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Reinforced concrete

May 04, 2023

Reinforced concrete (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel bars (rebar) and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials.[1][2] In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion.[3]

Reinforced concrete
A heavy, reinforced concrete column, seen before and after the concrete has been cast in place around its rebar frame
Material typeComposite material
Mechanical properties
Tensile strength (σt)Stronger than concrete

Description

Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and/or structural failure. Modern reinforced concrete can contain varied reinforcing materials made of steel, polymers or alternate composite material in conjunction with rebar or not. Reinforced concrete may also be permanently stressed (concrete in compression, reinforcement in tension), so as to improve the behavior of the final structure under working loads. In the United States, the most common methods of doing this are known as pre-tensioning and post-tensioning.

For a strong, ductile and durable construction the reinforcement needs to have the following properties at least:

  • High relative strength
  • High toleration of tensile strain
  • Good bond to the concrete, irrespective of pH, moisture, and similar factors
  • Thermal compatibility, not causing unacceptable stresses (such as expansion or contraction) in response to changing temperatures.
  • Durability in the concrete environment, irrespective of corrosion or sustained stress for example.

History

 
The novel shape of the Philips Pavilion built in Brussels for Expo 58 was achieved using reinforced concrete

Leaning Tower of Nevyansk in the town of Nevyansk in Sverdlovsk Oblast, Russia is the first building known to use reinforced concrete as a construction method.[citation needed] It was built on the orders of the industrialist Akinfiy Demidov between 1721–1725.[4]

François Coignet used iron-reinforced concrete as a technique for constructing building structures.[5] In 1853, Coignet built the first iron reinforced concrete structure, a four-story house at 72 rue Charles Michels in the suburbs of Paris.[5] Coignet's descriptions of reinforcing concrete suggests that he did not do it for means of adding strength to the concrete but for keeping walls in monolithic construction from overturning.[6] The Pippen building in Brooklyn stands as a testament to his technique. In 1854, English builder William B. Wilkinson reinforced the concrete roof and floors in the two-story house he was constructing. His positioning of the reinforcement demonstrated that, unlike his predecessors, he had knowledge of tensile stresses.[7][8][9]

Joseph Monier, a 19th-century French gardener, was a pioneer in the development of structural, prefabricated and reinforced concrete, having been dissatisfied with the existing materials available for making durable flowerpots.[10] He was granted a patent for reinforcing concrete flowerpots by means of mixing a wire mesh and a mortar shell. In 1877, Monier was granted another patent for a more advanced technique of reinforcing concrete columns and girders, using iron rods placed in a grid pattern. Though Monier undoubtedly knew that reinforcing concrete would improve its inner cohesion, it is not clear whether he even knew how much the tensile strength of concrete was improved by the reinforcing.[11]

Before the 1870s, the use of concrete construction, though dating back to the Roman Empire, and having been reintroduced in the early 19th century, was not yet a proven scientific technology. Thaddeus Hyatt, published a report entitled An Account of Some Experiments with Portland-Cement-Concrete Combined with Iron as a Building Material, with Reference to Economy of Metal in Construction and for Security against Fire in the Making of Roofs, Floors, and Walking Surfaces, in which he reported his experiments on the behavior of reinforced concrete. His work played a major role in the evolution of concrete construction as a proven and studied science. Without Hyatt's work, more dangerous trial and error methods might have been depended on for the advancement in the technology.[6][12]

Ernest L. Ransome, an English-born engineer, was an early innovator of reinforced concrete techniques at the end of the 19th century. Using the knowledge of reinforced concrete developed during the previous 50 years, Ransome improved nearly all the styles and techniques of the earlier inventors of reinforced concrete. Ransome's key innovation was to twist the reinforcing steel bar, thereby improving its bond with the concrete.[13] Gaining increasing fame from his concrete constructed buildings, Ransome was able to build two of the first reinforced concrete bridges in North America.[14] One of his bridges still stands on Shelter Island in New Yorks East End, One of the first concrete buildings constructed in the United States was a private home designed by William Ward, completed in 1876. The home was particularly designed to be fireproof.

G. A. Wayss was a German civil engineer and a pioneer of the iron and steel concrete construction. In 1879, Wayss bought the German rights to Monier's patents and, in 1884, his firm, Wayss & Freytag, made the first commercial use of reinforced concrete. Up until the 1890s, Wayss and his firm greatly contributed to the advancement of Monier's system of reinforcing, established it as a well-developed scientific technology.[11]

One of the first skyscrapers made with reinforced concrete was the 16-story Ingalls Building in Cincinnati, constructed in 1904.[9]

The first reinforced concrete building in Southern California was the Laughlin Annex in downtown Los Angeles, constructed in 1905.[15][16] In 1906, 16 building permits were reportedly issued for reinforced concrete buildings in the City of Los Angeles, including the Temple Auditorium and 8-story Hayward Hotel.[17][18]

In 1906, a partial collapse of the Bixby Hotel in Long Beach killed 10 workers during construction when shoring was removed prematurely. That event spurred a scrutiny of concrete erection practices and building inspections. The structure was constructed of reinforced concrete frames with hollow clay tile ribbed flooring and hollow clay tile infill walls. That practice was strongly questioned by experts and recommendations for “pure” concrete construction were made, using reinforced concrete for the floors and walls as well as the frames.[19]

In April 1904, Julia Morgan, an American architect and engineer, who pioneered the aesthetic use of reinforced concrete, completed her first reinforced concrete structure, El Campanil, a 72-foot (22 m) bell tower at Mills College,[20] which is located across the bay from San Francisco. Two years later, El Campanil survived the 1906 San Francisco earthquake without any damage,[21] which helped build her reputation and launch her prolific career.[22] The 1906 earthquake also changed the public's initial resistance to reinforced concrete as a building material, which had been criticized for its perceived dullness. In 1908, the San Francisco Board of Supervisors changed the city's building codes to allow wider use of reinforced concrete.[23]

In 1906, the National Association of Cement Users (NACU) published Standard No. 1[24] and, in 1910, the Standard Building Regulations for the Use of Reinforced Concrete.[25]

Use in construction

 
Rebars of Sagrada Família's roof in construction (2009)
 
Christ the Redeemer statue in Rio de Janeiro, Brazil. It is made of reinforced concrete clad in a mosaic of thousands of triangular soapstone tiles.[26]

Many different types of structures and components of structures can be built using reinforced concrete including slabs, walls, beams, columns, foundations, frames and more.

Reinforced concrete can be classified as precast or cast-in-place concrete.

Designing and implementing the most efficient floor system is key to creating optimal building structures. Small changes in the design of a floor system can have significant impact on material costs, construction schedule, ultimate strength, operating costs, occupancy levels and end use of a building.

Without reinforcement, constructing modern structures with concrete material would not be possible.

Behavior

Materials

See also: Concrete, Cement, Construction aggregate, and Rebar

Concrete is a mixture of coarse (stone or brick chips) and fine (generally sand and/or crushed stone) aggregates with a paste of binder material (usually Portland cement) and water. When cement is mixed with a small amount of water, it hydrates to form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid shape.[27][28] The aggregates used for making concrete should be free from harmful substances like organic impurities, silt, clay, lignite, etc. Typical concrete mixes have high resistance to compressive stresses (about 4,000 psi (28 MPa)); however, any appreciable tension (e.g., due to bending) will break the microscopic rigid lattice, resulting in cracking and separation of the concrete. For this reason, typical non-reinforced concrete must be well supported to prevent the development of tension.

If a material with high strength in tension, such as steel, is placed in concrete, then the composite material, reinforced concrete, resists not only compression but also bending and other direct tensile actions. A composite section where the concrete resists compression and reinforcement "rebar" resists tension can be made into almost any shape and size for the construction industry.

Key characteristics

Three physical characteristics give reinforced concrete its special properties:

  1. The coefficient of thermal expansion of concrete is similar to that of steel, eliminating large internal stresses due to differences in thermal expansion or contraction.
  2. When the cement paste within the concrete hardens, this conforms to the surface details of the steel, permitting any stress to be transmitted efficiently between the different materials. Usually steel bars are roughened or corrugated to further improve the bond or cohesion between the concrete and steel.
  3. The alkaline chemical environment provided by the alkali reserve (KOH, NaOH) and the portlandite (calcium hydroxide) contained in the hardened cement paste causes a passivating film to form on the surface of the steel, making it much more resistant to corrosion than it would be in neutral or acidic conditions. When the cement paste is exposed to the air and meteoric water reacts with the atmospheric CO2, portlandite and the calcium silicate hydrate (CSH) of the hardened cement paste become progressively carbonated and the high pH gradually decreases from 13.5 – 12.5 to 8.5, the pH of water in equilibrium with calcite (calcium carbonate) and the steel is no longer passivated.

As a rule of thumb, only to give an idea on orders of magnitude, 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. Carbonation of concrete along with chloride ingress are amongst the chief reasons for the failure of reinforcement bars in 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. Reinforcing bars are normally round in cross-section and vary in diameter. Reinforced concrete structures sometimes have provisions such as ventilated hollow cores to control their moisture & humidity.

Distribution of concrete (in spite of reinforcement) strength characteristics along the cross-section of vertical reinforced concrete elements is inhomogeneous.[29]

Mechanism of composite action of reinforcement and concrete

The reinforcement in a RC structure, such as a steel bar, has to undergo the same strain or deformation as the surrounding concrete in order to prevent discontinuity, slip or separation of the two materials under load. Maintaining composite action requires transfer of load between the concrete and steel. 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. 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. The reasons that the two different material components concrete and steel can work together are as follows: (1) Reinforcement can be well bonded to the concrete, thus they can jointly resist external loads and deform. (2) The thermal expansion coefficients of concrete and steel are so close (1.0×10−5 to 1.5×10−5 for concrete and 1.2×10−5 for steel) that the thermal stress-induced damage to the bond between the two components can be prevented. (3) Concrete can protect the embedded steel from corrosion and high-temperature induced softening.

