Please read:A personal appeal from

Wikipedia author Dr. Sengai Podhuvan We now accept ₹(INR)

Portland cementFrom Wikipedia, the free encyclopediaJump to: navigation, search

A pallet with Portland cement

Blue Circle Southern Cement works near Berrima, New South Wales, Australia.

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 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·SiO 2 and 2   CaO·SiO 2), 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 [5–25 mm]) 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 becomes 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 sintering 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%. Second raw materials (materials in the rawmix other than limestone) depend on the purity of the limestone. Some of the second raw 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.

Contents

 [hide] 

1 History o 1.1 Cement grinding

2 Setting and hardening 3 Use 4 Types

o 4.1 General o 4.2 ASTM C150 o 4.3 EN 197 o 4.4 White Portland cement

5 Safety issues 6 Environmental effects 7 Cement plants used for waste disposal or processing 8 See also

9 References 10 External links

[edit] History

Portland cement was developed from natural cements made in Britain in the early part of the nineteenth century, and its name is derived from its similarity to Portland stone, a type of building stone that was quarried on the Isle of Portland in Dorset, England.[1]

The Portland cement is considered to originate from Joseph Aspdin, a British bricklayer from Leeds. It was one of his employees (Isaac Johnson), however, who developed the production technique, which resulted in a more fast-hardening cement with a higher compressive strength. This process was patented in 1824.[1] His cement was an artificial cement similar in properties to the material known as "Roman cement" (patented in 1796 by James Parker) and his process was similar to that patented in 1822 and used since 1811 by James Frost who called his cement "British Cement". The name "Portland cement" is also recorded in a directory published in 1823 being associated with a William Lockwood, Dave Stewart, and possibly[vague] others.[citation needed]

Aspdin's son William, in 1843, made an improved version of this cement and he initially called it "Patent Portland cement" although he had no patent. In 1848 William Aspdin further improved his cement and in 1853 he moved to Germany where he was involved in cement making.[2] Many people have claimed to have made the first Portland cement in the modern sense, but it is generally accepted that it was first manufactured by William Aspdin at Northfleet, England in about 1842.[3] The German Government issued a standard on Portland cement in 1878.[4]

[edit] Cement grinding

Main article: Cement mill

A 10 MW cement mill, producing cement at 270 tonnes per hour

In order to achieve the desired setting qualities in the finished product, a quantity (2-8%, but typically 5%) of calcium sulfate (usually gypsum or 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. 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", 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 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 1–20 weeks 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.

Typical constituents of Portland clinker plus GypsumCement chemists notation under CCN.

Clinker CCN Mass %

Tricalcium silicate (CaO)3 · SiO2 C3S 45-75%

Dicalcium silicate (CaO)2 · SiO2 C2S  7-32%

Tricalcium aluminate (CaO)3 · Al2O3 C3A  0-13%

Tetracalcium aluminoferrite (CaO)4 · Al2O3 · Fe2O3 C4AF  0-18%

Gypsum CaSO4 · 2 H2O  2-10%

Typical constituents of Portland cementCement chemists notation under CCN.

Cement CCN Mass %

Calcium oxide, CaO C 61-67%

Silicon oxide, SiO2 S 19-23%

Aluminum oxide, Al2O3 A  2.5-6%

Ferric oxide, Fe2O3 F  0-6%

Sulfate 1.5-4.5%

An alternative fabrication technique EMC (Energetically modified cement) uses very finely ground cements that are made from mixtures of cement with sand or with slag or other pozzolan type minerals which are extremely finely ground together. Such cements can have the same physical characteristics as normal cement but with 50% less cement particularly due to their increased surface area for the chemical reaction. Even with intensive grinding they can use up to 50% less energy to fabricate than ordinary Portland cements.[5]

Chemical composition of EMC (50/50 OPC/FA - Fly Ash)

Compound OPC % FA % EMC %

CaO 62.4 15.0 40.9

SiO2 17.8 49.4 33.2

Al2O3  4.0 19.6  6.3

Fe2O3  3.9  5.2  4.1

SO3  3.2  0.8  1.6

Na2O <0.1  0.3  0.1

K2O  0.3  1.2  1.2

Insolubles  0.5 51.3 21.6

[edit] 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 is slowly absorbed to convert the portlandite (Ca(OH)2) into insoluble calcium carbonate. After the initial setting, immersion in warm water will speed up setting. In Portland cement, gypsum is added as a compound preventing cement flash setting.

[edit] Use

This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2010)

Decorative use of Portland cement panels on London’s Grosvenor estate [6]

The most common use for Portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and 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. Users may be involved in the factory production of pre-cast units, such as panels, beams, road furniture, or may make cast-in-situ concrete such as building superstructures, roads, 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 mortars (with sand and water only) for plasters and screeds, and in grouts (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 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.

[edit] Types

This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2010)

[edit] General

There are different standards for classification of Portland cement. The two major standards are the ASTM C150 used primarily in the U.S. and European EN-197. EN 197 cement types CEM I, II, III, IV, and V do not correspond to the similarly named cement types in ASTM C 150.

[edit] ASTM C150

There are five types of Portland cements 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.

A limitation on the composition is that the (C3A) shall not exceed fifteen percent.

Type II is intended to have moderate sulfate resistance with or without moderate heat of 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 eight percent which reduces its vulnerability to sulfates. This type is for general construction that is 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 soil. 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 Type I and II has become commonly available on the world market.

Type III is 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 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 types I and II 28 day compressive strengths. 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 a little. It is usually used for precast concrete manufacture, where high 1-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 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 slag 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 five percent for Type V Portland cement. Another limitation is that the (C4AF) + 2(C3A) composition cannot exceed twenty percent. This type is used in concrete that is to be exposed to alkali soil and ground water sulfates 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 but can only be found 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 recently been added with a similar composition as types II and IIa but with a mild heat. The cements were added to ASTM C-150 in 2009 and will be in publication in 2010.

[edit] EN 197

EN 197-1 defines 5 classes of common cement that comprise Portland cement as a main constituent. These classes differ from the ASTM classes.

I Portland cementComprising Portland cement and up to 5% of minor additional constituents

IIPortland-composite cement

Portland cement and up to 35% of other single constituents

III Blastfurnace cement Portland cement and higher percentages of blastfurnace slag

IV Pozzolanic cementPortland cement and up to 55% of pozzolanic constituents(volcaince ashs)

V Composite cement Portland cement, blastfurnace slag or fly ash and pozzolana

Constituents that are permitted in Portland-composite cements are artificial pozzolans (blastfurnace slag, silica fume, and fly ashes) or natural pozzolans (siliceous or siliceous aluminous materials such as volcanic ash glasses, calcined clays and shale).

[edit] White Portland cement

Main article: White Portland cement

White Portland cement or white ordinary Portland cement (WOPC) is similar to ordinary, gray Portland cement in all respects except for its high degree of whiteness. Obtaining this color requires substantial modification to the method of manufacture and, because of this, it is somewhat more expensive than the gray product.

Sampling fast set concrete made from Portland cement

[edit] Safety issues

Bags of cement routinely have health and safety warnings printed on them because not only is cement highly alkaline, but the setting process is exothermic. As a result, wet cement is strongly caustic and can easily cause severe skin burns if not promptly washed off with water. Similarly, dry cement powder in contact with mucous membranes can cause severe eye or respiratory irritation. Cement users should wear protective clothing.[7][8][9]

When traditional Portland cement is mixed with water the dissolution of calcium, sodium and potassium hydroxides produces a highly alkaline solution (pH ~13): gloves, goggles and a filter mask should be used for protection, and hands should be washed after contact as most cement can cause acute ulcerative damage 8–12 hours after contact if skin is not washed promptly.[10] The reaction of cement dust with moisture in the sinuses and lungs can also cause a chemical burn as well as headaches, fatigue,[11] and lung cancer.[12] The development of formulations of cement that include fast-reacting pozzolans such as silica fume as well as some slow-reacting products such as fly ash have allowed for the production of comparatively low-alkalinity cements (pH<11)[13] that are much less toxic and which have become widely commercially available, largely replacing high-pH formulations in much of the United States. Once any cement sets, the hardened mass loses chemical reactivity and can be safely touched without gloves.

In Scandinavia, France and the UK, the level of chromium(VI), which is considered to be toxic and a major skin irritant, may not exceed 2 ppm (parts per million).

[edit] 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, states "Workers at Portland cement facilities, particularly those burning fuel containing sulfur, should be aware of the acute and chronic effects of exposure to SO2 [sulfur dioxide], and peak and full-shift concentrations of SO2 should be periodically measured."—[14]

"The Arizona Department of Environmental Quality was informed this week that the Arizona Portland Cement Co. failed a second round of testing for emissions of hazardous air pollutants at the company's Rillito plant near Tucson. The latest round of testing, performed in January 2003 by the company, is designed to ensure that the facility complies with federal standards governing the emissions of dioxins and furans, which are byproducts of the manufacturing process." [15] Cement Reviews' "Environmental News" web page details case after case of environmental problems with cement manufacturing.[16]

An independent research effort of AEA Technology to identify critical issues for the cement industry today concluded the most important environment, health and safety performance issues facing the cement industry are atmospheric releases (including greenhouse gas emissions, dioxin, NOx, SO2, and particulates), accidents and worker exposure to dust.[17]

The CO2 associated with Portland cement manufacture falls into 3 categories:

Source 1. CO2 derived from decarbonation of limestone,

Source 2. CO2 from kiln fuel combustion,

Source 3. CO2 produced by vehicles in cement plants and distribution.

Source 1 is fairly constant: minimum around 0.47 kg CO2 per kg of cement, maximum 0.54, typical value around 0.50 worldwide.[citation needed] Source 2 varies with plant efficiency: efficient precalciner plant 0.24 kg CO2 per kg cement, low-efficiency wet process as high as 0.65, typical modern practices (e.g. UK) averaging around 0.30.[citation needed] Source 3 is almost insignificant at 0.002-0.005. So typical total CO2 is around 0.80 kg CO2 per kg finished cement. This leaves aside the CO2 associated with electric power consumption, since this varies according to the local generation type and efficiency. Typical electrical energy consumption is of the order of 90-150 kWh per tonne cement, equivalent to 0.09-0.15 kg CO2 per kg finished cement if the electricity is coal-generated.

Overall, with nuclear- or hydroelectric power and efficient manufacturing, CO2 generation can be reduced to 0.7 kg per kg cement, but can be as high as twice this amount. 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 favorably with other building systems in this regard[citation needed].

[edit] Cement plants used for waste disposal or processing

Used tires being fed to a pair of cement kilns

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 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:[18]

Car and truck tires – steel belts are easily tolerated in the kilns Paint sludge from automobile industries Waste solvents and lubricants Meat and bone meal - slaughterhouse waste due to bovine spongiform encephalopathy

contamination concerns Waste plastics Sewage sludge Rice hulls Sugarcane waste Used wooden railroad ties (railway sleepers) Spent Cell Liner (SCL) from the aluminium smelting industry (also called Spent Pot

Liner or SPL)

Portland cement manufacture also has the potential to benefit from using industrial by-products from the waste-stream.[19] These include in particular:

Slag Fly ash (from power plants) Silica fume (from steel mills)

Synthetic gypsum (from desulfurisation)

[edit] See also

Cement Lime mortar Mortar (masonry) Rosendale cement White Portland cement Calcium Silicate Hydrate

[edit] References

1. ^ a b Gillberg, G.; Jönsson, Å.; Tillman, A-M. (1999) (in Swedish). Betong och miljö [Concrete and environment]. Stockholm: AB Svensk Byggtjenst. ISBN 91-7332-906-1.

2. ̂ "The Cement Industry 1796-1914: A History," by A. J. Francis, 19773. ̂ P. C. Hewlett (Ed)Lea's Chemistry of Cement and Concrete: 4th Ed, Arnold, 1998,

ISBN 0-340-56589-6, Chapter 14. ̂ German Cement Works' Association http://www.vdz-online.de/314.html?&L=15. ̂ Performance of Energetically Modified Cement (EMC) and Energetically Modified Fly

Ash (EMFA) as Pozzolan. SINTEF. http://www.sintef.info/upload/Performance_of_energetically_modified_cement.pdf.

