machine, finishing—a power-operated machine used to produce the desired surface texture on a concrete slab.
machine-base grout—see grout, machine base.
macrocell corrosion—process whereby one layer of metallic reinforcement corrodes preferentially to another layer. (See also microcell corrosion.)
macrofiber—a fiber with an equivalent diameter equal to or greater than 0.012 in. (0.3 mm) for use in concrete.
macroscopic—visible to the naked eye (preferred term).
magnesium phosphate cement—see cement, magnesium phosphate.
magnetite—a mineral, ferrous ferric oxide (FeO·Fe2O3); the principal constituent of magnetic black iron ore; density approximately 5.2 g/cc and Mohs hardness approximately 6; used as an aggregate in high-density concrete.
maintenance—taking periodic actions that will delay damage or deterioration or both. (See also preservation and protection.)
manifold—see grout header.
manual batcher—see batcher manual.
manufactured sand—see sand.
map cracking—see cracking, map.
marble—a metamorphic rock composed essentially of recrystallized calcite, dolomite, or both.
marl—calcareous clay, usually containing from 35 to 65% calcium carbonate (CaCO3), found in the bottoms of shallow lakes, swamps, or extinct fresh-water basins.
mason—an artisan who builds with concrete masonry units, bricks, stone, and tile; name sometimes given a concrete finisher.
masonry—construction composed of shaped or molded units, usually small enough to be handled by one person and composed of stone, ceramic brick or tile, concrete, glass, adobe, or the like.
masonry, ashlar—masonry composed of bonded blocks of concrete, either rectangular or square, always of two or more sizes; if the pattern is repeated, it is patterned ashlar; if the pattern is not repeated, it is random ashlar.
masonry, bonded hollow-wall—a cavity wall, built of masonry units, in which the inner and outer walls are tied together by bonders (masonry units placed perpendicular to the plane of the wall that act as ties).
masonry, cement—a hydraulic cement manufactured for use in mortars for masonry construction or in plasters, or both, which contains a plasticizing material and, possibly, other performance-enhancing addition(s).
masonry, exposed—masonry constructed to have no surface finish other than paint.
masonry, grouted—unit masonry composed of either hollow units wherein the cells are filled with grout or multiple wythes where spaces between the wythes are filled with grout.
masonry, hollow-unit—masonry consisting either entirely or partially of hollow masonry units laid in mortar.
masonry, plain—(1) masonry without reinforcement; or (2) masonry reinforced only for shrinkage or thermal change.
masonry, reinforced—unit masonry in which reinforcement is embedded in such a manner that the two materials act together in resisting forces.
masonry, solid-unit—masonry consisting wholly of solid masonry units laid in mortar.
masonry cement—see cement, masonry.
masonry filler unit—masonry unit used to fill in between joists or beams to provide a platform for a cast-in-place concrete slab.
masonry grout—see grout, masonry.
masonry lift—the height to which masonry is laid between periods of grouting.
masonry structure—a structure of individual masonry units laid in and bonded together with mortar.
masonry unit, concrete—either a hollow or solid unit (block) composed of portland-cement concrete; often referred referred to by indicating the type of mineral aggregate incorporated (for example, lightweight or sand-gravel block).
masonry wall, solid—a wall built of blocks or solid masonry units, the mortar completely filling the joints between units.
mason’s putty—a pasty substance, composed of water and hydrated lime mixed with portland cement and stone dust; used only for jointing ashlar masonry.
mass—the physical property of matter that causes it to have weight in a gravitational field; the quantity of matter in a body.
mass concrete—see concrete, mass.
mass curing—see curing, mass.
mass density—see density.
mastic—a thick adhesive material used to hold waterproofing membranes in place or as a sealant.
mat— (1) an assembly of steel reinforcement composed of two or more layers of bars placed at angles to each other and secured together either by welding or tying; or (2) a thin layer of randomly oriented chopped filaments, short fibers (with or without a carrier fabric), or long random filaments loosely held together with a binder and used as reinforcing for a fiber reinforced polymer composite material.
mat foundation—see foundation, mat.
match—to provide, by selection, formulation, adjustment, or other means, a surface repair that is indistinguishable from or within specified tolerances of the surrounding area.
