What is "hydraulic lime"

Hydraulic \Hy*drau"lic\, a. [F. hydraulique, L. hydraulicus, fr. Gr. ?, ?, a water organ; "y`dwr water + ? flute, pipe. See Hydra.] Of or pertaining to hydraulics, or to fluids in motion; conveying, or acting by, water; as, an hydraulic clock, crane, or dock. Hydraulic accumulator, an accumulator for hydraulic machinery of any kind. See Accumulator, 2. Hydraulic brake, a cataract. See Cataract, 3. Hydraulic cement, a cement or mortar made of hydraulic lime, which will harden under water. Hydraulic elevator, a lift operated by the weight or pressure of water. Hydraulic jack. See under Jack. Hydraulic lime, quicklime obtained from hydraulic limestone, and used for cementing under water, etc. Hydraulic limestone, a limestone which contains some clay, and which yields a quicklime that will set, or form a firm, strong mass, under water. Hydraulic main (Gas Works), a horizontal pipe containing water at the bottom into which the ends of the pipes from the retorts dip, for passing the gas through water in order to remove ammonia. Hydraulic mining, a system of mining in which the force of a jet of water is used to wash down a bank of gold-bearing gravel or earth. [Pacific Coast] Hydraulic press, a hydrostatic press. See under Hydrostatic. Hydraulic propeller, a device for propelling ships by means of a stream of water ejected under water rearward from the ship. Hydraulic ram, a machine for raising water by means of the energy of the moving water of which a portion is to be raised. When the rush of water through the main pipe d shuts the valve at a, the momentum of the current thus suddenly checked forces part of it into the air chamber b, and up the pipe c, its return being prevented by a valve at the entrance to the air chamber, while the dropping of the valve a by its own weight allows another rush through the main pipe, and so on alternately. Hydraulic valve. (Mach.)

1. A valve for regulating the distribution of water in the cylinders of hydraulic elevators, cranes, etc.

2. (Gas Works) An inverted cup with a partition dipping into water, for opening or closing communication between two gas mains, the open ends of which protrude about the water.

n. quicklime obtained from hydraulic limestone, and used for cementing underwater, etc.

Hydraulic lime (HL) is a general term for varieties of lime (calcium oxide), or slaked lime (calcium hydroxide), used to make lime mortar which set through hydration: thus they are called hydraulic. The other common types of lime mortar set through carbonation (re-absorbing carbon dioxide (CO) from the air) and are sometimes called air lime. Hydraulic lime provides a faster initial set and higher compressive strength than air lime and eminently hydraulic lime will set in more extreme conditions including under water. Calcium reacts in the lime kiln with the clay minerals to produce silicates that enable some of the lime to set through hydration; any unreacted calcium is slaked to calcium hydroxide which sets through carbonation: These are sometimes called semi-hydraulic lime and include feebly and moderately hydraulic lime, NHL 2 and NHL 3.5. The terms hydraulic lime and hydrated lime are quite similar and may be confused but are not necessarily the same material: hydrated lime is any lime which has been slaked whether it sets through hydration, carbonation, or both.

The two basic types of hydraulic limes are natural hydraulic lime (NHL) and artificial hydraulic lime (AHL):

Natural hydraulic lime (NHL) is produced by heating (calcining) limestone that naturally contains clay and other impurities: no materials may be added to create the hydraulicity. In the United States NHL may be called hydrated hydraulic lime (HHL) per ASTM C-141 Standard Specification for Hydrated Hydraulic Lime for Structural Purposes.

Artificial hydraulic lime (AHL) or artificial lime (AL) becomes hydraulic when hydraulic and/or pozzolan materials are added either before or after burning in a lime kiln. Artificial limes are more specifically identified as hydraulic lime (HL), as defined European Norm 459 (EN-459), "Consists of lime and other materials such as Portland cement, blast furnace slag, fly ash, limestone filler and other suitable materials."; formulated lime (FL) (EN-459) consists of "...mainly of hydrated lime and or NHL with added hydraulic and/or pozzolanic material. It is identical to HL but its composition must be declared on the CE marking."; pozzolanic hydraulic lime (PHL) (ASTM C-1707)is "very similar to HL or FL. Consists mainly of hydrated lime with one or more pozzolans with possible inclusion of inert filler. When Portland cement, even traces, is present (can be up to 20% of binder weight), it has to be labeled as 'PHLc'."