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Seminar Report

On

SPECIAL STRUCTURAL CONCRETE

NAME:ROLL:

INTRODUCTION

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Concrete is a construction material composed of cement (commonly Portlandcement ) as well as other cementitious materials such as fly ash and slag cement , aggregate(generally a coarse aggregate such as gravel limestone or granite, plus a fine aggregate suchas sand and water ) and chemical admixtures. The word concrete comes from the Latin word

"concretus", which means "hardened" or "hard".

oncrete solidifies and hardens after mixing with water and placement due to a chemical process !nown as hydration .The water reacts with the cement, which onds the other components together, eventually creating a stone#li!e material. The reactions are highlyexothermic and care must e ta!en that the uild#up in heat does not affect the integrity of thestructure. oncrete is used to ma!e pavements , architectural structures , foundations ,motorways $roads , ridges$overpasses , par!ing structures, ric! $ loc! walls and footings for gates, fences and poles.

%ore concrete is used than any other man#made material in the world. &' s of *00+, a outseven illion cu ic meters of concrete are made each year more than one cu ic meter for every person on -arth. &* oncrete powers a / 12# illion industry which employs more thantwo million wor!ers in the nited /tates alone. %ore than 22,000 miles of highways in

merica are paved with this material. The People3s 4epu lic of hina currently consumes506 of the world3s cement &concrete production.

History

7n /er ia , remains of a hut dating from 2+00 8 have een found, with a floor made of redlime , sand, and gravel. The pyramids of /haanxi in

hina , uilt thousands of years ago, contain a mixture of lime and volcanic ash or clay. The secret of concrete waslost for '1 centuries until '92+ , when the 8ritishengineer :ohn /meaton pioneered the use of hydrauliclime in concrete, using pe les and powdered ric! asaggregate. Portland cement was first used in concrete inthe early ';50s.4ecently, the use of recycled materials asconcrete ingredients is gaining popularity ecause of increasingly stringent environmental legislation. The most conspicuous of these is fly ash, a

yproduct of coal#fired power plants. This has a significant impact y reducing the amount of


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Types of concrete

highway paved with concrete.

4egular concrete paving loc!s

=arious types of concrete have een developed for specialist application and have ecome!nown y these names.

Regu ar concrete

Regular concrete is the lay term descri ing concrete that is produced y following the mixinginstructions that are commonly pu lished on pac!ets of cement, typically using sand or other common material as the aggregate, and often mixed in improvised containers. This concretecan e produced to yield a varying strength from a out '0 %Pa to a out 50 %Pa, dependingon the purpose, ranging from linding to structural concrete respectively. %any types of pre#mixed concrete are availa le which include powdered cement mixed with an aggregate,needing only water.

Typically, a atch of concrete can e made y using ' part Portland cement, * parts dry sand,1 parts dry stone, '$* part water. The parts are in terms of weight > not volume. ?or example,' cu ic foot of concrete would e made using ** l s cement, '0 l s water, 5' l s dry sand, 90l s dry stone ('$*" to 1$5" stone). This would ma!e ' cu ic foot of concrete and would weigha out '51 l s. The sand should e mortar or ric! sand (washed and filtered if possi le) andthe stone should e washed if possi le. @rganic materials (leaves, twigs, etc) should eremoved from the sand and stone to ensure the highest strength.

!ig"#strengt" concrete

High-strength concrete has a compressive strength generally greater than +,000 pounds per s


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hydroxide crystals in the cement matrix, which might reduce the strength at the cement#aggregate ond.

Low B$ ratios and the use of silica fume ma!e concrete mixes significantly less wor!a le,

which is particularly li!ely to e a pro lem in high#strength concrete applications wheredense re ar cages are li!ely to e used. To compensate for the reduced wor!a ility,superplasticiCers are commonly added to high#strength mixtures. ggregate must e selectedcarefully for high#strength mixes, as wea!er aggregates may not e strong enough to resistthe loads imposed on the concrete and cause failure to start in the aggregate rather than in thematrix or at a void, as normally occurs in regular concrete.

7n some applications of high#strength concrete the design criterion is the elastic modulusrather than the ultimate compressive strength.