material hose—see delivery hose.
materials, cementitious—cements and pozzolans used in concrete and masonry construction. (See also blast-furnace slag; cement, hydraulic; masonry; and mortar.)
matrix—(1) in the case of mortar, the cement paste in which the fine aggregate particles are embedded; in the case of concrete, the mortar in which coarse aggregate particles are embedded; (2) in the case of fiber-reinforced composites, the resin or binders in which the fiber reinforcements are embedded.
mats, cotton—cotton-filled quilts fabricated for use as a water-retaining covering in curing concrete surfaces.
maturity factor—see factor, maturity.
maximum service temperature (refractory concrete)— the temperature above which excessive shrinkage occurs in refractory concrete; usually between 150 F (66 C) and 200 F (93 C) below the temperature at which the refractory concrete softens.
maximum size (of aggregate)—in specifications for and in description of aggregate, the smallest sieve opening through which the entire amount of aggregate is required to pass. (See also nominal maximum size [of aggregate].)
maximum-temperature period—a time interval throughout which the maximum temperature is held constant in an autoclave or steam-curing room.
mean stress—see stress, mean.
mechanical analysis—the process of determining particle-size distribution of an aggregate. (See analysis, sieve.)
mechanical anchorage—see anchorage, mechanical.
mechanical bond—see bond, mechanical.
mechanical connection—the complete assembly of an end-bearing sleeve, a coupler, or a coupling sleeve, and possibly additional intervening material or other components to effect connection of reinforcing bars. (See also barend check; coupler; coupling sleeve; and end-bearing sleeve.)
mechanical properties—those properties of a material that are associated with elastic and inelastic reaction when force is applied, or which involve the relationship between stress and strain.
mechanical shearing—a method for removal of concrete and steel with hydraulically powered jaws; especially applicable for demolition work. (See also jaw crusher.)
medium, grinding—a hard, free-moving charge in a ball or tube mill to reduce the particle size of introduced materials by attrition or impact.
megascopic—see macroscopic (preferred term).
melilite—a group of minerals ranging from the calcium magnesium silicate (akermanite) to the calcium aluminate silicate (gehlenite) that occur as crystals in blast-furnace slag. (See also akermanite; gehlenite; and merwinite.)
melt—the molten portion of the raw material mass during the burning of cement clinker, firing of lightweight aggregates, or expanding of blast-furnace slags.
member, compression—any member in which the primary stress is longitudinal compression.
member, segmental—a structural member made up of individual elements prestressed together to act as a monolithic unit under service loads.
membrane—protective surface treatment with a thickness greater than 30 mils (0.75 mm) and less than 250 mils (6 mm) applied to the surface of concrete.
membrane, liquid—a liquid material applied to a surface to form a continuous waterproof film after it cures.
membrane, sheet—any functionally continuous flexible structure of felt, fabric, or mat, or combinations thereof, and plying cement.
membrane curing—see curing, membrane.
membrane theory—a theory of design for thin shells, based on the premise that a shell cannot resist bending because it deflects; the only stresses that exist in any section, therefore, are shear stress and direct compression or tension.
merwinite—one of the principal crystalline phases found in blast-furnace slags; the chemical formula is Ca3Mg(SiO4)2, the crystal system is monoclinic, and the density is 3.15 g/cc. (See also akermanite; gehlenite; and melilite.)
mesh—the number of openings (including fractions thereof) per unit of length in either a screen or sieve in which the openings are 1/4 in. (6 mm) or less.
mesh, diamond—a metallic fabric having rhomboidal openings in a geometric pattern. (See also lath, expanded-metal.)
mesh reinforcement—see fabric, welded-wire and reinforcement, welded-wire fabric.
mesh roller—a finishing tool consisting of a rolling drum attached to a handle, of which the surface of the drum is made of mesh, sometimes used for rolling over the surface of fresh concrete to embed coarse aggregate.