6. ̂ Housing Prototypes: Page Street7. ̂ http://www.hse.gov.uk/pubns/cis26.pdf8. ̂ "Mother left with horrific burns to her knees after kneeling in B&Q cement while doing

kitchen DIY". Daily Mail (London). 2011-02-15. http://www.dailymail.co.uk/news/article-1357208/Mother-left-horrific-burns-knees-kneeling-cement-doing-kitchen-DIY.html.

9. ̂ Pyatt, Jamie (2011-02-15). "Mums horror cement burns". The Sun (London). http://www.thesun.co.uk/sol/homepage/news/3412957/Mums-horror-cement-burns.html.

10. ̂ Bolognia, Jean L.; Joseph L. Jorizzo, Ronald P. Rapini (2003). Dermatology, volume 1. Mosby. ISBN 0323024092.

11. ̂ Oleru, U. G. (1984). "Pulmonary function and symptoms of Nigerian workers exposed to cement dust". Environ. Research 33: 379–385.

12. ̂ Rafnsson, V; H. Gunnarsdottir and M. Kiilunen (1997). "Risk of lung cancer among masons in Iceland". Occup. Environ. Med 54: 184–188.

13. ̂ Coumes, Céline Cau Dit; Simone Courtois, Didier Nectoux, Stéphanie Leclercq, Xavier Bourbon (December 2006). "Formulating a low-alkalinity, high-resistance and low-heat concrete for radioactive waste repositories". Cement and Concrete Research (Elsevier Ltd.) 36 (12): 2152–2163. doi:10.1016/j.cemconres.2006.10.005.

14. ̂ Epidemiologic Notes and Reports Sulfur Dioxide Exposure in Portland Cement Plants15. ̂ http://www.azdeq.gov/function/news/2003/jan.html16. ̂ CemNet.com | The latest cement news and information17. ̂ Toward a Sustainable Cement Industry: Environment, Health & Safety Performance

Improvement

18. ̂ Chris Boyd (December 2001). "Recovery of Wastes in Cement Kilns". World Business Council for Sustainable Development. Archived from the original on 2008-06-24. http://web.archive.org/web/20080624230936/http://www.wbcsdcement.org/pdf/lafarge1_en.pdf. Retrieved 2008-09-25.

19. ̂ Design and Control of Concrete Mixtures. Skokie, Illinois: Portland Cement Association. 1988. pp. 15. ISBN 0-89312-087-1. "As a generalization, probably 50% of all industrial byproducts have potential as raw materials for the manufacture of Portland cement."

[edit] External links

World Production of Hydraulic Cement, by Country PCA - The Portland Cement Association Alpha The Guaranteed Portland Cement Company: 1917 Trade Literature from

Smithsonian Institution Libraries Cement Sustainability Initiative A cracking alternative to cement What is the Difference Between Cement, Portland Cement & Concrete? Aerial views of the world's largest concentration of cement manufacturing capacity,

Saraburi Province, Thailand, at 14°37′57″N 101°04′38″E / 14.6325°N 101.0771°E Fountain, Henry (March 30, 2009). "Concrete Is Remixed With Environment in Mind".

The New York Times. http://www.nytimes.com/2009/03/31/science/earth/31conc.html. Retrieved 2009-03-30.

Retrieved from "http://en.wikipedia.org/w/index.php?title=Portland_cement&oldid=466688126" View page ratingsRate this pageWhat's this?Trustworthy

Objective

Complete

Well-written

I am highly knowledgeable about this topic (optional)

I have a relevant college/university degree

It is part of my profession

It is a deep personal passion

The source of my knowledge is not listed here

I would like to help improve Wikipedia, send me an e-mail (optional)

We will send you a confirmation e-mail. We will not share your e-mail address with outside parties as per our feedback privacy statement.Submit ratings Saved successfullyYour ratings have not been submitted yetYour ratings have expiredPlease reevaluate this page and submit new ratings.An error has occured. Please try again later.Thanks! Your ratings have been saved.Please take a moment to complete a short survey.Start survey Maybe later Thanks! Your ratings have been saved.Do you want to create an account?An account will help you track your edits, get involved in discussions, and be a part of the community.Create an accountorLog in Maybe later Thanks! Your ratings have been saved.Did you know that you can edit this page?Edit this page Maybe later Categories:

Cement Concrete English inventions Limestone Isle of Portland

Hidden categories:

All Wikipedia articles needing clarification Wikipedia articles needing clarification from January 2010 All articles with unsourced statements Articles with unsourced statements from January 2010 Articles needing additional references from January 2010 All articles needing additional references Articles with unsourced statements from August 2010 Articles with unsourced statements from July 2008

Personal tools

Log in / create account

Namespaces

Article Discussion

Variants

Views

Read Edit View history

Actions

Search

Navigation

Main page Contents Featured content Current events Random article Donate to Wikipedia

Interaction

Help About Wikipedia Community portal Recent changes Contact Wikipedia

Toolbox

What links here Related changes Upload file Special pages Permanent link Cite this page Rate this page

Print/export

Create a book Download as PDF Printable version

Special:Search

Languages

Afrikaans Česky Deutsch Español فارسی Français עברית ქართული Latviešu Nederlands 日本語 Norsk (bokmål) Polski Português Русский Slovenščina Suomi Українська Tiếng Việt 中文

This page was last modified on 19 December 2011 at 14:06. Text is available under the Creative Commons Attribution-ShareAlike License;

additional terms may apply. See Terms of use for details.Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.

Contact us

Privacy policy About Wikipedia Disclaimers Mobile view

Indian Standard IS 455: 1888 ( Reaffiid 1995 1

PORTLAND SLAG CEMENT-SPECIFICATION ( Fourth Revision ) Second Reprint SEPTEMBER 1998 UDC 666’943 @ BIS 1990

BUREAU OF INDIAN STANDARDS

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 May 1990 e-4 Cenmnt and Concrete Sectional Committee, CED 2 FOREWORD This Indian Standard ( Fourth Revision ) was adopted by the Bureau of Indian Standards on 30 October 1989, after the draft finalized by the Cement .and Concrete Sectional Committee had been approved by the Civil Engineering Division Council. Portland slag cement is obtained by mixing, Portland cement clinker, gypsum and granulated slag in suitable proportions and grinding the mixture to get a thorough and intimate mix between the constituents. It may also be manufactured by separately grinding Portland cement clinker, gypsum and granulated slag and then mixing them intimately.. The resultant product is a cement which has physical properties similar to those of ordinary Portland cement. In addition, it has low heat of hydration and is relatively better resistant to soils and water containing excessive amounts of sulphater of alkali metals. alumina and iron, as well- as to acidic waters, and can, therefore, be ‘used for marine works with advantage. The manufacture of Portland slag cement has been developed primarily to utilize blastfumace slag, a waste product from blastfurnaces. The development of manufacture of this type of cement will considerably increase the total output of cement production in the country and will, in addition, provide a profitable use for an otherwise waste product. The slags obtained from other types of furnaces, but having identical properties as those of granulated blastfumace slag conforming to this standard, may also be used for manufacture of Portland slag cement. This standard was first published in lb53 and subsequently revised in 1962,1967 and 1976. This fourth revision incorporates the modifications required as a result of experience gained with the use of this specification and to bring the standard in line with tlse present practices followed in the production and testing of cement. Since publication of the third revision of this standard, large number of amendments have been issued from time to time in order to modify various requirements based on the experience gained with the use of the standard and the requirements of the users and also keeping in view the raw materials and fuel available in the country for manufacture of cement. The important amendments include incorporating a value of 28 day compressive strength, increasing the requirement regarding loss on ignition from 4’0 to 5’0, increasing the insoluble residue content from 2’5 to 4 percent, making aumdave soundness test compulsory, incorpoiating a provision for retest in respect of autoclave soundness test after aeration of the cement, incorporating a clause on false set of cement and permitting packaging of cement in 25 kg bags. In view of these large number of amendments, the Sectiolral Committee decided to bring out the fourth revision of the standard incorporating all these amendments so as to make it more convenient for the users. The desirable requirements of granulated slag suitable for the manufacture of Portland slag cement have been deleted from this revision and reference has been made to IS 12089 : 1987 ‘Specification for granulated slag for the manufacture of Portland slag cement’. This standard contains clauses 5.1 and 11.4.1 which permit the purchaser to use his option and clauses 6.5,9.2.1 and 9.3 which call for agreement between the purchaser and the manufacturer. In the formulation of this standard considerable assistance has been rendered by National Corncil for Cement and Building Materials, New Delhi as many of these modifications are based on studies carried out by them. The composition of the committee responsible for the formulation of this standard is given in Annex C. Mass of cement packed in bags and the tolerance requirements shall be in accordance with the relevant provisions of the Standards of Weights and Measures ( Packaged Commodities ) Rules, 1977 and,B-1.2 ( see Annex B for information ). Any modification in these rules in respect of tolerance on mass of cement would apply automatically to this standard. For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values ( r&vised )‘. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. Is 395 : 1999

Indian Standard

PORTLAND SLAG CEMENT - SPECIFICATION

( Fourth Revision ) 1 SCOPE 1.1 This standard covers the manufacture and chemical and physical requirements for Portland slag cement. 2 REFERENCES 2.1 The Indian Standards listed in Annex A are necessary adjuncts to this standard. 3 TERMINOLOGY 3.1 For the purpose of this standard, the definitions given in 1S 4845 : 1968 and the following shall apply. 3.2 Portland Slag Cement An intimately interground mixture of Portland cement clinker and granulated slag with addition of gypsum and permitted additives or an intimate and uniform blend of Portland cement and finely ground granulated slag. 33. Portland Clinker Clinker, consisting mostly of calcium silicates, obtained by heating to incipient fusion a predetermined and homogeneous mixture of materials principally containing lime ( CaO ) and silica ( SiO, ) with a smaller proportion of alumina ( AlgO ) and iron oxide ( FezOI ). 3.4 Granulated Slag Slag in granulated form is used for the manuf?cture of hydraulic cement. Slag is a non-metallic product consisting essentially of glass containing silicates and alumino-silicates of lime and other bases, as in the case of blastfurnace slag, which is developed simultaneously with iron in blastfurnace or electric pig iron furnace. Granulated slag is obtained by further processing the molten slag by rapidly chilling or quenching it with water or steam and air. 4 MANUFACTURE 4.1 Portland slag cement shall be manufactured either by intimately intergrinding a mixture of Portland cement clinker and granulated slag with addition of gypsum ( natural or chemical ) or calcium sulphate, or by an intimate and uniform blending of Portland cement and finely ground A granulated slag, so that the resultant mixture would produce a cement capable of complying with this specification. No material shall be added other than gypsum ( natural or chemical ) or water or both. However, when gypsum is added it shall be in such amounts that the sulphur trioxide ( SO? ) in the cement produced does not exceed the ltmits specified in 5.2. Besides,not more than one percent of air-entraining agents or surfactants which have proved not to be’harmful.