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, current international codes of specifications use the concept of development length rather than bond stress. 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. However, if the actual available length is inadequate for full development, special anchorages must be provided, such as cogs or hooks or mechanical end plates. 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.

Anticorrosion measures

In wet and cold climates, reinforced concrete for roads, bridges, parking structures and other structures that may be exposed to deicing salt may benefit from use of corrosion-resistant reinforcement such as uncoated, low carbon/chromium (micro composite), epoxy-coated, hot dip galvanized or stainless steel rebar. Good design and a well-chosen concrete mix will provide additional protection for many applications. Uncoated, low carbon/chromium rebar looks similar to standard carbon steel rebar due to its lack of a coating; its highly corrosion-resistant features are inherent in the steel microstructure. It can be identified by the unique ASTM specified mill marking on its smooth, dark charcoal finish. Epoxy coated rebar can easily be identified by the light green color of its epoxy coating. Hot dip galvanized rebar may be bright or dull gray depending on length of exposure, and stainless rebar exhibits a typical white metallic sheen that is readily distinguishable from carbon steel reinforcing bar. Reference ASTM standard specifications A1035/A1035M Standard Specification for Deformed and Plain Low-carbon, Chromium, Steel Bars for Concrete Reinforcement, A767 Standard Specification for Hot Dip Galvanized Reinforcing Bars, A775 Standard Specification for Epoxy Coated Steel Reinforcing Bars and A955 Standard Specification for Deformed and Plain Stainless Bars for Concrete Reinforcement.

Another, cheaper way of protecting rebars is coating them with zinc phosphate.[30] Zinc phosphate slowly reacts with calcium cations and the hydroxyl anions present in the cement pore water and forms a stable hydroxyapatite layer.

Penetrating sealants typically must be applied some time after curing. Sealants include paint, plastic foams, films and aluminum foil, felts or fabric mats sealed with tar, and layers of bentonite clay, sometimes used to seal roadbeds.

Corrosion inhibitors, such as calcium nitrite [Ca(NO2)2], can also be added to the water mix before pouring concrete. Generally, 1–2 wt. % of [Ca(NO2)2] with respect to cement weight is needed to prevent corrosion of the rebars. 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 them to precipitate as an insoluble ferric hydroxide (Fe(OH)3). This causes the passivation of steel at the anodic oxidation sites. Nitrite is a much more active corrosion inhibitor than nitrate, which is a less powerful oxidizer of the divalent iron.

Reinforcement and terminology of beams

 
Two intersecting beams integral to parking garage slab that will contain both reinforcing steel and the wiring, junction boxes and other electrical components necessary to install the overhead lighting for the garage level beneath it.
A short video of the last beam being placed on a raised road, part of a new road near Cardiff Bay, Wales

A beam bends under bending moment, resulting in a small curvature. At the outer face (tensile face) of the curvature the concrete experiences tensile stress, while at the inner face (compressive face) it experiences compressive stress.

A singly reinforced beam is one in which the concrete element is only reinforced near the tensile face and the reinforcement, called tension steel, is designed to resist the tension.

A doubly reinforced beam is the section in which besides the tensile reinforcement the concrete element is also reinforced near the compressive face to help the concrete resist compression and take stresses. The latter reinforcement is called compression steel. When the compression zone of a concrete is inadequate to resist the compressive moment (positive moment), extra reinforcement has to be provided if the architect limits the dimensions of the section.

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). When the reinforced concrete element is subject to increasing bending moment, the tension steel yields while the concrete does not reach its ultimate failure condition. As the tension steel yields and stretches, an "under-reinforced" concrete also yields in a ductile manner, exhibiting a large deformation and warning before its ultimate failure. In this case the yield stress of the steel governs the design.

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). So the "over-reinforced concrete" beam fails by crushing of the compressive-zone concrete and before the tension zone steel yields, which does not provide any warning before failure as the failure is instantaneous.

A balanced-reinforced beam is one in which both the compressive and tensile zones reach yielding at the same imposed load on the beam, and the concrete will crush and the tensile steel will yield at the same time. This design criterion is however as risky as over-reinforced concrete, because failure is sudden as the concrete crushes at the same time of the tensile steel yields, which gives a very little warning of distress in tension failure.[31]

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.

The characteristic strength is the strength of a material where less than 5% of the specimen shows lower strength.

The design strength or nominal strength is the strength of a material, including a material-safety factor. The value of the safety factor generally ranges from 0.75 to 0.85 in Permissible stress design.

The ultimate limit state is the theoretical failure point with a certain probability. It is stated under factored loads and factored resistances.

Reinforced concrete structures are normally designed according to rules and regulations or recommendation of a code such as ACI-318, CEB, Eurocode 2 or the like. WSD, USD or LRFD methods are used in design of RC structural members. Analysis and design of RC members can be carried out by using linear or non-linear approaches. When applying safety factors, building codes normally propose linear approaches, but for some cases non-linear approaches. To see the examples of a non-linear numerical simulation and calculation visit the references:[32][33]

Prestressed concrete

Main article: Prestressed concrete

Prestressing concrete is a technique that greatly increases the load-bearing strength of concrete beams. The reinforcing steel in the bottom part of the beam, which will be subjected to tensile forces when in service, is placed in tension before the concrete is poured around it. Once the concrete has hardened, the tension on the reinforcing steel is released, placing a built-in compressive force on the concrete. When loads are applied, the reinforcing steel takes on more stress and the compressive force in the concrete is reduced, but does not become a tensile force. Since the concrete is always under compression, it is less subject to cracking and failure.[34]

Common failure modes of steel reinforced concrete

Reinforced concrete can fail due to inadequate strength, leading to mechanical failure, or due to a reduction in its durability. Corrosion and freeze/thaw cycles may damage poorly designed or constructed reinforced concrete. When rebar corrodes, the oxidation products (rust) expand and tends to flake, cracking the concrete and unbonding the rebar from the concrete. Typical mechanisms leading to durability problems are discussed below.

Mechanical failure

Cracking of the concrete section is nearly impossible to prevent; however, the size and location of cracks can be limited and controlled by appropriate reinforcement, control joints, curing methodology and concrete mix design. Cracking can allow moisture to penetrate and corrode the reinforcement. This is a serviceability failure in limit state design. Cracking is normally the result of an inadequate quantity of rebar, or rebar spaced at too great a distance. The concrete cracks either under excess loading, or due to internal effects such as early thermal shrinkage while it cures.

Ultimate failure leading to collapse can be caused by crushing the concrete, which occurs when compressive stresses exceed its strength, by yielding or failure of the rebar when bending or shear stresses exceed the strength of the reinforcement, or by bond failure between the concrete and the rebar.[35]

Carbonation

 
Concrete wall cracking as steel reinforcing corrodes and swells. Rust has a lower density than metal, so it expands as it forms, cracking the decorative cladding off the wall as well as damaging the structural concrete. The breakage of material from a surface is called spalling.
 
Detailed view of spalling probably caused by a too thin layer of concrete between the steel and the surface, accompanied by corrosion from external exposure.
Main article: Carbonation

Carbonation, or neutralisation, is a chemical reaction between carbon dioxide in the air and calcium hydroxide and hydrated calcium silicate in the concrete.

When a concrete structure is designed, it is usual to specify the concrete cover for the rebar (the depth of the rebar within the object). The minimum concrete cover is normally regulated by design or building codes. If the reinforcement is too close to the surface, early failure due to corrosion may occur. The concrete cover depth can be measured with a cover meter. However, carbonated concrete incurs a durability problem only when there is also sufficient moisture and oxygen to cause electropotential corrosion of the reinforcing steel.

One method of testing a structure for carbonatation is to drill a fresh hole in the surface and then treat the cut surface with phenolphthalein indicator solution. This solution turns pink when in contact with alkaline concrete, making it possible to see the depth of carbonation. Using an existing hole does not suffice because the exposed surface will already be carbonated.

Chlorides

Chlorides can promote the corrosion of embedded rebar if present in sufficiently high concentration. Chloride anions induce both localized corrosion (pitting corrosion) and generalized corrosion of steel reinforcements. For this reason, one should only use fresh raw water or potable water for mixing concrete, ensure that the coarse and fine aggregates do not contain chlorides, rather than admixtures which might contain chlorides.

 
Rebar for foundations and walls of a sewage pump station.
 
The Paulins Kill Viaduct, Hainesburg, New Jersey, is 115 feet (35 m) tall and 1,100 feet (335 m) long, 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 Lackawanna Railroad was a pioneer in the use of reinforced concrete.

It was once common for calcium chloride to be used as an admixture to promote rapid set-up of the concrete. It was also mistakenly believed that it would prevent freezing. However, this practice fell into disfavor once the deleterious effects of chlorides became known. It should be avoided whenever possible.

The use of de-icing salts on roadways, used to lower the freezing point of water, is probably one of the primary causes of premature failure of reinforced or prestressed concrete bridge decks, roadways, and parking garages. The use of epoxy-coated reinforcing bars and the application of cathodic protection has mitigated this problem to some extent. Also FRP (fiber-reinforced polymer) rebars are known to be less susceptible to chlorides. Properly designed concrete mixtures that have been allowed to cure properly are effectively impervious to the effects of de-icers.

Another important source of chloride ions is sea water. Sea water contains by weight approximately 3.5% salts. These salts include sodium chloride, magnesium sulfate, calcium sulfate, and bicarbonates. In water these salts dissociate in free ions (Na+, Mg2+, Cl−, SO2−
4, HCO−
3) and migrate with the water into the capillaries of the concrete. Chloride ions, which make up about 50% of these ions, are particularly aggressive as a cause of corrosion of carbon steel reinforcement bars.