!ig"#performance concrete

High-performance concrete (AP ) is a relatively new term used to descri e concrete thatconforms to a set of standards a ove those of the most common applications, ut not limitedto strength. Bhile all high#strength concrete is also high#performance, not all high#

performance concrete is high#strength. /ome examples of such standards currently used inrelation to AP areD

-ase of placement ompaction without segregation -arly age strength

Long#term mechanical properties Permea ility Eensity Aeat of hydration Toughness =olume sta ility Long life in severe environments

Se f#conso i$ating concretes

Euring the 'F;0s a num er of countries including :apan, /weden and ?rance developedconcretes that are self-compacting , !nown as self#consolidating concrete in the nited /tates.This self#consolidating concrete ( SCC s) is characteriCed yD

extreme fluidity as measured y flow , typically etween +20#920 mm on a flow ta le,rather than slump(height)

no need for vi rators to compact the concrete placement eing easier. no leed water, or aggregate segregation 7ncreased Li


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s of *002 , self#consolidating concretes account for '0#'26 of concrete sales in some-uropean countries. 7n the / precast concrete industry, / represents over 926 of concrete production. 1; departments of transportation in the / accept the use of / for road and ridge proGects.

This emerging technology is made possi le y the use of polycar oxylates plasticiCer insteadof older naphthalene ased polymers, and viscosity modifiers to address aggregatesegregation.

S"otcrete

Shotcrete (also !nown y the trade name Gunite ) uses compressed air to shoot concrete onto(or into) a frame or structure. /hotcrete is fre the dry mixture of cement and aggregates is filled into the machine andconveyed with compressed air through the hoses. The water needed for the hydrationis added at the noCCle.

wet-mix > the mixes are prepared with all necessary water for hydration. The mixesare pumped through the hoses. t the noCCle compressed air is added for spraying.

?or oth methods additives such as accelerators and fi er reinforcement may e used. &*0

Per%ious concrete

Pervious concrete contains a networ! of holes or voids, to allow air or water to move throughthe concrete.

7t is formed y leaving out some or all of the fine aggregate (fines), the remaining largeaggregate then is ound y a relatively small amount of cement paste. Bhen set, typically

etween '2 and *26 of the concrete volume are voids, allowing water to drain at around 2gal$ftH$ min or *00 L$mH$min) through the concrete.

Pervious concrete allows water to drain naturally through roadway or other structures,reducing the amount of artificial drainage needed, and allowing the water to naturallyreplenish groundwater

7t can significantly reduce noise, y allowing air s


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erated concrete produced y the addition of an air entraining agent to the concrete (or alightweight aggregate li!e expanded clay pellets or cor! granules and vermiculite ) issometimes called Cellular concrete .

See also: Aerated autoclaved concrete

Corcement composites

or! granules are o tained during production of ottle stoppers from the treated ar! of or! oa! or uercus su!er trees. &*' These trees are mainly found in Portugal, /pain and Iorth

frica. &** Portugal is the largest cor! producing country, followed y /pain. The waste cor! granules have a density of a out 100 !g$mJ, which is lower than that of most of thelightweight aggregates used for ma!ing lightweight concrete. 7t has een found that cor! granules do not significantly influence cement hydration. Aowever, cor! dust can influencehydration. &*1 or! cement composites have several advantages over standard concrete, suchas lower thermal conductivities, lower densities and good energy a sorption characteristics.These composites can e made of density from 500 to '200 !g$mJ, compressive strength from' to *+ %Pa, and flexural strength from 0.2 to 5.0 %Pa.

Ro er#compacte$ concrete

Roller-compacted concrete , sometimes called rollcrete , is a low#cement#content stiff concrete placed using techni


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Ru((eri)e$ concrete

Bhile " ru eriCed asphalt concrete" is common, ru eriCed Portland cement concrete("ru eriCed P ") is still undergoing experimental tests, as of *009 &* &1 &5 &2.

Po ymer concrete

Polymer concrete is concrete which uses polymers to ind the aggregate. Polymer concretecan gain a lot of strength in a short amount of time. ?or example, a polymer mix may reach2000 psi in only four hours. Polymer concrete is generally more expensive than conventionalconcretes.