Mesnager hinge—see hinge, Mesnager.
meter, air—a device for measuring the air content of concrete and mortar.
metering pump—a device incorporating one or more pumps for pressurizing and delivering fluids such as grout; for multi-component materials, the flow rates of the pumps are synchronized to dispense the components at the desired ratio.
methacrylate—see resin, methacrylate.
method, advancing-slope—a method of placing concrete as in tunnel linings in which the face of the fresh concrete is not vertical and moves forward as concrete is placed.
methods of measurement—the definition of how repair areas will be quantified for billing purposes during performance of work, e.g., per linear foot, per square foot, per cubic foot, etc.
methyl methacrylate—a colorless, volatile liquid derived from acetone cyanohydrin, methanol, and dilute sulfuric acid.
microcell corrosion—localized corrosion in which anodic and cathodic reaction sites are in close proximity to one another. (See also macrocell corrosion.)
microconcrete—a mixture of portland cement, water, and suitably graded sand for simulating concrete in small-scale structural models.
microcracks—cracks too small to be seen with the unaided eye.
microscope, polarizing—a microscope equipped with elements permitting observations and determinations to be made using polarized light. (See also Nicol prism.)
microscope, scanning electron (SEM)—an electron microscope in which the image is formed by a beam operating in synchronism with an electron probe scanning the object; the intensity of the image-forming beam is proportional to the scattering or secondary emission of electrons by the specimen where the probe beam strikes it.
microscopic—discernible only with the aid of a microscope.
microsilica—see silica fume (preferred term).
middle strip—see strip, middle.
mil—one thousandth of an inch, 0.001 in. (0.0254 mm); typically used as the unit of measurement for thickness of thin coatings.
mildew—a superficial growth produced by fungi in the presence of moisture that causes surface discoloration and decomposition.
mill, ball—horizontal, cylindrical, rotating mill charged with large grinding media. (See also mill, rod.)
mill, rod—horizontal, cylindrical, rotating mill charged with steel rods for grinding. (See also mill, ball.)
mill scale—the partially adherent layers of oxidation products (heavy oxides) developed on metallic surfaces during either hot fabrication or heat treatment of metals, as on hot-rolled steel reinforcing bars.
milling—method commonly used for removal of a specified depth of concrete from large areas of horizontal or vertical surfaces. (See also scarifier.)
mineral aggregate—see aggregate, mineral.
mineral filler—a finely divided mineral product at least 65% of which passes the U. S. Standard 75-μm (No. 200) sieve. (See also silt.)
minimum-film-forming temperature—the lowest temperature at which latex will coalesce to form a continuous film.
mist—a process in which a very fine spray of water is applied to, (a) a fresh concrete surface to minimize the potential for plastic shrinkage cracking, or (b) a hardened concrete surface for moist curing.
mix—to combine or blend two or more materials into a single mixture; a compound of two or more materials.
mix, dry—a concrete, mortar, or plaster mixture, commonly sold in bags, containing all components except water; also a concrete of near zero slump.
mix design—see mixture proportioning (preferred term).
mixer—a machine used for blending the constituents of concrete, grout, mortar, cement paste, or other mixtures.
mixer, batch—a machine that mixes batches of either concrete or mortar.
mixer, central—a stationary concrete mixer from which the freshly mixed concrete is transported to the work.
mixer, colloidal—a mixer designed to produce colloidal grout.
mixer, continuous—a mixer into which the ingredients of the mixture are fed without stopping, and from which the mixed product is discharged in a continuous stream.
mixer, high-discharge—see mixer, inclined-axis (preferred term).
mixer, horizontal-axis—a concrete mixer of the revolving drum type in which the drum rotates about a horizontal axis.
mixer, horizontal-shaft—a mixer having a stationary cylindrical mixing compartment, with the axis of the cylinder horizontal, and one or more rotating horizontal shafts to which mixing blades or paddle are attached; also called pugmill.
mixer, inclined-axis—a truck with a revolving drum that rotates about an axis inclined to the bed of the truck chassis.
mixer, nontilting—a horizontal rotating drum mixer that charges, mixes, and discharges without tilting.
mixer, open-top—a truck-mounted mixer consisting of a trough or a segment of a cylindrical mixing compartment within which paddles or blades rotate about the horizontal axis of the trough. (See also mixer, horizontal- shaft).
mixer, paddle—see open-top mixer (preferred term).