In the 1960s and 1970s it was also relatively common for magnesite, a chloride rich carbonate mineral, to be used as a floor-topping material. This was done principally as a levelling and sound attenuating layer. However it is now known that when these materials come into contact with moisture they produce a weak solution of hydrochloric acid due to the presence of chlorides in the magnesite. Over a period of time (typically decades), the solution causes corrosion of the embedded rebars. This was most commonly found in wet areas or areas repeatedly exposed to moisture.

Alkali silica reaction

Main article: Alkali–silica reaction

This a reaction of amorphous silica (chalcedony, chert, siliceous limestone) sometimes present in the aggregates with the hydroxyl ions (OH−) from the cement pore solution. Poorly crystallized silica (SiO2) dissolves and dissociates at high pH (12.5 - 13.5) in alkaline water. 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). The alkali–silica reaction (ASR) causes localised swelling responsible for tensile stress and cracking. The conditions required for alkali silica reaction are threefold: (1) aggregate containing an alkali-reactive constituent (amorphous silica), (2) sufficient availability of hydroxyl ions (OH−), and (3) sufficient moisture, above 75% relative humidity (RH) within the concrete.[36][37] This phenomenon is sometimes popularly referred to as "concrete cancer". This reaction occurs independently of the presence of rebars; massive concrete structures such as dams can be affected.

Conversion of high alumina cement

Resistant to weak acids and especially sulfates, this cement cures quickly and has very high durability and strength. It was frequently used after World War II to make precast concrete objects. However, it can lose strength with heat or time (conversion), especially when not properly cured. After the collapse of three roofs made of prestressed concrete beams using high alumina cement, this cement was banned in the UK in 1976. Subsequent inquiries into the matter showed that the beams were improperly manufactured, but the ban remained.[38]

Sulfates

Sulfates (SO4) in the soil or in groundwater, in sufficient concentration, can react with the Portland cement in concrete causing the formation of expansive products, e.g., ettringite or thaumasite, which can lead to early failure of the structure. The most typical attack of this type is on concrete slabs and foundation walls at grades where the sulfate ion, via alternate wetting and drying, can increase in concentration. As the concentration increases, the attack on the Portland cement can begin. For buried structures such as pipe, this type of attack is much rarer, especially in the eastern United States. 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. A chemical analysis of soil borings to check for the presence of sulfates should be undertaken during the design phase of any project involving concrete in contact with the native soil. If the concentrations are found to be aggressive, various protective coatings can be applied. Also, in the US ASTM C150 Type 5 Portland cement can be used in the mix. This type of cement is designed to be particularly resistant to a sulfate attack.

Steel plate construction

Main article: Steel plate construction

In steel plate construction, stringers join parallel steel plates. The plate assemblies are fabricated off site, and welded together on-site to form steel walls connected by stringers. The walls become the form into which concrete is poured. Steel plate construction speeds reinforced concrete construction by cutting out the time-consuming on-site manual steps of tying rebar and building forms. The method results in excellent strength because the steel is on the outside, where tensile forces are often greatest.

Fiber-reinforced concrete

Main article: Fiber reinforced concrete

Fiber reinforcement is mainly used in shotcrete, but can also be used in normal concrete. Fiber-reinforced normal concrete is mostly used for on-ground floors and pavements, but can also be considered for a wide range of construction parts (beams, pillars, foundations, etc.), either alone or with hand-tied rebars.

Concrete reinforced with fibers (which are usually steel, glass, plastic fibers) or cellulose polymer fiber is less expensive than hand-tied rebar.[citation needed] The shape, dimension, and length of the fiber are important. A thin and short fiber, for example short, hair-shaped glass fiber, is only effective during the first hours after pouring the concrete (its function is to reduce cracking while the concrete is stiffening), but it will not increase the concrete tensile strength. A normal-size fiber for European shotcrete (1 mm diameter, 45 mm length—steel or plastic) will increase the concrete's tensile strength. Fiber reinforcement is most often used to supplement or partially replace primary rebar, and in some cases it can be designed to fully replace rebar.[39]

Steel is the strongest commonly available fiber,[citation needed] and comes in different lengths (30 to 80 mm in Europe) and shapes (end-hooks). Steel fibers can only be used on surfaces that can tolerate or avoid corrosion and rust stains. In some cases, a steel-fiber surface is faced with other materials.

Glass fiber is inexpensive and corrosion-proof, but not as ductile as steel. Recently, spun basalt fiber, long available in Eastern Europe, has become available in the U.S. and Western Europe. Basalt fiber is stronger and less expensive than glass, but historically has not resisted the alkaline environment of Portland cement well enough to be used as direct reinforcement. New materials use plastic binders to isolate the basalt fiber from the cement.

The premium fibers are graphite-reinforced plastic fibers, which are nearly as strong as steel, lighter in weight, and corrosion-proof.[citation needed] Some experiments have had promising early results with carbon nanotubes, but the material is still far too expensive for any building.[citation needed]

Non-steel reinforcement

There is considerable overlap between the subjects of non-steel reinforcement and fiber-reinforcement of concrete. The introduction of non-steel reinforcement of concrete is relatively recent; it takes two major forms: non-metallic rebar rods, and non-steel (usually also non-metallic) fibers incorporated into the cement matrix. For example, there is increasing interest in glass fiber reinforced concrete (GFRC) and in various applications of polymer fibers incorporated into concrete. Although currently there is not much suggestion that such materials will replace metal rebar, some of them have major advantages in specific applications, and there also are new applications in which metal rebar simply is not an option. However, the design and application of non-steel reinforcing is fraught with challenges. For one thing, concrete is a highly alkaline environment, in which many materials, including most kinds of glass, have a poor service life. Also, the behavior of such reinforcing materials differs from the behavior of metals, for instance in terms of shear strength, creep and elasticity.[40][41]

Fiber-reinforced plastic/polymer (FRP) and glass-reinforced plastic (GRP) consist of fibers of polymer, glass, carbon, aramid or other polymers or high-strength fibers set in a resin matrix to form a rebar rod, or grid, or fiber. These rebars are installed in much the same manner as steel rebars. The cost is higher but, suitably applied, the structures have advantages, in particular a dramatic reduction in problems related to corrosion, either by intrinsic concrete alkalinity or by external corrosive fluids that might penetrate the concrete. These structures can be significantly lighter and usually have a longer service life. The cost of these materials has dropped dramatically since their widespread adoption in the aerospace industry and by the military.

In particular, FRP rods are useful for structures where the presence of steel would not be acceptable. For example, MRI machines have huge magnets, and accordingly require non-magnetic buildings. Again, toll booths that read radio tags need reinforced concrete that is transparent to radio waves. Also, where the design life of the concrete structure is more important than its initial costs, non-steel reinforcing often has its advantages where corrosion of reinforcing steel is a major cause of failure. In such situations corrosion-proof reinforcing can extend a structure's life substantially, for example in the intertidal zone. FRP rods may also be useful in situations where it is likely that the concrete structure may be compromised in future years, 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.

Plastic reinforcement often is stronger, or at least has a better strength to weight ratio than reinforcing steels. Also, because it resists corrosion, it does not need a protective concrete cover as thick as steel reinforcement does (typically 30 to 50 mm or more). FRP-reinforced structures therefore can be lighter and last longer. Accordingly, for some applications the whole-life cost will be price-competitive with steel-reinforced concrete.

The material properties of FRP or GRP bars differ markedly from steel, so there are differences in the design considerations. FRP or GRP bars have relatively higher tensile strength but lower stiffness, so that deflections are likely to be higher than for equivalent steel-reinforced units. Structures with internal FRP reinforcement typically have an elastic deformability comparable to the plastic deformability (ductility) of steel reinforced structures. Failure in either case is more likely to occur by compression of the concrete than by rupture of the reinforcement. Deflection is always a major design consideration for reinforced concrete. Deflection limits are set to ensure that crack widths in steel-reinforced concrete are controlled to prevent water, air or other aggressive substances reaching the steel and causing corrosion. For FRP-reinforced concrete, aesthetics and possibly water-tightness will be the limiting criteria for crack width control. FRP rods also have relatively lower compressive strengths than steel rebar, and accordingly require different design approaches for reinforced concrete columns.

One drawback to the use of FRP reinforcement is their limited fire resistance. Where fire safety is a consideration, structures employing FRP have to maintain their strength and the anchoring of the forces at temperatures to be expected in the event of fire. For purposes of fireproofing, an adequate thickness of cement concrete cover or protective cladding is necessary. The addition of 1 kg/m3 of polypropylene fibers to concrete has been shown to reduce spalling during a simulated fire.[42] (The improvement is thought to be due to the formation of pathways out of the bulk of the concrete, allowing steam pressure to dissipate.[42])

Another problem is the effectiveness of shear reinforcement. FRP rebar stirrups formed by bending before hardening generally perform relatively poorly in comparison to steel stirrups or to structures with straight fibers. When strained, the zone between the straight and curved regions are subject to strong bending, shear, and longitudinal stresses. Special design techniques are necessary to deal with such problems.

There is growing interest in applying external reinforcement to existing structures using advanced materials such as composite (fiberglass, basalt, carbon) rebar, which can impart exceptional strength. Worldwide, there are a number of brands of composite rebar recognized by different countries, such as Aslan, DACOT, V-rod, and ComBar. The number of projects using composite rebar increases day by day around the world, in countries ranging from USA, Russia, and South Korea to Germany.