may be added. The slag constituent shall be not less than 25 percent nor more than 65 percent of the PortJand slag cement. 5 CHEMICAL REQUIREMENTS 5.1 Portland cement clinker used in the manufacture of Portland slag cement shall comply in all respects with the chemical requirements specified for the 33 grade ordinary Portland cement in IS 269 : 1989, and the purchaser shall have the right, if he so desires, to obtain samples of the clinker used in the manufacture of Portland slag cement. 5.2 The Portland slag cement shall comply with the following chemical requirements when tested in accordance with the methods given ip IS 4032 : 1985: Percent, Max Magnesium oxide ( MgO ) Sulphur trioxide ( SO, ) Sulphide sulphur ( S ) Loss on ignition Insoluble residue NOTES 8’0 3-o 1’5 5’0 4’d 1 Total chloride content in cement rball not exceed 0.05 percent by mass for cement used in prestressed concrete structures and long rpan reinforced concrete structures. ( Method of test for determination of chloride content in cement is given in IS 12423 : 1988. ) 2 The limit of total chloride content in cement for use in plain and other reinforced concrete structures is being reviewed. Till that time, the limit may be mutually agreed to between the purchaser and the manufacturer. 3 Granulated slag conforming to IS I2i)89 : 1987 bar been found suitable for the manufacture of Portland slag cement. IS 455 : I989 6 PHYSICAL REQUIREMENTS 6.1 Fineness When tested for fineness in terms of specific surface by Blaine’s Air permeability method described in IS 4031 ( Part 2 ) : 1988, the specific surface of slslg cement shall be not less than 225 m’/kg. 6.2 Soundness 6.2.1 When tested by ‘Le-Chatelier’ method and autoclave test described in IS 4031 ( Part 3 ) : 1988, unaerated Portland slag cement shall not have an expansion of more than 10 mm and 0’8 Percent respectively. 6.2.1.1 In the event of cements failing to comply with any one or both the requirements specified in 63.1, further tests in respect of each fail&e shall be made as described in IS 4031 ( Part 3 ) : 1988

from another portion of the same sample after aeration. The aeration shall be done by spreading out the sample to a depth of 75 mm at a relative humidity of 50 to 80 percent fo,r a total period of 7 days. The expansion of cements so aerated shall be not more than 5 mm and 0’6 percent when tested by ‘Le-Chatelier’ method and autoclave test respectively. 6.3 Setting Time The setting time of slag cement, when tested by the Vicat apparatus method described in 1S 4031 ( Part 5 ) : 1988, shall be as follows: a) Initial setting time Not less than 30 minutes b) Final setting time Not more than 600 minutes 6.3.1 If cement exhibits false set, the ratio of final Penetration measured after 5 minutes of completion of mixing period to the initial penetration measured exactly after 20 seconds of completion of mixing period, expressed as percent, shall be not less than 50. In the event of cemerit exhibiting false set, the initial and final setting time of cement when tested by the method described in 1s 4031 ( Part 5 ) : 1988 after breaking the false set, shall conform to 6.3. 6.4 Compressive Strength The average compressive strength of at least !hree mortar cubes ( area of face 50 cm* ) composed of one part of cement, three parts of standard sand ( see Note 1 ) by mass and ( P/4+3*0 ) percent’( of combined mass of cement plus sand ) water, and prepared, stored and tested in the manner described in IS 4031 ( Part 6 ) : 1988, shall be as follows: a) 72&l h Not less than 16 MPa b) 168 f2 h Not less than 22 MPa c) 672 f4 h Not less than 33 MPa NOTES 1 Standard sand shall conform to IS 650 : 1966. 2 P ijFthe percentage of water required to produce a patte’of standard consistency (see 11.3). 6.5 By agreement between the purchaser and ihe manufacturer, transverse strength test of plastic mortar in accordance with the method described in IS 4031 ( Part 8 ) : 1988 may be specified in addition to the test specified in 6.4. The permissible values of the transverse strength by this method shall be as agreed to between the purchaser and the manufacturer at the time. of placing the order. 6.6 Notwithstanding the strength requirements in 6.4 and 6.5. the Portland slag cement shall show a progressive increase in strength from the strength at 72 hours. 7 STORAGE 7.1 The cement shall be stored in such a manner as to permit easy access for proper inspection and identification and in a suitable weather-tight building

to protect the cement from dampness and to minimize warehouse deterioration. 8 MANUFACTURER’S CERTIFICATION 8.1 The manufacturer shall satisfy him+f that the cemeni conforms to the requirements of this standard, and if requested, shall furnish a certificate to this effect to the purchaser or his representative, within ten days of despatch of cement. 8.2 The manufacturer shall furnish a certificate, within ten days of despatch of the cement, indicating the total chloride content in Percent by mass of cement. 9 DELIVERY 9.1 The cement shall be packed in bags [jute sacking bag conforming to IS 2580 : 1982, double hessian bituminized ( CR1 type ), multi-wall paper conforming to IS 11761 : 1986, polyethylene lined ( CR1 type ) jute, light weight0 jute conforming to 1s 12154 : 1987, woven HDPE conforming to 1s 11652 : 1986, woven polypropylene conforming to IS 11653 : 1986, jute synthetic union conforming to IS 12174 : 1987 or any other approved composite bags ] bearing the manufacturer’s name or his registered trade-mark, if any. The words ‘Portland Slag Cement’ or a suitable mark to distinguish Portland slag cement froqr other Portland cements shall be clearly and indelibly marked on each bag. The number of bags ( net mass ) to the tonne or the average net mass of the cement shall be legibly and indelibly marked on each bag. The bags shall be in good condition at the time of inspection. 2 Is 455 : 1989 9.1.1 Similar information shall be provided in the delivery advices accompanying the shipment of packed or bulk cement ( see 9.3 ). 9.2 The average net mass of cement per bag shall be 50 kg ( see Annex B ). 9.2.1 The average net mass of cement per bag may also be 25 kg subject to tolerances as given in 9.2.1.1 and packed in suitable bags as agreed to between the purchaser and the manufacturer. 9.2.1.1 The number of bags in a sample taken for weighment showing a minus error greater than 2 percent of the specified net mass shall be not more than 5 percent of the bags in the sample. Also the minus error in none of such bags in the sample shall exceed 4 percent of the specified net mass of cement in the bag. However, the average net mass of cement in a sample shall be equal to or more than 25 kg. 9.3 Supplies of cement in bulk may be made by agreement between the purchaser’and the supplier ( manufacturer or stockist ). NOTE -A single bag or container containing

1 000 kg or more net mass of cement shall be considered

as bulk supply of cement. Supplies of cement

may also be made in intermediate containers, for

example drurrs of 200 kg, by agreement between the

purchaser and the manufacturer.

10 SAMPLING 10.1 Samples for Testing A sample or samples for testing may be !aken by the purchaser or his representative, or by any person appointed to superintend the work for the purpose of which the cement is required, or by the latter’s representative. 10.1.1 The samples shall be taken within three weeks of the delivery and ail the tests shall be commenced within one week of sampnng. 10.1.2 When it is not possible to test the samples within one week, the samples shall be packed. and stored in air-tight containers till such time that they are tested. 10.2 In addition to the requirements of 10.1, the methods and procedure of sampling shall be in accordance with IS 3535 : 1986, 10.3 Facilities for Sampling and Identifying The manufacturer or tipplier shall afford every facility, and shall provide all labour and materials for taking and packing the samples for testing the cement and for subsequent identification of the cement sampled. 11 TESTS 11.1 The sample or samples of cement for tests shall be taken as described in IS 3535 : 1986 and s!~$ll be tested in the manner prescri&d in the relevant clauses. 11.2 Temperature for Testing The temperature at which the physical tests may be carried out shall, as far as possible, be 27 %!“C. The actual temperature during the testing shall be recorded. 11.3 Consistency of Standard Cement Paste The quantity of water required to produce a paste of standard tionsistency, to be used for the determination of the water content of mortar for the compressive strength test and for the determination of soundness and setting time. shall be obtained by the method descrilbed in IS 4031 (Part4): 1988. 11.4 Independent Testing 11.4.1 If the purchaser or his representative requires independent test, the samples shall be taken before or immediately after delivery at the option of the purchaser or his representative, and the tests shall be carried out in accordance with this standard on the written instructions of the purchaser or his representative. 1 t .4.2 Cost of Testing The manufacturer shall supply, free of charge, the cement required for testing. Unless otherwise specified in the enquiry and order, the cost of tests shall be borne as follows: a) By the manufacturer if the results show that the cement does not comply with this standard; and

b) By the purchaser if the results show that the cement complies with this standard, 11.4.3 After a representative sample has been drawn and hermetically sealed. tests on the sample shall be carried out as expeditiously as possible. 12 REJECTION 12.1 Cement may be rejected if it does not comply with any of the requirements specified in this specification. 12.2 Cement remaining in bulk storage at the mill, prior to shipment, for more than six months, or cement in bags in local storages in the hands of a vendor for more than three months after compia tion of tests, may be retested before use and may be rejected if it fails to conform to any of the requirements in this specification. 3 Is 455 : 198) IS No. 269 : 1989 650 : 1966 2580 : 1982 3535 : 1986 4031 ( Part 1 toPart 13) 4032 : 1985 4845 : 1968 4905 : 1968 ANNEX A ( Clullse 2.1 ) LIST OF REFER’RED INDIAN STANDARDS Title IS No. Specification for 33 grade ordi- 11652 ! 1986 nary Portland cement (fourth revision ) Title Specification for standard sand 11653 : 1986 for testing of cement (first revision ) Specification for high density polyethylene ( HDPE ) woven sacks fdr packing cement Specification for polypropylene I PP ) woven sacks fey packing cement Specification for jute sacking 11761 : 1986 bags for packing cement ( second Specification for multi-wall paper sacks for cement valved-sewn revision ) gussetted type Methods of sampling hydraulic 12089 : 1987 cements (first revision ) Methods of physical test for hydraulic cement (first revision ) 12154: 1987 Method of chemical analysis of hydraulic Cement (firsf revision ) 12174 .. 1987 Definitions and terminology relating to hydraulic cement

12423 : 1988 Methods for randam sampling Specification for granulated slag for the manufacture of Portland slag cement Specification for light weight jute bags for packing cement Specification for jute -synthetic union bag for packing cement Met hod for cblorimetric analysis of hydraulic cement ANNEX B ( Clause 9.2 ) TOLERANCE REQUIREMENTS FOR THE MASS OF CEMENT PACKED IN BAGS B-1 The average net mass of cement packed in bags at the plant in a sample shall be equal to or more than 50 kg. The number of bags in a sample shall be as given below: Batch Size 100 to 150 151 to280 281 to 500 Sample Size 20 32 50 net mass ( 50 kg ) shall be not more than 5 percent of the bags in the sample. Also the minus error in none of such bags in the sample shall exceed 4 percent of the specified net mas of cement in the bag. NOTE -The matter given in B-l and B-l.1 are extracts based on the Srandurds of We&&s qnd Measures ( Pcckaged Commodities ) Rules, ‘1977 to which reference shall be made for full details. Any modification made in these Rules and other related Acts and Rules would apply automatically. 501 to 1 200 80 B-l.2 In case of a wagon/truck load of 20 to 25 1 201 to 3 200 125 tonnes, the overall tolerance on net mass of cement 3 201 and over 200 shall be 0 to -t 0.5 percent. NOTE -The mass of a jute sacking bag confor- The bags in a sample shall bc selected at random ming to IS 2580 : 1982 to hold 50 kg of cement in ( see 1s 4905 : 1968 ). 531 g, the mass of a double hessian bituminized ( CRI type ) bag to hold 50 kg of cement is 630 g. the mass of a 6-ply paper bag to hold 50 kg of cement is B-l.1 The number of bags in a sample showing a minus error greater than 2 percent of the specified approximately 400 g and the mass of a polyethylene lined ( CR1 type ) jute bag to hold 50 kg of cement is approximately 480 g. 4

ANNEX C ( Fofeword ) Is 455 : 1989 COMPOSITION OF THE TECHNICAL COMMWIEFi CEMENT AND CONCRETE SECTIONAL COMMITTEE, CED 2

Chairman Representing .Dn H. C. ~ISYESVARAY.4

Members National Council for Cement and Building Materials, New Delhi

SHRI K. P. BANERIRE

SHRI HARISfl N. MALANI ( A/t~~re )

SHRI S. K. BANRRJEE

CHIEF ENCIINE~R ( BD ) SHRI J. C. BASUR ( Akrnatc )

Larsen and Toubro Limited, Bombay

National Test House, Calcutta

Bhakra Beas Management Board, Nangal Township

CHIEP ENGINEER( DF~IONS ) Central Public Works Department, New Delhi

SUPERIN~NDINQ ENQINEER ( S & S )

( Alternate )

CHIEF ENGINEER ( RESEARCH-CUMD~

RECXOR )

RESEARCH OFFICER ( CONCRETE

TECHNOLOGY ) ( Alternote ) DIRECTOR

JOINT DIRXTOR ( Alternafe )

DIRECTOR

CHEEP RESEARCH GFFXER ( Alternate ) DIRECTOR(C & MDD-II )

DEPUTY DIRECTOR ( C 8c MDD-II )

( Alternafe ) SHRI V. K. GHANEKAR

SHRI S. GOPINATH

SHRI A. K. GUPTA

SHRI J. S~?N GUPTA

SHRI P. J. JANUS

DR A. K. CHATTERJFE ( Alternate ) JOINT DIRIXTOR STANDARDS ( B & S )/CB-I

JOINT DIRECTOR STANDARDS ( B & S )/

CB-II ( Alternate ) SHRI N. G. J&HI

SHRI R. L. KAP~OR

SHRI R. K. SAXENA ( AIternore )