mixer, pan—see mixer, vertical shaft.
mixer, revolving-blade (or paddle)—see mixer, open-top.
mixer, tilting—a revolving-drum mixer that discharges by tilting the drum about a fixed or movable horizontal axis at right angles to the drum axis; the drum axis may be horizontal or inclined while charging and mixing.
mixer, transit—see mixer, truck.
mixer, trough—see mixer, open-top (preferred term).
mixer, truck—a concrete mixer suitable for mounting on a truck chassis and capable of mixing concrete in transit. (See also mixer, horizontal-axis; mixer, inclined-axis; mixer, open-top; and agitator.)
mixer, tub—see mixer, open-top (preferred term).
mixer, turbine—see mixer, open-top (preferred term).
mixer, vertical-shaft—a cylindrical or annular mixing compartment having an essentially level floor and containing one or more vertical rotating shafts to which blades or paddles are attached; the mixing compartment may be stationary or rotate about a vertical axis.
mixer efficiency—the adequacy of a mixer in rendering a homogeneous product within a stated period; homogeneity is determinable by testing for relative differences in physical properties or composition of samples extracted from different portions of a freshly mixed batch.
mixing cycle—the time taken for a complete cycle in a batch mixer, that is, the time elapsing between successive repetitions of the same operation (for example, successive discharges of the mixer).
mixing, dry—blending of the solid materials for mortar or concrete before adding the mixing water.
mixing plant—see batch plant (preferred term).
mixing speed—rotation rate of a mixer drum or of the paddles in an open-top, pan, or trough mixer, when mixing a batch;expressed in revolutions per minute (rpm), or in peripheral feet per minute of a point on the circumference at maximum diameter.
mixing time—the time from completion of mixer charging until the beginning of discharge.
mixing water—see water, mixing.
mixture—the assembled, blended, commingled ingredients of mortar, concrete, or the like; or the proportions for their assembly.
mixture, harsh—a concrete mixture that lacks desired workability and consistency due to a deficiency of mortar or aggregate fines.
mixture, lean—see concrete, lean.
mixture, rich—see rich mixture.
mixture proportion—the proportions of ingredients that make the most economical use of available materials to produce mortar or concrete of the required properties. (See also proportion.)
mobile placer—a small belt conveyor, mounted on wheels or truck-mounted, that can be readily moved to the job site for conveying concrete from the ready-mixed concrete truck to the forms or slab.
moderate sulfate-resisting cement—see cement, moderate sulfate-resisting.
modified cube—a portion of a rectangular beam of hardened concrete previously broken in flexure; used in determining the compressive strength of the concrete.
modified portland cement—a portland cement having moderate heat of hydration; this term was replaced by Type II cement beginning in 1960. (See also cement, modified.)
modular ratio—the ratio of modulus of elasticity of steel Es to that of concrete Ec; usually denoted by the symbol n.
module—any in a series of standardized units for use together in erecting a structure.
modulus, bulk—the ratio of the change in average stress to the change in unit volume. (See also modulus of compression.)
modulus, chord—see modulus of elasticity.
modulus, elastic—see modulus of elasticity (preferred term).
modulus, initial-tangent—see modulus of elasticity.
modulus, secant—see modulus of elasticity.
modulus, section—a term pertaining to the cross section of a flexural member; the section modulus with respect to either principal axis is the moment of inertia with respect to that axis divided by the distance from that axis to the most remote point of the tension or compression area of the section, as required; the section modulus is used to determine the flexural stress in a beam.
modulus, shear—see modulus of rigidity.
modulus, sonic—see modulus of elasticity, dynamic.
modulus, subgrade—see coefficient of subgrade reaction.
modulus, tangent—see modulus of elasticity.
modulus, Young’s—see modulus of elasticity (preferred term).
modulus of deformation— (1) a concept of modulus of elasticity expressed as a function of two time variables; strain in loaded concrete as a function of the age at which the load is initially applied and of the length of time the load is sustained; and (2) the ratio of stress to strain for a material that does not deform in accordance with Hooke’s law when subjected to applied load. (See also modulus of elasticity.)
