Reinforced concrete - Wikipedia, the free encyclo...http://en.wikipedia.org/wiki/Reinforced_concrete Reinforced concrete From Wikipedia, the free encyclopedia Jump to: navigation, search Reinforced concrete is concrete in which the material's undesirably low tensile strength and elasticity are counteracted by the inclusion of reinforcing structures that have high tensile strength. The structures usually, though not necessarily, are reinforcing bars of steel (rebar) and also usually, though also not necessarily, are embedded passively in the concrete before it sets. Such reinforcing structures are designed primarily to take up working stresses that otherwise would have placed regions within the concrete mass under unacceptable tension. Modern concrete reinforcing structures however, may instead or in addition contain non-steel materials with high tensile strength. They also may be permanently stressed before or after the mass sets, so as to improve the behaviour of the final structure under working loads. These two expedients are known as (pre-stressing) and (post-stressing) respectively. For a strong, ductile and durable construction the reinforcement needs to have the following properties at least: High strength High toleration of tensile strain Good bond to the concrete, irrespective of pH, moisture, and similar factors Thermal compatibility, not causing unacceptable stresses in response to changing temperatures. Durability in the concrete environment, irrespective of corrosion or sustained stress for example. Contents 1 Use in construction 2 Behavior of reinforced concrete 2.1 Materials 2.2 Key characteristics 2.3 Mechanism of composite action of reinforcement and concrete 2.4 Anchorage (bond) in concrete: Codes of specifications 2.5 Anti-corrosion measures 3 Reinforcement and terminology of Beams 4 Prestressed concrete 1 of 18 Tuesday 24 July 2012 02:53 PM without reinforcement. frames and more.Reinforced concrete . http://en. many concrete buildings would not have been possible.2 Carbonation 5. the cement hydrates to form 2 of 18 Tuesday 24 July 2012 02:53 PM . construction schedule. occupancy levels and end use of a building.4 Alkali silica reaction 5.wikipedia.. When mixed with a small amount of water. Reinforced concrete can be classified as precast or cast in-situ concrete..3 Chlorides 5.5 Conversion of high alumina cement 5.Wikipedia. foundations. the free encyclo. Designing and implementing the most efficient floor system is key to creating optimal building structures. [edit] Behavior of reinforced concrete [edit] Materials Concrete is a mixture of coarse (stone or brick chips) and fine (generally sand or crushed stone) aggregates with a binder material (usually Portland cement). Small changes in the design of a floor system can have significant impact on material costs. walls.org/wiki/Reinforced_concrete 5 Common failure modes of steel reinforced concrete 5.6 Sulphates 6 Steel plate construction 7 Fiber-reinforced concrete 8 Non-steel reinforcement 9 See also 10 References 11 Further reading 12 External links [edit] Use in construction Rebars of Sagrada Família's roof in construction (2009) Concrete is reinforced to give it extra tensile strength. columns. including slabs. Reinforced concrete can encompass many types of structures and components. operating costs. beams.1 Mechanical failure 5. ultimate strength. only to give an idea on orders of magnitude.org/wiki/Reinforced_concrete microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid structure. As a rule of thumb. making it much more resistant to corrosion than it would be in neutral or acidic conditions.g. NaOH) and the portlandite (calcium hydroxide) contained in the hardened cement paste causes a passivating film to form on the surface of the steel.. such as steel. the free encyclo. When the cement paste exposed to the air and meteoric water reacts with the atmospheric CO2.Reinforced concrete . reinforced concrete . the alkaline chemical environment provided by the alkali reserve (KOH. portlandite and the Calcium Silicate Hydrate (CSH) of the hardened cement paste become progressively carbonated and the high pH gradually decreases from 13. Carbonation of concrete along with chloride ingress are amongst the chief reasons for the failure of reinforcement bars in concrete. is placed in concrete.Wikipedia. 