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  • Concrete is reinforced to give it extra tensile strength; without reinforcement, many concrete buildings would not have been possible.Reinforced concrete can encompass many types of structures and components, including slabs, walls, beams, columns, foundations, frames and more.Reinforced concrete can be classified as precast concrete and cast in-situ concrete.Much of the focus on reinforcing concrete is placed on floor systems. 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.
  • Bottom bars - resist tensionTop bars - hold links togetherVertical loop bars - ‘links’Links - work with concrete toresist shearStage 1 - cast beam tounderside of slabStage 2 - cast slab
  • Ordinary Reinforced ConcreteRelatively easy manual constructionCurved forms relatively easyContinuity easyLarge proportion of the concrete does not assist in loadcarryingPre-stressed ConcreteMore efficient use of concrete (precompressed)Hence smaller section or longer spansMore specialised mechanical processes (usually factory based)[edit] Prestressed concrete structuresMain article: Prestressed concretePrestressed concrete is a form of reinforced concrete which builds in compressive stresses during construction to oppose those found when in use. This can greatly reduce the weight of beams or slabs, by better distributing the stresses in the structure to make optimal use of the reinforcement.For example a horizontal beam will tend to sag down. If the reinforcement along the bottom of the beam is prestressed, it can counteract this.In pre-tensioned concrete, the prestressing is achieved by using steel or polymer tendons or bars that are subjected to a tensile force prior to casting, or for post-tensioned concrete, after casting.Prestressed concrete is a method for overcoming the concrete's natural weakness in tension.[1][2] It can be used to produce beams, floors or bridges with a longer span than is practical with ordinary reinforced concrete. Prestressing tendons (generally of high tensilesteelcable or rods) are used to provide a clamping load which produces a compressive stress that offsets the tensile stress that the concrete compression member would otherwise experience due to a bending load. Traditional reinforced concrete is based on the use of steel reinforcement bars, rebars, inside poured concrete.Prestressing can be accomplished in three ways: pre-tensioned concrete, and bonded or unbonded post-tensioned concrete.Pre-tensioned concrete is cast around already tensioned tendons. This method produces a good bond between the tendon and concrete, which both protects the tendon from corrosion and allows for direct transfer of tension. The cured concrete adheres and bonds to the bars and when the tension is released it is transferred to the concrete as compression by static friction. However, it requires stout anchoring points between which the tendon is to be stretched and the tendons are usually in a straight line. Thus, most pretensioned concrete elements are prefabricated in a factory and must be transported to the construction site, which limits their size. Pre-tensioned elements may be balcony elements, lintels, floor slabs, beams or foundation piles. An innovative bridge construction method using pre-stressing is described in Stressed ribbon bridge.Stage 1Tendons and reinforcement are positioned in the beam mould.Stage 2Tendons are stressed to about 70% of their ultimate strength.Stage 3Concrete is cast into the beam mould and allowed to cure to the required initial strength.Stage 4When the concrete has cured the stressing force is released and the tendons anchor themselves in the concrete.
  • El sistema Postensado en estructuras de concreto aumenta la capacidad a la tracción mediante la aplicación de una fuerza externa; esta característica se traduce en mayor economía del proyecto al brindar menores tiempos de construcción y disminuir la cantidad de los materiales utilizados.   ¿Que brindan para su proyecto los sistemas postensados?Esta tecnología ofrece múltiples alternativas para sus proyectos de construcción mediante el aumento de la capacidad de carga y la disminución de las secciones del elemento de concreto hasta de un 30% siendo así una excelente opción estructural.  Algunos beneficios para su proyecto se mencionan a continuación:• Eficiencia en la utilización del concreto, tiempos de desencofrado y velocidad de construcción.• Amplias posibilidades para la gestación de espacios y elementos arquitectónicos complejos.• Mayor flexibilidad en la generación de amplios espacios (grandes luces) para usos comerciales, vivienda, parqueaderos, entre otros.• Optimización de las alturas de entrepiso gracias a la disminución de espesores de la estructura.• Reducción de acero de refuerzo a cantidades mínimas.• Aligeramiento y menor peso total de la estructura.• Disminuye los efectos de sismo.• Menos peso de cimientos.Se denomina concreto postensado o postesado a aquel concreto al que se somete, después del vertido y fraguado, a esfuerzos decompresión por medio de armaduras activas (cables de acero) montadas dentro de vainas. A diferencia del concreto pretensado, en el que las armaduras se tensan antes del concretoado, en el postensado las armaduras se tensan una vez que el concreto ha adquirido su resistencia característica.Al igual que en el concreto pretensado, la ventaja del postensado consiste en comprimir el concreto antes de su puesta en servicio, de modo que las tracciones que aparecen al flectar la pieza se traducen en una pérdida de la compresión previa, evitando en mayor o menor medida que el concreto trabaje a tracción, esfuerzo para el que no es un material adecuado.Stage 1Cable ducts and reinforcement are positioned in the beam mould. The ducts are usually raised towards the neutral axis at the ends to reduce the eccentricity of the stressing force.Stage 2Concrete is cast into the beam mould and allowed to cure to the required initial strength.Stage 3Tendons are threaded through the cable ducts and tensioned to about 70% of their ultimate strength.Stage 4Wedges are inserted into the end anchorages and the tensioning force on the tendons is released. Grout is then pumped into the ducts to protect the tendons.Loss of PrestressWhen the tensioning force is released and the tendons are anchored to the concrete a series of effects result in a loss of stress in the tendons. The effects are :relaxation of the steel tendons elastic deformation of the concrete shrinkage and creep of the concrete slip or movement of the tendons at the anchorages during anchoring other causes in special circumstances , such as when steam curing is used with pre-tensioning. Over the last 5 years, the UK has begun to take note of the potential of post tensioned (PT) suspended concrete floors with an increased number of buildings being constructed using PT. The use of PT offers several benefits, not least of which is the fact that the PT floor slabs are generally thinner than an ordinary reinforced concrete slab. They can also be up to 300mm thinner than a floor in a steel frame. This minimises the building's height to the extent that this could mean an extra