modulus of elasticity—the ratio of normal stress to corresponding strain for tensile or compressive stress below the proportional limit of the material; also referred to as elastic modulusor Young's modulus of elasticity; denoted by the symbol E. (See also modulus of rigidity.)
modulus of elasticity, dynamic—the modulus of elasticity computed from the size, weight, shape, and fundamental frequency of vibration of a concrete test specimen, or from pulse velocity. (See also modulus of elasticity, static and velocity, pulse.)
modulus of elasticity, static—the value of Young’s modulus of elasticity obtained by arbitrary criteria from measured stress-strain relationships derived from other than dynamic loading. (See also modulus of elasticity.)
modulus of elasticity, sustained—term including elastic and inelastic effects in one expression to aid in visualizing net effects of stress-strain up to any given time; computed by dividing the unit sustained stress by the sum of the elastic and inelastic deformations at that time. (See also modulus of elasticity.)
modulus of rigidity—the ratio of unit shearing stress to the corresponding unit shearing strain; referred to as shear modulus and modulus of elasticity in shear, denoted by the symbol G. (See also modulus of elasticity.)
modulus of rupture—a measure of the load-carrying capacity of a beam and sometimes referred to as rupture modulus or rupture strength; it is calculated for apparent tensile stress in the extreme fiber of a transverse test specimen under the load that produces rupture. (See also strength, flexural.)
modulus of subgrade reaction—see coefficient of subgrade reaction.
Mohs scale—arbitrary quantitative units, ranging from 1 through 10, by means of which the scratch hardness of a mineral is determined; each unit of hardness is represented by a mineral that can scratch any other mineral having a lower-ranking number; the minerals are ranked from: talc, or 1 (the softest); gypsum, or 2; calcite, or 3; fluorite, or 4; apatite, or 5; orthoclase, or 6; quartz, or 7; topaz, or 8; corundum, or 9; and diamond, or 10 (the hardest).
moist—slightly damp but not quite dry to the touch; the term “wet” implies visible free water, “damp” implies less wetness than “wet,” and “moist” implies not quite dry. (See also damp and wet.)
moist-air curing—see curing, moist-air.
moist cabinet—see cabinet, moist.
moist room—a room in which the atmosphere is maintained at a selected temperature (usually 23.0 ± 2 C or 73.0 ± 3.0 F) and a relative humidity of at least 95%, for the purpose of curing and storing cementitious test specimens; the facilities must be sufficient to maintain free moisture continuously on the exteriors of test specimens; also known as a fog room.
moisture, absorbed—moisture that has entered the permeable voids of a solid and has physical properties not substantially different from ordinary water at the same temperature and pressure. (See also absorption.)
moisture, free—moisture having essentially the properties of pure water in bulk; moisture not absorbed by aggregate. (See also moisture, surface.)
moisture, surface—free water retained on surfaces of aggregate particles and considered to be part of the mixing water in concrete, as distinguished from absorbed moisture.
moisture barrier—see barrier, moisture.
moisture content of aggregate—the ratio, expressed as a percentage, of the mass of water in a given granular mass to the dry weight of the mass.
moisture content of concrete masonry unit—the amount of water contained in the hardened concrete at the time of sampling and expressed as a percentage of its capacity for total absorption.
moisture-free—the condition of a material that has been dried in air until there is no further significant change in its mass. (See also mass and ovendry.)
moisture movement—(1) the movement of moisture through a porous medium; and (2) in the UK, the effects of such movement on efflorescence and volume change in hardened cement paste, mortar, concrete, or rock. (See also shrinkage and swelling.)
moisture vapor transmission rate—see water vapor transmission rate.
mold—(1) a device containing a cavity into which neat cement, mortar, or concrete test specimens are cast; and (2) a form used in the fabrication of precast mortar or concrete units (for example, masonry units).
mold, plaster— a mold or form made from gypsum plaster, usually to permit concrete to be formed or cast in intricate shapes or in conspicuous relief. (See also mold and form.)
mold oil—see oil, mold.
moment—the colloquial expression for the more descriptive term, bending moment. (See also moment, bending.)
moment, bending—the bending effect at any section of a structural element; it is equal to the algebraic sum of the moments of the vertical and horizontal forces, with respect to the centroidal axis of a member, acting on a freebody of the member.