3. any appreciable tension (e. Typical concrete mixes have high resistance to compressive stresses (about 4. A reinforced concrete section where the concrete resists the compression and steel resists the tension can be made into almost any shape and size for the construction industry.wikipedia. http://en. eliminating large internal stresses due to differences in thermal expansion or contraction.5 to 8. For this reason.. 2. due to bending) will break the microscopic rigid lattice. resulting in cracking and separation of the concrete. If a material with high strength in tension. then the composite material. the coefficient of thermal expansion of concrete is similar to that of steel. typical non-reinforced concrete must be well supported to prevent the development of tension.000 psi (28 MPa)).5 – 12.. permitting any stress to be transmitted efficiently between the different materials. this conforms to the surface details of the steel. [edit] Key characteristics Three physical characteristics give reinforced concrete its special properties: 1.5. the pH of water in equilibrium with calcite (calcium carbonate) and the steel is no longer passivated.[1] 3 of 18 Tuesday 24 July 2012 02:53 PM . Usually steel bars are roughened or corrugated to further improve the bond or cohesion between the concrete and steel. however. resists not only compression but also bending and other direct tensile actions. steel is protected at pH above ~11 but starts to corrode below ~10 depending on steel characteristics and local physico-chemical conditions when concrete becomes carbonated. when the cement paste within the concrete hardens. Wikipedia.wikipedia. The same concept applies to lap splice length mentioned in the codes where splices (overlapping) provided between two adjacent bars in order to maintain the required continuity of stress in the splice zone. such as a steel bar. parking structures and other structures that may be exposed to deicing salt may benefit from use of epoxy-coated. special anchorages must be provided. Maintaining composite action requires transfer of load between the concrete and steel. current international codes of specifications use the concept of development length rather than bond stress. Reinforcing bars are normally round in cross-section and vary in diameter. slip or separation of the two materials under load. http://en.Reinforced concrete . The direct stress is transferred from the concrete to the bar interface so as to change the tensile stress in the reinforcing bar along its length.. However. hot dip galvanised or stainless steel rebar. has to undergo the same strain or deformation as the surrounding concrete in order to prevent discontinuity. reinforced concrete for roads. [edit] Anchorage (bond) in concrete: Codes of specifications Because the actual bond stress varies along the length of a bar anchored in a zone of tension.[2] [edit] Mechanism of composite action of reinforcement and concrete The reinforcement in a RC structure. although good design and a well-chosen cement mix may provide sufficient 4 of 18 Tuesday 24 July 2012 02:53 PM . This load transfer is achieved by means of bond (anchorage) and is idealized as a continuous stress field that develops in the vicinity of the steel-concrete interface. if the actual available length is inadequate for full development. Reinforced concrete structures sometimes have provisions such as ventilated hollow cores to control their moisture & humidity.org/wiki/Reinforced_concrete The relative cross-sectional area of steel required for typical reinforced concrete is usually quite small and varies from 1% for most beams and slabs to 6% for some columns. bridges. [edit] Anti-corrosion measures In wet and cold climates. The main requirement for safety against bond failure is to provide a sufficient extension of the length of the bar beyond the point where the steel is required to develop its yield stress and this length must be at least equal to its development length. Distribution of concrete (in spite of reinforcement) strength characteristics along the cross-section of vertical reinforced concrete elements is inhomogeneous. such as cogs or hooks or mechanical end plates.. the free encyclo. http://en. Sealants include paint.Reinforced concrete .. sometimes used to seal roadbeds. while at the inner face (compressive face ) it experiences compressive stress. called tension steel.