Limecrete

"imecrete or lime concrete is concrete where cement is replaced y lime.

*i(er reinforce$ concrete

*i(er reinforce$ concrete (?4 ) is concrete containing fi rous material which increases itsstructural integrity. 7t contains short discrete fi res that are uniformly distri uted andrandomly oriented. ?i res include steel fi res, glass fi res , synthetic fi res and natural fi res .Bithin these different fi res that character of fi re reinforced concrete changes with varyingconcretes, fi re materials, geometries, distri ution, orientation and densitie

!istorica perspecti%eThe concept of using fi ers as reinforcement is not new. ?i ers have een used asreinforcement since ancient times. Aistorically, horsehair was used in mortar and straw inmud ric!s . 7n the early 'F00s, as estos fi ers were used in concrete, and in the 'F20s theconcept of composite materials came into eing and fi er reinforced concrete was one of thetopics of interest. There was a need to find a replacement for the as estos used in concreteand other uilding materials once the health ris!s associated with the su stance werediscovered. 8y the 'F+0s, steel , glass ( ?4 ), and synthetic fi ers such as polypropylenefi ers were used in concrete, and research into new fi er reinforced concretes continuestoday.

Effect of fi(ers in concrete

?i ers are usually used in concrete to control plastic shrin!age crac!ing and drying shrin!agecrac!ing. They also lower the permea ility of concrete and thus reduce leeding of water ./ome types of fi ers produce greater impact, a rasion and shatter resistance in concrete.

enerally fi ers do not increase the flexural strength of concrete, so it can not replacemoment resisting or structural steel reinforcement. /ome fi ers reduce the strength of

concrete.

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http://en.wikipedia.org/wiki/Rubberized_asphalthttp://www.precast.org/publications/solutions/2004_fall/crumb_rubber.htmhttp://www.ecn.purdue.edu/ECT/Civil/rubberizedcon.htmhttp://www.innovations-report.de/html/berichte/verkehr_logistik/bericht-11612.htmlhttp://pubsindex.trb.org/document/view/default.asp?lbid=801926http://en.wikipedia.org/wiki/Polymer_concretehttp://en.wikipedia.org/wiki/Lime_(mineral)http://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Fibreshttp://en.wikipedia.org/wiki/Fiberglasshttp://en.wikipedia.org/wiki/Synthetic_fibrehttp://en.wikipedia.org/wiki/Natural_fibrehttp://en.wikipedia.org/wiki/Horsehairhttp://en.wikipedia.org/wiki/Mortar_(masonry)http://en.wikipedia.org/wiki/Strawhttp://en.wikipedia.org/wiki/Mudhttp://en.wikipedia.org/wiki/Brickhttp://en.wikipedia.org/wiki/Asbestoshttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Carcinogenhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Glasshttp://en.wikipedia.org/wiki/Glass_Fiber_Reinforced_Concrete_(GFRC)http://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Plasticity_(physics)http://en.wikipedia.org/wiki/Permeability_(fluid)http://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Moment_(physics)http://en.wikipedia.org/wiki/Structural_steelhttp://en.wikipedia.org/wiki/Rubberized_asphalthttp://www.precast.org/publications/solutions/2004_fall/crumb_rubber.htmhttp://www.ecn.purdue.edu/ECT/Civil/rubberizedcon.htmhttp://www.innovations-report.de/html/berichte/verkehr_logistik/bericht-11612.htmlhttp://pubsindex.trb.org/document/view/default.asp?lbid=801926http://en.wikipedia.org/wiki/Polymer_concretehttp://en.wikipedia.org/wiki/Lime_(mineral)http://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Fibreshttp://en.wikipedia.org/wiki/Fiberglasshttp://en.wikipedia.org/wiki/Synthetic_fibrehttp://en.wikipedia.org/wiki/Natural_fibrehttp://en.wikipedia.org/wiki/Horsehairhttp://en.wikipedia.org/wiki/Mortar_(masonry)http://en.wikipedia.org/wiki/Strawhttp://en.wikipedia.org/wiki/Mudhttp://en.wikipedia.org/wiki/Brickhttp://en.wikipedia.org/wiki/Asbestoshttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Carcinogenhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Glasshttp://en.wikipedia.org/wiki/Glass_Fiber_Reinforced_Concrete_(GFRC)http://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Plasticity_(physics)http://en.wikipedia.org/wiki/Permeability_(fluid)http://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Moment_(physics)http://en.wikipedia.org/wiki/Structural_steel


