Glossary - Design and Control of Concrete Mixtures - page 330

Mortar cement —hydraulic cement, primarily used in
masonry construction, consisting of a mixture of port-
land or blended hydraulic cement and plasticizing
materials (such as limestone, hydrated or hydraulic
lime) together with other materials introduced to
enhance one or more properties such as setting time,
workability, water retention, and durability. Mortar
cement and masonry cement are similar in use and
function. However, specifications for mortar cement
usually require lower air contents and they include a
flexural bond strength requirement.

L
Lightweight aggregate —low-density aggregate used
to produce lightweight (low-density) concrete. Could
be expanded or sintered clay, slate, diatomaceous shale,
perlite, vermiculite, or slag; natural pumice, scoria,
volcanic cinders, tuff, or diatomite; sintered fly ash or
industrial cinders.
Lightweight concrete —low-density concrete com-
pared to normal-density concrete.
Lime —general term that includes the various chemical
and physical forms of quicklime, hydrated lime, and
hydraulic lime. It may be high-calcium, magnesian, or
dolomitic.

N
Normal weight concrete —class of concrete made with
normal density aggregates, usually crushed stone or
gravel, having a density of approximately 2400 kg/m 3
(150 lb/ft 3 ). (See also Lightweight concrete and High-
density concrete. )
No-slump concrete —concrete having a slump of less
than 6 mm ( 1 ⁄ 4 in.).

M
Masonry —concrete masonry units, clay brick, struc-
tural clay tile, stone, terra cotta, and the like, or combi-
nations thereof, bonded with mortar, dry-stacked, or
anchored with metal connectors to form walls, building
elements, pavements, and other structures.
Masonry cement —hydraulic cement, primarily used
in masonry and plastering construction, consisting of a
mixture of portland or blended hydraulic cement and
plasticizing materials (such as limestone, hydrated or
hydraulic lime) together with other materials intro-
duced to enhance one or more properties such as
setting time, workability, water retention, and durabil-
ity.
Mass concrete —cast-in-place concrete in volume
large enough to require measures to compensate for
volume change caused by temperature rise from heat
of hydration in order to keep cracking to a minimum.
Metakaolin —highly reactive pozzolan made from
kaolin clays.
Metric units —also called System International (SI)
Units. System of units adopted by most of the world by
the 21st Century. These include but are not limited to:
(1) length—millimeters, meters, and kilometers;
(2) area—square millimeters and square meters;
(3) volume—cubic meters and liters; (4) mass—milli-
grams, grams, kilograms, and megagrams; and (5)
degrees Celsius.
Mineral admixtures —see Supplementary cementitious
materials.
Modulus of elasticity —ratio of normal stress to corre-
sponding strain for tensile or compressive stress below
the proportional limit of the material; also referred to as
elastic modulus, Young's modulus, and Young's modu-
lus of elasticity; denoted by the symbol E .
Moist-air curing —curing with moist air (no less than
95% relative humidity) at atmospheric pressure and a
temperature of about 23ºC (73ºF).
Mortar —mixture of cementitious materials, fine aggre-
gate, and water, which may contain admixtures, and is
usually used to bond masonry units.

O
Overlay —layer of concrete or mortar placed on or
bonded to the surface of an existing pavement or slab.
Normally done to repair a worn or cracked surface.
Overlays are seldom less than 25 mm (1 in.) thick.

P
Pavement (concrete) —highway, road, street, path, or
parking lot surfaced with concrete. Although typically
applied to surfaces that are used for travel, the term
also applies to storage areas and playgrounds.
Permeability —property of allowing passage of fluids
or gases.
Pervious concrete (no-fines or porous concrete) —
concrete containing insufficient fines or no fines to fill
the voids between aggregate particles in a concrete
mixture. The coarse aggregate particles are coated with
a cement and water paste to bond the particles at their
contact points. The resulting concrete contains an inter-
connected pore system allowing storm water to drain
through the concrete to the subbase below.
pH —chemical symbol for the logarithm of the recipro-
cal of hydrogen ion concentration in gram atoms per
liter, used to express the acidity or alkalinity (base) of a
solution on a scale of 0 to 14, where less than 7 repre-
sents acidity, and more than 7 alkalinity
Plastic cement —special hydraulic cement product
manufactured for plaster and stucco application. One
or more inorganic plasticizing agents are interground
or blended with the cement to increase the workability
and molding characteristics of the resultant mortar,
plaster, or stucco.
Plasticity —that property of freshly mixed cement
paste, concrete, mortar, grout, or plaster that deter-
mines its workability, resistance to deformation, or ease
of molding.
Plasticizer —admixture that increases the plasticity of
portland cement concrete, mortar, grout, or plaster.