[3] Zinc phosphate slowly reacts with calcium cations and the hydroxyl anions present in the cement pore water and forms a stable hydroxyapatite layer. resulting in a small curvature. A775 Standard Specification for Epoxy Coated Steel Reinforcing Bars and A955 Standard Specification for Deformed and Plain Stainless Bars for Concrete Reinforcement. The latter reinforcement is called compression steel. At the outer face (tensile face ) of the curvature the concrete experiences tensile stress. is designed to resist the tension. felts or fabric mats sealed with tar. Reference ASTM standard specifications A767 Standard Specification for Hot Dip Galvanised Reinforcing Bars. 1–2 wt.wikipedia. a less powerful oxidizer of the divalent iron. Another. Penetrating sealants typically must be applied some time after curing.Wikipedia. such as calcium nitrite [Ca(NO2)2]. cheaper way of protecting rebars is coating them with zinc phosphate. A singly reinforced beam is one in which the concrete element is only reinforced near the tensile face and the reinforcement. plastic foams. [edit] Reinforcement and terminology of Beams A beam bends under bending moment. Hot dip galvanized rebar may be bright or dull grey depending on length of exposure. the free encyclo. and stainless rebar exhibits a typical white metallic sheen that is readily distinguishable from carbon steel reinforcing bar. Nitrite is a much more active corrosion inhibitor than nitrate. Corrosion inhibitors. can also be added to the water mix before pouring concrete. Epoxy coated rebar can easily be identified by the light green colour of its epoxy coating. The nitrite anion is a mild oxidizer that oxidizes the soluble and mobile ferrous ions (Fe2+) present at the surface of the corroding steel and causes it to precipitate as an insoluble ferric hydroxide (Fe(OH) 3). When the compression zone of a concrete is inadequate to resist the 5 of 18 Tuesday 24 July 2012 02:53 PM . and layers of bentonite clay. films and aluminum foil. Generally. This causes the passivation of steel at the anodic oxidation sites. A doubly reinforced beam is one in which besides the tensile reinforcement the concrete element is also reinforced near the compressive face to help the concrete resist compression..org/wiki/Reinforced_concrete protection for many applications. % of [Ca(NO2)2] with respect to cement weight is needed to prevent corrosion of the rebars. Wikipedia. [edit] Prestressed concrete Main article: Prestressed concrete 6 of 18 Tuesday 24 July 2012 02:53 PM . When the reinforced concrete element is subject to increasing bending moment. The value of the safety factor generally ranges from 0. An over-reinforced beam is one in which the tension capacity of the tension steel is greater than the combined compression capacity of the concrete and the compression steel (over-reinforced at tensile face). the free encyclo. the tension steel yields while the concrete does not reach its ultimate failure condition. A balanced-reinforced beam is one in which both the compressive and tensile zones reach yielding at the same imposed load on the beam. The characteristic strength is the strength of a material where less than 5% of the specimen shows lower strength. because failure is sudden as the concrete crushes at the same time of the tensile steel yields.85 in Allowable Stress Design. which does not provide any warning before failure as the failure is instantaneous.org/wiki/Reinforced_concrete compressive Moment(positive moment). including a material-safety factor. extra reinforcement has to be provided if the architect limits the dimensions of the section. exhibiting a large deformation and warning before its ultimate failure. So the "over-reinforced concrete" beam fails by crushing of the compressive-zone concrete and before the tension zone steel yields.[4] Steel-reinforced concrete moment-carrying elements should normally be designed to be under-reinforced so that users of the structure will receive warning of impending collapse. and the concrete will crush and the tensile steel will yield at the same time.wikipedia.75 to 0. The ultimate limit state is the theoretical failure point with a certain probability. As the tension steel yields and stretches.Reinforced concrete . It is stated under factored loads and factored resistances. The design strength or nominal strength is the strength of a material. This design criterion is however as risky as over-reinforced concrete. http://en.. an "under-reinforced" concrete also yields in a ductile manner. An under-reinforced beam is one in which the tension capacity of the tensile reinforcement is smaller than the combined compression capacity of the concrete and the compression steel (under-reinforced at tensile face). In this case the yield stress of the steel governs the design.. which gives a very little warning of distress in