DR A. K. MULLlCK

&RI G. K. MAJUMDAR

SHRI P. N. MEHTA

SHRI S. K. MATHUR ( Alternate )

SHRI NORMAL SIN~H

SHRI S. S. MIGLANI ( Alternate ) SHRI S. N. PAL

SHRI BIMAN DASODTA ( Alternate ) SHRI R. C. PARATE

LT-COL R. K. SINGH ( Afternate )

SHRI H. S. PASRICHA

SHRI Y. R. PHULL

SHR~ S. S. SEEHRA ( Alternate ) DR MOHAN RAI

DR S. S. REHSI ( Alternote ) SHRI A. V. RAMANA

DR K. C. NARANO ( Alternate )

.SHRI G. RAMDAS

SHRI T. N. SUBBA RAO

SHrtt S. A. REDDI ( Alternate ) Irrigation Department, Government of Punjab

A. P. Engineering Research Laboratories, Hyderabad

Central Soil and Materials Research Station, New Delhi

Central Water Commission, New Delhi Structural Engineering Research Centre ( CSIR ), Ghaziabad The India Cements Limited, Madras

Hyderabad Industries Limited, Hyderabad

National Buildings Organization, New Delhi

The Associated Cement Companies Ltd. Bombay

Research, Designs and Standards Organization ( Ministry of

Railways ), Lucknow

Indian Hume Pipes Co Limited, Bombay

Roads Wing ( Ministry of Transport ), Department of Surface Transport, New Delhi National Council for Cement and Building Materials, New Delhi Hospital Services Consultancy Corporation ( India ) Ltd, New Delhi Geological Survey of India, Calcutta Development Commissioner for Cement Industry ( Ministry of Industry ), New Delhi M.N. Dastur and Company Private Limited, Calcutta Engineer-in-Chief’s Branch, Army Headquarters Hindustan Prefab Limited, New Delhi Indian Roads Congress, New Delhi; and Central Road Research

Institute.( CSIK ). New Delhi Central Road Research Institute ( CSIR ), New Delhi Central Building Research Institute ( CSIR ). Roorkee Dalmia Cement ( Bharat ) Limited, New Delhi Directorate General of Supplies and Disposals, New Delhi Gammon India Limited, Bombay S Membera Representing Du M. RAMAIAA

DR A. 0. MAIX~AVA RAO ( Alternate )

SHRI A. U. RIJHSWOHANI

SiiIl C. S. SHAiUtA ( AIternate )

SEcw!YhRY

Smr K. R. SAXEIM ( Alternote )

SUPEERINTENDIENNOC ~NEER( DESIGNS ) EXECUTIVE ENQINEER ( SMD DWIS~ON )

( Alfemute )

Structural Edgineering Research Ccntre ( CSIR ), Madras Cement Corporation of India, New Delhi Central Board of Irrigation and Power, New Delhi Public Works Department, Government of Tamil Nadu SHRI L. SWAROOP

SHRI H. BHA~ACHARYA

( Alterrare )

Orissa Cement Limited, New Delhi SHR~ S. K. GUHA THAIUJRTA

SHRI S.P. SANKARNARAYANAN

( Alternate )

Gannon Dunkerly & Co Ltd, Bombay DR H. C. VISVESVARAYA

SARI D. C. CHAIWRVEDI ( Alternate )

SHRI G. RAMAN.

Director ( Civ Engg ) The Institution of Engineers ( India ), Calcutta Director General, BIS ( Ex-oficlo Member ) Secretary

SHRI N. C. BANDYOPADHYAY Joint Director ( Civ Engg ), BIS \ Cement, Pozzolana and Cement Additives Subcommittee, CED 2 : 1 Cmmener

DR H. C. VI~VESVARAYA Members National Council for Cement and Bqilding Materials, New Delhi DR A. K. MULLICK

DR (-Svr ) S. LAXMI 3 ( Alternates to Dr H. C. Visvesvaraya ) SIIRI S. K. BA- National TestHouse. Calcutta Snu N. 0. BASAK SHRI T. MADNESHWAR ( Alternate )

Directorate General bf Technical Development, New Delhi Snu SOMNATH BANIXJEII Cement Manufacturers Association, Bombay Ctscesce~p ( RESEARCH-CUM- Irrigation Department, Government of Punjab RINEARCHO PPICER( CT ) ( Alternote )

Ssm N. B. D~sal SHRI J. K. PAPAL ( Alternate )

Gujarat Engineering Research Institute, Vadodara DIRgCToa -ARCH OFFICIZR ( Alternote )

Maharashtra Engineering Research Institute, Nasik m(C&MDDII) Central Water Commission, New Delhi Darun DIRFXTOR ( C A MDD II ) ( Afternore )

Spur i. K. GATTANI

SHRI R. K. VAHHNAM ( AIternatc )

Shree Digvijay Cement Co Ltd, Bombay SWRI J. SEN GIJPTA &IN P. J. JAOLJS DR A. K. CHATTERJEB( Alternate )

National Buildings Organization, New Delhi The Associated Cement Companies Ltd, Bombay Jomy D~recrou, STANDARDS

( B & S )/CB-I &XNT DIRECTOR. STANDARDS

Research, Designs and Standards Organization, Lucknow ( B & S )/CB-11 ( Ahmate )

SRI: R. L KA~OOR SHRI R. K. DANA ( Alternate )

!&RI W. N. KARODE

SW R. KUNJITHA~A~AM

SIIRI 0. K. MANMDAR

Roads Wing (Ministry of Transport ) ( Department of Surface Transport ). New Delhi The Hindusta;l Construction Co Ltd, Bombay Chettinad Cement Corporation Ltd. Poliyur, Tamil Nadu Hospital Services Consultancy Corporation ( India ) Ltd, -New Delhi 6 Is 455 : 1989 MembcrJ ,SHRI K. P. kIiIDEEN SHRIN~RHALSINQH SHRI S. S. MI~LANI ( Alrcrno~c ) SHRt Y. R. PHULL SHRI S. S. SEEHRA ( Alternafe) SHRI A. V. RAMANA DR K. C. NARAN~ ( Aflernale ) COL V. K. Rao SHRI N. S. GALANDE ( Altemufe )

SHRI S. A. REDDI

DR S. S. REHSI DR IRSHAD MASOOD (’ Rlfemate ) SHRI A. U. RIJHSINQHANI SHRI M. P. SINGH SUPERINTENDINGE NGINEER( D) SENIOR DEPUTY CHIRP EN~INEZR ( GENERAL ) ( Alternate ) SHRI L. SWAROOP Srrru H. BHAT~ACHARYA( AIrernole ) SHR~ V. M. WAD Represenfing Central Warehousiog Corporation, New Delhi Development Commissioner for Cement Industry ( Ministry of Industry ) Ceotral Road Research Institute ( CSlR ). New Delhi Dalmia Cement ( Bharat ) Ltd. New Delhi Engineer-ln&Zhief’s Branch, Army Headquarters Gammon India Ltd. Bombay Central Building Research lnstitute ( CSIR ), Roorkee Cement Corporation of India Ltd, New Delhi Federation of Mini Cement Plants, New Delhi Public Works Department, Government of Tamil Nadu Orissa Cement Ltd, New Delhi Bhilai Steel Plant, Bhilai 7 Bureau of Indian Standards BIS is a statutory institution established under the Bureuu of Indian Standards Act, 1986 to promote harmonious development of the activities of standardization, marking and quality certification of goods and attending to connected matters in the country. Copyright BIS has the copyright of all its publications. No part of these publications may be reproduced in any form without the prior permission in writing of BIS. This does not preclude the free use, in the course of implementing the standard, of necessary details, such as symbols and sizes, type or grade designations. Enquiries relating to copyright be addressed to the Director (Publication), BIS. Review of Indian Standards Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of ‘BIS Handbook’ and ‘Standards Monthly Additions’. This Indian Standard has been developed from Dot: No. CED 2 ( 4745 ) Amendments Issued Since Publication Amend No. Date of Issue Text Affected Headquarters: BUREAU OF INDIAN STANDARDS Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 Telephones: 323 01 31,323 33 75,323 94 02 Regional Offices: Telegrams: Manaksanstha (Common to all offices) Telephone Ceutral : Eastern : Northern : Manak Bhavan, 9 Bahadur Shah Zafar Marg NEW DEL Y 1110002 l/14 C.I.T. Scheme VII M, V.I.P. Road, Maniklola

CALCUTTA 700054 SC0 335-336, Sector 34-A; CHANDIGARH 160022 Southern : C.I.T. Campus, IV Cross Road, CHENNAI 600113 Western : Branches : Manakalaya, E9 MIDC, Marol, Andheri (East) { 832 92 95,832 78 58 MUMBAI 400093 832 78 91,832 78 92 AHMADABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE. FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR. LUCKNOW. NAGPUR. PATNA. PUNE. THIRUVANANTHAPURAM. tinted at Dee Kay Printers, New Delhi, India

323 76 17,323 38 41 337 84 99,337 85 61 337 86 26,337 9120 1 60 38 43 60 20 25 { 235 02 16,235 04 42 235 15 19,235 23 15 AMENDMENT NO. 1 APRIL 1991 IS 455 : 1989 f TO PORTLAND SLAG CEMENT-- SPECIFICATION Fourth Revision / ( Page 3, clause 9.2.1.1 ) - Insert the following new clauses after 9.2.1.1: “9.2.2 When cement is intended for export and if the putch,>scr so requires, packing of cement may be done in bags with an average 11~1

mass per bag as agreed to by the purchaser and the manufacturer.. 9.2.2.1 For this purpose the permission of the certifying authority shall be obtained in advance for each export order. 9.2.2.2 The words ‘FOR EXPORT’ and the average net mass (It cement per bag shall be clearly marked in indelible ink on each bag. 9.2.2.3 The packing material shall be aa agreed to between the supplier and the purchaser. 9.2.2.4 The tolerance requirements for the mass of cement’ packed in bags shall be as given in 9.2.1.1 except the average net mass wlricll shall be equal to or more than the quantity in 9.2.2.” (CXDZ) Printed nt JJcc Kay Printers. New l)clhi, India

AMENDMENT NO. 2 NOVEMBER 1991 TO IS 4i5 : 1989 PORTLAND SLAG CEMENT - SPECIFICATION (Fourth Revision) (Page 4, clnme B-l.2 ) - Substitute ‘up to 25 tonncs’/or ‘of 20 to 25 tonnes’.

FED21 Reprography Unit. BIS. New Delhi. Ida

AMENDMENT NO. 3 JUNE1993 TO

IS455: 1989 PORTLAND SLAG CEMENT - SPECIFICATION ( Fourth Revision) [ Ptqe 3, clnrrse 9.2.1.1 ( see u/so Amendment No. 1 ) ] - Substitute tbe following for the existing clauses 9.2.2 to 9.2.2.4: “9.2.2 When cement is intended for export and if the purchaser so requires, paching of cement may be done in bags or in drums with an average net mass of cement per bag or drum as agreed to between the purchaser and the manufacturer. 9.2.2.1 For this purpose the pemlission of tbe certifying authority shall be obtained in advance for each export order. 9.2.2.2 Tbe words ‘FOR EXPORT’ and the average net mass of cement per bag/drum shall be clearly marked in indelible inkon each bag/drum. 9.2.2.3 The packing material shall be as agreed to between the manufacturer and the purchaser. 9.2.2.4 The tolerance requirements for the mass of cement packed in bags/drum shall be as given in 9.2.1.1 except the average net mass which shall be equal to or more than the quantity in 9.2.2.” (CED2) ReprographUy nit, BIS, New Delhi, India

AMENDMENT NO. 4 MAY 2000 TO IS 455 : 1989 PORTLAND SLAG CEMENT - SPECIFICATION (Fourth Revision) Substitute ‘net mass’ for ‘average net mass’ wherever it appears in the standard. ( Page 1, clause 4.1, lust sentence ) - Substitute ‘70 percent’ jor ‘65 percent’. (CED2) Reprography Unit, BIS, New Delhi, India

Slag cement, or ground granulated blast-furnace slag (GGBFS), has been used in concrete projects in the United States for over a century. Earlier usage of slag cement in Europe and elsewhere demonstrates that long-term concrete performance is enhanced in many ways. Based on these early experiences, modern designers have found that these improved durability characteristics help further reduce life-cycle costs, lower maintenance costs and makes concrete more sustainable. For more information on how slag cement is manufactured and it enhances the durablity and sustainability of concrete, click here.