storey on a ten storey building. The amount of prestress can be adjusted to control deflection, thus enabling the minimum depth of slab to be used. Deflection calculation can also be simpler than for reinforced concrete because the section is uncracked. PT slabs can economically span further than a reinforced concrete slab. This in turn reduces the required number of columns and foundations and increases flexibility for space planning. Flexibility is further enhanced by a PT slab being able to accommodate irregular grids. The clear flat soffits of PT slabs enable complete flexibility of service layout. The absence of trimming beams around service cores avoid conflicts between services and structure. There is also flexibility in positioning holes through the slab because tendons are widely spaced and can be positioned around openings. In addition to all the above benefits, PT equals rapid construction. Thin slabs equals less concrete which equals fewer lorries. There is less reinforcement which reduces fixing time and early stressing of the concrete allows the formwork to be struck quickly. There are two methods of PT: unbonded and bonded.BondedWith bonded systems, the prestressing tendons run through small continuous flat ducts that are grouted up after the tendons are stressed. The bonded systems generally develop high ultimate strengths. However, the bonded ducts are larger than for unbonded. This reduces the effective section depth for design purposes but there is less reliance on the anchorages after grouting.UnbondedWith unbonded systems, the tendons run through a small protective sheath that allows the tendons to move independently of the concrete. They can be manufactured off-site thereby reducing the on-site programme.The tendons are more flexible and can be deflected in plan to be placed easily around holes. There is also no need for another trade to carry out the grouting.  PT slabs generally become economic at spans greater than 7.5m. Typically three   main forms of construction are used: flat slab, band beams and slab and ribbed slab. Bonded post-tensioned concrete is the descriptive term for a method of applying compression after pouring concrete and the curing process (in situ). The concrete is cast around a plastic, steel or aluminium curved duct, to follow the area where otherwise tension would occur in the concrete element. A set of tendons are fished through the duct and the concrete is poured. Once the concrete has hardened, the tendons are tensioned by hydraulicjacks that react against the concrete member itself. When the tendons have stretched sufficiently, according to the design specifications (see Hooke's law), they are wedged in position and maintain tension after the jacks are removed, transferring pressure to the concrete. The duct is then grouted to protect the tendons from corrosion. This method is commonly used to create monolithic slabs for house construction in locations where expansive soils (such as adobeclay) create problems for the typical perimeter foundation. All stresses from seasonal expansion and contraction of the underlying soil are taken into the entire tensioned slab, which supports the building without significant flexure. Post-tensioning is also used in the construction of various bridges, both after concrete is cured after support by falsework and by the assembly of prefabricated sections, as in the segmental bridge.The advantages of this system over unbonded post-tensioning are:Large reduction in traditional reinforcement requirements as tendons cannot destress in accidents. Tendons can be easily 'weaved' allowing a more efficient design approach. Higher ultimate strength due to bond generated between the strand and concrete. No long term issues with maintaining the integrity of the anchor/dead end. Unbonded post-tensioned concrete differs from bonded post-tensioning by providing each individual cable permanent freedom of movement relative to the concrete. To achieve this, each individual tendon is coated with a grease (generally lithium based) and covered by a plastic sheathing formed in an extrusion process. The transfer of tension to the concrete is achieved by the steel cable acting against steel anchors embedded in the perimeter of the slab. The main disadvantage over bonded post-tensioning is the fact that a cable can destress itself and burst out of the slab if damaged (such as during repair on the slab). The advantages of this system over bonded post-tensioning are:The ability to individually adjust cables based on poor field conditions (For example: shifting a group of 4 cables around an opening by placing 2 to either side). The procedure of post-stress grouting is eliminated. The ability to de-stress the tendons before attempting repair work. Picture number one (below) shows rolls of post-tensioning (PT) cables with the holding end anchors displayed. The holding end anchors are fastened to rebar placed above and below the cable and buried in the concrete locking that end. Pictures numbered two, three and four shows a series of black pulling end anchors from the rear along the floor edge form. Rebar is placed above and below the cable both in front and behind the face of the pulling end anchor. The above and below placement of the rebar can be seen in picture number three and the placement of the rebar in front and behind can be seen in picture number four. The blue cable seen in picture number four is electrical conduit. Picture number five shows the plastic sheathing stripped from the ends of the post-tensioning cables before placement through the pulling end anchors. Picture number six shows the post-tensioning cables in place for concrete pouring. The plastic sheathing has been removed from the end of the cable and the cable has been pushed through the black pulling end anchor attached to the inside of the concrete floor side form. The greased cable can be seen protruding from the concrete floor side form. Pictures seven and eight show the post-tensioning cables protruding from the poured concrete floor. After the concrete floor has been poured and has set for about a week, the cable ends will be pulled with a hydraulic jack, shown in picture number nine, until it is stretched to achieve the specified tension.
  • Three physical characteristics give reinforced concrete its special properties. First, the coefficient of thermal expansion of concrete is similar to that of steel, eliminating internal stresses due to differences in thermal expansion or contraction. Second, 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. Third, the alkaline chemical environment provided by calcium carbonate (lime) 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.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.Advantages of RC as a Construction Material- Resistance to action of water(Used almost exclusively in water-retaining and underground structures, bridge piers, etc.)- Compressive loading applications- Economy (unskilled labor)- Architectural advantages (shell structures)Disadvantages- Reliability of material properties- Labor-intensiveQuality controlReinforced 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.
