Concrete Waterproofing Glossary

Obsidian

a natural volcanic glass of relatively low water content, usually of rhyolite composition. (See also perlite.)

Offset

(1) an abrupt change in alignment or dimension, either horizontally or vertically;
(2) a horizontal ledge occurring along a change in wall thickness of the wall above.

(1) an intentional distortion from the normal straightness of a steel reinforcing bar to move the center line of a segment of the bar to aposition parallel to the original position of the center line;
(2) a mechanical operation commonly applied to vertic

Offset Yield Strength

the stress at which the strain exceeds, by a specified amount, an extensionof the initially proportional part of the stress-strain curve.

Oil-well Cement

hydraulic cement suitable for use under high pressure and temperature in sealing water and gas pockets and setting casing during the drilling and repair of wells, and often contains retarders to meet the requirements of use.

One-way System

the arrangement of steel reinforcement within a slab that presumably bends in only one direction.

Opal

a mineral composed of amorphous hydrous silica (SiO 2 – nH 2 O).

Opaline Chert

chert composed entirely or mainly of opal.

Open-graded Aggregate

aggregate where the voids between the particles are relatively large when compacted.

Open-top Mixer

a truck-mounted mixer consisting of a trough or a segment of a cylindricalmixing compartment within which paddles or blades rotate about the horizontal axis of the trough. (See also horizontal-shaft mixer.)

Ordinary Portland Cement

the term used in the United Kingdom and elsewhere to designate the equivalent to ASTM C150 Type I cement.

Orthotropic

a hypothetical plate consisting of beams and a slab acting together with different flexural rigidities in the longitudinal and transverse directions, as in a composite beam bridge. (This term is a contraction of the terms “orthogonal anisotropic” as in

Oven-dry Specific Gravity

the ratio of the mass of a volume of a material (including the permeable and impermeable pores in the material but not including the voids between particles of the material) at a stated temperature to the mass of an equal volume of distilled water at a st