Concrete Waterproofing Glossary
Lagging
heavy sheathing used in underground work to withstand earth pressure. (See also sheathing.)
Laitance
a layer of weak material derived from cementitious material and aggregate fines either: (1) carried by bleeding to the surface or to internal cavities of freshly placed mixture;
(2) separated from the mixture and deposited onthe surface or internal cavit
Latex
a dispersion of organic polymer particles in water.
Lean Concrete
concrete of low cementitious material content.
Length Change
increase or decrease in length. (See also volume change anddeformation.)
Licensed Design Professional
(1) an engineer or architect who is licensed to practice structural design as defined by the statutory requirements of the professional licensing laws of a state or jurisdiction;
(2) the architect or engineer, licensed as described, who is responsible fo
Lift
the concrete placed between two consecutive horizontal construction joints, usually consisting of several layers or courses.
Lift Joint
surface at which two successive lifts meet.
Lift Slab
(1) a method of concrete construction in which floor and roof slabs are cast on or at ground level and hoisted into position by jacking;
(2) a slab that is a component of such construction.
Lightweight Aggregate
aggregate of low density such as (1) expanded or sintered clay, shale,slate, diatomaceous shale, perlite, vermiculite, or slag;
(2) natural pumice, scoria, volcanic cinders, tuff, and diatomite;
(3) sintered fly ash or industrial cinders.
Lightweight Concrete
concrete of substantially lower density than that made using aggregates of normal density; consists entirely of lightweight aggregate or a combination of lightweight aggregate and normal-density aggregate; its equilibrium densities are generally between 7
Lime
specifically, calcium oxide (CaO), loosely, a general term for the variouschemical and physical forms of quicklime, hydrated lime, and hydraulic hydrated lime. (See also hydrated lime, hydraulic hydrated lime, and quicklime.)
Limestone
a sedimentary rock consisting primarily of calcium carbonate.
Limit Design
a method of proportioning reinforced-concrete members based on calculation of their strength. (See also strength-design method.)
Limonite
an iron ore composed of a mixture of hydrated ferric oxides occasionally used in heavyweight concrete because of its high density and combined- water content, which contribute to its effectiveness in radiation shielding; a mineral occurring commonly as a
Lining
any sheet, plate, or layer of material attached directly to the inside face of formwork to improve or alter the surface texture and quality of the finished concrete. (See also form lining, tunnel lining, and sheathing.)
Lintel
a horizontal supporting member above an opening, such as a window or a door.
Live Load
(1) load that is not permanently applied to a structure but is likely to occur during the service life of the structure (excluding environmental loads);
(2) loads meeting specific criteria found in the governing building code(without load factors).
Load Balancing
a technique used in the design of prestressed-concrete members in which the amount and path of the prestressing is selected so that the forces imposed upon the member or structure by the prestressing counteractor balance a portion of the dead and live loa
Load Factor
a factor by which a service load is multiplied to determine a factored load used in the strength-design method.
Load-bearing Wall
a wall designed and built to carry superimposed vertical loads, in-plane and shear loads, or both. (See also nonbearing wall.)
Long Column
a column whose load capacity is limited by buckling rather than strength. (See also slender column.)
Longitudinal Crack
a crack that develops parallel to the length of a member.
Longitudinal Joint
a joint parallel to the length of a structure or pavement.
Longitudinal Reinforcement
reinforcement parallel to the length of a concrete member or pavement.
Los Angeles Abrasion Test
test for abrasion resistance of concrete aggregates.
Loss of Prestress
(1) the reduction in the prestressing force that results from the combined effects of slip at anchorage;
(2) relaxation of steel stress;
(3) frictional loss due to curvature in the tendons; (4) the effects of elastic shortening, creep, and shrinkage of
Loss On Ignition
the percentage loss in mass of a sample ignited to constant mass at aspecified temperature, usually 1650 to 1830°F (900 to 1000°C).
Low-alkali Cement
(1) a portland cement that contains a relatively small amount of sodium, potassium, or both;
(2) in ASTM C150, a portland cement containing notmore than 0.60 percent Na 2 O equivalent, that is, percent Na 2 O + 0.658percent K 2 O.
Low-density Concrete
concrete having an oven-dry density of less than 50 lb/ft 3 (800 kg/m 3 ).(See also insulating concrete and lightweight concrete.)
Low-heat Cement
a portland cement for use when a low heat of hydration is desired, referred to as ASTM C150 Type IV cement.