  • Fiber reinforced concrete (FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers. Within these different fibers that character of fiber reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation and de[edit] Historical perspectiveThe concept of using fibers as reinforcement is not new. Fibers have been used as reinforcement since ancient times. Historically, horsehair was used in mortar and straw in mudbricks. In the early 1900s, asbestos fibers were used in concrete, and in the 1950s the concept of composite materials came into being and fiber reinforced concrete was one of the topics of interest. There was a need to find a replacement for the asbestos used in concrete and other building materials once the health risks associated with the substance were discovered. By the 1960s, steel, glass (GFRC), and synthetic fibers such as polypropylene fibers were used in concrete, and research into new fiber reinforced concretes continues today.[edit] Effect of fibers in concreteFibers are usually used in concrete to control plastic shrinkage cracking and drying shrinkage cracking. They also lower the permeability of concrete and thus reduce bleeding of water. Some types of fibers produce greater impact, abrasion and shatter resistance in concrete. Generally fibers do not increase the flexural strength of concrete, so it can not replace moment resisting or structural steel reinforcement. Some fibers reduce the strength of concrete.The amount of fibres added to a concrete mix is measured as a percentage of the total volume of the composite (concrete and fibres) termed volume fraction (Vf). Vf typically ranges from 0.1 to 3%. Aspect ratio (l/d) is calculated by dividing fibre length (l) by its diameter (d). Fibres with a non-circular cross section use an equivalent diameter for the calculation of aspect ratio. If the modulus of elasticity of the fibre is higher than the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile strength of the material. Increase in the aspect ratio of the fibre usually segments the flexural strength and toughness of the matrix. However, fibres which are too long tend to "ball" in the mix and create workability problems.Some recent research indicated that using fibers in concrete has limited effect on the impact resistance of concrete materials[1 & 2]. This finding is very important since traditionally people think the ductility increases when concrete reinforced with fibers. The results also pointed out that the micro fibers is better in impact resistance compared with the longer fibers.[1]The High Speed 1 tunnel linings incorporated concrete containing 1 kg/m³ of polypropylene fibres, of diameter 18 & 32 μm, giving the benefits noted below.[2][edit] BenefitsPolypropylene fibres can:Improve mix cohesion, improving pumpability over long distances Improve freeze-thaw resistance Improve resistance to explosive spalling in case of a severe fire Improve impact resistance Increase resistance to plastic [edit] Some developments in fiber reinforced concreteThe newly developed FRC named Engineered Cementitious Composite (ECC) is 500 times more resistant to cracking and 40 percent lighter than traditional concrete. ECC can sustain strain-hardening up to several percent strain, resulting in a material ductility of at least two orders of magnitude higher when compared to normal concrete or standard fiber reinforced concrete. ECC also has unique cracking behavior. When loaded to beyond the elastic range, ECC maintains crack width to below 100 µm, even when deformed to several percent tensile strains.Recent studies performed on a high-performance fiber-reinforced concrete in a bridge deck found that adding fibers provided residual strength and controlled cracking. There were fewer and narrower cracks in the FRC even though the FRC had more shrinkage than the control. Residual strength is directly proportional to the fiber content.A new kind of natural fiber reinforced concrete (NFRC) made of cellulose fibers processed from genetically modified slash pine trees is giving good results. The cellulose fibers are longer and greater in diameter than other timber sources. Some studies were performed using waste carpet fibers in concrete as an environmentally friendly use of recycled carpet waste. A carpet typically consists of two layers of backing (usually fabric from polypropylene tape yarns), joined by CaCO3 filled styrene-butadiene latex rubber (SBR), and face fibers (majority being nylon 6 and nylon 66 textured yarns). Such nylon and polypropylene fibers can be used for concrete reinforcement.For statical calculations there is a new modelling in the book: B.Wietek, Stahlfaserbeton, edited by Vieweg + Teubner, 2008, ISBN 978-3-8348-0592-8. Here is the possibility to calculate also colums, platforms, beams and also shear situations which show a better behaviour than concrete allone. We hope that a translation of this book is available soon, that we can reconstruct all the theory which is given.[edit] See alsonsities.