See also

References

  1. ^ "16 Materials Every Architect Needs to Know (And Where to Learn About Them)". ArchDaily. December 19, 2016. from the original on July 9, 2021. Retrieved July 9, 2021.
  2. ^ Sarah (March 22, 2017). "When should you use reinforced concrete?". EKA Concrete | Direct Supplier of Ready Mix and Site Mix Concrete. Retrieved July 9, 2021.
  3. ^ Structural materials. George Weidmann, P. R. Lewis, Nick Reid, Open University. Materials Department. Milton Keynes, U.K.: Materials Dept., Open University. 1990. p. 360. ISBN 0-408-04658-9. OCLC 20693897.{{cite book}}: CS1 maint: others (link)
  4. ^ Slukin, V. M. (2001). Demidovskie gnezda : Nevʹi︠a︡nsk, Verkhniĭ Tagil, Nizhniĭ Tagil. Elena Arapova, Tatiana Kononova. Ekaterinburg: ID "Sokrat". p. 26. ISBN 5-88664-106-8. OCLC 56187883.
  5. ^ a b "Building construction: The invention of reinforced concrete". Encyclopedia Britannica. from the original on September 28, 2018. Retrieved September 27, 2018.
  6. ^ a b Condit, Carl W. (January 1968). "The First Reinforced-Concrete Skyscraper: The Ingalls Building in Cincinnati and Its Place in Structural History". Technology and Culture. 9 (1): 1–33. doi:10.2307/3102041. JSTOR 3102041.
  7. ^ Richard W. S (1995). (PDF). The Aberdeen Group. Archived from the original (PDF) on 28 May 2015. Retrieved 25 April 2015.
  8. ^ W. Morgan (1995). "Reinforced Concrete". The Elements of Structure. from the original on October 12, 2018. Retrieved April 25, 2015 – via John F. Claydon's website.
  9. ^ a b Department of Civil Engineering (2015). "History of Concrete Building Construction". CIVL 1101 – History of Concrete. University of Memphis. from the original on February 27, 2017. Retrieved April 25, 2015.
  10. ^ Day, Lance (2003). Biographical Dictionary of the History of Technology. Routledge. p. 284. ISBN 0-203-02829-5.
  11. ^ a b Mörsch, Emil (1909). Concrete-steel Construction: (Der Eisenbetonbau). The Engineering News Publishing Company. pp. 204–210.
  12. ^ Collins, Peter (1920–1981). Concrete: The Vision of a New Architecture. McGill-Queen's University Press. pp. 58–60. ISBN 0-7735-2564-5. from the original on July 9, 2021. Retrieved November 2, 2020.
  13. ^ Mars, Roman. "Episode 81: Rebar and the Alvord Lake Bridge". 99% Invisible. from the original on August 8, 2014. Retrieved August 6, 2014.
  14. ^ Collins, Peter (1920–1981). Concrete: The Vision of a New Architecture. McGill-Queen's University Press. pp. 61–64. ISBN 0-7735-2564-5. from the original on July 9, 2021. Retrieved April 3, 2016.
  15. ^ McGroarty, John Steven (1921). Los Angeles from the Mountains to the Sea. Vol. 2. Los Angeles, CA: American Historical Society. p. 176. from the original on August 9, 2016. Retrieved November 29, 2017.
  16. ^ Annual Report of the City Auditor, City of Los Angeles, California for the Year Ending June 30. Los Angeles, CA: Los Angeles City Auditor. 1905. pp. 71–73. from the original on September 27, 2020. Retrieved November 30, 2017.
  17. ^ Williams, D. (February 1907). "What Builders are Doing". Carpentry and Building: 66. from the original on September 1, 2020. Retrieved November 29, 2017.
  18. ^ W.P.H. (April 19, 1906). "Reinforced Concrete Buildings at Los Angeles, Cal". Letters to the Editor. Engineering News-Record. 55: 449. from the original on September 19, 2020. Retrieved November 29, 2017.
  19. ^ Austin, J. C.; Neher, O. H.; Hicks, L. A.; Whittlesey, C. F.; Leonard, J. B. (November 1906). "Partial Collapse of the Bixby Hotel at Long Beach". Architect and Engineer of California. Vol. VII, no. 1. pp. 44–48. from the original on September 20, 2020. Retrieved May 29, 2018.
  20. ^ "El Campanil, Mills College: Julia Morgan 1903-1904". from the original on December 30, 2018. Retrieved April 18, 2019.
  21. ^ Callen, Will (February 4, 2019). "Julia Morgan-designed Mills bell tower counts down to its 115th anniversary". hoodline.com. from the original on April 19, 2019. Retrieved April 18, 2019. Morgan had studied the material in Paris, where some of its pioneers, François Hennebique and Auguste Perret, were exploring its non-industrial uses. Fascinated by its combination of stability and plasticity, she may have been the first architect in the U.S. to put it towards something other than bridges or piers.
  22. ^ Littman, Julie (March 7, 2018). "Bay Area Architect Julia Morgan's Legacy Wasn't Just Hearst Castle". busnow.com. from the original on April 20, 2019. Retrieved April 18, 2019.
  23. ^ Olsen, Erik (May 1, 2020). . California Science Weekly. Archived from the original on July 2, 2020. Retrieved July 1, 2020.
  24. ^ Standard Specifications for Portland Cement of the American Society for Testing Materials, Standard No. 1. Philadelphia, PA: National Association of Cement Users. 1906.
  25. ^ Standard Building Regulations for the Use of Reinforced Concrete. Philadelphia, PA: National Association of Cement Users. 1910.
  26. ^ Murray, Lorraine. "Christ the Redeemer (last updated 13 January 2014)". Encyclopædia Britannica. Retrieved November 5, 2022.
  27. ^ Materials principles and practice. Charles Newey, Graham Weaver, Open University. Materials Department. Milton Keynes, England: Materials Dept., Open University. 1990. p. 61. ISBN 0-408-02730-4. OCLC 19553645.{{cite book}}: CS1 maint: others (link)
  28. ^ Structural materials. George Weidmann, P. R. Lewis, Nick Reid, Open University. Materials Department. Milton Keynes, U.K.: Materials Dept., Open University. 1990. p. 357. ISBN 0-408-04658-9. OCLC 20693897.{{cite book}}: CS1 maint: others (link)
  29. ^ "Concrete Inhomogeneity of Vertical Cast-In-Situ Elements In Frame-Type Buildings". 2021-01-15 at the Wayback Machine
  30. ^ Simescu, Florica; Idrissi, Hassane (December 19, 2008). "Effect of zinc phosphate chemical conversion coating on corrosion behavior of mild steel in alkaline medium: protection of rebars in reinforced concrete". Science and Technology of Advanced Materials. National Institute for Materials Science. 9 (4): 045009. Bibcode:2008STAdM...9d5009S. doi:10.1088/1468-6996/9/4/045009. PMC 5099651. PMID 27878037.
  31. ^ Nilson, Darwin, Dolan. Design of Concrete Structures. the MacGraw-Hill Education, 2003. p. 80-90.
  32. ^ . April 2, 2015. Archived from the original on April 2, 2015.
  33. ^ Sadeghi, Kabir (September 15, 2011). "Energy based structural damage index based on nonlinear numerical simulation of structures subjected to oriented lateral cyclic loading". International Journal of Civil Engineering. 9 (3): 155–164. ISSN 1735-0522. Retrieved December 23, 2016.
  34. ^ Structural materials. George Weidmann, P. R. Lewis, Nick Reid, Open University. Materials Department. Milton Keynes, U.K.: Materials Dept., Open University. 1990. p. 372-373. ISBN 0-408-04658-9. OCLC 20693897.{{cite book}}: CS1 maint: others (link)
  35. ^ Janowski, A.; Nagrodzka-Godycka, K.; Szulwic, J.; Ziółkowski, P. (2016). "Remote sensing and photogrammetry techniques in diagnostics of concrete structures". Computers and Concrete. 18 (3): 405–420. doi:10.12989/cac.2016.18.3.405. from the original on July 9, 2021. Retrieved December 14, 2016.
  36. ^ "Concrete Cancer". h2g2. BBC. March 15, 2012 [2005]. from the original on February 23, 2009. Retrieved October 14, 2009.
  37. ^ . the cement industry. British Cement Association. January 4, 2006. Archived from the original on October 29, 2006. Retrieved November 26, 2006.
  38. ^ . Archived from the original on September 11, 2005. Retrieved October 14, 2009.
  39. ^ Fiber Concrete in Construction , Wietek B. , Springer 2021 , pages 268 ; ISBN 978-3-658-34480-1
  40. ^ BS EN 1169:1999 Precast concrete products. General rules for factory production control of glass-fiber reinforced cement. British Standards Institute. November 15, 1999. ISBN 0-580-32052-9. from the original on June 12, 2018. Retrieved May 29, 2018.
  41. ^ BS EN 1170-5:1998 Precast concrete products. Test method for glass-fiber reinforced cement. British Standards Institute. March 15, 1998. ISBN 0-580-29202-9. from the original on June 12, 2018. Retrieved May 29, 2018.
  42. ^ a b Arthur W. Darby (2003). (PDF). Proceedings of the Rapid Excavation & Tunneling Conference, New Orleans, June 2003. p. 645. Archived from the original (PDF) on May 22, 2006 – via www.tunnels.mottmac.com.