tension failure. When loads are applied. This is a serviceability failure in limit state design. placing a built-in compressive force on the concrete. which will be subjected to tensile forces when in service. Corrosion and freeze/thaw cycles may damage poorly designed or constructed reinforced concrete. cracking the concrete and unbonding the rebar from the concrete.Reinforced concrete . or rebar spaced at too great a distance. or by bond failure between the concrete and the rebar. by yielding or failure of the rebar. the size and location of the cracks can be limited and controlled by reinforcement. Typical mechanisms leading to durability problems are discussed below. Once the concrete has hardened. http://en. the tension on the reinforcing steel is released.[5] [edit] Common failure modes of steel reinforced concrete Reinforced concrete can fail due to inadequate strength. When rebar corrodes. Since the concrete is always under compression. The reinforcing steel in the bottom part of the beam.. when bending or shear stresses exceed the strength of the reinforcement. the curing methodology and the mix design of the concrete. leading to mechanical failure. or due to a reduction in its durability. [edit] Mechanical failure Cracking of the concrete section can not be prevented. or due to internal effects such as early thermal shrinkage when it cures.org/wiki/Reinforced_concrete Prestressed concrete is a technique that greatly increases loadbearing strength of concrete beams. [edit] Carbonation Concrete wall cracking as steel reinforcing corrodes 7 of 18 Tuesday 24 July 2012 02:53 PM . Ultimate failure leading to collapse can be caused by crushing of the concrete.. however. placement of control joints. it is less subject to cracking and failure.Wikipedia. the oxidation products (rust) expand and tends to flake. is placed in tension prior to the concrete being poured around it. The concrete then cracks either under excess loading.wikipedia. when compressive stresses exceed its strength. Cracking is normally the result of an inadequate quantity of rebar. the free encyclo. but does not become a tensile force. the reinforcing steel takes on more stress and the compressive force in the concrete is reduced. Cracking defects can allow moisture to penetrate and corrode the reinforcement. it is normal to state the concrete cover for the rebar (the depth within the object that the rebar will be).Reinforced concrete . However.Wikipedia. This solution will turn [pink] when in contact with alkaline concrete. One method of testing a structure for carbonation is to drill a fresh hole in the surface and then treat the cut surface with phenolphthalein indicator solution.org/wiki/Reinforced_concrete and swells. early failure due to corrosion may occur.. as well as damaging the structural concrete. http://en. or similar problems of corrosion from external exposure Main article: carbonatation Carbonation. including sodium chloride. can promote the corrosion of embedded steel rebar if present in sufficienty high concentration. making it possible to see the depth of carbonation. or neutralisation. Rust has a lower density than metal. If the reinforcement is too close to the surface. The apparently thin layer of concrete between the steel and the surface suggests.. The concrete cover depth can be measured with a cover meter.wikipedia. [edit] Chlorides Chlorides. When designing a concrete structure. An existing hole is no good because the exposed surface will already be carbonated. so it expands as it forms. Chloride anions induce 8 of 18 Tuesday 24 July 2012 02:53 PM . Detailed view of spalling. The breakage of material from the surface is called spalling. The minimum concrete cover is normally regulated by design or building codes. is a chemical reaction between carbon dioxide in the air with calcium hydroxide and hydrated calcium silicate in the concrete. the free encyclo. cracking the decorative cladding off the wall. carbonated concrete only becomes a durability problem when there is also sufficient moisture and oxygen to cause electro-potential corrosion of the reinforcing steel. http://en. New Jersey..5 wt. and was heralded as the largest reinforced concrete structure in the world when it was completed in 1910 as part of the Lackawanna Cut-Off rail line project. The use of de-icing salts on roadways. The Paulins Kill Viaduct. However.100 feet (335 m) long. and parking garages. It was also mistakenly believed that it would prevent freezing. ensure that the coarse and fine aggregates do not contain chlorides. For this reason. is 115 feet (35 m) tall and 1. In water these 9 of 18 Tuesday 24 July 2012 02:53 PM . Hainesburg. Also FRP rebars are known to be less susceptible to chlorides.