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Portland cement is the most common type of
cement A cement is a binder (material), binder, a substance used for construction that solidification, sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (constru ...
in general use around the world as a basic ingredient of
concrete Concrete is a composed of fine and coarse bonded together with a fluid (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its ...

concrete
,
mortar Mortar may refer to: * Mortar (weapon), an indirect-fire infantry weapon * Mortar (masonry), a material used to fill the gaps between blocks and bind them together * Mortar and pestle, a tool pair used to crush or grind * Mortar, Bihar, a village in ...
,
stucco Stucco or render is a construction material made of Construction aggregate, aggregates, a binder (material), binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, ...
, and non-specialty
grout Grout is a dense fluid which is used to fill gaps or used as reinforcement in existing structures. Grout is generally a mixture of water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorl ...
. It was developed from other types of
hydraulic lime Hydraulic lime (HL) is a general term for calcium oxide Calcium Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride ...
in England in the early 19th century by
Joseph Aspdin Joseph Aspdin (December 1778 – 20 March 1855) was an English cement manufacturer who obtained the patent for Portland cement on 21 October 1824. Life Aspdin (or Aspden) was the eldest of the six children of Thomas Aspdin, a bricklayer living ...
, and is usually made from
limestone Limestone is a common type of carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its nat ...

limestone
. It is a fine
powder A powder is a dry, bulk solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A soli ...
, produced by heating limestone and clay minerals in a
kiln , Wrecclesham Wrecclesham is a village on the southern outskirts of the large town of Farnham Farnham is a market town in Surrey, England, within the Borough of Waverley Borough Council, Waverley.OS Explorer map 145:Guildford and Farnham ...

kiln
to form clinker, grinding the clinker, and adding 2 to 3 percent of
gypsum Gypsum is a soft sulfate mineralThe sulfate minerals are a class of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the ...

gypsum
. Several types of portland cement are available. The most common, called ordinary portland cement (OPC), is grey, but white portland cement is also available. Its name is derived from its resemblance to Portland stone which was quarried on the
Isle of Portland The Isle of Portland is a tied island Tied islands, or land-tied islands as they are often known, are landforms consisting of an island upright=1.15, Great_Britain.html"_;"title="Ireland_(left)_and_Great_Britain">Ireland_(left)_and ...
in
Dorset Dorset (; archaically In language A language is a structured system of communication used by humans, including speech (spoken language), gestures (Signed language, sign language) and writing. Most languages have a writing system composed ...

Dorset
, England. It was named by
Joseph Aspdin Joseph Aspdin (December 1778 – 20 March 1855) was an English cement manufacturer who obtained the patent for Portland cement on 21 October 1824. Life Aspdin (or Aspden) was the eldest of the six children of Thomas Aspdin, a bricklayer living ...
who obtained a patent for it in 1824. However, his son William Aspdin is regarded as the inventor of "modern" portland cement due to his developments in the 1840s. Portland cement is
caustic Caustic most commonly refers to: * Causticity, a property of various corrosive substances ** Sodium hydroxide, sometimes called ''caustic soda'' ** Potassium hydroxide, sometimes called ''caustic potash'' ** Calcium oxide, sometimes called ''caustic ...
, so it can cause chemical burns. The powder can cause irritation or, with severe exposure, lung cancer, and can contain a number of hazardous components, including crystalline
silica Silicon dioxide, also known as silica, is an oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any su ...

silica
and
hexavalent chromium Hexavalent chromium (chromium(VI), Cr(VI), chromium 6) is chromium Chromium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is ...
. Environmental concerns are the high energy consumption required to mine, manufacture, and transport the cement, and the related air pollution, including the release of the
greenhouse gas A greenhouse gas (GHG or GhG) is a gas Gas is one of the four fundamental states of matter (the others being solid, liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformat ...
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
,
dioxin Dioxin may refer to: *1,2-Dioxin or 1,4-Dioxin, two unsaturated Heterocyclic#6-Membered rings, heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the chemical formula#Molecular formula, molecular formul ...

dioxin
, , SO2, and
particulates Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM), or suspended particulate matter (SPM) – are microscopic The microscopic scale (from , ''mikrós'', "small" and σκοπ ...
. Production of portland cement contributes about 10% of world
carbon dioxide emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without ...
. The
International Energy Agency The International Energy Agency (IEA; french: Agence internationale de l'énergie) is a Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estima ...
has estimated that cement production will increase by between 12 and 23% by 2050 to meet the needs of the world's growing population. There are several ongoing researches targeting a suitable replacement of portland cement by supplementary cementitious materials. The low cost and widespread availability of the limestone,
shales Shale is a fine-grained, clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defi ...

shales
, and other naturally-occurring materials used in portland cement make it one of the lowest-cost materials widely used over the last century. Concrete produced from Portland cement is one of the world's most versatile construction materials.