Further reading

  • Threlfall A., et al. Reynolds's Reinforced Concrete Designer's Handbook – 11th ed. ISBN 978-0-419-25830-8.
  • Newby F., Early Reinforced Concrete, Ashgate Variorum, 2001, ISBN 978-0-86078-760-0.
  • Kim, S., Surek, J and J. Baker-Jarvis. Journal of Research of the National Institute of Standards and Technology, Vol. 116, No. 3 (May–June 2011): 655–669.
  • Daniel R., Formwork UK .
  • Materials principles and practice. Charles Newey, Graham Weaver, Open University. Materials Department. Milton Keynes, England: Materials Dept., Open University. 1990. ISBN 0-408-02730-4. OCLC 19553645.{{cite book}}: CS1 maint: others (link)
  • Structural materials. George Weidmann, P. R. Lewis, Nick Reid, Open University. Materials Department. Milton Keynes, U.K.: Materials Dept., Open University. 1990. p. 357. ISBN 0-408-04658-9. OCLC 20693897.{{cite book}}: CS1 maint: others (link)
  • Corrosion of reinforcement in concrete construction. C. L. Page, P. B. Bamforth, J. W. Figg, International Symposium on Corrosion of Reinforcement in Concrete Construction. Cambridge: Royal Society of Chemistry, Information Services. 1996. ISBN 0-85404-731-X. OCLC 35233292.{{cite book}}: CS1 maint: others (link)
  • Reinforced concrete. June 19, 2020.