  • Fiber reinforced concrete (FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers. Within these different fibers that character of fiber reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation and de[edit] Historical perspectiveThe concept of using fibers as reinforcement is not new. Fibers have been used as reinforcement since ancient times. Historically, horsehair was used in mortar and straw in mudbricks. In the early 1900s, asbestos fibers were used in concrete, and in the 1950s the concept of composite materials came into being and fiber reinforced concrete was one of the topics of interest. There was a need to find a replacement for the asbestos used in concrete and other building materials once the health risks associated with the substance were discovered. By the 1960s, steel, glass (GFRC), and synthetic fibers such as polypropylene fibers were used in concrete, and research into new fiber reinforced concretes continues today.[edit] Effect of fibers in concreteFibers are usually used in concrete to control plastic shrinkage cracking and drying shrinkage cracking. They also lower the permeability of concrete and thus reduce bleeding of water. Some types of fibers produce greater impact, abrasion and shatter resistance in concrete. Generally fibers do not increase the flexural strength of concrete, so it can not replace moment resisting or structural steel reinforcement. Some fibers reduce the strength of concrete.The amount of fibres added to a concrete mix is measured as a percentage of the total volume of the composite (concrete and fibres) termed volume fraction (Vf). Vf typically ranges from 0.1 to 3%. Aspect ratio (l/d) is calculated by dividing fibre length (l) by its diameter (d). Fibres with a non-circular cross section use an equivalent diameter for the calculation of aspect ratio. If the modulus of elasticity of the fibre is higher than the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile strength of the material. Increase in the aspect ratio of the fibre usually segments the flexural strength and toughness of the matrix. However, fibres which are too long tend to "ball" in the mix and create workability problems.Some recent research indicated that using fibers in concrete has limited effect on the impact resistance of concrete materials[1 & 2]. This finding is very important since traditionally people think the ductility increases when concrete reinforced with fibers. The results also pointed out that the micro fibers is better in impact resistance compared with the longer fibers.[1]The High Speed 1 tunnel linings incorporated concrete containing 1 kg/m³ of polypropylene fibres, of diameter 18 & 32 μm, giving the benefits noted below.[2][edit] BenefitsPolypropylene fibres can:Improve mix cohesion, improving pumpability over long distances Improve freeze-thaw resistance Improve resistance to explosive spalling in case of a severe fire Improve impact resistance Increase resistance to plastic [edit] Some developments in fiber reinforced concreteThe newly developed FRC named Engineered Cementitious Composite (ECC) is 500 times more resistant to cracking and 40 percent lighter than traditional concrete. ECC can sustain strain-hardening up to several percent strain, resulting in a material ductility of at least two orders of magnitude higher when compared to normal concrete or standard fiber reinforced concrete. ECC also has unique cracking behavior. When loaded to beyond the elastic range, ECC maintains crack width to below 100 µm, even when deformed to several percent tensile strains.Recent studies performed on a high-performance fiber-reinforced concrete in a bridge deck found that adding fibers provided residual strength and controlled cracking. There were fewer and narrower cracks in the FRC even though the FRC had more shrinkage than the control. Residual strength is directly proportional to the fiber content.A new kind of natural fiber reinforced concrete (NFRC) made of cellulose fibers processed from genetically modified slash pine trees is giving good results. The cellulose fibers are longer and greater in diameter than other timber sources. Some studies were performed using waste carpet fibers in concrete as an environmentally friendly use of recycled carpet waste. A carpet typically consists of two layers of backing (usually fabric from polypropylene tape yarns), joined by CaCO3 filled styrene-butadiene latex rubber (SBR), and face fibers (majority being nylon 6 and nylon 66 textured yarns). Such nylon and polypropylene fibers can be used for concrete reinforcement.For statical calculations there is a new modelling in the book: B.Wietek, Stahlfaserbeton, edited by Vieweg + Teubner, 2008, ISBN 978-3-8348-0592-8. Here is the possibility to calculate also colums, platforms, beams and also shear situations which show a better behaviour than concrete allone. We hope that a translation of this book is available soon, that we can reconstruct all the theory which is given.[edit] See alsonsities.
  • The UK has been slow to realise the benefits of hybrid concrete construction (HCC), despite the widely appreciated construction benefits. One of the barriers to the use of HCC has been the lack of comprehensive guidance. This has now been addressed by The Concrete Centre's 'Best Practice Guidance for Hybrid Concrete Construction'. Hybrid concrete construction can be described as being 'best of both worlds'. It marries together the advantages of precast and insitu concrete construction with often significant benefits. For example, the adoption of a hybrid concrete frame instead of a composite steel frame on a shell-and core office project in central London resulted in construction savings of 29 percent and a 13 percent increase in net lettable floor area. The time is right for hybrid construction. Reports such as Accelerating Change from the Strategic Forum for Construction and the Egan Rethinking Construction report have focused attention on the need for the UK construction industry to move on from its inherent conservatism and modernise and increase efficiency. The business environment of the UK construction industry is changing. If the industry is to answer its critics and modernise, then it has to examine the potential of different construction techniques and contractual arrangements. In terms of costs, insitu reinforced concrete is commonly viewed as being the most economic framing option while precast concrete promotes speed and factory quality. Combining the two as a hybrid frame results in even greater construction speed, quality and overall economy. Traditional formwork typically accounts for up to 40 percent of an insitu frame costs. These costs can be significantly reduced by increasing the use of precast concrete which has no on-site formwork requirement. This reduces the duration of operations critical to the overall construction programme. Precasting is not constrained by site progress or conditions and can continue independently of on-site operations. Some HCC techniques can remove the need for follow-on trades such as ceilings and finishes. This allows for an even faster programme. HCC also encourages speed of construction by promoting increased buildability, which should be a fundamental design objective. Concrete produces robust, and adaptable buildings that are inherently fire resistant, vibration free and quiet. Exposure of the hybrid concrete frame can be used to exploit concrete's inherent thermal properties in naturally ventilated, low-energy buildings. The finish and shape of the exposed units can also assist with even distribution of lighting levels and the reduction of noise levels. Long spans can be easily achieved using large units or by pre-stressing or post-tensioning. HCC is about providing best value. It is not necessarily about first cost, although this alone can result in hybrid concrete construction being chosen. Gains from improved buildability on site soon overtake any material cost differences. Inherent benefits, such as occupier comfort and increased efficiency, lead to potentially massive cost benefits in comparison with other structural approaches. For the full potential of economy, safety, speed, buildability and performance to be realised then HCC should be considered at the beginning of the design process. The new best practice guidance shows how that full potential can be achieved.
  • There are two methods of fabricating reinforced concrete. The first is to pour the liquid material into forms at the building site; this is so-called in situ concrete. The other method is called precast concrete, in which building components are manufactured in a central plant and later brought to the building site for assembly.Cast-in place concrete also called poured in place or in situ and site cast is poured directly on site.
  • La mezcla se puede disenar en peso o en volumen
  • Bachada. Cantidad de mezcla asfáltica o de concreto que se prepara durante un ciclo del mezclador en las plantas de tipo discontinuo o por peso.