History

Portland cement was developed from natural cements made in Britain beginning in the middle of the 18th century. Its name is derived from its similarity to Portland stone, a type of building stone quarried on the
Isle of Portland The Isle of Portland is a tied island Tied islands, or land-tied islands as they are often known, are landforms consisting of an island upright=1.15, Great_Britain.html"_;"title="Ireland_(left)_and_Great_Britain">Ireland_(left)_and ...
in Dorset, England. The development of modern portland cement (sometimes called ordinary or normal portland cement) began in 1756, when
John Smeaton John Smeaton (8 June 1724 – 28 October 1792) was a British civil engineer A civil engineer is a person who practices civil engineering Civil engineering is a Regulation and licensure in engineering, professional engineering discip ...

John Smeaton
experimented with combinations of different limestones and additives, including
trassTrass is the local name of a volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's sur ...
and
pozzolana Pozzolana or pozzuolana ( , ), also known as pozzolanic ash ( la, pulvis puteolanus), is a natural silica, siliceous or siliceous-Aluminium oxide, aluminous material which reacts with calcium hydroxide in the presence of water at room temperature ( ...
s, relating to the planned construction of a lighthouse,Robert G. Blezard, "The History of Calcareous Cements" in Hewlett, Peter C., ed.. ''Leaʼs chemistry of cement and concrete''. 4. ed. Amsterdam: Elsevier Butterworth-Heinemann, 2004. 1–24. Print. now known as
Smeaton's Tower Smeaton's Tower is a memorial to civil engineer John Smeaton, designer of the third and most notable Eddystone Lighthouse#Smeaton.27s lighthouse, Eddystone Lighthouse. A major step forward in lighthouse design, Smeaton's structure was in use from ...

Smeaton's Tower
. In the late 18th century,
Roman cement Roman cement is a substance developed by James Parker in the 1780s, being patented in 1796. The name is misleading, as it is nothing like any material used by the Romans, but was a "natural cement A cement is a binder (material), binder, ...
was developed and patented in 1796 by James Parker.Saikia, Mimi Das. Bhargab Mohan Das, Madan Mohan Das. ''Elements of Civil Engineering''. New Delhie: PHI Learning Private Limited. 2010. 30. Print. Roman cement quickly became popular, but was largely replaced by portland cement in the 1850s. In 1811,
James Frost James Martin Frost (born 22 August 1986, Cowbridge, Wales) is the guitarist, keyboardist and backing vocalist of Welsh band The Automatic, and guitarist and backing vocalist for Cardiff-based band Effort. As well as his musical duties for The Au ...
produced a cement he called British cement. James Frost is reported to have erected a manufactory for making of an artificial cement in 1826. In 1811 Edgar Dobbs of Southwark patented a cement of the kind invented 7 years later by the French engineer
Louis Vicat 250px, Portrait of Louis Vicat young. Louis Vicat (31 March 1786, Nevers Nevers ( , ; la, Noviodunum, later ''Nevirnum'' and ''Nebirnum'') is the prefecture of the Nièvre Departments of France, department in the Bourgogne-Franche-Comté Regi ...
. Vicat's cement is an artificial
hydraulic lime Hydraulic lime (HL) is a general term for calcium oxide Calcium Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride ...
, and is considered the "principal forerunner" of portland cement. The name ''portland cement'' is recorded in a directory published in 1823 being associated with a William Lockwood and possibly others. In his 1824 cement patent,
Joseph Aspdin Joseph Aspdin (December 1778 – 20 March 1855) was an English cement manufacturer who obtained the patent for Portland cement on 21 October 1824. Life Aspdin (or Aspden) was the eldest of the six children of Thomas Aspdin, a bricklayer living ...
called his invention "portland cement" because of its resemblance to Portland stone. However, Aspdin's cement was nothing like modern portland cement, but was a first step in the development of modern portland cement, and has been called a "proto-portland cement". William Aspdin had left his father's company, to form his own cement manufactury. In the 1840s William Aspdin, apparently accidentally, produced
calcium silicate Calcium silicate is the chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held togeth ...
s which are a middle step in the development of portland cement. In 1848, William Aspdin further improved his cement. Then, in 1853, he moved to Germany, where he was involved in cement making. William Aspdin made what could be called "meso-portland cement" (a mix of portland cement and hydraulic lime).
Isaac Charles Johnson Isaac Charles Johnson (28 January 1811 – 29 November 1911) was a British cement manufacturer, and a pioneer of the Portland cement industry. Born in London, his father was a charge-hand at Francis & White's "Roman Cement" plant in Nine Elms. He ...
further refined the production of "meso-portland cement" (middle stage of development), and claimed to be the real father of portland cement. In 1859, John Grant of the Metropolitan Board of Works, set out requirements for cement to be used in the London sewer project. This became a specification for portland cement. The next development in the manufacture of portland cement was the introduction of the
rotary kiln A rotary kiln is a pyroprocessing Pyroprocessing (from Greek Πυρος = ''fire'') is a process in which materials are subjected to high temperatures (typically over 800 °C) in order to bring about a chemical or physical change. Pyropro ...

