Portland cement (often referred to as OPC, from Ordinary Portland Cement) is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout. It usually originates from limestone. It is a fine powder produced by grinding Portland cement clinker (more than 90%), a limited amount of calcium sulfate (which controls the set time) and up to 5% minor constituents as allowed by various standards such as the European Standard EN197-1:
Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates (3 CaO·SiO2 and 2 CaO·SiO2), the remainder consisting of aluminium- and iron-containing clinker phases and other compounds. The ratio of CaO to SiO2 shall not be less than 2.0. The magnesium oxide content (MgO) shall not exceed 5.0% by mass.
(The last two requirements were already set out in the German Standard, issued in 1909).
ASTM C 150 defines portland cement as "hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) produced by pulverizing clinkers consisting essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulfate as an inter ground addition." Clinkers are nodules (diameters, 0.2-1.0 inch ) of a sintered material that is produced when a raw mixture of predetermined composition is heated to high temperature. The low cost and widespread availability of the limestone, shales, and other naturally occurring materials make portland cement one of the lowest-cost materials widely used over the last century throughout the world. Concrete is one of the most versatile construction materials available in the world.
Portland cement clinker is made by heating, in a kiln, a homogeneous mixture of raw materials to a calcining temperature, which is about 1450 °C for modern cements. The aluminium oxide and iron oxide are present as a flux and contribute little to the strength. For special cements, such as Low Heat (LH) and Sulfate Resistant (SR) types, it is necessary to limit the amount of tricalcium aluminate (3 CaO·Al2O3) formed. The major raw material for the clinker-making is usually limestone (CaCO3) mixed with a second material containing clay as source of alumino-silicate. Normally, an impure limestone which contains clay or SiO2 is used. The CaCO3 content of these limestones can be as low as 80%. Secondary raw materials (materials in the rawmix other than limestone) depend on the purity of the limestone. Some of the materials used are clay, shale, sand, iron ore, bauxite, fly ash and slag. When a cement kiln is fired by coal, the ash of the coal acts as a secondary raw material.
Other articles related to "cement, portland cement":
... As the century ended, the natural-cement industry dominated the market ... The Snyder family was proud that their cement had been used in the Brooklyn Bridge, an icon of the era ... But the development of the cheaper Portland cement during that time period eventually toppled the Rosendale variety, whose market share dropped 90% in the first decade of the 20th century ...
... Soil cement is a construction material, a mix of pulverized natural soil with small amount of portland cement and water, usually processed in a tumble, compacted to high density ... Hard, semi-rigid durable material is formed by hydration of the cement particles ... Soil cement is frequently used as a construction material for pipe bedding, slope protection, and road construction as a subbase layer reinforcing and protecting the ...
... Due to the high temperatures inside cement kilns, combined with the oxidizing (oxygen-rich) atmosphere and long residence times, cement kilns are used as a processing option for ... Waste materials used in cement kilns as a fuel supplement Car and truck tires – steel belts are easily tolerated in the kilns Paint sludge from automobile industries Waste solvents and lubricants Meat ...
... A cement industry had been established in the Cliffe area since 1860 when Francis and Co ... opened the Nine Elms Cement Works on Cliffe Marsh, to the west of the village where the chalk cliffs came almost to within a mile of the River Thames ... The site was taken over by the British Portland Cement Company in 1900 and works continued until 1920 ...
3 sawdust 3 builder's lime (not agricultural) 2 Portland cement ... A commercial cement retarder can be substituted for sawdust, but has a larger environmental impact ... flexible, breathable, and self healing because it takes longer to completely set than cement ...
Famous quotes containing the words cement and/or portland:
“It is fair to assume that when women in the past have achieved even a second or third place in the ranks of genius they have shown far more native ability than men have needed to reach the same eminence. Not excused from the more general duties that constitute the cement of society, most women of talent have had but one hand free with which to work out their ideal conceptions.”
—Anna Garlin Spencer (18511931)
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—For the State of New Hampshire, U.S. public relief program (1935-1943)