CAPILLARY ATTRACTION- The tendency of water to move into fine spaces, as between soil particles, regardless of gravity.

CASING- A pipe lining for a drilled hole.

CAT- (1) A trademark designation for any machine made by the Caterpillar Tractor Company. (2) Widely used to indicate a crawler tractor of any make.

CAT HEAD- A capstan winch.

CATWALK- A pathway, usually of wood or metal, that gives access to parts of large machines.

CENTRIFUGAL FORCE- Outward force exerted by a body moving in a curved line. It is the force that tends to tip a car over in going around a curve.

C-FRAME- An angling dozer lift and push frame.

CHECK VALVE- Any device that will allow fluid or air to pass through it in only one direction.

CHOKER- A chain or cable so fastened that it tightens on its load as it is pulled.

CIRCLE REVERSE- The mechanism that changes the angle of a grader blade.

CLAM- A clamshell bucket.

CLAMSHELL- (1) A shovel bucket with two jaws that clamp together by their own weight when it is lifted by the closing line. (2) A crane equipped with a clamshell bucket.

CLAMSHELL BUCKET- Usually consists of two or more similar scoops hinged together and a head assembly connected to the outer corners by struts. When the head and hinge are pulled toward each other, the scoops are forced together to dig and hold material. Control is by a holding line reeved over a boom point sheave and attached to the head assembly to support the bucket in open position and usually by a closing line also reeved over a boom point sheave, ending in a force amplifying tackle or other means between the head assembly and scoop hinge to close the bucket.

CLAMSHELL BUCKET, HYDRAULIC- Usually consists of two or more scoops hinged to a head assembly housing the hydraulic cylinder or cylinders and the force amplifying linkage to open and close the scoops and to supply the digging force for the scoops. The bucket assembly is suspended from the boom by a rope. Because digging ability is largely dependent upon bucket weight, buckets are supplied in various weight classes which range from light, for easily dug stockpiled materials, to heavy, for excavating hardpan material and the like.

CLAMSHELL EQUIPMENT- Machines with clamshell attachments are used to load material from stockpiles, gondola cars, barges, and the like, or from virgin soil generally out of small-area holes, deep trenches, or from below water. Orange peel buckets, grapples, and similar rope suspended attachments are included in this classification.

CLOSING LINE- The rope reeved from the hoist drum to control closing of a rope-operated clamshell bucket.

COFFERDAM- A set of temporary walls, designed to keep soil and/or water from entering an excavation.

COLLAR- A sliding ring, mounted on a shaft so that it does not revolve with it, used in clutches and transmissions.

COMPACTION- The act of compressing a given volume. Insufficient compaction of the asphalt pavement courses may result in channeling on the _{pavement surface.} Compaction is usually accomplished by rolling.

CONVEYOR BELT- An endless belt of rubbercovered fabric that transports material on its upper surface.

CORRUGATIONS (WASHBOARDING) AND SHOVING- Are types of pavement distortion. Corrugation is a form of plastic movement typified by ripples across the asphalt pavement surface. Shoving is a form of plastic movement, resulting in localized bulging of the pavement surface. These distortions usually occur at points where traffic starts and stops, on hills where vehicles brake on the downgrade, on sharp curves, or where vehicles hit a bump and bounce up and down. They occur in asphalt layers that lack stability. Lack of stability may be caused by a mixture that is too rich in asphalt, has too high a proportion of fine aggregate, has coarse or fine aggregate that is too round or too smooth, or has asphalt cement that is too soft. It may also be due to excessive moisture, contamination due to oil spillage, or lack of aeration when placing mixes using liquid asphalt.

CRACKS- Breaks in the surface of an asphalt pavement.

CRACKS, ALLIGATOR- Interconnected cracks forming a series of small blocks resembling an alligator's skin or chicken wire, caused by excessive deflection of the surface over unstable subgrade or lower courses of the pavement.

CRACKS, EDGE JOINT- Are the separation of the joints between the pavement and the shoulder, commonly caused by the alternate wetting and drying beneath the shoulder surface. Other causes are shoulder settlement, mix shrinkage, and trucks straddling the joint.

CRACKS, LANE JOINT- Longitudinal separation along the seam between two paving lanes caused by a weak scam between adjoining spreads in the courses of the pavement.

CRACKS, REFLECTION- Cracks in asphalt overlays that reflect the crack pattern in the pavement structure underneath. They are caused by vertical or horizontal movements in the pavement beneath the overlay, brought on by expansion and contraction with temperature or moisture changes.

CRACKS, SHRINKAGE- Are interconnected cracks forming a series of large blocks, usually with sharp corners or angles. Frequently they are caused by volume change in either the asphalt mix or in the base or subgrade.

CRACKS, SLIPPAGE- Are crescent-shaped cracks that are open in the direction of the thrust of wheels on the pavement surface. They result when there is a lack of good bond between the surface layer and the course beneath.

CRANE- A mobile machine, used for lifting and moving loads without the use of a bucket.

CRANE MATS- A device, used for supporting machines on soft ground, usually of timber construction.

CREEP- (1) Very slow travel of a machine or a part. (2) Unwanted turning of a shaft due to drag in a fluid coupling or other disconnect device.

CRUMBER- A blade that follows the wheel or ladder of a ditching machine to clean and shape the bottom.

CULVERT- A pipe or small bridge for drainage under a road or structure.

CURVE, VERTICAL- A change in gradient of the center line of a road or pipe.

CUTBACK ASPHALTS- Mixture of asphalt cement and a cutting agent. There are three main types.

DATUM- Any level surface taken as a plane of reference from which to measure elevations.

DEADHEADING- Traveling without a load, except when traveling from the dumping area to the loading point.

DENSITY- The ratio of the weight of a substance to its volume.

DIESELING- In a compressor, explosions of mixtures of air and lubricating oil in the compression chambers and/or other parts of the air system.

DOLLY- A unit consisting of a draw tongue, an axle with wheels, and a turntable platform to support a gooseneck trailer.

DOUBLE-CLUTCHING- Disengaging and engaging the clutch twice during a single-gear shift (change of gears) to synchronize gear speeds.

DOWNSTREAM FACE- The dry side of a dam.

DOZER- Abbreviation of bulldozer.

DRAFT- Resistance to movement of a towed load.

DRAGLINE- A crane with a dragline attachment, used to excavate material from below the grade on which the crane is sitting.

DRAWBAR- A fixed or hinged bar, extending to the rear of a tractor and used as a fastening for lines and towed machines or loads.

DRAWBAR HORSEPOWER- A tractor's flywheel horsepower minus friction and slippage losses in the drive mechanism and the tracks or tires.

DRAWBAR PULL- The pull that a tractor can exert on a load attached to the drawbar. Depends on power, weight, and traction.

DRILL COLLAR- Thick-walled drill pipe, used immediately above a rotary bit to provide extra weight.

DRILL, PERCUSSION- A drill that hammers and rotates a steel and bit. Sometimes limited to large blast hole drills of the percussion type.

DRILL PIPE- The sections of a rotary drilling string, connecting the kelly with the bit or collars.

DRIVE SPROCKET- A drive roller with teeth that engage matching recesses or pins (bushings) in the track assembly.

DROP HAMMER- A pile-driving hammer that is lifted by a cable and that obtains striking power by falling freely.

DRUM, SPUDDING- In a churn drill, the winch that controls the drilling line.