rotary kiln
, patented by
Frederick Ransome Frederick Ransome (1818–1893) was a British inventor and industrialist, creator of Ransome's artificial stone Artificial stone is a name for various synthetic stone products produced from the 18th century onward. Uses include statuary, archit ...
in 1885 (U.K.) and 1886 (U.S.); which allowed a stronger, more homogeneous mixture and a continuous manufacturing process. The Hoffmann "endless" kiln which was said to give "perfect control over combustion" was tested in 1860, and showed the process produced a better grade of cement. This cement was made at the Portland Cementfabrik Stern at Stettin, which was the first to use a Hoffmann kiln. The Association of German Cement Manufacturers issued a standard on portland cement in 1878. Portland cement had been imported into the United States from Germany and England, and in the 1870s and 1880s, it was being produced by Eagle Portland cement near Kalamazoo, Michigan. In 1875, the first portland cement was produced in the Coplay Cement Company Kilns under the direction of David O. Saylor in
Coplay, Pennsylvania Coplay is a borough in Lehigh County, Pennsylvania, Lehigh County, Pennsylvania, six miles (10 km) northwest of Allentown, Pennsylvania, Allentown. It is part of the Lehigh Valley region of the state. In 1900, 1,581 people lived in Coplay; i ...
. By the early 20th century, American-made portland cement had displaced most of the imported portland cement.


Composition

ASTM ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization ( ...
C150 defines portland cement as: The
European Standard European Standards (abbreviated EN, from the German name ("European Norm")) are technical standard A technical standard is an established norm (social), norm or requirement for a repeatable technical task which is applied to a common and repeated ...
EN 197-1 uses the following definition: (The last two requirements were already set out in the German Standard, issued in 1909). Clinkers make up more than 90% of the cement, along with a limited amount of
calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that cove ...

calcium sulfate
(CaSO4, which controls the set time), and up to 5% minor constituents (fillers) as allowed by various standards. Clinkers are nodules (diameters, ) of a sintered material that is produced when a raw mixture of predetermined composition is heated to high temperature. The key chemical reaction which defines portland cement from other hydraulic limes occurs at these high temperatures (>) as
belite Belite is an industrial mineral Industrial resources (minerals) are geological materials which are mined for their commercial value, which are not fuel (fuel minerals or mineral fuels A fossil fuel is a fuel formed by natural processes, su ...
(Ca2SiO4) combines with calcium oxide (CaO) to form
alite Alite is an impure form of tricalcium silicate, , sometimes formulated as ( in cement chemist notation), typically with 3-4% of substituent oxides. It is the major, and characteristic, phase in Portland cement. The name was given by Törnebohm in ...
(Ca3SiO5).