  • Formwork can be a major cost consideration. It can be specially constructed for each project or can be reusable. It needs to be strong and stiff enough to support large weight and fluid pressure of wet concrete. It needs to be tight to prevent loss of liquid . The higher the quality of formwork, the better the resulting concrete apperance. It is coated with an agent to prevent water absorption and unwanted bonding with concrete.
  • “Encofrar” quiere decir formar molde, esto es, crear una forma ennegativo para rellenar y desmoldar en positivo.Fundamentalmente, cuando se habla de concreto se encofra paradarle forma.La función del encofrado es garantizar la forma del elemento de concreto,la colocación del armado y su recubrimiento y que mantengasu posición durante el vertido y vibrado del concreto.El encofrado debe garantizar el buen curado del concreto, evitar lapérdida de agua durante el proceso de fraguado, así como protegerlode las temperaturas externas. Ha de ser estanco; la pérdida de lechadao de mortero (cemento y áridos finos) empobrece el concreto.Por la misma razón, cuando los encofrados son de madera se tienenque humedecer antes de concretoarpara evitar que tomen agua delconcreto y, por lo tanto, absorban cemento.La modificación de la consistencia (fluidez) del concreto fresco(debido al contenido de agua) altera su tiempo de fraguado y, deeste modo, la disminución de agua en la mezcla acelera el procesode fraguado y de endurecimiento. Asimismo, la resistencia del concretodisminuye al aumentar la cantidad del agua de amasado.La colocación de encofrados no debe dañar las estructuras ya existentes,antiguas ni ejecutadas en fases previas de la obra.
  • Hasta hace algunos años el material más común para los encofradosera la madera. Posteriormente la aplicación del acero, el aluminio y elplástico hizo que esta actividad fuese derivando hacia unos procesosmucho más industrializados, de rápido montaje, lo que proporcionauna alta rotación y reduce mucho los tiempos de ejecución.
  • encofradospesados4 encofradosracionalizadosencofradoslivianosMESA VOLADORATREPADORESMUROS Y PILARES
  • La industrialización de los procesos constructivos acorta los tiemposde ejecución de las obras. Al modular se pueden repetir elementosy ahorrar tiempo en el montaje y en el desmontaje.Asimismo, el uso de elementosprefabricados de concretoeliminariesgos en campo; es decir, evita los riesgos que se derivarían de larealización en la obra de los trabajos de encofrado, armado, puestaen obra del concreto y desencofrado de dichos elementos
  • encofradospesados4 encofradosracionalizadosencofradoslivianosMESA VOLADORATREPADORESMUROS Y PILARES
  • encofradospesados4 encofradosracionalizadosencofradoslivianosMESA VOLADORATREPADORESMUROS Y PILARES
  • encofradospesados4 encofradosracionalizadosencofradoslivianosMESA VOLADORATREPADORESMUROS Y PILARES
  • Edificaciónresidencial / No Residencial.􀂉 Posibilidad movimiento mesas: vertical (extracción por fachada) y horizontal (solera).
  • Right after placement, concrete contains up to20% entrapped air. The amount varies accordingto the type of mix and itsslump, the placementmethod, form size, and theamount of reinforcing steelused. Concrete vibration canimprove the compressivestrength of the concrete byabout 3% to 5% for eachpercent of air removed.Vibration consolidatesconcrete in two stages: firstby moving the concreteparticles, then by removingentrapped air.Vibration settles the concreteby subjecting the individualparticles to a rapid succession of impulses, causingdifferential motion (each particle movingindependently of the other). The particles consolidateas trapped air are forced to the surface, allowing the concrete to flow into corners,around rebar and flush against the form face.This eliminates voids (honeycombing) and bringspaste to the surface to assist in finishing. Sinceconcrete flows better with vibration, the mix cancontain less water, thereby providing greaterstrength for the finished product.Until both vibration stages are complete, theconcrete isn’t fully consolidated. If the vibrator isremoved too soon, some of the smaller bubblesdon’t have enough time to move to the surface.Following are terms used in the process of concretevibration:CENTRIFUGAL FORCE—a measure of the ability tomove the mix based on the speed of rotation andsize of the eccentric rotor. The higher the force, theheavier the mix it can move.AMPLITUDE—a measurement of the outermostdistance the vibrator head will move from its staticaxis; important with large aggregate mixes.FREQUENCY— measured by vibrations perminute, or VPM, the speed at which the vibratorhead moves within the confines of its amplitude.High VPM vibrators (up to 12,000 VPM) willprimarily affect fine particles. This is ideal becausethe majority of the trapped air occursaround these particles. High VPM gives thecement paste the opportunity to coat these fineparticles after the air is removed, thus helping tounify the mass. Frequency liquefies or moves theconcrete mix. The greater the VPM, the greaterthe ability to liquefy stiff mixes.Truck agitator for ready mixed concrete (PCA No.69926)Cast-in-place concrete is transported in an unhardened state, primarily as ready-mix, and placed in forms. Ready mixed concrete is proportioned and mixed off the project site. The concrete is delivered to the site in a truck agitator (often incorrectly called a “cement truck”) but can also be delivered in a non-agitating truck. Specialized paving equipment may be used to mix and spread concrete for pavement.   Most foundations and slabs-on-ground Walls, beams, columns, floors, roofs Large portions of bridges, pavements, and other infrastructure. Concrete was selected for ceilings, floors and framing inside this station. (PCA No. 10074)Cast-in-place concrete is the material of choice for slab-on-ground and foundations because of its long-term durability and structural support. It is also used in all types of buildings for either structural support as beams and columns, as well as for floors, walls, and roofs.  Ready mixed concrete has many environmental benefits during construction and for the life of the structure.  See associated sustainability solutions and technical briefs (right) for more detail. During construction:  Waste Minimization.  Concrete is ordered and placed as needed and does not need to be trimmed or cut after installation.  Wash water is frequently recycled using trucks equipped with devices that collect wash water and return it to the drum where it can be returned to the ready mixed concrete plant for recycling. Extra concrete is often returned to the ready-mix plant where it is recycled or used to make jersey barriers or retaining wall blocks; or it can be washed to recycle the coarse aggregate. Special set retarding admixtures can be added to returned concrete to allow for storage and future use.  