A

Admixture
a material other than water, aggregate, hydraulic cement, supplementary cementing materials, and fiber reinforcement, used as an ingredient of concrete or mortar, and added to the batch immediately before or during its mixing

Admixture, accelerating
an admixture that causes an increase in the rate of hydration of the hydraulic cement, and thus shortens the time of setting, or increases the rate of strength development, or both

Admixture, air-entraining
an admixture that causes the development of a system of microscopic air bubbles in concrete, mortar, or cement paste during mixing

Admixture, water-reducing
an admixture that either increases slump of freshly mixed mortar or concrete without increasing water content or maintains slump with a reduced amount of water, the effect being due to factors other than air-entrainment

Admixture, high-range water-reducing (Superplasticizer)
a water-reducing admixture capable of producing large water reduction or great flowability without causing undue set retardation or entrainment or air in mortar or concrete

Aggregate
granular material, such as sand, gravel, crushed stone, crushed hydraulic cement concrete, or iron blast-furnace slag, used with a hydraulic cementing medium to produce either concrete or mortar

Air, entrained
microscopic air bubbles intentionally incorporated in mortar or concrete during mixing, usually by use of a surface active agent; typically between 10 and 1000mm in diameter and spherical or nearly so

Air content
the volume of air voids in cement paste, mortar, or concrete, exclusive of pore space in aggregate particles, usually expressed as a percentage of total volume of the paste, mortar, or concrete

B

Batch
quantity of either concrete or mortar mixed at one time

Batch weights
the weights of the various materials (cement, supplementary cementing materials, water, the several sizes of aggregate, and admixtures if used) which compose a batch of concrete

Bleeding
the autogenous flow of mixing water within, or its emergence from, newly placed concrete or mortar; caused by the settlement of the solid materials within the mass; also called water gain

Broom finish
the surface texture obtained by stroking a broom over freshly placed concrete

Brushed surface
a sandy texture obtained by brushing the surface of freshly placed or slightly hardened concrete with a stiff brush for architectural effect or, in pavements, to increase skid resistance

Bug holes
small regular or irregular cavities, usually not exceeding 15 mm in diameter, resulting from entrapment of air bubbles in the surface of formed concrete during placement and consolidation

C

Caisson pile
a cast-in place pile made by driving a tube, excavating it, and filling the cavity with concrete

Calcium-silicate hydrate
any of the various reaction products of calcium silicate and water, produced in the hydration of cement

Cast-in-place
mortar or concrete which is deposited in the place where it is required to harden as part of the structure, as opposed to precast concrete

Cement, high early strength
cement characterized by attaining a given level of strength in mortar or concrete earlier than normal cement; referred to as Type 30

Cement, hydraulic
cement that sets and hardens by chemical interaction with water and is capable of doing so under water

Cement, Portland
a hydraulic cement produced by pulverizing portland cement clinker and usually containing calcium sulfate

Compressive strength
the measured maximum resistance of a concrete or mortar specimen to axial compressive loading; expressed as force per unit cross-sectional area; or the specified resistance used in design calculations

Concrete
A composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggregate, usually a combination of fine aggregate and coarse aggregate; in portland-cement concrete, the binder is a mixture of portland cement and water

Concrete, architectural
concrete which will be permanently exposed to view and which therefore requires special care in selection of the concrete materials, forming, placing, and finishing to obtain the desired architectural appearance

Concrete, normal weight refractory
refractory concrete having a unit weight (bulk density) greater than 1600 kilograms per cu.m

Concrete, roller-compacted
concrete compacted by roller compaction; concrete that, in its unhardened state, will support a roller while being compacted

Concrete, structural
concrete used to carry structural load or to form an integral part of a structure; concrete of a quality specified for structural use

Curing
the maintenance of a satisfactory moisture content and temperature in concrete during its early stages so that desired properties may develop

D

Durability
the ability of concrete to resist weathering action, chemical attack, abrasion, and other conditions of service

E

Early strength
strength of concrete or mortar usually as developed at various times during the first 72 hr after placement

F

Final set
a degree of stiffening of a mixture of cement and water greater than initial set, generally stated as an empirical value indicating the time in hours and minutes required for a cement paste to stiffen sufficiently to resist to an established degree, the penetration of a weighted test needle; also applicable to concrete and mortar mixtures with use of suitable test procedures

Final setting time
the time required for a freshly mixed cement paste, mortar, or concrete to achieve final set

Finishing
leveling, smoothing, consolidating, and otherwise treating surfaces of fresh or recently placed concrete or mortar to produce desired appearance and service.

Float finish
a rather rough concrete surface texture obtained by finishing with a float.

Floating
the operation of finishing a fresh concrete or mortar surface by use of a float, preceding trowelling when that is to be the final finish.

Fly ash
the finely divided residue resulting from the combustion of ground or powdered coal and which is transported from the firebox through the boiler by flue gases.

Formwork
total system of support for freshly placed concrete including the mold or sheathing which contacts the concrete as well as all supporting members, hardware, and necessary bracing.

H

Heat of hydration
heat evolved by chemical reactions with water, such as that evolved during the setting and hardening of portland cement, or the difference between the heat of solution of dry cement and that of partially hydrated cement

Hydration
formation of a compound by the combining of water with some other substance; in concrete, the chemical reaction between hydraulic cement and water

I

Initial Set
a degree of stiffening of mixture of cement and water less than final set, generally stated as an empirical value indicating the time in hours and minutes required for cement paste to stiffen sufficiently to resist to an established degree, the penetration a weighted test needle; also applicable to concrete or mortar with use of suitable test procedures

Initial setting time
the time required for a freshly mixed cement paste, mortar, or concrete to achieve initial set

M

Mixing water
the water in freshly mixed sand-cement grout, mortar, or concrete, exclusive of any previously absorbed by the aggregate

Moist-air curing
curing in moist air (not less than 95 percent relative humidity) at atmospheric pressure and normally at a temperature approximating 22.8 C

P

Plastic consistency
condition of freshly mixed cement paste, mortar, or concrete such that deformation will be sustained continuously in any direction without rupture

Pozzolan
a siliceous or siliceous and aluminous material, which in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties

Precast
a concrete member that is cast and cured in other than its final position; the process of placing and finishing precast concrete

R

Retardation
reduction in the rate of either hardening or setting or both, i.e., and increase in the time required to reach time initial and final setting or to develop early strength of fresh concrete, mortar, or grout

S

Set
the condition reached by a cement paste, mortar, or concrete when it has lost plasticity to an arbitrary degree, usually measured in terms of resistance to penetration or deformation; initial set refers to first stiffening; final set refers to attainment of significant rigidity

Slump
a measure of consistency of freshly placed concrete, mortar, or stucco equal to the subsidence measured to the nearest 6 mm of the molded specimen immediately after removal of the slump cone

T

Trowel finish
the smooth or textured finish of an unformed concrete surface obtained by trowelling