% salts. magnesium sulfate. is probably one of the primary causes of premature failure of reinforced or prestressed concrete bridge decks. calcium sulfate. Rebar for foundations and walls of sewage pump station. this practice has fallen into disfavor once the deleterious effects of chlorides became known. The use of epoxy-coated reinforcing bars and the application of cathodic protection has mitigated this problem to some extent. Properly designed concrete mixtures that have been allowed to cure properly are effectively impervious to the effects of deicers. The Lackawanna Railroad was a pioneer in the use of reinforced concrete. Another important source of chloride ions is from sea water.Wikipedia.. one should only use fresh raw water or potable water for mixing concrete. Sea water contains by weight approximately 3. and bicarbonates.wikipedia. used to reduce the freezing point of water. and not use admixtures that contain chlorides.Reinforced concrete . It was once common for calcium chloride to be used as an admixture to promote rapid set-up of the concrete. These salts include sodium chloride. roadways. It should be avoided when ever possible. the free encyclo.org/wiki/Reinforced_concrete both localized corrosion (pitting corrosion) and generalized corrosion of steel reinforcements. http://en. causes localised swelling responsible of tensile stress and cracking. but the ban 10 of 18 Tuesday 24 July 2012 02:53 PM .Wikipedia.org/wiki/Reinforced_concrete 2- salts dissociate in free ions (Na+. to be used as a floor-topping material. Subsequent inquiries into the matter showed that the beams were improperly manufactured.13. The alkali silica reaction (ASR). However it is now known that when these materials came into contact with moisture it produced a weak solution of hydrochloric acid due to the presence of chlorides in the magnesite. Over a period of time (typically decades) the solution caused corrosion of the embedded steel rebars. a chloride rich carbonate mineral. Chloride ions are particularly aggressive for the corrosion of the carbon steel reinforcement bars and make up about 50% of these ions. It was greatly used after World War II for making precast concrete objects. However. this cement cures quickly and reaches very high durability and strength. In the 1960s and 1970s it was also relatively common for Magnesite. siliceous limestone) sometimes present in the aggregates with the hydroxyl ions (OH-) from the cement pore solution. chert. Poorly crystallized silica (SiO2) dissolves and dissociates at high pH (12. The conditions required for alkali silica reaction are threefold: (1) aggregate containing an alkali-reactive constituent (amorphous silica). Mg2+. (2) sufficient availability of hydroxyl ions (OH-). [edit] Conversion of high alumina cement Resistant to weak acids and especially sulfates. Cl-. [edit] Alkali silica reaction Main article: Alkali Silica Reaction This a reaction of amorphous silica (chalcedony.. SO4 . This was done principally as a levelling and sound attenuating layer. the free encyclo. This was most commonly found in wet areas or areas repeatedly exposed to moisture. especially when not properly cured.5 . it can lose strength with heat or time (conversion). With the collapse of three roofs made of prestressed concrete beams using high alumina cement. The soluble dissociated silicic acid reacts in the porewater with the calcium hydroxide (portlandite) present in the cement paste to form an expansive calcium silicate hydrate (CSH). This reaction occurs independently of the presence of rebars: massive concrete structures such as dams can be affected.[6][7] This phenomenon is sometimes popularly referred to as "concrete cancer".wikipedia.Reinforced concrete . above 75 % relative humidity (RH) within the concrete.5) in alkaline water.. this cement was banned in the UK in 1976. and (3) sufficient moisture. HCO3 ) and migrate with the water into the capillaries of the concrete. . the attack on the Portland cement can begin. and welded together on-site to form steel walls connected by stringers. in the US ASTM C150 Type 5 Portland cement can be used in the mix.. As the concentration increases. Also. foundations. e. Fiber-reinforced normal concrete is mostly used for on-ground floors and pavements.). glass. pillars. which can lead to early failure