Silica fumeFrom Wikipedia, the free encyclopedia

Jump to: navigation, search

Not to be confused with fumed silica.

Silica fume, 380m²/g

Silica fume, also known as microsilica, is a fine-grain, thin, and very high surface area silica.

It is sometimes confused with fumed silica (also known as pyrogenic silica) and colloidal silica. These materials have different derivations, technical characteristics, and applications.

Contents

[hide]

1 History 2 Properties 3 Production 4 Applications

o 4.1 Concrete 5 See also 6 Notes

7 References 8 External links

[edit] History

The history of silica fume is relatively short, the first recorded testing of silica fume in Portland cement based concretes was in 1952 and it wasn’t until the early 1970’s that concretes containing silica fume came into even limited use. The biggest drawback to discovering the unique properties of silica fume and its potential was a lack of silica fume to experiment with. Early research used an expensive additive called Fumed silica, a colloidal form of silica made by combustion of silicon tetrachloride in hydrogen-oxygen furnaces. Silica fume on the other hand, is a by-product or a very fine pozzolanic material, composed of mostly amorphous silica produced by electric arc furnaces during the production of elemental silicon or ferro silicon alloys. Before the late 1960’s in Europe and the mid1970’s in the United States, silica fume simply went up the stack as smoke vented into the atmosphere .

Only with the implementation of tougher environmental laws during the mid-1970’s did silicon smelters begin to capture and collect the silica fume, instead of sending it to the landfill. Thus the push was on to find uses for it. Obviously, the early work done in Norway received most of the attention, since it had shown that Portland cement based concretes containing silica fumes had very high strengths and low porosities. Since then silica fume usage and development has continued making it one of the world’s most valuable and versatile admixtures for concrete and cementitous products. Typically purchased by the refractory market in a 50 lb. bag this very fine gray powder has come along way from being known only as “smoke”.

[edit] Properties

Silica fume consists of fine vitreous particles with a surface area on the order of 215,280 ft²/lb (20,000 m²/kg) when measured by nitrogen adsorption techniques, with particles approximately one hundredth the size of the average cement particle.[1]

[edit] Production

Silica fume is a byproduct in the reduction of high-purity quartz with coke in electric arc furnaces in the production of silicon and ferrosilicon alloys.

[edit] Applications

[edit] Concrete

Because of its extreme fineness and high silica content, silica fume is a very effective pozzolanic material.[2][3] Standard specifications for silica fume used in cementitious mixtures are ASTM C1240,[4] EN 13263.[5]

Silica fume is added to Portland cement concrete to improve its properties, in particular its compressive strength, bond strength, and abrasion resistance. These improvements stem from both the mechanical improvements resulting from addition of a very fine powder to the cement paste mix as well as from the pozzolanic reactions between the silica fume and free calcium hydroxide in the paste.[6]

Addition of silica fume also reduces the permeability of concrete to chloride ions, which protects the reinforcing steel of concrete from corrosion, especially in chloride-rich environments such as coastal regions and those of humid continental roadways and runways (because of the use of deicing salts) and saltwater bridges.[7]

Prior to the mid-1970s, nearly all silica fume was discharged into the atmosphere. After environmental concerns necessitated the collection and landfilling of silica fume, it became economically viable to use silica fume in various applications, in particular high-performance concrete.[8] effect of silica fume on different properties of fresh and harden concrete:-

a) Workability: With the addition of silica fume, the slump loss with time is directly proportional to increase in the silica fume content due to the introduction of large surface area in the concrete mix by its addition. Although the slump decreases, the mix remains highly cohesive.

b) Segregation and Bleeding: Silica fume reduces bleeding significantly because the free water is consumed in wetting of the large surface area of the silica fume and hence the free water left in the mix for bleeding also decreases. Silica fume also blocks the pores in the fresh concrete so water within the concrete is not allowed to come to the surface.

[edit] See also

Engineered Cementitious Composite Fly ash Kaolinite Pozzolan Rice husk ash Metakaolin

[edit] Notes

1. ̂ "Silica Fume". U.S. Department of Transportation, Federal Highway Administration. http://www.fhwa.dot.gov/infrastructure/materialsgrp/silica.htm.

2. ̂ ACI Committee 226. 1987b. "Silica fume in concrete: Preliminary report", ACI Materials Journal March–April: 158–66.

3. ̂ Luther, M. D. 1990. "High-performance silica fume (microsilica)—Modified cementitious repair materials". 69th annual meeting of the Transportation Research Board, paper no. 890448 (January)

4. ̂ ASTM C1240. Standard Specification for Silica Fume Used in Cementitious Mixtures, http://astm.org

5. ̂ EN 13263 Silica fume for concrete. http://www.cen.eu

6. ̂ Detwiler, R.J. and Mehta, P.K., Chemical and Physical Effects of Silica Fume on the Mechanical Behavior of Concrete, Materials Journal Nov. 1989

7. ̂ Rachel J. Detwiler, Chris A. Fapohunda, and Jennifer Natale (January 1994). "Use of supplementary cementing materials to increase the resistance to chloride ion penetration of concretes cured at elevated temperatures". Materials Journal. http://www.concreteinternational.com/pages/featured_article.asp?ID=4451.

8. ̂ ACI 234R-06. Guide to Silica Fume in Concrete, American Concrete Institute

[edit] References

U.S. Federal Highway Administration . "Silica Fume". http://www.fhwa.dot.gov/infrastructure/materialsgrp/silica.htm. Retrieved 2007-01-24.

[edit] External links

Wikimedia Commons has media related to: Silicon dioxide

Silica Fume Association Microsilica Union

Retrieved from "http://en.wikipedia.org/w/index.php?title=Silica_fume&oldid=461748234" View page ratings

Rate this page

What's this?

Trustworthy

Objective

Complete

Well-written

I am highly knowledgeable about this topic (optional)

I have a relevant college/university degree

It is part of my profession

It is a deep personal passion

The source of my knowledge is not listed here

I would like to help improve Wikipedia, send me an e-mail (optional)

We will send you a confirmation e-mail. We will not share your e-mail address with outside parties as per our feedback privacy statement.

Submit ratings

Saved successfully

Your ratings have not been submitted yet

Your ratings have expired

Please reevaluate this page and submit new ratings.

An error has occured. Please try again later.

Thanks! Your ratings have been saved.

Please take a moment to complete a short survey.

Start survey Maybe later

Thanks! Your ratings have been saved.

Do you want to create an account?

An account will help you track your edits, get involved in discussions, and be a part of the community.

Create an accountorLog in Maybe later

Thanks! Your ratings have been saved.

Did you know that you can edit this page?

Edit this page Maybe later

Categories:

Ceramic materials Glass types Silicon dioxide

Personal tools

Log in / create account

Namespaces

Article Discussion

Variants

Views

Read Edit View history

Actions

Search

Navigation

Main page Contents Featured content Current events Random article Donate to Wikipedia

Interaction

Help About Wikipedia Community portal Recent changes Contact Wikipedia

Special:Search

Toolbox

What links here Related changes Upload file Special pages Permanent link Cite this page Rate this page

Print/export

Create a book Download as PDF Printable version

Languages

Español Italiano עברית Nederlands Русский

This page was last modified on 21 November 2011 at 10:53. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms

may apply. See Terms of use for details.Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.

Contact us

Privacy policy About Wikipedia Disclaimers Mobile view

Please read:A personal appeal from

Wikipedia author Dr. Sengai Podhuvan We now accept

₹

(INR)

Fly ashFrom Wikipedia, the free encyclopedia

Jump to: navigation, search

Photomicrograph made with a Scanning Electron Microscope (SEM): Fly ash particles at 2,000x magnification

Fly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal. Fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys of coal-fired power plants, and together with bottom ash removed from the bottom of the furnace is in this case jointly known as coal ash. Depending upon the source and makeup of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO2) (both amorphous and crystalline) and calcium oxide (CaO), both being endemic ingredients in many coal-bearing rock strata.

Toxic constituents depend upon the specific coal bed makeup, but may include one or more of the following elements or substances in quantities from trace amounts to several percent: arsenic, beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, thallium, and vanadium, along with dioxins and PAH compounds.[1][2]

In the past, fly ash was generally released into the atmosphere, but pollution control equipment mandated in recent decades now require that it be captured prior to release. In the US, fly ash is generally stored at coal power plants or placed in landfills. About 43 percent is recycled,[3] often

used to supplement Portland cement in concrete production. Some have expressed health concerns about this.[4]

In some cases, such as the burning of solid waste to create electricity ("resource recovery" facilities a.k.a. waste-to-energy facilities), the fly ash may contain higher levels of contaminants than the bottom ash and mixing the fly and bottom ash together brings the proportional levels of contaminants within the range to qualify as nonhazardous waste in a given state, whereas, unmixed, the fly ash would be within the range to qualify as hazardous waste.

Contents

[hide]

1 Chemical composition and classification o 1.1 Class F fly ash o 1.2 Class C fly ash

2 Disposal and market sources 3 Fly ash reuse

o 3.1 Portland cement o 3.2 Embankment o 3.3 Soil stabilization o 3.4 Flowable fill o 3.5 Asphalt concrete o 3.6 Geopolymers o 3.7 Roller compacted concrete o 3.8 Bricks o 3.9 Metal matrix composites o 3.10 Waste treatment and stabilization

4 Environmental problems o 4.1 Present production rate of fly ash o 4.2 Groundwater contamination o 4.3 Spills of bulk storage o 4.4 Contaminants

5 Exposure concerns 6 See also 7 External links 8 References

[edit] Chemical composition and classification

Component

Bituminous

Subbituminous

Lignite

SiO2

(%)20-60 40-60

15-45

Al2O3

(%)5-35 20-30

20-25

Fe2O3

(%)10-40 4-10

4-15

CaO (%)

1-12 5-3015-40

LOI (%)

0-15 0-3 0-5

Fly ash material solidifies while suspended in the exhaust gases and is collected by electrostatic precipitators or filter bags. Since the particles solidify while suspended in the exhaust gases, fly ash particles are generally spherical in shape and range in size from 0.5 µm to 100 µm. They consist mostly of silicon dioxide (SiO2), which is present in two forms: amorphous, which is rounded and smooth, and crystalline, which is sharp, pointed and hazardous; aluminium oxide (Al2O3) and iron oxide (Fe2O3). Fly ashes are generally highly heterogeneous, consisting of a mixture of glassy particles with various identifiable crystalline phases such as quartz, mullite, and various iron oxides.

Fly ash also contains environmental toxins in significant amounts, including arsenic (43.4 ppm); barium (806 ppm); beryllium (5 ppm); boron (311 ppm); cadmium (3.4 ppm); chromium (136 ppm); chromium VI (90 ppm); cobalt (35.9 ppm); copper (112 ppm); fluorine (29 ppm); lead (56 ppm); manganese (250 ppm); nickel (77.6 ppm); selenium (7.7 ppm); strontium (775 ppm); thallium (9 ppm); vanadium (252 ppm); and zinc (178 ppm).[5]

The above concentrations of trace elements vary according to the kind of coal burnt to form it. In fact, in the case of bituminous coal, with the notable exception of boron, trace element concentrations are generally similar to trace element concentrations in unpolluted soils.[6]

Two classes of fly ash are defined by ASTM C618: Class F fly ash and Class C fly ash. The chief difference between these classes is the amount of calcium, silica, alumina, and iron content in the ash. The chemical properties of the fly ash are largely influenced by the chemical content of the coal burned (i.e., anthracite, bituminous, and lignite).[7]

Not all fly ashes meet ASTM C618 requirements, although depending on the application, this may not be necessary. Ash used as a cement replacement must meet strict construction standards, but no standard environmental regulations have been established in the United States. 75% of the ash must have a fineness of 45 µm or less, and have a carbon content, measured by the loss on ignition (LOI), of less than 4%. In the U.S., LOI needs to be under 6%. The particle size distribution of raw fly ash is very often fluctuating constantly, due to changing performance of

the coal mills and the boiler performance. This makes it necessary that, if fly ash is used in an optimal way to replace cement in concrete production, it needs to be processed using beneficiation methods like mechanical air classification. But if fly ash is used also as a filler to replace sand in concrete production, unbeneficiated fly ash with higher LOI can be also used. Especially important is the ongoing quality verification. This is mainly expressed by quality control seals like the Bureau of Indian Standards mark or the DCL mark of the Dubai Municipality.

