriented
fibers in 2 or 3 dimensions through out the concrete
matrix.
Fine aggregate —aggregate that passes the 9.5-mm ( 3 ⁄ 8 -
in.) sieve, almost entirely passes the 4.75-mm (No. 4)
sieve, and is predominantly retained on the 75-µm (No.
200) sieve.
Fineness modulus (FM) —factor obtained by adding
the cumulative percentages of material in a sample of
aggregate retained on each of a specified series of
sieves and dividing the sum by 100.
Finishing —mechanical operations like screeding,
consolidating, floating, troweling, or texturing that
establish the final appearance of any concrete surface.
Fire resistance —that property of a building material,
element, or assembly to withstand fire or give protec-
tion from fire; it is characterized by the ability to
confine a fire or to continue to perform a given struc-
tural function during a fire, or both.
Flexural strength —ability of solids to resist bending.
Fly ash —residue from coal combustion, which is
carried in flue gases, and is used as a pozzolan or ce-
menting material in concrete.
Forms —temporary supports for keeping fresh
concrete in place until it has hardened to such a degree
as to be self supporting (when the structure is able to
support its dead load).
Freeze-thaw resistance —ability of concrete to with-
stand cycles of freezing and thawing. (See also Air en-
trainment and Air-entraining admixture. )
Fresh concrete —concrete that has been recently
mixed and is still workable and plastic.

I
Inch-pound units —units of length, area, volume,
weight, and temperature commonly used in the United
States during the 18th to 20th centuries. These include,
but are not limited to: (1) length—inches, feet, yards,
and miles; (2) area—square inches, square feet, square
yards, and square miles; (3) volume—cubic inches,
cubic feet, cubic yards, gallons, and ounces;
(4) weight—pounds and ounces; and (5) temperature—
degrees Fahrenheit.
Isolation Joint —separation that allows adjoining parts
of a structure to move freely to one another, both hori-
zontally and vertically.

J
Joint —see Construction joint, Contraction joint, Isolation
joint, and Expansion joint.

K
Kiln —rotary furnace used in cement manufacture to
heat and chemically combine raw inorganic materials,
such as limestone, sand and clay, into calcium silicate
clinker.