kaolin—a rock, generally white, consisting primarily of clay minerals of the kaolinite group, composed principally of hydrous aluminum silicate of low iron content, used as raw material in the manufacture of white cement.
kaolinite—a common clay mineral having the general formula Al2(Si2O5)(OH4), the primary constituent of kaolin.
Keene’s cement—see cement, Keene’s.
Kelly ball—an apparatus used for indicating the consistency of fresh concrete, consisting of a cylindrical weight 6 in. (150 mm) in diameter, weighing 30 lb (14 kg) with a hemispherically shaped bottom, a handle consisting of a graduated rod, and a stirrup to guide the handle and serve as a reference for measuring depth of penetration. (See also test, ball.)
Kelly ball test—see test, ball and Kelly ball.
kerb form; kerb tool—see curb form and curb tool (preferred terms in U.S.; kerb is used in the UK).
kerf—a saw cut in a concrete surface for embedment of the perimeter of a membrane or other thin surface treatment.
kern area—the area within a geometric shape in which a compressive force may be applied without tensile stresses resulting in any of the extreme fibers of the section.
kern distance—the distance from the centroid of a section to the farthest point from the centroid at which a resultant force can act without inducing a stress of opposite sign at the extreme fiber on the opposite side of the centroid.
key—see keyway.
keyed—fastened or fixed in position in a notch or other recess.
keyway—a recess or groove in one lift or placement of concrete that is filled with concrete of the next lift, giving shear strength to the joint. (See also tongue and groove.)
kick strip—see kicker (preferred term).
kicker—a wood block or board attached to a formwork member in a building frame or formwork to make the structure more stable; in formwork it acts as a haunch. (See also wall, stub.)
kiln—a furnace or oven for drying, charring, hardening, baking, calcining, sintering, or burning various materials. (See also steam-curing room.)
kiln, cement—a kiln in which the ground and proportioned raw mixture is dried, calcined, and burned into clinker at a temperature of 2600 to 3000 F (1420 to 1650 C); can be of the rotary, shaft, fluid-bed, or traveling-grate type; fuel may be coal, oil, or gas.
kiln, rotary—a long steel cylinder with a refractory lining, supported on rollers so that it can rotate about its own axis, and erected with a slight inclination from the horizontal so that prepared raw materials fed into the higher end move to the lower end where fuel is blown in by air blast.
kiln, steam—see steam-curing room (preferred term).
kip—1000 lb force, equals 4448 N.
knee brace—brace between horizontal and vertical members in a building frame or formwork to make the structure more stable; in formwork it acts as a haunch.