moment, negative—a condition of flexure in which top fibers of a horizontally placed member, or external fibers of a vertically placed exterior member, are subjected to tensile stresses.
moment, positive—a condition of flexure in which, for a horizontal simply supported member, the deflected shape is normally considered to be concave downward and the top fibers subjected to compression stresses; for other members and other conditions consider positive and negative as relative terms. (See also moment, negative.)
moment, secondary—in statically indeterminate structures, the additional moments caused by deformation of the structure due to the applied forces; in statically indeterminate prestressed-concrete structures, the additional moments caused by the use of a nonconcordant prestressing tendon.
moment, ultimate—obsolete term; see strength, flexural.
moment distribution—a method of structural analysis for continuous beams and rigid frames whereby successive converging corrections are made to an assumed set of moments until the desired precision is obtained; also known as the Hardy Cross method.
monolith—a body of plain or reinforced concrete cast or erected as a single integral mass or structure.
monolithic concrete—see concrete, monolithic.
monolithic surface treatment—see dry-shake.
monolithic terrazzo—the application of a 5/8 in. (15 mm) terrazzo topping directly to a specially prepared concrete substrate, eliminating an underbed.
monolithic topping—see topping, monolithic.
monomer—an organic liquid, of relatively low molecular weight, that creates a solid polymer by reacting with itself or other compounds of low molecular weight or both.
monomolecular—composed of single molecules; specifically, films that are one molecule thick; denotes a thickness equal to one molecule, for example, certain chemical compounds develop a monomolecular film over bleeding water at the surface of freshly placed concrete or mortar as a means of reducing the rate of evaporation. (See also evaporation retardant.)
montmorillonite—a swelling clay mineral of the smectite group; main constituent of bentonite. (See also smectite.)
mortar—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. (See also cement, hydraulic and masonry.)
mortar, air-blown—see shotcrete (preferred term).
mortar, expansive-cement—see concrete (mortar or grout), expansive-cement.
mortar, epoxy—a mixture of epoxy resin, catalyst, and fine aggregate. (See also resins, epoxy.)
mortar, fat—mortar containing a high percentage of fine-grained solid components; sufficiently sticky to adhere to a steel trowel.
mortar, lean—mortar that is harsh and difficult to spread because of either insufficient cement content or the presence of coarse sand.
mortar, plastic—a mortar of plastic consistency.
mortar, polymer—a composite material of fine aggregates bound together by an organic polymer.
mortar, resin—see concrete, polymer.
mortar, sprayed—see shotcrete (preferred term).
mortar, stringing—the procedure of spreading enough mortar on the bed joint to ensure laying several masonry units.
mortar board—a platform or tray for holding freshly mixed mortar. (See also hawk and hod.)
mortar-flow—see flow 2.
mosaic—inlaid exposed surface designs of aggregates or other material.
mottled—adjacent spots of different tones and colors in a coating film that create a blotchy effect.
moving forms—see forms, moving.
mud balls—lumps of clay or silt (“mud”).
mud pumping—see pumping (of pavements).
mud sill—a timber or timber assembly bedded into the earth at grade to support framed construction.
mud slab—a 2 to 6 in. (50 to 150 mm) layer of concrete beneath a structural concrete floor or footing over soft, wet soil; also called mud mat.
mudcracking—a coating defect characterized by a broken network of cracks in the surface film.
multielement prestressing—prestressing accomplished by stressing an assembly of several individual structural elements as a means of producing one integrated structural member.
multistage stressing—prestressing performed in stages as the construction progresses.
multiwall-bag—a flexible container for transporting a cementitious material and usually consisting of four plies of kraft paper previously treated to ensure resistance to moisture.
muriatic acid—see hydrochloric acid (preferred term).
mushroom system of flat-slab construction—a four-way reinforced-concrete girderless floor slab in which the column reinforcing bars are bent down into the slab around the column head in radial directions and additional reinforcing bars are bent into rings laid upon the radials, thus forming a spider web to provide additional reinforcement at the column head and to support the slab steel; mushroom designs of the true flat-slab type do not involve drop panels around the capitals of the columns.