Manufacturing

Portland cement clinker is made by heating, in a
cement kiln Cement kilns are used for the pyroprocessing Pyroprocessing (from Greek Πυρος = ''fire'') is a process in which materials are subjected to high temperatures (typically over 800 °C) in order to bring about a chemical or physical change. ...
, a mixture of raw materials to a
calcining Calcination refers to heating a solid to high temperatures in absence of air or oxygen, generally for the purpose of removing impurities or volatile substances. However, calcination is also used to mean a thermal treatment process in the absence o ...
temperature of above and then a fusion temperature, which is about for modern cements, to sinter the materials into clinker. The materials in cement clinker are alite, belite,
tricalcium aluminate Tricalcium aluminate Ca3Al2O6, often formulated as 3CaO·Al2O3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates. It does not occur in nature, but is an important mineral phase in Portl ...
, and tetracalcium alumino ferrite. The aluminium, iron, and magnesium oxides are present as a
flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
allowing the calcium silicates to form at a lower temperature, 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 Limestone is a common type of carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its nat ...

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 raw mix other than limestone) depend on the purity of the limestone. Some of the materials used are
clay Clay is a type of fine-grained natural soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic m ...

clay
,
shale Shale is a fine-grained, clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defi ...

shale
,
sand Sand is a granular material composed of finely divided rock (geology), rock and mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer ...

sand
,
iron ore Iron ores are rocks In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it i ...
,
bauxite Bauxite is a sedimentary rock Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation ( ...

bauxite
,
fly ash Fly ash, flue ash, coal ash, or pulverised fuel ash (in the UK) plurale tantum A ''plurale tantum'' (Latin for "plural only"; ) is a noun that appears only in the plural The plural (sometimes abbreviated An abbreviation (from Latin ''brev ...
, and
slag Slag is a by-product of smelting Smelting is a process of applying heat to ore in order to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including Silver mining#Ore processing, ...

slag
. When a cement kiln is fired by coal, the ash of the coal acts as a secondary raw material.


Cement grinding

To achieve the desired setting qualities in the finished product, a quantity (2–8%, but typically 5%) of calcium sulfate (usually
gypsum Gypsum is a soft sulfate mineralThe sulfate minerals are a class of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the ...

gypsum
or
anhydrite Anhydrite, or anhydrous calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hyd ...

anhydrite
) is added to the clinker, and the mixture is finely ground to form the finished cement powder. This is achieved in a
cement mill A cement mill (or finish mill in North American usage) is the equipment used to grind the hard, nodular clinker from the cement kiln Cement kilns are used for the pyroprocessing stage of manufacture of Portland cement, Portland and other types of ...

cement mill
. The grinding process is controlled to obtain a powder with a broad particle size range, in which typically 15% by mass consists of particles below 5 μm diameter, and 5% of particles above 45 μm. The measure of fineness usually used is the '
specific surface area Specific surface area (SSA) is a property of solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kin ...
', which is the total particle surface area of a unit mass of cement. The rate of initial reaction (up to 24 hours) of the cement on addition of water is
directly proportional In mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). ...
to the specific surface area. Typical values are 320–380 m2·kg−1 for general purpose cements, and 450–650 m2·kg−1 for 'rapid hardening' cements. The cement is conveyed by belt or powder pump to a silo for storage. Cement plants normally have sufficient silo space for one to 20 weeks of production, depending upon local demand cycles. The cement is delivered to end users either in bags, or as bulk powder blown from a pressure vehicle into the customer's silo. In industrial countries, 80% or more of cement is delivered in bulk.


Setting and hardening

Cement sets when mixed with water by way of a complex series of chemical reactions still only partly understood. The different constituents slowly crystallise, and the interlocking of their crystals gives cement its strength.
Carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

Carbon dioxide
is slowly absorbed to convert the
portlandite Portlandite is an oxide mineral The oxide mineral class includes those mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the ...
(Ca(OH)2) into insoluble
calcium carbonate Calcium carbonate is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held togethe ...

calcium carbonate
. After the initial setting, immersion in warm water will speed up setting.
Gypsum Gypsum is a soft sulfate mineral The sulfate minerals are a class of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with ...

Gypsum
is added as an inhibitor to prevent flash (or quick) setting.