May 04, 2023
reinforced, concrete, also, called, reinforced, cement, concrete, ferroconcrete, composite, material, which, concrete, relatively, tensile, strength, ductility, compensated, inclusion, reinforcement, having, higher, tensile, strength, ductility, reinforcement,. Reinforced concrete RC also called reinforced cement concrete RCC and ferroconcrete is a composite material in which concrete s relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility The reinforcement is usually though not necessarily steel bars rebar and is usually embedded passively in the concrete before the concrete sets However post tensioning is also employed as a technique to reinforce the concrete In terms of volume used annually it is one of the most common engineering materials 1 2 In corrosion engineering terms when designed correctly the alkalinity of the concrete protects the steel rebar from corrosion 3 Reinforced concreteA heavy reinforced concrete column seen before and after the concrete has been cast in place around its rebar frameMaterial typeComposite materialMechanical propertiesTensile strength st Stronger than concrete Contents 1 Description 2 History 3 Use in construction 4 Behavior 4 1 Materials 4 2 Key characteristics 4 3 Mechanism of composite action of reinforcement and concrete 4 4 Anchorage bond in concrete Codes of specifications 4 5 Anticorrosion measures 5 Reinforcement and terminology of beams 6 Prestressed concrete 7 Common failure modes of steel reinforced concrete 7 1 Mechanical failure 7 2 Carbonation 7 3 Chlorides 7 4 Alkali silica reaction 7 5 Conversion of high alumina cement 7 6 Sulfates 8 Steel plate construction 9 Fiber reinforced concrete 10 Non steel reinforcement 11 See also 12 References 12 1 Further readingDescription EditReinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and or structural failure Modern reinforced concrete can contain varied reinforcing materials made of steel polymers or alternate composite material in conjunction with rebar or not Reinforced concrete may also be permanently stressed concrete in compression reinforcement in tension so as to improve the behavior of the final structure under working loads In the United States the most common methods of doing this are known as pre tensioning and post tensioning For a strong ductile and durable construction the reinforcement needs to have the following properties at least High relative strength High toleration of tensile strain Good bond to the concrete irrespective of pH moisture and similar factors Thermal compatibility not causing unacceptable stresses such as expansion or contraction in response to changing temperatures Durability in the concrete environment irrespective of corrosion or sustained stress for example History Edit The novel shape of the Philips Pavilion built in Brussels for Expo 58 was achieved using reinforced concrete Leaning Tower of Nevyansk in the town of Nevyansk in Sverdlovsk Oblast Russia is the first building known to use reinforced concrete as a construction method citation needed It was built on the orders of the industrialist Akinfiy Demidov between 1721 1725 4 Francois Coignet used iron reinforced concrete as a technique for constructing building structures 5 In 1853 Coignet built the first iron reinforced concrete structure a four story house at 72 rue Charles Michels in the suburbs of Paris 5 Coignet s descriptions of reinforcing concrete suggests that he did not do it for means of adding strength to the concrete but for keeping walls in monolithic construction from overturning 6 The Pippen building in Brooklyn stands as a testament to his technique In 1854 English builder William B Wilkinson reinforced the concrete roof and floors in the two story house he was constructing His positioning of the reinforcement demonstrated that unlike his predecessors he had knowledge of tensile stresses 7 8 9 Joseph Monier a 19th century French gardener was a pioneer in the development of structural prefabricated and reinforced concrete having been dissatisfied with the existing materials available for making durable flowerpots 10 He was granted a patent for reinforcing concrete flowerpots by means of mixing a wire mesh and a mortar shell In 1877 Monier was granted another patent for a more advanced technique of reinforcing concrete columns and girders using iron rods placed in a grid pattern Though Monier undoubtedly knew that reinforcing concrete would improve its inner cohesion it is not clear whether he even knew how much the tensile strength of concrete was improved by the reinforcing 11 Before the 1870s the use of concrete construction though dating back to the Roman Empire and having been reintroduced in the early 19th century was not yet a proven scientific technology Thaddeus Hyatt published a report entitled An Account of Some Experiments with Portland Cement Concrete Combined with Iron as a Building Material with Reference to Economy of Metal in Construction and for Security against Fire in the Making of Roofs Floors and Walking Surfaces in which he reported his experiments on the behavior of reinforced concrete His work played a major role in the evolution of concrete construction as a proven and studied science Without Hyatt s work more dangerous trial and error methods might have been depended on for the advancement in the technology 6 12 Ernest L Ransome an English born engineer was an early innovator of reinforced concrete techniques at the end of the 19th century Using the knowledge of reinforced concrete developed during the previous 50 years Ransome improved nearly all the styles and techniques of the earlier inventors of reinforced concrete Ransome s key innovation was to twist the reinforcing steel bar thereby improving its bond with the concrete 13 Gaining increasing fame from his concrete constructed buildings Ransome was able to build two of the first reinforced concrete bridges in North America 14 One of his bridges still stands on Shelter Island in New Yorks East End One of the first concrete buildings constructed in the United States was a private home designed by William Ward completed in 1876 The home was particularly designed to be fireproof G A Wayss was a German civil engineer and a pioneer of the iron and steel concrete construction In 1879 Wayss bought the German rights to Monier s patents and in 1884 his firm Wayss amp Freytag made the first commercial use of reinforced concrete Up until the 1890s Wayss and his firm greatly contributed to the advancement of Monier s system of reinforcing established it as a well developed scientific technology 11 One of the first skyscrapers made with reinforced concrete was the 16 story Ingalls Building in Cincinnati constructed in 1904 9 The first reinforced concrete building in Southern California was the Laughlin Annex in downtown Los Angeles constructed in 1905 15 16 In 1906 16 building permits were reportedly issued for reinforced concrete buildings in the City of Los Angeles including the Temple Auditorium and 8 story Hayward Hotel 17 18 In 1906 a partial collapse of the Bixby Hotel in Long Beach killed 10 workers during construction when shoring was removed prematurely That event spurred a scrutiny of concrete erection practices and building inspections The structure was constructed of reinforced concrete frames with hollow clay tile ribbed flooring and hollow clay tile infill walls That practice was strongly questioned by experts and recommendations for pure concrete construction were made using reinforced concrete for the floors and walls as well as the frames 19 In April 1904 Julia Morgan an American architect and engineer who pioneered the aesthetic use of reinforced concrete completed her first reinforced concrete structure El Campanil a 72 foot 22 m bell tower at Mills College 20 which is located across the bay from San Francisco Two years later El Campanil survived the 1906 San Francisco earthquake without any damage 21 which helped build her reputation and launch her prolific career 22 The 1906 earthquake also changed the public s initial resistance to reinforced concrete as a building material which had been criticized for its perceived dullness In 1908 the San Francisco Board of Supervisors changed the city s building codes to allow wider use of reinforced concrete 23 In 1906 the National Association of Cement Users NACU published Standard No 1 24 and in 1910 the Standard Building Regulations for the Use of Reinforced Concrete 25 Use in construction Edit Rebars of Sagrada Familia s roof in construction 2009 Christ the Redeemer statue in Rio de Janeiro Brazil It is made of reinforced concrete clad in a mosaic of thousands of triangular soapstone tiles 26 Many different types of structures and components of structures can be built using reinforced concrete including slabs walls beams columns foundations frames and more Reinforced concrete can be classified as precast or cast in place concrete Designing and implementing the most efficient floor system is key to creating optimal building structures Small changes in the design of a floor system can have significant impact on material costs construction schedule ultimate strength operating costs occupancy levels and end use of a building Without reinforcement constructing modern structures with concrete material would not be possible Behavior EditMaterials Edit See also Concrete Cement Construction aggregate and Rebar Concrete is a mixture of coarse stone or brick chips and fine generally sand and or crushed stone aggregates with a paste of binder material usually Portland cement and water When cement is mixed with a small amount of water it hydrates to form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid shape 27 28 The aggregates used for making concrete should be free from harmful substances like organic impurities silt clay lignite etc Typical concrete mixes have high resistance to compressive stresses about 4 000 psi 28 MPa however any appreciable tension e g due to bending will break the microscopic rigid lattice resulting in cracking and separation of the concrete For this reason typical non reinforced concrete must be well supported to prevent the development of tension If a material with high strength in tension such as steel is placed in concrete then the composite material reinforced concrete resists not only compression but also bending and other direct tensile actions A composite section where the concrete resists compression and reinforcement rebar resists tension can be made into almost any shape and size for the construction industry Key characteristics Edit Three physical characteristics give reinforced concrete its special properties The coefficient of thermal expansion of concrete is similar to that of steel eliminating large internal stresses due to differences in thermal expansion or contraction When the cement paste within the concrete hardens this conforms to the surface details of the steel permitting any stress to be transmitted efficiently between the different materials Usually steel bars are roughened or corrugated to further improve the bond or cohesion between the concrete and steel The alkaline chemical environment provided by the alkali reserve KOH NaOH and the portlandite calcium hydroxide contained in the hardened cement paste causes a passivating film to form on the surface of the steel making it much more resistant to corrosion than it would be in neutral or acidic conditions When the cement paste is exposed to the air and meteoric water reacts with the atmospheric CO2 portlandite and the calcium silicate hydrate CSH of the hardened cement paste become progressively carbonated and the high pH gradually decreases from 13 5 12 5 to 8 5 the pH of water in equilibrium with calcite calcium carbonate and the steel is no longer passivated As a rule of thumb only to give an idea on orders of magnitude 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 Carbonation of concrete along with chloride ingress are amongst the chief reasons for the failure of reinforcement bars in 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 Reinforcing bars are normally round in cross section and vary in diameter Reinforced concrete structures sometimes have provisions such as ventilated hollow cores to control their moisture amp humidity Distribution of concrete in spite of reinforcement strength characteristics along the cross section of vertical reinforced concrete elements is inhomogeneous 29 Mechanism of composite action of reinforcement and concrete Edit The reinforcement in a RC structure such as a steel bar has to undergo the same strain or deformation as the surrounding concrete in order to prevent discontinuity slip or separation of the two materials under load Maintaining composite action requires transfer of load between the concrete and steel 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 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 The reasons that the two different material components concrete and steel can work together are as follows 1 Reinforcement can be well bonded to the concrete thus they can jointly resist external loads and deform 2 The thermal expansion coefficients of concrete and steel are so close 1 0 10 5 to 1 5 10 5 for concrete and 1 2 10 5 for steel that the thermal stress induced damage to the bond between the two components can be prevented 3 Concrete can protect the embedded steel from corrosion and high temperature induced softening Anchorage bond in concrete Codes of specifications Edit Because the actual bond stress varies along the length of a bar anchored in a zone of tension current international codes of specifications use the concept of development length rather than bond stress 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 However if the actual available length is inadequate for full development special anchorages must be provided such as cogs or hooks or mechanical end plates 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 Anticorrosion measures Edit In wet and cold climates reinforced concrete for roads bridges parking structures and other structures that may be exposed to deicing salt may benefit from use of corrosion resistant reinforcement such as uncoated low carbon chromium micro composite epoxy coated hot dip galvanized or stainless steel rebar Good design and a well chosen concrete mix will provide additional protection for many applications Uncoated low carbon chromium rebar looks similar to standard carbon steel rebar due to its lack of a coating its highly corrosion resistant features are inherent in the steel microstructure It can be identified by the unique ASTM specified mill marking on its smooth dark charcoal finish Epoxy coated rebar can easily be identified by the light green color of its epoxy coating Hot dip galvanized rebar may be bright or dull gray depending on length of exposure and stainless rebar exhibits a typical white metallic sheen that is readily distinguishable from carbon steel reinforcing bar Reference ASTM standard specifications A1035 A1035M Standard Specification for Deformed and Plain Low carbon Chromium Steel Bars for Concrete Reinforcement A767 Standard Specification for Hot Dip Galvanized Reinforcing Bars A775 Standard Specification for Epoxy Coated Steel Reinforcing Bars and A955 Standard Specification for Deformed and Plain Stainless Bars for Concrete Reinforcement Another cheaper way of protecting rebars is coating them with zinc phosphate 30 Zinc phosphate slowly reacts with calcium cations and the hydroxyl anions present in the cement pore water and forms a stable hydroxyapatite layer Penetrating sealants typically must be applied