[edit] Class F fly ash

The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. This fly ash is pozzolanic in nature, and contains less than 20% lime (CaO). Possessing pozzolanic properties, the glassy silica and alumina of Class F fly ash requires a cementing agent, such as Portland cement, quicklime, or hydrated lime, with the presence of water in order to react and produce cementitious compounds. Alternatively, the addition of a chemical activator such as sodium silicate (water glass) to a Class F ash can lead to the formation of a geopolymer.

[edit] Class C fly ash

Fly ash produced from the burning of younger lignite or subbituminous coal, in addition to having pozzolanic properties, also has some self-cementing properties. In the presence of water, Class C fly ash will harden and gain strength over time. Class C fly ash generally contains more than 20% lime (CaO). Unlike Class F, self-cementing Class C fly ash does not require an activator. Alkali and sulfate (SO4) contents are generally higher in Class C fly ashes.

At least one US manufacturer has announced a fly ash brick containing up to 50 percent Class C fly ash. Testing shows the bricks meet or exceed the performance standards listed in ASTM C 216 for conventional clay brick; it is also within the allowable shrinkage limits for concrete brick in ASTM C 55, Standard Specification for Concrete Building Brick. It is estimated that the production method used in fly ash bricks will reduce the embodied energy of masonry construction by up to 90%.[8] Bricks and pavers were expected to be available in commercial quantities before the end of 2009.[9]

[edit] Disposal and market sources

In the past, fly ash produced from coal combustion was simply entrained in flue gases and dispersed into the atmosphere. This created environmental and health concerns that prompted laws which have reduced fly ash emissions to less than 1 percent of ash produced. Worldwide, more than 65% of fly ash produced from coal power stations is disposed of in landfills and ash ponds.

The recycling of fly ash has become an increasing concern in recent years due to increasing landfill costs and current interest in sustainable development. As of 2005, U.S. coal-fired power plants reported producing 71.1 million tons of fly ash, of which 29.1 million tons were reused in various applications.[10] If the nearly 42 million tons of unused fly ash had been recycled, it would have reduced the need for approximately 27,500 acre·ft (33,900,000 m3) of landfill space.

[10][11] Other environmental benefits to recycling fly ash includes reducing the demand for virgin materials that would need quarrying and substituting for materials that may be energy-intensive to create such as Portland cement.

As of 2006, about 125 million tons of coal-combustion byproducts, including fly ash, were produced in the U.S. each year, with about 43 percent of that amount used in commercial applications, according to the American Coal Ash Association Web site. As of early 2008, the United States Environmental Protection Agency hoped that figure would increase to 50 percent as of 2011.[12]

[edit] Fly ash reuse

There is no U.S. governmental registration or labelling of fly ash utilization in the different sectors of the economy - industry, infrastructures and agriculture. Fly ash utilization survey data, acknowledged as incomplete, are published annually by the American Coal Ash Association.[13]

The ways of fly ash utilization include (approximately in order of decreasing importance):

Concrete production, as a substitute material for Portland cement and sand Embankments and other structural fills (usually for road construction) Grout and Flowable fill production Waste stabilization and solidification Cement clinkers production - (as a substitute material for clay) Mine reclamation Stabilization of soft soils Road subbase construction As Aggregate substitute material (e.g. for brick production) Mineral filler in asphaltic concrete Agricultural uses: soil amendment, fertilizer, cattle feeders, soil stabilization in stock feed yards,

and agricultural stakes Loose application on rivers to melt ice[14]

Loose application on roads and parking lots for ice control[15]

Other applications include cosmetics, toothpaste, kitchen counter tops, floor and ceiling tiles, bowling balls, flotation devices, stucco, utensils, tool handles, picture frames, auto bodies and boat hulls, cellular concrete, geopolymers, roofing tiles, roofing granules, decking, fireplace mantles, cinder block, PVC pipe, Structural Insulated Panels, house siding and trim, running tracks, blasting grit, recycled plastic lumber, utility poles and crossarms, railway sleepers, highway sound barriers, marine pilings, doors, window frames, scaffolding, sign posts, crypts, columns, railroad ties, vinyl flooring, paving stones, shower stalls, garage doors, park benches, landscape timbers, planters, pallet blocks, molding, mail boxes, artificial reef, binding agent, paints and undercoatings, metal castings, and filler in wood and plastic products.[11][16][17]

[edit] Portland cement

Owing to its pozzolanic properties, fly ash is used as a replacement for some of the Portland cement content of concrete.[18] The use of fly ash as a pozzolanic ingredient was recognized as

early as 1914, although the earliest noteworthy study of its use was in 1937.[19] Before its use was lost to the Dark Ages, Roman structures such as aqueducts or the Pantheon in Rome used volcanic ash (which possesses similar properties to fly ash) as pozzolan in their concrete.[20] As pozzolan greatly improves the strength and durability of concrete, the use of ash is a key factor in their preservation.

Use of fly ash as a partial replacement for Portland cement is generally limited to Class F fly ashes. It can replace up to 30% by mass of Portland cement, and can add to the concrete’s final strength and increase its chemical resistance and durability. Recently concrete mix design for partial cement replacement with High Volume Fly Ash (50 % cement replacement) has been developed. For Roller Compacted Concrete (RCC)[used in dam construction] replacement values of 70% have been achieved with processed fly ash at the Ghatghar Dam project in Maharashtra, India. Due to the spherical shape of fly ash particles, it can also increase workability of cement while reducing water demand.[21] The replacement of Portland cement with fly ash is considered by its promoters to reduce the greenhouse gas "footprint" of concrete, as the production of one ton of Portland cement produces approximately one ton of CO2 as compared to zero CO2 being produced using existing fly ash. New fly ash production, i.e., the burning of coal, produces approximately twenty to thirty tons of CO2 per ton of fly ash. Since the worldwide production of Portland cement is expected to reach nearly 2 billion tons by 2010, replacement of any large portion of this cement by fly ash could significantly reduce carbon emissions associated with construction, as long as the comparison takes the production of fly ash as a given.

[edit] Embankment

Fly ash properties are somewhat unique as an engineering material. Unlike typical soils used for embankment construction, fly ash has a large uniformity coefficient consisting of clay-sized particles. Engineering properties that will affect fly ash’s use in embankments include grain size distribution, compaction characteristics, shear strength, compressibility, permeability, and frost susceptibility.[21] Nearly all fly ash used in embankments are Class F fly ashes.

[edit] Soil stabilization

Soil stabilization is the permanent physical and chemical alteration of soils to enhance their physical properties. Stabilization can increase the shear strength of a soil and/or control the shrink-swell properties of a soil, thus improving the load-bearing capacity of a sub-grade to support pavements and foundations. Stabilization can be used to treat a wide range of sub-grade materials from expansive clays to granular materials. Stabilization can be achieved with a variety of chemical additives including lime, fly ash, and Portland cement, as well as by-products such as lime-kiln dust (LKD) and cement-kiln dust (CKD). Proper design and testing is an important component of any stabilization project. This allows for the establishment of design criteria as well as the determination of the proper chemical additive and admixture rate to be used to achieve the desired engineering properties. Benefits of the stabilization process can include: Higher resistance (R) values, Reduction in plasticity, Lower permeability, Reduction of pavement thickness, Elimination of excavation - material hauling/handling - and base importation, Aids compaction, Provides “all-weather” access onto and within projects sites. Another form of soil treatment closely related to soil stabilization is soil modification, sometimes

referred to as “mud drying” or soil conditioning. Although some stabilization inherently occurs in soil modification, the distinction is that soil modification is merely a means to reduce the moisture content of a soil to expedite construction, whereas stabilization can substantially increase the shear strength of a material such that it can be incorporated into the project’s structural design. The determining factors associated with soil modification vs soil stabilization may be the existing moisture content, the end use of the soil structure and ultimately the cost benefit provided. Equipment for the stabilization and modification processes include: chemical additive spreaders, soil mixers (reclaimers), portable pneumatic storage containers, water trucks, deep lift compactors, motor graders.

[edit] Flowable fill

Fly ash is also used as a component in the production of flowable fill (also called controlled low strength material, or CLSM), which is used as self-leveling, self-compacting backfill material in lieu of compacted earth or granular fill. The strength of flowable fill mixes can range from 50 to 1,200 lbf/in² (0.3 to 8.3 MPa), depending on the design requirements of the project in question. Flowable fill includes mixtures of Portland cement and filler material, and can contain mineral admixtures. Fly ash can replace either the Portland cement or fine aggregate (in most cases, river sand) as a filler material. High fly ash content mixes contain nearly all fly ash, with a small percentage of Portland cement and enough water to make the mix flowable. Low fly ash content mixes contain a high percentage of filler material, and a low percentage of fly ash, Portland cement, and water. Class F fly ash is best suited for high fly ash content mixes, whereas Class C fly ash is almost always used in low fly ash content mixes.[21][22]

[edit] Asphalt concrete

Asphalt concrete is a composite material consisting of an asphalt binder and mineral aggregate. Both Class F and Class C fly ash can typically be used as a mineral filler to fill the voids and provide contact points between larger aggregate particles in asphalt concrete mixes. This application is used in conjunction, or as a replacement for, other binders (such as Portland cement or hydrated lime). For use in asphalt pavement, the fly ash must meet mineral filler specifications outlined in ASTM D242. The hydrophobic nature of fly ash gives pavements better resistance to stripping. Fly ash has also been shown to increase the stiffness of the asphalt matrix, improving rutting resistance and increasing mix durability.[21][23]

[edit] Geopolymers

More recently, fly ash has been used as a component in geopolymers, where the reactivity of the fly ash glasses is used to generate a binder comparable to a hydrated Portland cement in appearance and properties, but with possibly reduced CO2 emissions.[24]

It should be noted that when the total carbon footprint of the alkali required to form geopolymer cement is considered, including the calcining of limestone as an intermediate to the formation of alkali, the net reduction in total CO2 emissions may be negligible. Moreover, handling of alkali can be problematic and setting of geopolymer cements is very rapid (minutes versus hours) as

compared to Portland cements, making widespread use of geopolymer cements impractical at the ready mix level.

[edit] Roller compacted concrete

Another application of using fly ash is in roller compacted concrete dams. Many dams in the US have been constructed with high fly ash contents. Fly ash lowers the heat of hydration allowing thicker placements to occur. Data for these can be found at the US Bureau of Reclamation. This has also been demonstrated in the Ghatghar Dam Project in India.

[edit] Bricks

There are several techniques for manufacturing construction bricks from fly ash, producing a wide variety of products. One type of fly ash brick is manufactured by mixing fly ash with an equal amount of clay, then firing in a kiln at about 1000 degrees C. This approach has the principal benefit of reducing the amount of clay required. Another type of fly ash brick is made by mixing soil, plaster of paris, fly ash and water, and allowing the mixture to dry. Because no heat is required, this technique reduces air pollution. More modern manufacturing processes use a greater proportion of fly ash, and a high pressure manufacturing technique, which produces high strength bricks with environmental benefits.

In the United Kingdom, fly ash has been used for over fifty years to make concrete building blocks. They are widely used for the inner skin of cavity walls. They are naturally more thermally insulating than blocks made with other aggregates.[citation needed]

Ash bricks have been used in house construction in Windhoek, Namibia since the 1970s. There is, however, a problem with the bricks in that they tend to fail or produce unsightly pop-outs. This happens when the bricks come into contact with moisture and a chemical reaction occurs causing the bricks to expand.[citation needed]

In India, fly ash bricks are used for construction. Leading manufacturers use an industrial standard known as "Pulverized fuel ash for lime-Pozzolana mixture" using over 75% post-industrial recycled waste, and a compression process. This produces a strong product with good insulation properties and environmental benefits. [25][26]

American civil engineer Henry Liu announced the invention of a new type of fly ash brick in 2007. Liu's brick is compressed at 4,000 psi and cured for 24 hours in a 150 °F (66 °C) steam bath, then toughened with an air entrainment agent, so that it lasts for more than 100 freeze-thaw cycles. Owing to the high concentration of calcium oxide in class C fly ash, the brick can be described as self-cementing. Since this method contains no clay and uses pressure instead of heat, it saves energy, reduces mercury pollution, and costs 20% less than traditional manufacturing techniques. [27][28] This type of brick is now manufactured under license in the USA. [29]

Some varieties of fly ash brick gain strength as they age.[citation needed]

[edit] Metal matrix composites

Hollow fly ash can be infiltrated by molten metal to form solid, alumina encased spheres. Fly ash can also be mixed with molten metal and cast to reduce overall weight and density, due to the low density of fly ash. Research is underway to incorporate fly ash into lead acid batteries in a lead calcium tin fly ash composite in an effort to reduce weight of the battery.