of the structure. where tensile forces are often greatest. but can also be used in normal concrete. The method has excellent strength because the steel is on the outside. in sufficient concentration. this type of attack is much rarer especially in the Eastern half of the United States. but can be considered for a wide range of construction parts (beams.wikipedia. various protective coatings can be used. stringers join parallel steel plates. or plastic 11 of 18 Tuesday 24 July 2012 02:53 PM .org/wiki/Reinforced_concrete remained. the free encyclo. etc. [edit] Steel plate construction Main article: Steel plate construction In steel plate construction. ettringite or thaumasite. Concrete reinforced with fibers (which are usually steel.[8] [edit] Sulphates Sulfates (SO4) in the soil or in groundwater. For buried structures such as pipe. The plate assemblies are fabricated off site. The chemical analysis of soil borings should be done during the design phase of any project involving concrete in contact with the native soil to check for the presence of sulfates. The sulfate ion concentration increases much slower in the soil mass and is especially dependent upon the initial amount of sulfates in the native soil. can react with the Portland cement in concrete causing the formation of expansive products. http://en. The walls become the form into which concrete is poured.Wikipedia. Steel plate construction speeds reinforced concrete construction by cutting out the time consuming on-site manual steps of tying rebar and building forms. [edit] Fiber-reinforced concrete Main article: Fiber reinforced concrete Fiber reinforcement is mainly used in shotcrete. via alternate wetting and drying. either alone or with hand-tied rebars. This type of cement is designed to be particularly resistant to a sulfate attack.g. The most typical attack of this type is on concrete slabs and foundation walls at grade where the sulfate ion. can increase in concentration. If the concentrations are found to be aggressive.Reinforced concrete . and length of fiber are important. concrete is a highly alkaline environment. spun basalt fiber. which are nearly as strong as steel. 45 mm length—steel or plastic) will increase the concrete's tensile strength. Steel fibers can only be used on surfaces that can tolerate or avoid corrosion and rust stains. dimension. Basalt fibre is stronger and less expensive than glass. in which many materials. but historically has not resisted the alkaline environment of portland cement well enough to be used as direct reinforcement.. Shape. However. The introduction of non-steel reinforcement of concrete is relatively recent. will only be effective the first hours after pouring the concrete (reduces cracking while the concrete is stiffening) but will not increase the concrete tensile strength. but the material is still far too expensive for any building. the design and application of non-steel reinforcing is fraught with challenges. it takes two major forms: non-metallic rebar rods.S. In some cases. http://en. Steel is the strongest commonly-available fiber. Some experiments have had promising early results with carbon nanotubes. Also. the behaviour of such reinforcing materials differ from the behaviour of metals. A thin and short fiber. long available in Eastern Europe. hair-shaped glass fiber. For example there is increasing interest in glass fiber reinforced concrete (GFRC ) and in various applications of polymer fibres incorporated into concrete.[9][10] Fibre-Reinforced Polymer (FRP) (Fibre-reinforced plastic or FRP) and Glass12 of 18 Tuesday 24 July 2012 02:53 PM . for instance in terms of shear strength. A normal-size fiber for European shotcrete (1 mm diameter. but not as ductile as steel. a steel-fiber surface is faced with other materials..Wikipedia. lighter-weight. has become available in the U. Glass fiber is inexpensive and corrosion-proof. including most kinds of glass. New materials use plastic binders to isolate the basalt fiber from the cement. The premium fibers are graphite-reinforced plastic fibers. the free encyclo. and corrosion-proof. [edit] Non-steel reinforcement There is considerable overlap between the subjects of non-steel reinforcement and fiber-reinforcment of concrete. and Western Europe. for example short. some of them have major advantages in specific applications.org/wiki/Reinforced_concrete fibers) is less expensive than hand-tied rebar. and there also are new applications in which metal rebar simply is not an option. Recently.wikipedia. while