some time after curing Sealants include paint plastic foams films and aluminum foil felts or fabric mats sealed with tar and layers of bentonite clay sometimes used to seal roadbeds Corrosion inhibitors such as calcium nitrite Ca NO2 2 can also be added to the water mix before pouring concrete Generally 1 2 wt of Ca NO2 2 with respect to cement weight is needed to prevent corrosion of the rebars 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 them to precipitate as an insoluble ferric hydroxide Fe OH 3 This causes the passivation of steel at the anodic oxidation sites Nitrite is a much more active corrosion inhibitor than nitrate which is a less powerful oxidizer of the divalent iron Reinforcement and terminology of beams Edit Two intersecting beams integral to parking garage slab that will contain both reinforcing steel and the wiring junction boxes and other electrical components necessary to install the overhead lighting for the garage level beneath it source source source source source source source source source source source source A short video of the last beam being placed on a raised road part of a new road near Cardiff Bay Wales A beam bends under bending moment resulting in a small curvature At the outer face tensile face of the curvature the concrete experiences tensile stress while at the inner face compressive face it experiences compressive stress A singly reinforced beam is one in which the concrete element is only reinforced near the tensile face and the reinforcement called tension steel is designed to resist the tension A doubly reinforced beam is the section in which besides the tensile reinforcement the concrete element is also reinforced near the compressive face to help the concrete resist compression and take stresses The latter reinforcement is called compression steel When the compression zone of a concrete is inadequate to resist the compressive moment positive moment extra reinforcement has to be provided if the architect limits the dimensions of the section 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 When the reinforced concrete element is subject to increasing bending moment the tension steel yields while the concrete does not reach its ultimate failure condition As the tension steel yields and stretches an under reinforced concrete also yields in a ductile manner exhibiting a large deformation and warning before its ultimate failure In this case the yield stress of the steel governs the design 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 So the over reinforced concrete beam fails by crushing of the compressive zone concrete and before the tension zone steel yields which does not provide any warning before failure as the failure is instantaneous A balanced reinforced beam is one in which both the compressive and tensile zones reach yielding at the same imposed load on the beam and the concrete will crush and the tensile steel will yield at the same time This design criterion is however as risky as over reinforced concrete because failure is sudden as the concrete crushes at the same time of the tensile steel yields which gives a very little warning of distress in tension failure 31 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 The characteristic strength is the strength of a material where less than 5 of the specimen shows lower strength The design strength or nominal strength is the strength of a material including a material safety factor The value of the safety factor generally ranges from 0 75 to 0 85 in Permissible stress design The ultimate limit state is the theoretical failure point with a certain probability It is stated under factored loads and factored resistances Reinforced concrete structures are normally designed according to rules and regulations or recommendation of a code such as ACI 318 CEB Eurocode 2 or the like WSD USD or LRFD methods are used in design of RC structural members Analysis and design of RC members can be carried out by using linear or non linear approaches When applying safety factors building codes normally propose linear approaches but for some cases non linear approaches To see the examples of a non linear numerical simulation and calculation visit the references 32 33 Prestressed concrete EditMain article Prestressed concrete Prestressing concrete is a technique that greatly increases the load bearing strength of concrete beams The reinforcing steel in the bottom part of the beam which will be subjected to tensile forces when in service is placed in tension before the concrete is poured around it Once the concrete has hardened the tension on the reinforcing steel is released placing a built in compressive force on the concrete When loads are applied the reinforcing steel takes on more stress and the compressive force in the concrete is reduced but does not become a tensile force Since the concrete is always under compression it is less subject to cracking and failure 34 Common failure modes of steel reinforced concrete EditReinforced concrete can fail due to inadequate strength leading to mechanical failure or due to a reduction in its durability Corrosion and freeze thaw cycles may damage poorly designed or constructed reinforced concrete When rebar corrodes the oxidation products rust expand and tends to flake cracking the concrete and unbonding the rebar from the concrete Typical mechanisms leading to durability problems are discussed below Mechanical failure Edit Cracking of the concrete section is nearly impossible to prevent however the size and location of cracks can be limited and controlled by appropriate reinforcement control joints curing methodology and concrete mix design Cracking can allow moisture to penetrate and corrode the reinforcement This is a serviceability failure in limit state design Cracking is normally the result of an inadequate quantity of rebar or rebar spaced at too great a distance The concrete cracks either under excess loading or due to internal effects such as early thermal shrinkage while it cures Ultimate failure leading to collapse can be caused by crushing the concrete which occurs when compressive stresses exceed its strength by yielding or failure of the rebar when bending or shear stresses exceed the strength of the reinforcement or by bond failure between the concrete and the rebar 35 Carbonation Edit Concrete wall cracking as steel reinforcing corrodes and swells Rust has a lower density than metal so it expands as it forms cracking the decorative cladding off the wall as well as damaging the structural concrete The breakage of material from a surface is called spalling Detailed view of spalling probably caused by a too thin layer of concrete between the steel and the surface accompanied by corrosion from external exposure Main article Carbonation Carbonation or neutralisation is a chemical reaction between carbon dioxide in the air and calcium hydroxide and hydrated calcium silicate in the concrete When a concrete structure is designed it is usual to specify the concrete cover for the rebar the depth of the rebar within the object The minimum concrete cover is normally regulated by design or building codes If the reinforcement is too close to the surface early failure due to corrosion may occur The concrete cover depth can be measured with a cover meter However carbonated concrete incurs a durability problem only when there is also sufficient moisture and oxygen to cause electropotential corrosion of the reinforcing steel One method of testing a structure for carbonatation is to drill a fresh hole in the surface and then treat the cut surface with phenolphthalein indicator solution This solution turns pink when in contact with alkaline concrete making it possible to see the depth of carbonation Using an existing hole does not suffice because the exposed surface will already be carbonated Chlorides Edit Chlorides can promote the corrosion of embedded rebar if present in sufficiently high concentration Chloride anions induce both localized corrosion pitting corrosion and generalized corrosion of steel reinforcements For this reason one should only use fresh raw water or potable water for mixing concrete ensure that the coarse and fine aggregates do not contain chlorides rather than admixtures which might contain chlorides Rebar for foundations and walls of a sewage pump station The Paulins Kill Viaduct Hainesburg New Jersey is 115 feet 35 m tall and 1 100 feet 335 m long 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 Lackawanna Railroad was a pioneer in the use of reinforced concrete It was once common for calcium chloride to be used as an admixture to promote rapid set up of the concrete It was also mistakenly believed that it would prevent freezing However this practice fell into disfavor once the deleterious effects of chlorides became known It should be avoided whenever possible The use of de icing salts on roadways used to lower the freezing point of water is probably one of the primary causes of premature failure of reinforced or prestressed concrete bridge decks roadways and parking garages The use of epoxy coated reinforcing bars and the application of cathodic protection has mitigated this problem to some extent Also FRP fiber reinforced polymer rebars are known to be less susceptible to chlorides Properly designed concrete mixtures that have been allowed to cure properly are effectively impervious to the effects of de icers Another important source of chloride ions is sea water Sea water contains by weight approximately 3 5 salts These salts include sodium chloride magnesium sulfate calcium sulfate and bicarbonates In water these salts dissociate in free ions Na Mg2 Cl SO2 4 HCO 3 and migrate with the water into the capillaries of the concrete Chloride ions which make up about 50 of these ions are particularly aggressive as a cause of corrosion of carbon steel reinforcement bars In the 1960s and 1970s it was also relatively common for magnesite a chloride rich carbonate mineral to be used as a floor topping material This was done principally as a levelling and sound attenuating layer However it is now known that when these materials come into contact with moisture they produce a weak solution of hydrochloric acid due to the presence of chlorides in the magnesite Over a period of time typically decades the solution causes corrosion of the embedded rebars This was most commonly found in wet areas or areas repeatedly exposed to moisture Alkali silica reaction Edit Main article Alkali silica reaction This a reaction of amorphous silica chalcedony chert siliceous limestone sometimes present in the aggregates with the hydroxyl ions OH from the cement pore solution Poorly crystallized silica SiO2 dissolves and dissociates at high pH 12 5 13 5 in alkaline water 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 The alkali silica reaction ASR causes localised swelling responsible for tensile stress and cracking The conditions required for alkali silica reaction are threefold 1 aggregate containing an alkali reactive constituent amorphous silica 2 sufficient availability of hydroxyl ions OH and 3 sufficient moisture above 75 relative humidity RH within the concrete 36 37 This phenomenon is sometimes popularly referred to as concrete cancer This reaction occurs independently of the presence of rebars massive concrete structures such as dams can be affected Conversion of high alumina cement Edit Resistant to weak acids and especially sulfates this cement cures quickly and has very high durability and strength It was frequently used after World War II to make precast concrete objects However it can lose strength with heat or time conversion especially when not properly cured After the collapse of three roofs made of prestressed concrete beams using high alumina cement this cement was banned in the UK in 1976 Subsequent inquiries into the matter showed that the beams were improperly manufactured but the ban remained 38 Sulfates Edit Sulfates SO4 in the soil or in groundwater in sufficient concentration can react with the Portland cement in concrete causing the formation of expansive products e g ettringite or thaumasite which can lead to early failure of the structure The most typical attack of this type is on concrete slabs and foundation walls at grades where the sulfate ion via alternate wetting and drying can increase in concentration As the concentration increases the attack on the Portland cement can begin For buried structures such as pipe this type of attack is much rarer especially in the eastern United States 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 A chemical analysis of soil borings to check for the presence of sulfates should be undertaken during the design phase of any project involving concrete in contact with the native soil If the concentrations are found to be aggressive various protective coatings can be applied Also in the US ASTM C150 Type 5 Portland cement can be used in the mix This type of cement is designed to be particularly resistant to a sulfate attack Steel plate construction EditMain article Steel plate construction In steel plate construction stringers join parallel steel plates The plate assemblies are fabricated off site and welded together on site to form steel walls connected by stringers The walls become the form into which concrete is poured Steel plate construction speeds reinforced concrete construction by cutting out the time consuming on site manual steps of tying rebar and building forms The method results in excellent strength because the steel is on the outside where tensile forces are often greatest Fiber reinforced concrete EditMain article Fiber reinforced concrete Fiber reinforcement is mainly used in shotcrete but can also be used in normal concrete Fiber reinforced normal concrete is mostly used for on ground floors and pavements but can also be considered for a wide range of construction parts beams pillars foundations etc either alone or with hand tied rebars Concrete reinforced with fibers which are usually steel glass plastic fibers or cellulose polymer fiber is less expensive than hand tied rebar citation needed The shape dimension and length of the fiber are important A thin and short fiber for example short hair shaped glass fiber is only effective during the first hours after pouring the concrete its function is to reduce cracking while the concrete is stiffening but it will not increase the concrete tensile strength A normal size fiber for European shotcrete 1 mm diameter 45 mm length steel or plastic will increase the concrete s tensile strength Fiber reinforcement is most often used to supplement or partially replace primary rebar and in some cases it can be designed to fully replace rebar 39 Steel is the strongest commonly available fiber citation needed and comes in different lengths 30 to 80 mm in Europe and shapes end hooks Steel fibers can only be used on surfaces that can tolerate or avoid corrosion and rust stains In some cases a steel fiber surface is faced with other materials Glass fiber is inexpensive and corrosion proof but not as ductile as steel Recently spun basalt fiber long available in Eastern Europe has become available in the U S and Western Europe Basalt fiber is stronger and less expensive than glass but historically has not resisted the alkaline environment of Portland cement well enough to be used as direct reinforcement New materials use plastic binders to isolate the basalt fiber from the cement The premium fibers are graphite reinforced plastic fibers which are nearly as strong as steel lighter in weight and corrosion proof citation needed Some experiments have had