Local. Materials are usually extracted and manufactured locally.  May contribute to LEED Credit M 5.Recycled content. Fly ash, slag cement, or silica fume can substitute partially for cement, and recycled aggregates can replace newly mined gravel.  Recycled content can contribute to LEED Credit M 4.During the life of the structure:Energy Performance and Thermal Mass. Thermal mass improves energy performance when appropriately insulated. When 3 in. or more in thickness, concrete forms an air barrier.  May contribute to LEED Credit EA 1.Durable.  Concrete stands up to natural disasters, wind-driven rain, moisture damage, and vermin.  Less replacement means reduced resource requirements. Cool. Using light- or natural-colored material helps reduce the heat island affect. When used for exposed horizontal surfaces may contribute to LEED Credit SS 7.Low emitting. Concrete has low VOC emission and does not degrade indoor air quality. Recyclable.  Concrete is commonly recycled in urban areas into fill and road base material at the end of service life.   When existing concrete is recycled during construction, may contribute to LEED Credit M 2.Concrete was the primary building material used to construct the Pierce Transit North End Turna Around Facility in Tacoma, Washington.  A pedestrian ramp snakes between more than 60 cast-in-place waterfall and landscaping containers at the Turnaround.  The ramp connects the assembly plaza with the downtown transit bus transfer area below.  The compex geometry of the project, combined with the watertightness and durability considerations, made concrete the logical choice. (PCA No. 10088). Mix. The design professional specifies the appropriate concrete properties for a particular project and use, and an appropriate mix design is developed. The mix design specifies the amount and type of cementitious materials, water, and aggregate (sand, gravel, or crushed rock). Mixing, transporting, and handling of concrete are coordinated with placing and finishing operations. Placement. Concrete should not be placed more rapidly than it can be spread, struck off, and consolidated. It should be deposited continuously as near as possible to its final position. In many types of construction, concrete is placed in forms and consolidated. Consolidation compacts fresh concrete to mold it within the forms around embedded items and reinforcement and eliminates stone pockets, honeycombing, and entrapped air. Vibration is the most widely used method for consolidating concrete. Self-compacting concrete, also referred to self-consolidating concrete, is able to flow and consolidate under its own weight and requires no vibration. Curing. After the concrete is placed, a satisfactory moisture content and temperature is required for concrete to develop adequate strength and durability; this is called the curing process. Curing compounds or other surface treatments prevent the rapid loss of moisture from the surface of concrete and aid in the curing process. Finishing. Exposed concrete surfaces, usually the top surface, generally require finishing if they will be visible. This includes driveways, pavements, sidewalks, floors, slabs, and other flatwork. Options include various colors and textures, such as exposed aggregate or a pattern-stamped surface. Some surfaces may require only strikeoff or screeding (which removes excess concrete and evens out the exposed surface) to the proper contour and elevation. Other surfaces may have a broomed, floated, or trowel finish. Sawcut joints, if required, are made after the concrete is sufficiently hard or strong to prevent raveling (is the disintegration of the surface to leave loose or protruding aggregates).
  • Curing. After the concrete is placed, a satisfactory moisture content and temperature is required for concrete to develop adequate strength and durability; this is called the curing process. Curing compounds or other surface treatments prevent the rapid loss of moisture from the surface of concrete and aid in the curing process. Why cure concrete?Curing serves two main purposes.It retains moisture in the slab so that the concrete continues to gain strength.  It delays drying shrinkage until the concrete is strong enough to resist shrinkage cracking. All the desirable properties of concrete are improved by proper curing!In all but the least critical applications, care needs to be taken to properly cure concrete, and achieve best strength and hardness. This happens after the concrete has been placed. Cement requires a moist, controlled environment to gain strength and harden fully. The cement paste hardens over time, initially setting and becoming rigid though very weak, and gaining in strength in the days and weeks following. In around 3 weeks, over 90% of the final strength is typically reached though it may continue to strengthen for decades.[17]Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained significant strength, resulting in greater shrinkage cracking. The early strength of the concrete can be increased by keeping it damp for a longer period during the curing process. Minimizing stress prior to curing minimizes cracking. High early-strength concrete is designed to hydrate faster, often by increased use of cement which increases shrinkage and cracking.During this period concrete needs to be in conditions with a controlled temperature and humid atmosphere. In practice, this is achieved by spraying or ponding the concrete surface with water, thereby protecting concrete mass from ill effects of ambient conditions. The pictures to the right show two of many ways to achieve this, ponding – submerging setting concrete in water, and wrapping in plastic to contain the water in the mix.Properly curing concrete leads to increased strength and lower permeability, and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing, or overheating due to the exothermic setting of cement (the Hoover Dam used pipes carrying coolant during setting to avoid damaging overheating). Improper curing can cause scaling, reduced strength, poor abrasion resistance and cracking.Finishing. Exposed concrete surfaces, usually the top surface, generally require finishing if they will be visible. This includes driveways, pavements, sidewalks, floors, slabs, and other flatwork. Options include various colors and textures, such as exposed aggregate or a pattern-stamped surface. Some surfaces may require only strikeoff or screeding (which removes excess concrete and evens out the exposed surface) to the proper contour and elevation. Other surfaces may have a broomed, floated, or trowel finish. Sawcut joints, if required, are made after the concrete is sufficiently hard or strong to prevent raveling (is the disintegration of the surface to leave loose or protruding aggregates).