still increasing the tensile strength many times. creep and elasticity.Reinforced concrete . have a poor service life. for one thing. and comes in different lengths (30 to 80 mm in Europe) and shapes (end-hooks). Although currently there is not much suggestion that such materials will in general replace metal rebar. and non-steel (usually also non-metallic) fibres incorporated into the cement matrix. air or other aggressive substances reaching the steel and causing corrosion. for example the edges of balconies when balustrades are replaced and bathroom floors in multi-story construction where the service life of the floor structure is likely to be many times the service life of the waterproofing building membrane. FRP-reinforced structures therefore can be lighter and last longer. the structures have advantages. The material properties of FRP or GRP bars differ markedly from steel.Wikipedia. so that Deflections are likely to be higher than for equivalent steel-reinforced units. Also. Deflection limits are set to ensure that crack widths in steelreinforced concrete are controlled to prevent water.Reinforced concrete .. Again. it does not need a protective concrete cover as thick as steel reinforcement does (typically 30 to 50 mm or more).wikipedia. Plastic reinforcement often is stronger. and accordingly require non-magnetic buildings. Accordingly. Failure in either case is more likely to occur by compression of the concrete than by rupture of the reinforcement. glass. either by intrinsic concrete alkalinity or by external corrosive fluids that might penetrate the concrete. aramid or other polymers or high-strength fibres set in a resin matrix to form a rebar rod or grid or fibres. MRI machines have huge magnets. In such situations corrosion-proof reinforcing can extend a structure's life substantially. so there are differences in the design considerations.. non-steel reinforcing often has its advantages where corrosion of reinforcing steel is a major cause of failure. toll booths that read radio tags need reinforced concrete that is transparent to radio waves. These rebars are installed in much the same manner as steel. http://en. where the design life of the concrete structure is more important than its initial costs. Also. FRP rods may also be useful in situations where it is likely that the concrete structure may be compromised in future years. for example in the intertidal zone. The cost of these materials has dropped dramatically since their widespread adoption in the aerospace industry and by the military. Structures with internal FRP reinforcement typically have an elastic deformability comparable to the plastic deformability (ductility) of steel reinforced structures. In particular FRP rods are useful for structures where the presence of steel would not be acceptable. in particular a dramatic reduction in problems related to corrosion. aesthetics and possibly water-tightness will be the limiting criteria 13 of 18 Tuesday 24 July 2012 02:53 PM . suitably applied. For FRP-reinforced concrete. FRP or GRP bars have relatively higher tensile strength but lower stiffness. for some applications the whole-life cost will be price-competitive with steel-reinforced concrete. These structures can be significantly lighter and usually have a longer service life. Deflection is always a major design consideration for reinforced concrete.org/wiki/Reinforced_concrete reinforced plastic (GRP) consist of fibres of polymer. carbon. For example. or at least has a better strength to weight ratio than reinforcing steels. because it resists corrosion. the free encyclo. The cost is higher but. ^ Emerging Corrosion Control Technologies for Repair and Rehabilitation of Concrete Structures 2. shear.[11] (The improvement is thought to be due to the formation of pathways out of the bulk of the concrete. and longitudinal stresses.Wikipedia. 