[edit] Waste treatment and stabilization

Fly ash, in view of its alkalinity and water absorption capacity, may be used in combination with other alkaline materials to transform sewage sludge into organic fertilizer or biofuel.[30]

In addition, fly ash, mainly class C, may be used in the stabilization/solidification process of hazardous wastes and contaminated soils.[31] For example, the Rhenipal process uses fly ash as an admixture to stabilize sewage sludge and other toxic sludges. This process has been used since 1996 to stabilize large amounts of chromium(VI) contaminated leather sludges in Alcanena, Portugal.[32][33]

[edit] Environmental problems

[edit] Present production rate of fly ash

In the United States about 131 million tons of fly ash are produced annually by 460 coal-fired power plants. A 2008 industry survey estimated that 43 percent of this ash is re-used.[34]

[edit] Groundwater contamination

Since coal contains trace levels of arsenic, barium, beryllium, boron, cadmium, chromium, thallium, selenium, molybdenum and mercury, its ash will continue to contain these traces and therefore cannot be dumped or stored where rainwater can leach the metals and move them to aquifers.[35]

[edit] Spills of bulk storage

Tennessee Valley Authority Fly Ash containment failure on 23 December 2008 in Kingston, Tennessee

Where fly ash is stored in bulk, it is usually stored wet rather than dry so that fugitive dust is minimized. The resulting impoundments (ponds) are typically large and stable for long periods, but any breach of their dams or bunding will be rapid and on a massive scale.

In December 2008 the collapse of an embankment at an impoundment for wet storage of fly ash at the Tennessee Valley Authority's Kingston Fossil Plant resulted in a major release of 5.4 millon cubic yards of coal fly ash, damaging 3 homes and flowing into the Emory River. Cleanup costs may exceed $1.2 billion. This spill was followed a few weeks later by a smaller TVA-plant spill in Alabama, which contaminated Widows Creek and the Tennessee River.[36]

[edit] Contaminants

Fly ash contains trace concentrations of heavy metals and other substances that are known to be detrimental to health in sufficient quantities. Potentially toxic trace elements in coal include arsenic, beryllium, cadmium, barium, chromium, copper, lead, mercury, molybdenum, nickel, radium, selenium, thorium, uranium, vanadium, and zinc. Approximately 10 percent of the mass of coals burned in the United States consists of unburnable mineral material that becomes ash, so the concentration of most trace elements in coal ash is approximately 10 times the concentration in the original coal.[37] A 1997 analysis by the U.S. Geological Survey (USGS) found that fly ash typically contained 10 to 30 ppm of uranium, comparable to the levels found in some granitic rocks, phosphate rock, and black shale.[37]

In 2000, the United States Environmental Protection Agency (EPA) said that coal fly ash did not need to be regulated as a hazardous waste.[38] Studies by the U.S. Geological Survey and others of radioactive elements in coal ash have concluded that fly ash compares with common soils or

rocks and should not be the source of alarm.[37] However, community and environmental organizations have documented numerous environmental contamination and damage concerns.[39]

[40][41]

A revised risk assessment approach may change the way coal combustion wastes (CCW) are regulated, according to an August 2007 EPA notice in the Federal Register.[42] In June 2008, the U.S. House of Representatives held an oversight hearing on the Federal government's role in addressing health and environmental risks of fly ash.[43]

[edit] Exposure concerns

Crystalline silica and lime along with toxic chemicals are among the exposure concerns. Although industry has claimed that fly ash is "neither toxic nor poisonous," this is disputed. Exposure to fly ash through skin contact, inhalation of fine particle dust and drinking water may well present health risks. The National Academy of Sciences noted in 2007 that "the presence of high contaminant levels in many CCR (coal combustion residue) leachates may create human health and ecological concerns." [1]

Fine crystalline silica present in fly ash has been linked with lung damage, in particular silicosis. OSHA allows 0.10 mg/m3, (one ten-thousandth of a gram per cubic meter of air).

Another fly ash component of some concern is lime (CaO). This chemical reacts with water (H2O) to form calcium hydroxide [Ca(OH)2], giving fly ash a pH somewhere between 10 and 12, a medium to strong base. This can also cause lung damage if present in sufficient quantities.

In a study by NIOSH at a cement company, crystalline silica exposures from fly ash were determined to be of no concern. For maintaining a safe workplace emphasis must be placed on maintaining low nuisance dust levels and to use the appropriate personal protective equipment (PPE). The conclusion of this NIOSH study is supported by other studies devoted to the effects of fly ash on the health of workers in power plants. According to these studies, fly ash dust should not be considered as "silicotic dust", because most of the crystalline silica is coated by amorphic alumino-silicates (glass), the main constituent of fly ash particles. This was shown particularly on the basis of scanning electron microscopy observations, by a research work performed in the Netherlands [44], but similar findings were obtained also in other countries.

[edit] See also

Cement Concrete Pozzolan Pozzolana Pozzolanic reaction Alkali Silica Reaction (ASR) Alkali-aggregate reaction Silica fume

[edit] External links

Evaluation of Dust Exposures at Lehigh Portland Cement Company, Union Bridge, MD, a NIOSH Report, HETA 2000-0309-2857

Determination of Airborne Crystalline Silica Treatise by NIOSH "Coal Ash: 130 Million Tons of Waste" 60 Minutes (Oct. 4, 2009) American Coal Ash Association Fly Ash Information Center : Site explaining the history and uses of fly ash. United States Geological Survey - Radioactive Elements in Coal and Fly Ash (document) Public Employees for Environmental Responsibility: Coal Combustion Waste UK Quality Ash Association : A site promoting the many uses of fly ash in the UK Coal Ash Is More Radioactive than Nuclear Waste , Scientific American (13 December 2007)

[edit] References

1. ^ a b Managing Coal Combustion Residues in Mines, Committee on Mine Placement of Coal Combustion Wastes, National Research Council of the National Academies, 2006

2. ̂ Human and Ecological Risk Assessment of Coal Combustion Wastes, RTI, Research Triangle Park, August 6, 2007, prepared for the U.S. Environmental Protection Agency

3. ̂ American Coal Ash Association www.acaa-usa.org4. ̂ "Is fly ash an inferior building and structural material". Science in Dispute. 2003.

http://findarticles.com/p/articles/mi_gx5204/is_2003/ai_n19124302/?tag=content;col1.5. ̂ Figures refer to media values of samples of fly ash from pulverized coal combustion. See

Managing Coal Combustion Residues in Mines, Committee on Mine Placement of Coal Combustion Wastes, National Research Council of the National Academies, 2006.

6. ̂ EPRI (Project Manager K. Ladwig) 2010, Comparison of coal combustion products to other common materials - Chemical Characteristics, Electric Power Research Institute, Palo Alto, CA

7. ̂ "ASTM C618 - 08 Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete". ASTM International. http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/C618.htm?L+mystore+lsft6707. Retrieved 2008-09-18.

8. ̂ "The Building Brick of Sustainability". Chusid, Michael; Miller, Steve; & Rapoport, Julie. The Construction Specifier May 2009.

9. ̂ "Coal by-product to be used to make bricks in Caledonia". Burke, Michael. The Journal Times April 1, 2009.

10. ^ a b American Coal Ash Association. "CCP Production and Use Survey" (PDF). http://www.acaa-usa.org/PDF/2005_CCP_Production_and_Use_Figures_Released_by_ACAA.pdf.

11. ^ a b U.S. Environmental Protection Agency. "Using Coal Ash in Highway Construction - A Guide to Benefits and Impacts". http://www.epa.gov/epaoswer/osw/conserve/c2p2/pubs/greenbk508.pdf.

12. ̂ Robert McCabe (March 30, 2008). "Above ground, a golf course. Just beneath it, potential health risks". The Virginian-Pilot. http://hamptonroads.com/2008/03/above-ground-golf-course-just-beneath-it-potential-health-risks.

13. ̂ American Coal Ash Association. "Coal Combustion Products Production & Use Statistics". http://acaa.affiniscape.com/displaycommon.cfm?an=1&subarticlenbr=3.

14. ̂ Gaarder, Nancy. "Coal ash will fight flooding", Omaha World-Herald, February 17, 2010.

15. ̂ Josephson, Joan. "Coal ash under fire from Portland resident", "ObserverToday", February 13, 2010.

16. ̂ U.S. Federal Highway Administration. "Fly Ash". http://www.fhwa.dot.gov/infrastructure/materialsgrp/flyash.htm.

17. ̂ Public Employees for Environmental Responsibility. "Coal Combustion Wastes in Our Lives". http://www.peer.org/campaigns/publichealth/coalash/everywhere.php.

18. ̂ Scott, Allan N .; Thomas, Michael D. A. (January/February 2007). "Evaluation of Fly Ash From Co-Combustion of Coal and Petroleum Coke for Use in Concrete". ACI Materials Journal (American Concrete Institute) 104 (1): 62–70.

19. ̂ Halstead, W. (October 1986). "Use of Fly Ash in Concrete". National Cooperative Highway Research Project 127.

20. ̂ Moore, David. The Roman Pantheon: The Triumph of Concrete.21. ^ a b c d U.S. Federal Highway Administration. "Fly Ash Facts for Highway Engineers" (PDF).

http://www.fhwa.dot.gov/pavement/recycling/fafacts.pdf.22. ̂ Hennis, K. W.; Frishette, C. W. (1993). "A New Era in Control Density Fill". Proceedings of the

Tenth International Ash Utilization Symposium23. ̂ Zimmer, F. V. (1970). "Fly Ash as a Bituminous Filler". Proceedings of the Second Ash Utilization

Symposium24. ̂ Duxson, P.; Provis, J.L.; Lukey, G.C.; van Deventer, J.S.J. (2007). "The role of inorganic polymer

technology in the development of 'Green concrete'". Cement and Concrete Research 37 (12): 1590–1597. doi:10.1016/j.cemconres.2007.08.018

25. ̂ "FAQs - Fly Ash Bricks - Puzzolana Green Fly-Ash bricks". Fly Ash Bricks Delhi. http://www.flyashbricksdelhi.com/faqs#A2.

26. ̂ "List of important IS Codes related to bricks". Fly Ash Bricks Info. http://flyashbricksinfo.com/construction/list-of-important-is-codes-related-to-bricks.html.

27. ̂ Popular Science Magazine, INVENTION AWARDS : A Green Brick , May 200728. ̂ National Science Foundation, Press Release 07-058, "Follow the 'Green' Brick Road?", May 22,

200729. ̂ "Bricks – CalStar Products". CalStar Products. http://calstarproducts.com/products/fly-ash-

brick-fab.30. ̂ N-Viro International[dead link]

31. ̂ EPA, 2009. Technology performance review: selecting and using solidification/stabilization treatment for site remediation. NRMRL, U.S. Environmental Protection Agency, Cinicinnati, OH

32. ̂ "Toxic Sludge stabilisation for INAG, Portugal". DIRK group. http://www.dirkgroup.com/waterindustry/mobilesolutions/sludgestabilisationcase.html.

33. ̂ DIRK group (1996). "Pulverised fuel ash products solve the sewage sludge problems of the wastewater industry". Waste management 16 (1-3): 51–57. doi:10.1016/S0956-053X(96)00060-8.

34. ̂ Chemical & Engineering News, 23 February 2009, "The Foul Side of 'Clean Coal'", p. 4435. ̂ A December 2008 Maryland court decision levied a $54 million penalty against Constellation

Energy, which had performed a "restoration project" of filling an abandoned gravel quarry with fly ash; the ash contaminated area waterwells with heavy metals. C&EN/12 Feb. 2009, p. 45

36. ̂ "TVA Widows Creek coal waste spill". sourcewatch.org. http://www.sourcewatch.org/index.php?title=TVA_Widows_Creek_coal_waste_spill. Retrieved 2010-12-11.