  • Con-Tech es un sistema de construcción industrializado que utiliza módulos de aluminio fundido de diferentesdimensiones, que ensamblados conforman la formaleta para los muros de la edificación. Con el sistema se puedenrealizar los trabajos de colocación del refuerzo, instalaciones, formaleta y fundida del concreto en un solo día,dejando un tiempo adecuado para que el concreto fragüe y se pueda repetir el mismo proceso al día siguiente. Elsistema está compuesto esencialmente por moldes de aluminio fundido, separadores, pasadores y cuñas.
  • El sistema permite la modulació n de diferentes ambientes, variando el dise􀀀 o de un proyecto a otro, por la mismaconfiguració n de paneles peque􀀀 os que se arman. Prcticamente la limitació n en cuanto a ambientes estdada porel sistema de placa a utilizar, que determina las luces entre los muros. Fuera de su utilizació n en edificios, enColombia se ha empleado la formaleta para la construcció n en serie de casas de uno y dos pisos. De igual manerala formaleta permite su utilizació n en la construcció n de muros de cerramiento y construcciones peque􀀀 as. Debido altipo de sistema y a su modulació n, presenta cierta rigidez en tama􀀀 os y distribució n de espacios, que solo essuperable mediante unidades especiales que elevan el costo final.
  • El sistema permite la modulació n de diferentes ambientes, variando el dise􀀀 o de un proyecto a otro, por la mismaconfiguració n de paneles peque􀀀 os que se arman. Prcticamente la limitació n en cuanto a ambientes estdada porel sistema de placa a utilizar, que determina las luces entre los muros. Fuera de su utilizació n en edificios, enColombia se ha empleado la formaleta para la construcció n en serie de casas de uno y dos pisos. De igual manerala formaleta permite su utilizació n en la construcció n de muros de cerramiento y construcciones peque􀀀 as. Debido altipo de sistema y a su modulació n, presenta cierta rigidez en tama􀀀 os y distribució n de espacios, que solo esSuperabEl sistema Con–Tech fue inventado por un pequeño contratista en construcciones de concreto en Iowa (EstadosUnidos) a principios de los años 60. Su inicio se basó en la utilización de moldes de aleaciones de aluminio parapoder incorporar por medio de las cualidades de este metal, características que no se encontraban disponibles enotro tipo de encofrados como son la precisión de la pared terminada, la fuerte definición de la textura en la superficiede la pared, su alta resistencia con relación a su peso, y su buena vida útil.El inventor y un contratista iniciaron su desarrollo comercial en una escala limitada. A fines de los años 60 lacompañía fue vendida a Daniel K. Ludwing, quién la utilizó para construcciones de su propia compañía y luego lacomercializó a otros contratistas. Actualmente este sistema está siendo utilizado por contratistas en cerca de 53países para construir apartamentos, viviendas y centros comerciales.Con-Tech es un sistema de construcción industrializado que utiliza módulos de aluminio fundido de diferentesdimensiones, que ensamblados conforman la formaleta para los muros de la edificación. Con el sistema se puedenrealizar los trabajos de colocación del refuerzo, instalaciones, formaleta y fundida del concreto en un solo día,dejando un tiempo adecuado para que el concreto fragüe y se pueda repetir el mismo proceso al día siguiente. Elsistema está compuesto esencialmente por moldes de aluminio fundido, separadores, pasadores y cuñas.le mediante unidades especiales que elevan el costo final.
  • El principio b􀀀 sico es lograr que todas las actividades se realicen entre las 8 de la maana y las 6 de la tarde de cadadía, dejando un tiempo de 14 horas para el fraguado del concreto, suficiente para que este tenga una resistenciaadecuada para poder retirar los encofrados y repetir el ciclo.Es un sistema rígido puesto que los tneles no permiten la utilizació n de diversas alturas y tambin limitanlasluces.Se pueden manejar formas con 􀀀 ngulos diferentes al de 90º, adicionando secciones en diagonal, que permitenobtener secciones diferentes a la típica rectangular. Para construir las fachadas, se permite el empleo de otrasalternativas que van desde el uso de materiales como el concreto y elementos pre fabricados, hasta fachadasflotantes en vidrio. ( ! ! $ # ' ! % # )La forma del encofrado es el medio tnel o coquillo, consistente en una secció n rectangular compuesta por un panelvertical (P.V.) de una altura igual a la del muro a fundir y un panel horizontal (P.H). Ambos paneles est􀀀 nensamblados entre sí mediante pernos formando un 􀀀 ngulo. Este sistema puede ser utilizado para mltiplesproyectos. # ) ) " ! $ * # ! ! %El acabado superficial es completamente liso, ya que la superficie de los paneles es una plancha lisa de acero. Estenivel de acabado permite un ahorro entre el 85% y el 90 % por concepto de paetes, estucos y remates. Si se deseaun acabado superficial con textura, es posible adherir a la cara del panel elementos pl􀀀 sticos con diferentes motivos.El material que el sistema proporciona a la fachada es el concreto tratado, lo cual proporciona una gama de coloresmuy reducida, que só lo es ampliable con pintura en obra, con su correspondiente costo tanto en el momento deaplicació n como para su mantenimiento.