Use

The most common use for portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (
gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone Crushed may refer to ...

gravel
and
sand Sand is a granular material composed of finely divided rock (geology), rock and mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer ...

sand
), cement, and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. Concrete can be used in the construction of structural elements like panels, beams, and
street furniture Street furniture is a collective term (used in the United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in ...

street furniture
, or may be cast-''in situ'' for superstructures like roads and dams. These may be supplied with concrete mixed on site, or may be provided with ' ready-mixed' concrete made at permanent mixing sites. Portland cement is also used in
mortar Mortar may refer to: * Mortar (weapon), an indirect-fire infantry weapon * Mortar (masonry), a material used to fill the gaps between blocks and bind them together * Mortar and pestle, a tool pair used to crush or grind * Mortar, Bihar, a village in ...
s (with sand and water only), for
plaster Plaster is a building material Building material is material used for construction Construction is a general term meaning the art and science to form Physical object, objects, systems, or organizations,"Construction" def. 1.a. 1.b. an ...
s and
screed Screed has three meanings in building construction: # A flat board (screed board, floating screed) or a purpose-made aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of ...
s, and in
grout Grout is a dense fluid which is used to fill gaps or used as reinforcement in existing structures. Grout is generally a mixture of water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorl ...
s (cement/water mixes squeezed into gaps to consolidate foundations, road-beds, etc.). When water is mixed with portland cement, the product sets in a few hours, and hardens over a period of weeks. These processes can vary widely, depending upon the mix used and the conditions of curing of the product, but a typical concrete sets in about 6 hours and develops a
compressive strength In mechanics Mechanics (Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its populat ...
of 8 MPa in 24 hours. The strength rises to 15 MPa at 3 days, 23 MPa at 1 week, 35 MPa at 4 weeks, and 41 MPa at 3 months. In principle, the strength continues to rise slowly as long as water is available for continued hydration , but concrete is usually allowed to dry out after a few weeks and this causes strength growth to stop.


Types


General


ASTM C150

Five types of portland cements exist, with variations of the first three according to ASTM C150. Type I portland cement is known as common or general-purpose cement. It is generally assumed unless another type is specified. It is commonly used for general construction, especially when making precast, and precast-prestressed concrete that is not to be in contact with soils or ground water. The typical compound compositions of this type are: 55% (C3S), 19% (C2S), 10% (C3A), 7% (C4AF), 2.8% MgO, 2.9% (SO3), 1.0% ignition loss, and 1.0% free CaO (utilizing
Cement chemist notation Cement chemist notation (CCN) was developed to simplify the formula In , a formula is a concise way of expressing information symbolically, as in a mathematical formula or a . The informal use of the term ''formula'' in science refers to the . ...
). A limitation on the composition is that the (C3A) shall not exceed 15%. Type II provides moderate sulfate resistance, and gives off less heat during hydration. This type of cement costs about the same as type I. Its typical compound composition is: 51% (C3S), 24% (C2S), 6% (C3A), 11% (C4AF), 2.9% MgO, 2.5% (SO3), 0.8% ignition loss, and 1.0% free CaO. A limitation on the composition is that the (C3A) shall not exceed 8%, which reduces its vulnerability to sulfates. This type is for general construction exposed to moderate sulfate attack, and is meant for use when concrete is in contact with soils and ground water, especially in the western United States due to the high sulfur content of the soils. Because of similar price to that of type I, type II is much used as a general purpose cement, and the majority of portland cement sold in North America meets this specification. Note: Cement meeting (among others) the specifications for types I and II has become commonly available on the world market. Type III has relatively high early strength. Its typical compound composition is: 57% (C3S), 19% (C2S), 10% (C3A), 7% (C4AF), 3.0% MgO, 3.1% (SO3), 0.9% ignition loss, and 1.3% free CaO. This cement is similar to type I, but ground finer. Some manufacturers make a separate clinker with higher C3S and/or C3A content, but this is increasingly rare, and the general purpose clinker is usually used, ground to a
specific surface area Specific surface area (SSA) is a property of solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Defo ...
typically 50–80% higher. The gypsum level may also be increased a small amount. This gives the concrete using this type of cement a three-day compressive strength equal to the seven-day compressive strength of types I and II. Its seven-day compressive strength is almost equal to 28-day compressive strengths of types I and II. The only downside is that the six-month strength of type III is the same or slightly less than that of types I and II. Therefore, the long-term strength is sacrificed. It is usually used for precast concrete manufacture, where high one-day strength allows fast turnover of molds. It may also be used in emergency construction and repairs, and construction of machine bases and gate installations. Type IV portland cement is generally known for its low heat of hydration. Its typical compound composition is: 28% (C3S), 49% (C2S), 4% (C3A), 12% (C4AF), 1.8% MgO, 1.9% (SO3), 0.9% ignition loss, and 0.8% free CaO. The percentages of (C2S) and (C4AF) are relatively high and (C3S) and (C3A) are relatively low. A limitation on this type is that the maximum percentage of (C3A) is seven, and the maximum percentage of (C3S) is thirty-five. This causes the heat given off by the
hydration reaction In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the ...
to develop at a slower rate. However, as a consequence the strength of the concrete develops slowly. After one or two years the strength is higher than the other types after full curing. This cement is used for very large concrete structures, such as dams, which have a low surface to volume ratio. This type of cement is generally not stocked by manufacturers, but some might consider a large special order. This type of cement has not been made for many years, because portland-pozzolan cements and
ground granulated blast furnace slagGround-granulated blast-furnace slag (GGBS or GGBFS) is obtained by quenching molten iron slag '' (slag), an 1873 wood engraving Slag is the glass-like by-product left over after a desired metal has been separated (i.e., Smelting, smelted) from ...
addition offer a cheaper and more reliable alternative. Type V is used where sulfate resistance is important. Its typical compound composition is: 38% (C3S), 43% (C2S), 4% (C3A), 9% (C4AF), 1.9% MgO, 1.8% (SO3), 0.9% ignition loss, and 0.8% free CaO. This cement has a very low (C3A) composition which accounts for its high sulfate resistance. The maximum content of (C3A) allowed is 5% for type V portland cement. Another limitation is that the (C4AF) + 2(C3A) composition cannot exceed 20%. This type is used in concrete to be exposed to
alkali In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo dur ...

