Clinker is a general name given to waste from industrial processes — particularly those that involve smelting

Smelting

Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores...

 metals, burning fossil fuel

Fossil fuel

Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...

s and using a blacksmith

Blacksmith

A blacksmith is a person who creates objects from wrought iron or steel by forging the metal; that is, by using tools to hammer, bend, and cut...

's forge

Forge

A forge is a hearth used for forging. The term "forge" can also refer to the workplace of a smith or a blacksmith, although the term smithy is then more commonly used.The basic smithy contains a forge, also known as a hearth, for heating metals...

 which will usually result in a large buildup of clinker around the tuyère

Tuyere

A tuyere, also can be spelled as tuyère, is a tube, nozzle or pipe through which air is blown into a furnace or hearth.Air or oxygen is injected into a hearth under pressure from bellows or a blast engine or other devices...

. Clinker often forms a loose, black deposit that can consist of coke

Coke (fuel)

Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...

, coal

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

, slag

Slag

Slag is a partially vitreous by-product of smelting ore to separate the metal fraction from the unwanted fraction. It can usually be considered to be a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and metal atoms in the elemental form...

, charcoal

Charcoal

Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

, grit

Grit

Grit may refer to:* GRIT , also known as Arhgap32 or PX-RICS* Grit , a U.S. periodical founded as a newspaper in 1882* Grit , by Celtic fusion musician Martyn Bennett* Grit , by Norwegian rock band Madrugada...

, and other waste materials.

Clinker may be reused for paving

Pavement

Pavement may refer to:* Road surface, the durable surfacing of roads and walkways* Sidewalk, a walkway along the side of a road, in British English or Philadelphia/Baltimore dialect* Pavement , a floor-like stone or tile structure...

 footpath

Footpath

A Footpath is a thoroughfare intended for by pedestrians but not by motorized vehicles. The term is often for paths within an urban area that offer shorter quieter routes for pedestrians, they may also provide access to the surrounding countryside or parks...

s. It is laid and rolled, and forms a hard path with a rough surface.

Clinker often has a glassy look to it. It is much heavier than coke.

Also see

• Construction
  Construction
  In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
  
  
• Furnace
  Furnace
  A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...
  
  s
• Metallurgy
  Metallurgy
  Metallurgy is a domain of materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. It is also the technology of metals: the way in which science is applied to their practical use...
  
  
• Recycling
  Recycling
  Recycling is processing used materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution and water pollution by reducing the need for "conventional" waste disposal, and lower greenhouse...