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The amount of fi res added to a concrete mix is measured as a percentage of the total volumeof the composite (concrete and fi res) termed volume fraction (= f ). = f typically ranges from0.' to 16. spect ratio (l$d) is calculated y dividing fi re length (l) y its diameter (d).?i res with a non#circular cross section use an e


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polypropylene tape yarns), Goined y a @ 1 filled styrene# utadiene latex ru er (/84), andface fi ers (maGority eing nylon + and nylon ++ textured yarns). /uch nylon and

polypropylene fi ers can e used for concrete reinforcement. /tudies have shown that ?4containing carpet waste show ade


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s excellent thermal efficiency ma!es a maGor contri ution to environmental protection y sharply reducing the need for space heating and cooling in uildings.

7n addition, s easy wor!a ility allows accurate cutting that minimiCes the generation of

solid waste during use. nli!e other uilding materials can eliminate the need to eused in com ination with insulation products, which increase the environmental impact andcost of construction.

Ra, materia s

QuartC sand, lime and$or cement as inding agent. luminum powder in 26>;6 y volume(depending on the pre#specified density) and water. Bhen mixed and cast in forms, severalchemical reactions ta!e place that give its light weight and thermal properties.

luminium powder reacts with calcium hydroxide and water to form hydrogen . Thehydrogen gas foams the raw mix to dou le the volume (with gas u les up to '$; inch indiameter). t the end of the foaming process the hydrogen escapes to the atmosphere and isreplaced y air.

Bhen the forms are removed from the material, it is solid ut still soft. 7t is then cut intoeither loc!s or panels, and placed in an autoclave cham er for '* hours. Euring this steam

pressure hardening process, when the temperature reaches 195R ?ahrenheit and the pressurereaches '* ars,


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'.+ cu%. transit mixer

small atching plant for local small deliveries

9 cu%. transit mixer

The inside of a transit mixer uses a simple archimedes screw to mix and to lift the concrete tothe delivery chute.

Rea$y#mi- concrete is a type of concrete that is manufactured in a factory or atching plant,

according to a set recipe, and then delivered to a wor!site, y truc! mounted transit mixers .This results in a precise mixture, allowing specialty concrete mixtures to e developed andimplemented on construction sites. The first ready#mix factory was uilt in the 'F10s , ut the

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industry did not egin to expand significantly until the 'F+0s , and it has continued to growsince then.

4eady#mix concrete is sometimes preferred over on#site concrete mixing ecause of the

precision of the mixture and reduced wor!site confusion. Aowever, using a pre#determinedconcrete mixture reduces flexi ility, oth in the supply chain and in the actual components of the concrete.

/ome leading ready#mix concrete suppliers worldwide are the %exican concrete companiesP % and emex U their main competitor is ?rance # ased Lafarge . 4eady %ixed oncrete, or 4% as it is popularly called, refers to concrete that is specifically manufactured for deliveryto the customer3s construction site in a freshly mixed and plastic or unhardened state.

oncrete itself is a mixture of Portland cement, water and aggregates comprising sand andgravel or crushed stone. 7n traditional wor! sites, each of these materials is procuredseparately and mixed in specified proportions at site to ma!e concrete. 4eady %ixed

oncrete is ought and sold y volume # usually expressed in cu ic meters. 4% can ecustom#made to suit different applications. 4eady %ixed oncrete is manufactured under computer#controlled operations and transported and placed at site using sophisticatede


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CONCLUSION

Iotwithstanding its versatility, cement concrete suffers from several draw ac!s, such aslow tensile strength# permea!ility to li$uids and conse

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