alkali
soil and ground water
sulfates The sulfate or sulphate ion is a polyatomic anion An ion () is a particle, atom or molecule with a net electric charge, electrical charge. The charge of the electron is considered negative by convention. The negative charge of an ion is ...
which react with (C3A) causing disruptive expansion. It is unavailable in many places, although its use is common in the western United States and Canada. As with type IV, type V portland cement has mainly been supplanted by the use of ordinary cement with added ground granulated blast furnace slag or tertiary blended cements containing slag and fly ash. Types Ia, IIa, and IIIa have the same composition as types I, II, and III. The only difference is that in Ia, IIa, and IIIa, an air-entraining agent is ground into the mix. The air-entrainment must meet the minimum and maximum optional specification found in the ASTM manual. These types are only available in the eastern United States and Canada, only on a limited basis. They are a poor approach to air-entrainment which improves resistance to freezing under low temperatures. Types II(MH) and II(MH)a have a similar composition as types II and IIa, but with a mild heat.


EN 197 norm

The European norm EN 197-1 defines five classes of common cement that comprise portland cement as a main constituent. These classes differ from the ASTM classes. ''Constituents that are permitted in portland-composite cements are artificial pozzolans (blast furnace slag (in fact a latent hydraulic binder), silica fume, and fly ashes), or natural pozzolans (siliceous or siliceous aluminous materials such as volcanic ash glasses, calcined clays and shale).''


CSA A3000-08

The Canadian standards describe six main classes of cement, four of which can also be supplied as a blend containing ground limestone (where a suffix L is present in the class names).


White portland cement

White portland cement or white ordinary portland cement (WOPC) is similar to ordinary, grey, portland cement in all respects, except for its high degree of whiteness. Obtaining this colour requires high purity raw materials (low Fe2O3 content), and some modification to the method of manufacture, among others a higher kiln temperature required to sinter the clinker in the absence of ferric oxides acting as a flux in normal clinker. As Fe2O3 contributes to decrease the melting point of the clinker (normally 1450 °C), the white cement requires a higher sintering temperature (around 1600 °C). Because of this, it is somewhat more expensive than the grey product. The main requirement is to have a low iron content which should be less than 0.5 wt.% expressed as Fe2O3 for white cement, and less than 0.9 wt.% for off-white cement. It also helps to have the iron oxide as ferrous oxide (FeO) which is obtained via slightly reducing conditions in the kiln, i.e., operating with zero excess oxygen at the kiln exit. This gives the clinker and cement a green tinge. Other metallic oxides such as Cr2O3 (green), MnO (pink), TiO2 (white), etc., in trace content, can also give colour tinges, so for a given project it is best to use cement from a single batch.


