Datum - Any level surface taken as a plane of reference from which to measure elevations in concrete structures.

Density - The ratio of weight of a substance to its volume. Used in concrete material measurements

Deterioration - 1) Physical manifestation of Concrete failure (e.g., cracking delamination, flaking, pitting, scaling, spalling, staining) caused by environmental or

internal autogenous influences on rock and hardened concrete as well as other materials; 2) decomposition of material during either testing or exposure to service. See also Disintegration and Weathering.

Diamond Grinding - The process used to remove the upper surface of a concrete pavement to remove bumps and restore pavement ride ability; also, equipment using many diamond-impregnated saw blades on a shaft or arbor to shave the surface of concrete slabs.

Diaphragm - A part that divides or separates, sometimes in concrete wall construction.

Displacement - A dislocation caused by a slipping of rock masses along a concrete plane of fracture.

Dormancy period: Time period that concrete retains it workability