promising early results with carbon nanotubes but the material is still far too expensive for any building citation needed Non steel reinforcement EditThere is considerable overlap between the subjects of non steel reinforcement and fiber reinforcement of concrete The introduction of non steel reinforcement of concrete is relatively recent it takes two major forms non metallic rebar rods and non steel usually also non metallic fibers incorporated into the cement matrix For example there is increasing interest in glass fiber reinforced concrete GFRC and in various applications of polymer fibers incorporated into concrete Although currently there is not much suggestion that such materials will replace metal rebar some of them have major advantages in specific applications and there also are new applications in which metal rebar simply is not an option However the design and application of non steel reinforcing is fraught with challenges For one thing concrete is a highly alkaline environment in which many materials including most kinds of glass have a poor service life Also the behavior of such reinforcing materials differs from the behavior of metals for instance in terms of shear strength creep and elasticity 40 41 Fiber reinforced plastic polymer FRP and glass reinforced plastic GRP consist of fibers of polymer glass carbon aramid or other polymers or high strength fibers set in a resin matrix to form a rebar rod or grid or fiber These rebars are installed in much the same manner as steel rebars The cost is higher but suitably applied the structures have advantages in particular a dramatic reduction in problems related to corrosion either by intrinsic concrete alkalinity or by external corrosive fluids that might penetrate the concrete These structures can be significantly lighter and usually have a longer service life The cost of these materials has dropped dramatically since their widespread adoption in the aerospace industry and by the military In particular FRP rods are useful for structures where the presence of steel would not be acceptable For example MRI machines have huge magnets and accordingly require non magnetic buildings Again toll booths that read radio tags need reinforced concrete that is transparent to radio waves Also where the design life of the concrete structure is more important than its initial costs non steel reinforcing often has its advantages where corrosion of reinforcing steel is a major cause of failure In such situations corrosion proof reinforcing can extend a structure s life substantially for example in the intertidal zone FRP rods may also be useful in situations where it is likely that the concrete structure may be compromised in future years 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 Plastic reinforcement often is stronger or at least has a better strength to weight ratio than reinforcing steels Also because it resists corrosion it does not need a protective concrete cover as thick as steel reinforcement does typically 30 to 50 mm or more FRP reinforced structures therefore can be lighter and last longer Accordingly for some applications the whole life cost will be price competitive with steel reinforced concrete The material properties of FRP or GRP bars differ markedly from steel so there are differences in the design considerations FRP or GRP bars have relatively higher tensile strength but lower stiffness so that deflections are likely to be higher than for equivalent steel reinforced units Structures with internal FRP reinforcement typically have an elastic deformability comparable to the plastic deformability ductility of steel reinforced structures Failure in either case is more likely to occur by compression of the concrete than by rupture of the reinforcement Deflection is always a major design consideration for reinforced concrete Deflection limits are set to ensure that crack widths in steel reinforced concrete are controlled to prevent water air or other aggressive substances reaching the steel and causing corrosion For FRP reinforced concrete aesthetics and possibly water tightness will be the limiting criteria for crack width control FRP rods also have relatively lower compressive strengths than steel rebar and accordingly require different design approaches for reinforced concrete columns One drawback to the use of FRP reinforcement is their limited fire resistance Where fire safety is a consideration structures employing FRP have to maintain their strength and the anchoring of the forces at temperatures to be expected in the event of fire For purposes of fireproofing an adequate thickness of cement concrete cover or protective cladding is necessary The addition of 1 kg m3 of polypropylene fibers to concrete has been shown to reduce spalling during a simulated fire 42 The improvement is thought to be due to the formation of pathways out of the bulk of the concrete allowing steam pressure to dissipate 42 Another problem is the effectiveness of shear reinforcement FRP rebar stirrups formed by bending before hardening generally perform relatively poorly in comparison to steel stirrups or to structures with straight fibers When strained the zone between the straight and curved regions are subject to strong bending shear and longitudinal stresses Special design techniques are necessary to deal with such problems There is growing interest in applying external reinforcement to existing structures using advanced materials such as composite fiberglass basalt carbon rebar which can impart exceptional strength Worldwide there are a number of brands of composite rebar recognized by different countries such as Aslan DACOT V rod and ComBar The number of projects using composite rebar increases day by day around the world in countries ranging from USA Russia and South Korea to Germany See also EditAnchorage in reinforced concrete Concrete cover Concrete slab Corrosion engineering Cover Meter Falsework Ferrocement Formwork Kahn System Henri de Miffonis Interfacial Transition Zone Precast concrete Types of concrete Structural robustness Reinforced concrete structures durability Reinforced solidReferences Edit 16 Materials Every Architect Needs to Know And Where to Learn About Them ArchDaily December 19 2016 Archived from the original on July 9 2021 Retrieved July 9 2021 Sarah March 22 2017 When should you use reinforced concrete EKA Concrete Direct Supplier of Ready Mix and Site Mix Concrete Retrieved July 9 2021 Structural materials George Weidmann P R Lewis Nick Reid Open University Materials Department Milton Keynes U K Materials Dept Open University 1990 p 360 ISBN 0 408 04658 9 OCLC 20693897 a href Template Cite book html title Template Cite book cite book a CS1 maint others link Slukin V M 2001 Demidovskie gnezda Nevʹi a nsk Verkhniĭ Tagil Nizhniĭ Tagil Elena Arapova Tatiana Kononova Ekaterinburg ID Sokrat p 26 ISBN 5 88664 106 8 OCLC 56187883 a b Building construction The invention of reinforced concrete Encyclopedia Britannica Archived from the original on September 28 2018 Retrieved September 27 2018 a b Condit Carl W January 1968 The First Reinforced Concrete Skyscraper The Ingalls Building in Cincinnati and Its Place in Structural History Technology and Culture 9 1 1 33 doi 10 2307 3102041 JSTOR 3102041 Richard W S 1995 History of Concrete PDF The Aberdeen Group Archived from the original PDF on 28 May 2015 Retrieved 25 April 2015 W Morgan 1995 Reinforced Concrete The Elements of Structure Archived from the original on October 12 2018 Retrieved April 25 2015 via John F Claydon s website a b Department of Civil Engineering 2015 History of Concrete Building Construction CIVL 1101 History of Concrete University of Memphis Archived from the original on February 27 2017 Retrieved April 25 2015 Day Lance 2003 Biographical Dictionary of the History of Technology Routledge p 284 ISBN 0 203 02829 5 a b Morsch Emil 1909 Concrete steel Construction Der Eisenbetonbau The Engineering News Publishing Company pp 204 210 Collins Peter 1920 1981 Concrete The Vision of a New Architecture McGill Queen s University Press pp 58 60 ISBN 0 7735 2564 5 Archived from the original on July 9 2021 Retrieved November 2 2020 Mars Roman Episode 81 Rebar and the Alvord Lake Bridge 99 Invisible Archived from the original on August 8 2014 Retrieved August 6 2014 Collins Peter 1920 1981 Concrete The Vision of a New Architecture McGill Queen s University Press pp 61 64 ISBN 0 7735 2564 5 Archived from the original on July 9 2021 Retrieved April 3 2016 McGroarty John Steven 1921 Los Angeles from the Mountains to the Sea Vol 2 Los Angeles CA American Historical Society p 176 Archived from the original on August 9 2016 Retrieved November 29 2017 Annual Report of the City Auditor City of Los Angeles California for the Year Ending June 30 Los Angeles CA Los Angeles City Auditor 1905 pp 71 73 Archived from the original on September 27 2020 Retrieved November 30 2017 Williams D February 1907 What Builders are Doing Carpentry and Building 66 Archived from the original on September 1 2020 Retrieved November 29 2017 W P H April 19 1906 Reinforced Concrete Buildings at Los Angeles Cal Letters to the Editor Engineering News Record 55 449 Archived from the original on September 19 2020 Retrieved November 29 2017 Austin J C Neher O H Hicks L A Whittlesey C F Leonard J B November 1906 Partial Collapse of the Bixby Hotel at Long Beach Architect and Engineer of California Vol VII no 1 pp 44 48 Archived from the original on September 20 2020 Retrieved May 29 2018 El Campanil Mills College Julia Morgan 1903 1904 Archived from the original on December 30 2018 Retrieved April 18 2019 Callen Will February 4 2019 Julia Morgan designed Mills bell tower counts down to its 115th anniversary hoodline com Archived from the original on April 19 2019 Retrieved April 18 2019 Morgan had studied the material in Paris where some of its pioneers Francois Hennebique and Auguste Perret were exploring its non industrial uses Fascinated by its combination of stability and plasticity she may have been the first architect in the U S to put it towards something other than bridges or piers Littman Julie March 7 2018 Bay Area Architect Julia Morgan s Legacy Wasn t Just Hearst Castle busnow com Archived from the original on April 20 2019 Retrieved April 18 2019 Olsen Erik May 1 2020 How one building survived the San Francisco earthquake and changed the world California Science Weekly Archived from the original on July 2 2020 Retrieved July 1 2020 Standard Specifications for Portland Cement of the American Society for Testing Materials Standard No 1 Philadelphia PA National Association of Cement Users 1906 Standard Building Regulations for the Use of Reinforced Concrete Philadelphia PA National Association of Cement Users 1910 Murray Lorraine Christ the Redeemer last updated 13 January 2014 Encyclopaedia Britannica Retrieved November 5 2022 Materials principles and practice Charles Newey Graham Weaver Open University Materials Department Milton Keynes England Materials Dept Open University 1990 p 61 ISBN 0 408 02730 4 OCLC 19553645 a href Template Cite book html title Template Cite book cite book a CS1 maint others link Structural materials George Weidmann P R Lewis Nick Reid Open University Materials Department Milton Keynes U K Materials Dept Open University 1990 p 357 ISBN 0 408 04658 9 OCLC 20693897 a href Template Cite book html title Template Cite book cite book a CS1 maint others link Concrete Inhomogeneity of Vertical Cast In Situ Elements In Frame Type Buildings Archived 2021 01 15 at the Wayback Machine Simescu Florica Idrissi Hassane December 19 2008 Effect of zinc phosphate chemical conversion coating on corrosion behavior of mild steel in alkaline medium protection of rebars in reinforced concrete Science and Technology of Advanced Materials National Institute for Materials Science 9 4 045009 Bibcode 2008STAdM 9d5009S doi 10 1088 1468 6996 9 4 045009 PMC 5099651 PMID 27878037 Nilson Darwin Dolan Design of Concrete Structures the MacGraw Hill Education 2003 p 80 90 Techno Press April 2 2015 Archived from the original on April 2 2015 Sadeghi Kabir September 15 2011 Energy based structural damage index based on nonlinear numerical simulation of structures subjected to oriented lateral cyclic loading International Journal of Civil Engineering 9 3 155 164 ISSN 1735 0522 Retrieved December 23 2016 Structural materials George Weidmann P R Lewis Nick Reid Open University Materials Department Milton Keynes U K Materials Dept Open University 1990 p 372 373 ISBN 0 408 04658 9 OCLC 20693897 a href Template Cite book html title Template Cite book cite book a CS1 maint others link Janowski A Nagrodzka Godycka K Szulwic J Ziolkowski P 2016 Remote sensing and photogrammetry techniques in diagnostics of concrete structures Computers and Concrete 18 3 405 420 doi 10 12989 cac 2016 18 3 405 Archived from the original on July 9 2021 Retrieved December 14 2016 Concrete Cancer h2g2 BBC March 15 2012 2005 Archived from the original on February 23 2009 Retrieved October 14 2009 Special Section South West Alkali Incident the cement industry British Cement Association January 4 2006 Archived from the original on October 29 2006 Retrieved November 26 2006 High Alumina Cement Archived from the original on September 11 2005 Retrieved October 14 2009 Fiber Concrete in Construction Wietek B Springer 2021 pages 268 ISBN 978 3 658 34480 1 BS EN 1169 1999 Precast concrete products General rules for factory production control of glass fiber reinforced cement British Standards Institute November 15 1999 ISBN 0 580 32052 9 Archived from the original on June 12 2018 Retrieved May 29 2018 BS EN 1170 5 1998 Precast concrete products Test method for glass fiber reinforced cement British Standards Institute March 15 1998 ISBN 0 580 29202 9 Archived from the original on June 12 2018 Retrieved May 29 2018 a b Arthur W Darby 2003 Chapter 57 The Airside Road Tunnel Heathrow Airport England PDF Proceedings of the Rapid Excavation amp Tunneling Conference New Orleans June 2003 p 645 Archived from the original PDF on May 22 2006 via www tunnels mottmac com Further reading Edit Threlfall A et al Reynolds s Reinforced Concrete Designer s Handbook 11th ed ISBN 978 0 419 25830 8 Newby F Early Reinforced Concrete Ashgate Variorum 2001 ISBN 978 0 86078 760 0 Kim S Surek J and J Baker Jarvis Electromagnetic Metrology on Concrete and Corrosion Journal of Research of the National Institute of Standards and Technology Vol 116 No 3 May June 2011 655 669 Daniel R Formwork UK Concrete frame structures Materials principles and practice Charles Newey Graham Weaver Open University Materials Department Milton Keynes England Materials Dept Open University 1990 ISBN 0 408 02730 4 OCLC 19553645 a href Template Cite book html title Template Cite book cite book a CS1 maint others link Structural materials George Weidmann P R Lewis Nick Reid Open University Materials Department Milton Keynes U K Materials Dept Open University 1990 p 357 ISBN 0 408 04658 9 OCLC 20693897 a href Template Cite book html title Template Cite book cite book a CS1 maint others link Corrosion of reinforcement in concrete construction C L Page P B Bamforth J W Figg International Symposium on Corrosion of Reinforcement in Concrete Construction Cambridge Royal Society of Chemistry Information Services 1996 ISBN 0 85404 731 X OCLC 35233292 a href Template Cite book html title Template Cite book cite book a CS1 maint others link Reinforced concrete June 19 2020 Retrieved from https en wikipedia org w index php title Reinforced concrete amp oldid 1150240670, wikipedia, wiki, 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