14 of 18 Tuesday 24 July 2012 02:53 PM .wikipedia.. FRP rods also have relatively lower compressive strengths than steel rebar. addition of 1 kg/m3 of polypropylene fibers to concrete has been shown to reduce spalling during a simulated fire. the zone between the straight and curved regions are subject to strong bending. When strained..Reinforced concrete . There is growing interest in application of external reinforcement of existing structures with advanced materials such as carbon fibre. The disadvantages are not on the side of the FRP however. http://en. FRP rebar stirrups formed by bending before hardening generally perform relatively poorly in comparison to steel stirrups or to structures with straight fibres. structures employing FRP have to maintain their strength and the anchoring of the forces at temperatures to be expected in the event of fire. allowing steam pressure to dissipate.org/wiki/Reinforced_concrete for crack width control. Special design techniques are necessary to deal with such problems. For purposes of fireproofing an adequate thickness of cement concrete cover or protective cladding is necessary. the free encyclo. Where fire safety is a consideration. that can impart exceptional strength. One drawback to the use of FRP reinforcement is the limited fire resistance. ^ article "Concrete Inhomogeneity of Vertical Cast-In-Situ Elements In Frame-Type Buildings". [edit] See also Ferrocement Cover Meter Concrete cover Falsework Formwork François Coignet Types of concrete [edit] References 1. and accordingly require different design approaches for reinforced concrete columns.[11]) Another problem is the effectiveness of shear reinforcement. tunnels. the free encyclo.co. Heathrow Airport. ^ BS EN 1169:1999 Precast concrete products.html 6.mottmac. http://shop. Newby F.. ^ "h2g2 . No. http://web. ^ a b Arthur W. http://en. Test method for glass-fibre reinforced cement.mottmac.Concrete Cancer".com/files/project /3372/Airside_Road_Tunnel.uk /hac. www. Kim. 5. Early Reinforced Concrete.quest-tech. ^ Nilson. BBC. Archived from the original on 2005-09-11. http://www. 7. [edit] External links Short film on the early reinforced concrete buildings that Tecton designed with Ove Arup for Dudley Zoo in the 1930s Concrete Research: http://www. S. Ashgate Variorum. 9. ^ "Effect of zinc phosphate chemical conversion coating on corrosion behaviour of mild steel in alkaline medium: protection of rebars in reinforced concrete" Sci. General rules for factory production control of glass-fibre reinforced cement.bsigroup.. ^ [1] 8.org/web/20050911210803/http://www. Technol." Journal of Research of the National Institute of Standards and Technology ).ferrericon.co. ISBN 978-0-86078-760-0. 3 (May-June 2011): 655-669. ^ "HAC".uk/dna/h2g2 /A4014172. IIT Kharagpur Timeline of concrete 15 of 18 Tuesday 24 July 2012 02:53 PM .com/ ISBN 0-580-29202-9 11. 116.Wikipedia.com/ ISBN 0-580-32052-9 10. http://www. Darby (2003).bsigroup.archive.. Retrieved 2009-10-14. Baker-Jarvis. "Electromagnetic Metrology on Concrete and Corrosion.pdf [edit] Further reading Threlfall A. The Airside Road Tunnel. British Standards Institute: http://shop. Surek. Mater. Reynolds's Reinforced Concrete Designer's Handbook – 11th ed.Reinforced concrete .org. 57. " Unknown title". 645.com: p. Vol. Darwin .bbc. 2001.J and J. Design of Concrete Structures. 80-90. et al. Adv. 9 (2008) 045009 (free download) 4. Department of Civil Engineering. ^ BS EN 1170-5:1998 Precast concrete products.Dhang. Web.tunnels.wikipedia. the MacGraw-Hill Education. ISBN 978-0-419-25830-8. N. Retrieved 2009-10-14. England .org Reinforced Concrete Spructures Video Lectures By Prof.concreteresearch. ^ http://www.archive.. Dolan.. p. 2003.org/wiki/Reinforced_concrete 3.htm.com/Whatis. wikipedia.wikipedia.php?title=Reinforced_concrete&oldid=503080779" Categories: Composite materials Concrete Structural engineering Personal tools Create account Log in Namespaces Article Talk Variants Views Read Edit View history Actions Search Search Navigation Main page Contents Featured content Current events Random article Donate to Wikipedia Interaction 16 of 18 Tuesday 24 July 2012 02:53 PM .org /w/index.org/wiki/Reinforced_concrete Retrieved from "http://en. the free encyclo. http://en.Reinforced concrete .Wikipedia... Reinforced concrete . the free encyclo.. http://en.org/wiki/Reinforced_concrete Help About Wikipedia Community portal Recent changes Contact Wikipedia Toolbox What links here Related changes Upload file Special pages Permanent link Cite this page Print/export Create a book Download as PDF Printable version Languages ﺍﻟﻌﺮﺑﻴﺔ Български Català Česky Cymraeg Dansk Deutsch Español ﻓﺎﺭﺳﯽ Français Galego 한국어 िह�दी Hrvatski Italiano עברית Қазақша Latgaļu Latviešu Lietuvių 17 of 18 Tuesday 24 July 2012 02:53 PM ..Wikipedia.wikipedia. . the free encyclo..org/wiki/Reinforced_concrete Magyar Nederlands 日本語 Polski Português Română Русский Simple English Slovenčina Српски / srpski Srpskohrvatski / српскохрватски Svenska த�� ไทย Türkçe Українська Tiếng Việt Winaray 中文 This page was last modified on 19 July 2012 at 07:07. additional terms may apply. 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