Safety issues

Bags of cement routinely have health and safety warnings printed on them, because not only is cement highly
alkali In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo dur ...

alkali
ne, but the setting process is also
exothermic In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these qu ...

exothermic
. As a result, wet cement is strongly
caustic Caustic most commonly refers to: * Causticity, a property of various corrosive substances ** Sodium hydroxide, sometimes called ''caustic soda'' ** Potassium hydroxide, sometimes called ''caustic potash'' ** Calcium oxide, sometimes called ''caustic ...
, and can easily cause severe skin burns if not promptly washed off with water. Similarly, dry cement powder in contact with
mucous membrane A mucous membrane or mucosa is a biological membrane, membrane that lines various cavities in the body and covers the surface of internal organs. It consists of one or more layers of Epithelium, epithelial cells overlying a layer of loose connect ...
s can cause severe eye or respiratory irritation. The reaction of cement dust with moisture in the sinuses and lungs can also cause a chemical burn, as well as headaches, fatigue, and lung cancer. The production of comparatively low-alkalinity cements (pH<11) is an area of ongoing investigation. In
Scandinavia Scandinavia; Sami Places * Sápmi, a cultural region in Northern Europe * Sami, Burkina Faso, a district of the Banwa Province * Sami District, Gambia * Sami, Cephalonia, a municipality in Greece * Sami (ancient city), in Elis, Greece * Sa ...

Scandinavia
, France, and the United Kingdom, the level of chromium(VI), which is considered to be toxic and a major skin irritant, may not exceed 2
parts per million In science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form of Testability, testable explanations and predictio ...
(ppm). In the US, the
Occupational Safety and Health Administration The Occupational Safety and Health Administration (OSHA ) is a large regulatory agency of the United States Department of Labor The United States Department of Labor (DOL) is a cabinet-level department of the U.S. federal government, re ...
(OSHA) has set the legal limit (
permissible exposure limit The permissible exposure limit (PEL or OSHA PEL) is a legal Law is a system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and ...
) for portland cement exposure in the workplace as 50 mppcf (million particles per cubic foot) over an 8-hour workday. The
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury Injury, also known as physical ...
(NIOSH) has set a
recommended exposure limit A recommended exposure limit (REL) is an occupational exposure limit An occupational exposure limit is an upper limit on the acceptable concentration of a hazardous substance in workplace air for a particular material or class of materials. It i ...
(REL) of 10 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. At levels of 5000 mg/m3, portland cement is
immediately dangerous to life and health The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent adverse ...
.


Environmental effects

Portland cement manufacture can cause environmental impacts at all stages of the process. These include emissions of airborne pollution in the form of dust; gases; noise and vibration when operating machinery and during blasting in quarries; consumption of large quantities of fuel during manufacture; release of CO2 from the raw materials during manufacture, and damage to countryside from quarrying. Equipment to reduce dust emissions during quarrying and manufacture of cement is widely used, and equipment to trap and separate exhaust gases are coming into increased use. Environmental protection also includes the re-integration of quarries into the countryside after they have been closed down by returning them to nature or re-cultivating them. ''Epidemiologic Notes and Reports Sulfur Dioxide Exposure in Portland Cement Plants'', from the
Centers for Disease Control The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services The United States Department of Heal ...
, states: An independent research effort of
AEA Technology Ricardo-AEA Ltd, trading as Ricardo Energy & Environment, was formed on November 8, 2012, when Ricardo acquired the business, operating assets and employees engaged in the business of AEA Technology Plc (AEAT, in administration) (AEA Europe), for ...
to identify critical issues for the cement industry today concluded the most important
environment, health and safetyEnvironment (E), health (H) and safety (S), EHS is an acronym for the methodology that studies and implements the practical aspects of protecting the environment and maintaining health and safety at occupation. In simple terms it is what organization ...
performance issues facing the cement industry are atmospheric releases (including
greenhouse gas emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without ...
, dioxin, NOx, SO2, and particulates), accidents, and worker exposure to dust. The CO2 associated with portland cement manufacture comes mainly from four sources: Overall, with nuclear or hydroelectric power, and efficient manufacturing, CO2 generation can be reduced to per kg cement, but can be twice as high . The thrust of innovation for the future is to reduce sources 1 and 2 by modification of the chemistry of cement, by the use of wastes, and by adopting more efficient processes. Although cement manufacturing is clearly a very large CO2 emitter, concrete (of which cement makes up about 15%) compares quite favourably with other building systems in this regard.