37. ^ a b c U.S. Geological Survey (October 1997). "Radioactive Elements in Coal and Fly Ash: Abundance, Forms, and Environmental Significance" (PDF). U.S. Geological Survey Fact Sheet FS-163-97. http://pubs.usgs.gov/fs/1997/fs163-97/FS-163-97.pdf.

38. ̂ Environmental Protection Agency (May 22, 2000). "Notice of Regulatory Determination on Wastes From the Combustion of Fossil Fuels". Federal Register Vol. 65, No. 99. p. 32214. http://frwebgate.access.gpo.gov/cgi-bin/getpage.cgi?dbname=2000_register&position=all&page=32214.

39. ̂ McCabe, Robert; Mike Saewitz (2008-07-19). "Chesapeake takes steps toward Superfund designation of site.". The Virginian-Pilot. http://www.norfolk.com/2008/07/chesapeake-takes-steps-toward-superfund-designation-site?page=1.

40. ̂ McCabe, Robert."Above ground golf course, Just beneath if potential health risks", The Virginian-Pilot, 2008-03-30

41. ̂ Citizens Coal Council, Hoosier Environmental Council, Clean Air Task Force (March 2000), "Laid to Waste: The Dirty Secret of Combustion Waste from America's Power Plants"

42. ̂ Environmental Protection Agency (August 29, 2007). "Notice of Data Availability on the Disposal of Coal Combustion Wastes in Landfills and Surface Impoundments" (PDF). 72 Federal Register 49714. http://edocket.access.gpo.gov/2007/pdf/E7-17138.pdf.

43. ̂ House Committee on Natural Resources, Subcommittee on Energy and Mineral Resources (June 10, 2008). "Oversight Hearing: How Should the Federal Government Address the Health and Environmental Risks of Coal Combustion Wastes?". http://resourcescommittee.house.gov/index.php?option=com_jcalpro&Itemid=65&extmode=view&extid=184.

44. ̂ Meij R., 2003. Status report on the health issues associated with pulverized fuel ash and fly dust. Report 50131022-KPS/MEC 01-6032, KEMA Power Generation and Sustainables, Arnhem, NL)

Retrieved from "http://en.wikipedia.org/w/index.php?title=Fly_ash&oldid=467232362" View page ratings

Rate this page

What's this?

Trustworthy

Objective

Complete

Well-written

I am highly knowledgeable about this topic (optional)

I have a relevant college/university degree

It is part of my profession

It is a deep personal passion

The source of my knowledge is not listed here

I would like to help improve Wikipedia, send me an e-mail (optional)

We will send you a confirmation e-mail. We will not share your e-mail address with outside parties as per our feedback privacy statement.

Submit ratings

Saved successfully

Your ratings have not been submitted yet

Your ratings have expired

Please reevaluate this page and submit new ratings.

An error has occured. Please try again later.

Thanks! Your ratings have been saved.

Please take a moment to complete a short survey.

Start survey Maybe later

Thanks! Your ratings have been saved.

Do you want to create an account?

An account will help you track your edits, get involved in discussions, and be a part of the community.

Create an accountorLog in Maybe later

Thanks! Your ratings have been saved.

Did you know that you can edit this page?

Edit this page Maybe later

Categories:

Coal Coal-fired power stations Waste Waste treatment technology Environmental issues with energy Cement Concrete Silicates

Hidden categories:

All articles with dead external links Articles with dead external links from August 2011 Articles containing potentially dated statements from 2005 All articles containing potentially dated statements All articles with unsourced statements Articles with unsourced statements from August 2011

Personal tools

Log in / create account

Namespaces

Article Discussion

Variants

Views

Read Edit View history

Actions

Search

Navigation

Main page Contents

Special:Search

Featured content Current events Random article Donate to Wikipedia

Interaction

Help About Wikipedia Community portal Recent changes Contact Wikipedia

Toolbox

What links here Related changes Upload file Special pages Permanent link Cite this page Rate this page

Print/export

Create a book Download as PDF Printable version

Languages

Deutsch Español Esperanto हि�न्दी� Italiano עברית Nederlands 日本語 Norsk (bokmål) ភាសាខ្�រ Português Svenska ไทย

This page was last modified on 22 December 2011 at 19:52. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms

may apply. See Terms of use for details.

Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.

Contact us

Privacy policy About Wikipedia Disclaimers Mobile view

Please read:A personal appeal from

Wikipedia author Dr. Sengai Podhuvan We now accept

₹

(INR)

Rice hullsFrom Wikipedia, the free encyclopedia

Jump to: navigation, search

Rice hulls (or rice husks) are the hard protecting coverings of grains of rice. In addition to protecting rice during the growing season, rice hulls can be put to use as building material, fertilizer, insulation material, or fuel.

Contents

[hide]

1 Production 2 Use

o 2.1 Chemistry o 2.2 Pet food fiber

o 2.3 Building material o 2.4 Pillow stuffing o 2.5 Fertilizer o 2.6 SiC production o 2.7 Fuel o 2.8 Brewing o 2.9 Juice extraction o 2.10 Rice husk ash

3 See also 4 External links 5 References

[edit] Production

Rice hulls are the coating for the seeds, or grains, of the rice plant. To protect the seed during the growing season, the hull is made of hard materials, including opaline silica and lignin. The hull is mostly indigestible to humans.

One practice, started in the seventeenth century, to separate the rice from hulls, it to put the whole rice into a pan and throw it into the air while the wind blows. The hulls are blown away while the rice fell back into the pan. This happens because the hull isn't nearly as dense as the rice. These steps are known as winnowing. During the milling process, the hulls are removed from the grain to create brown rice, which is then milled further to remove the bran layer, creating white rice.

[edit] Use

A number of rice-producing countries, (e.g. Thailand), are currently conducting research on industrial uses of rice hulls. Some of the current and potential applications are listed below.

[edit] Chemistry

Rice hulls can be used to produce mesoporous molecular sieves (e.g., MCM),[1][2] which are applied as catalysts for various chemical reactions, as a support for drug delivery system and as adsorbent in waste water treatment.

[edit] Pet food fiber

Rice hulls are the outermost covering of the rice and come as organic rice hulls and natural rice hulls. Rice hulls are an inexpensive byproduct of human food processing, serving as a source of fiber that is considered a filler ingredient in cheap pet foods.[3]

[edit] Building material

Rice hulls are a class A insulating material because they are difficult to burn and less likely to allow moisture to propagate mold or fungi. It has been found out that when burned, rice hull produces significant amounts of silica. For these reasons it provides excellent thermal insulation.

[edit] Pillow stuffing

Rice hulls are used as pillow stuffing. The pillows are loosely stuffed and considered therapeutic as they retain the shape of the head.

[edit] Fertilizer

Rice hulls are organic material and can be composted. However, their high lignin content can make this a slow process. Sometimes earthworms are used to accelerate the process. Using vermicomposting techniques, the hulls can be converted to fertilizer in about four months.

[edit] SiC production

Rice hulls are a low-cost material from which silicon carbide "whiskers" can be manufactured. The SiC whiskers are then used to reinforce ceramic cutting tools, increasing their strength tenfold.[4]

[edit] Fuel

With proper techniques, rice hulls can be burned and used to power steam engines. Some rice mills originally disposed of hulls in this way.[citation needed]

However the direct combustion of rice hulls tends to produce a lot of smoke. A far better alternative is to gasify rice hulls. Rice hulls are easily gasified in top-lit updraft gasifiers. The combustion of this rice hull gas produces a beautiful blue flame, and rice hull biochar makes a wonderful soil amendment.[5]

[edit] Brewing

Rice hulls can be used in brewing beer to increase the lautering ability of a mash.

[edit] Juice extraction

Rice hulls are used as a "press aid" to improve extraction efficiency of apple pressing.[6]

[edit] Rice husk ash

The ash produced after the husks have been burned, (abbreviated to RHA), is high in silica. A number of possible uses are being investigated for this. These uses include

aggregates and fillers for concrete and board production

economical substitute for microsilica / silica fumes absorbents for oils and chemicals soil ameliorants as a source of silicon as insulation powder in steel mills as repellents in the form of "vinegar-tar" as a release agent in the ceramics industry as an insulation material for homes and refrigerants in Kerala, India- Rice husks (Umikari- in malayalam)was universally used for over centuries in

cleaning teeth - before toothpaste replaced it.

[edit] See also

Rice-hull bagwall construction

[edit] External links

Build Green with Recycled Rice

[edit] References

1. ̂ S. Chiarakorn et al. "Influence of functional silanes on hydrophobicity of MCM-41 synthesized from rice husk" Sci. Technol. Adv. Mater. 8 (2007) 110 free download

2. ̂ J. Chumee et al. "Characterization of platinum–iron catalysts supported on MCM-41 synthesized with rice husk silica and their performance for phenol hydroxylation" Sci. Technol. Adv. Mater. 9 (2008) 015006 free download

3. ̂ http://www.dogfoodproject.com/index.php?page=badingredients4. ̂ http://www.ms.ornl.gov/researchgroups/process/cpg/sic.htm5. ̂ See: http://esrla.com/pdf/landfill_06.pdf6. ̂ Press aids

Ma, Jian Feng; Kazunori Tamai, Naoki Yamaji, Namiki Mitani, Saeko Konishi, Maki Katsuhara, Masaji Ishiguro, Yoshiko Murata, Masahiro Yano (2006). "A silicon transporter in rice". Nature 440 (7084): 688–691. doi:10.1038/nature04590. PMID 16572174.

Mitani, Namiki; Jian Feng Ma, Takashi Iwashita (2005). "Identification of the silicon form in xylem sap of rice (Oryza sativa L.)". Plant Cell Physiol. 46 (2): 279–283. doi:10.1093/pcp/pci018. PMID 15695469. http://pcp.oxfordjournals.org/cgi/content/abstract/46/2/279. Retrieved 2008-05-05.

Mitani, Namiki; Jian Feng Ma (2005). "Uptake system of silicon in different plant species". J. Exp. Bot. 56 (414): 1255–1261. doi:10.1093/jxb/eri121. PMID 15753109. http://jxb.oxfordjournals.org/cgi/content/abstract/56/414/1255. Retrieved 2008-05-05.

The Rice Hull House where rice hulls are used for insulation Uses for rice husk ash, or RHA Rice hulls used in cutting tool industry

Retrieved from "http://en.wikipedia.org/w/index.php?title=Rice_hulls&oldid=464999445" View page ratings

Rate this page

What's this?

Trustworthy

Objective

Complete

Well-written

I am highly knowledgeable about this topic (optional)

I have a relevant college/university degree

It is part of my profession

It is a deep personal passion

The source of my knowledge is not listed here

I would like to help improve Wikipedia, send me an e-mail (optional)

We will send you a confirmation e-mail. We will not share your e-mail address with outside parties as per our feedback privacy statement.

Submit ratings

Saved successfully

Your ratings have not been submitted yet

Your ratings have expired

Please reevaluate this page and submit new ratings.

An error has occured. Please try again later.

Thanks! Your ratings have been saved.

Please take a moment to complete a short survey.

Start survey Maybe later

Thanks! Your ratings have been saved.

Do you want to create an account?

An account will help you track your edits, get involved in discussions, and be a part of the community.

Create an accountorLog in Maybe later

Thanks! Your ratings have been saved.

Did you know that you can edit this page?

Edit this page Maybe later

Categories:

Materials Building materials Cement Concrete Pet foods

Hidden categories:

All articles with unsourced statements Articles with unsourced statements from July 2011

Personal tools

Log in / create account

Namespaces

Article Discussion

Variants

Views

Read Edit View history

Actions

Search

Navigation

Main page Contents Featured content Current events Random article Donate to Wikipedia

Interaction

Help About Wikipedia Community portal Recent changes Contact Wikipedia

Toolbox

What links here Related changes Upload file Special pages Permanent link Cite this page Rate this page

Print/export

Create a book Download as PDF Printable version

Languages

Special:Search

Français Italiano

This page was last modified on 9 December 2011 at 19:24. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms

may apply. See Terms of use for details.Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.

Contact us

Privacy policy About Wikipedia Disclaimers Mobile view