Cement plants used for waste disposal or processing

Due to the high temperatures inside
cement kiln Cement kilns are used for the pyroprocessing Pyroprocessing (from Greek Πυρος = ''fire'') is a process in which materials are subjected to high temperatures (typically over 800 °C) in order to bring about a chemical or physical change. ...
s, combined with the oxidising (oxygen-rich) atmosphere and long residence times, cement kilns are used as a processing option for various types of waste streams; indeed, they efficiently destroy many hazardous organic compounds. The waste streams also often contain combustible materials which allow the substitution of part of the fossil fuel normally used in the process. Waste materials used in cement kilns as a fuel supplement: *Car and truck
tire A tire (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States ...

tire
s – steel belts are easily tolerated in the kilns *Paint sludge from automobile industries *Waste solvents and lubricants *
Meat and bone meal Meat and bone meal (MBM) is a product of the rendering industry. It is typically about 48–52% protein, 33–35% ash (analytical chemistry), ash, 8–12% fat, and 4–7% water. It is primarily used in the formulation of fodder, animal feed to i ...

Meat and bone meal
slaughterhouse A slaughterhouse, also called abattoir (), is a facility where animals are slaughtered to provide food for humans. Slaughterhouses supply meat, which then becomes the responsibility of a packaging facility. Slaughterhouses that produce mea ...

slaughterhouse
waste due to
bovine spongiform encephalopathy Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is a neurodegenerative disease A neurodegenerative disease is caused by the progressive loss of structure or function of neuron A neuron or nerve cell is an membr ...
contamination concerns *Waste plastics *Sewage
sludge Sludge is a semi-solid slurry A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids, the liquid being a carrier that is pumped on a device such as a cent ...

sludge
*
Rice hulls Rice hulls (or rice husks) are the hard protecting coverings of grains of rice Rice is the seed of the Poaceae, grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually us ...
*
Sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, ...

Sugarcane
waste *Used wooden
railroad tie A railroad tie, crosstie (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the Un ...
s (railway sleepers) * Spent cell liner from the aluminium smelting industry (also called spent pot liner) Portland cement manufacture also has the potential to benefit from using industrial byproducts from the waste stream. These include in particular: *
Slag Slag is a by-product of smelting Smelting is a process of applying heat to ore in order to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including Silver mining#Ore processing, ...

Slag
*
Fly ash Fly ash, flue ash, coal ash, or pulverised fuel ash (in the UK) plurale tantum A ''plurale tantum'' (Latin for "plural only"; ) is a noun that appears only in the plural The plural (sometimes abbreviated An abbreviation (from Latin ''brev ...
(from power plants) *
Silica fume Silica fume, also known as microsilica, (CAS number 69012-64-2, EINECS number 273-761-1) is an amorphous In condensed matter physics Condensed matter physics is the field of physics Physics (from grc, φυσική (ἐπιστήμ ...
(from steel mills) *Synthetic
gypsum Gypsum is a soft sulfate mineralThe sulfate minerals are a class of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the ...

gypsum
(from
desulfurisationDesulfurization or desulphurisation is a chemical process for the removal of sulfur from a material. This involves either the removal of sulfur from a molecule (''e.g.'' A=S → A:) or the removal of sulfur compounds from a mixture such as oil re ...

desulfurisation
)


See also

*
American Concrete Institute The American Concrete Institute (ACI, formerly National Association of Cement Users or NACU) is a non-profit technical society and standards developing organization. ACI was founded in January 1905 during a convention in Indianapolis. The Institut ...
*
Calcium silicate hydrateCalcium silicate hydrate (or C-S-H) is the main product of the hydration of Portland cement and is primarily responsible for the strength in cement based materials. Preparation Calcium silicate hydrate (also shown as C-S-H) is a result of the reacti ...
* Energetically modified cement * Environmental impact of concrete * Lime mortar * Marl * Portland Cement Association * Portland Cement Works Precinct


References


External links


World Production of Hydraulic Cement, by CountryAlpha The Guaranteed Portland Cement Company: 1917 Trade Literature from Smithsonian Institution LibrariesCement Sustainability Initiative
*Aerial views of the world's largest concentration of cement manufacturing capacity, Saraburi Province, Thailand, at *
CDC – NIOSH Pocket Guide to Chemical Hazards
{{DEFAULTSORT:Portland Cement Cement Concrete English inventions Limestone Isle of Portland, Cement Building materials 19th-century inventions de:Zement#Portlandzement