  • El principio b􀀀 sico es lograr que todas las actividades se realicen entre las 8 de la maana y las 6 de la tarde de cadadía, dejando un tiempo de 14 horas para el fraguado del concreto, suficiente para que este tenga una resistenciaadecuada para poder retirar los encofrados y repetir el ciclo.Es un sistema rígido puesto que los tneles no permiten la utilizació n de diversas alturas y tambin limitanlasluces.Se pueden manejar formas con 􀀀 ngulos diferentes al de 90º, adicionando secciones en diagonal, que permitenobtener secciones diferentes a la típica rectangular. Para construir las fachadas, se permite el empleo de otrasalternativas que van desde el uso de materiales como el concreto y elementos pre fabricados, hasta fachadasflotantes en vidrio. ( ! ! $ # ' ! % # )La forma del encofrado es el medio tnel o coquillo, consistente en una secció n rectangular compuesta por un panelvertical (P.V.) de una altura igual a la del muro a fundir y un panel horizontal (P.H). Ambos paneles est􀀀 nensamblados entre sí mediante pernos formando un 􀀀 ngulo. Este sistema puede ser utilizado para mltiplesproyectos. # ) ) " ! $ * # ! ! %El acabado superficial es completamente liso, ya que la superficie de los paneles es una plancha lisa de acero. Estenivel de acabado permite un ahorro entre el 85% y el 90 % por concepto de paetes, estucos y remates. Si se deseaun acabado superficial con textura, es posible adherir a la cara del panel elementos pl􀀀 sticos con diferentes motivos.El material que el sistema proporciona a la fachada es el concreto tratado, lo cual proporciona una gama de coloresmuy reducida, que só lo es ampliable con pintura en obra, con su correspondiente costo tanto en el momento deaplicació n como para su mantenimiento.
  • El principio b􀀀 sico es lograr que todas las actividades se realicen entre las 8 de la maana y las 6 de la tarde de cadadía, dejando un tiempo de 14 horas para el fraguado del concreto, suficiente para que este tenga una resistenciaadecuada para poder retirar los encofrados y repetir el ciclo.Es un sistema rígido puesto que los tneles no permiten la utilizació n de diversas alturas y tambin limitanlasluces.Se pueden manejar formas con 􀀀 ngulos diferentes al de 90º, adicionando secciones en diagonal, que permitenobtener secciones diferentes a la típica rectangular. Para construir las fachadas, se permite el empleo de otrasalternativas que van desde el uso de materiales como el concreto y elementos pre fabricados, hasta fachadasflotantes en vidrio. ( ! ! $ # ' ! % # )La forma del encofrado es el medio tnel o coquillo, consistente en una secció n rectangular compuesta por un panelvertical (P.V.) de una altura igual a la del muro a fundir y un panel horizontal (P.H). Ambos paneles est􀀀 nensamblados entre sí mediante pernos formando un 􀀀 ngulo. Este sistema puede ser utilizado para mltiplesproyectos. # ) ) " ! $ * # ! ! %El acabado superficial es completamente liso, ya que la superficie de los paneles es una plancha lisa de acero. Estenivel de acabado permite un ahorro entre el 85% y el 90 % por concepto de paetes, estucos y remates. Si se deseaun acabado superficial con textura, es posible adherir a la cara del panel elementos pl􀀀 sticos con diferentes motivos.El material que el sistema proporciona a la fachada es el concreto tratado, lo cual proporciona una gama de coloresmuy reducida, que só lo es ampliable con pintura en obra, con su correspondiente costo tanto en el momento deaplicació n como para su mantenimiento.
  • El principio b􀀀 sico es lograr que todas las actividades se realicen entre las 8 de la maana y las 6 de la tarde de cadadía, dejando un tiempo de 14 horas para el fraguado del concreto, suficiente para que este tenga una resistenciaadecuada para poder retirar los encofrados y repetir el ciclo.Es un sistema rígido puesto que los tneles no permiten la utilizació n de diversas alturas y tambin limitanlasluces.Se pueden manejar formas con 􀀀 ngulos diferentes al de 90º, adicionando secciones en diagonal, que permitenobtener secciones diferentes a la típica rectangular. Para construir las fachadas, se permite el empleo de otrasalternativas que van desde el uso de materiales como el concreto y elementos pre fabricados, hasta fachadasflotantes en vidrio. ( ! ! $ # ' ! % # )La forma del encofrado es el medio tnel o coquillo, consistente en una secció n rectangular compuesta por un panelvertical (P.V.) de una altura igual a la del muro a fundir y un panel horizontal (P.H). Ambos paneles est􀀀 nensamblados entre sí mediante pernos formando un 􀀀 ngulo. Este sistema puede ser utilizado para mltiplesproyectos. # ) ) " ! $ * # ! ! %El acabado superficial es completamente liso, ya que la superficie de los paneles es una plancha lisa de acero. Estenivel de acabado permite un ahorro entre el 85% y el 90 % por concepto de paetes, estucos y remates. Si se deseaun acabado superficial con textura, es posible adherir a la cara del panel elementos pl􀀀 sticos con diferentes motivos.El material que el sistema proporciona a la fachada es el concreto tratado, lo cual proporciona una gama de coloresmuy reducida, que só lo es ampliable con pintura en obra, con su correspondiente costo tanto en el momento deaplicació n como para su mantenimiento.
  • Este tipo de losa consta de una sección de concreto reforzado en dos direcciones.Dependiendo de cómo este apoyada, una losa maciza deberá tener mayor cantidad de refuerzo en un sentido que en el otro.Si la losa dispone de muros de apoyo en los cuatro lados su dirección principal será la del sentido mas corto, si es cuadrada cualquiera de los dos sentidos es igual.Si la losa dispone de muros en solo dos lados (deben ser opuestos), la dirección principal será en la dirección perpendicular a la dirección de los apoyos.Preparación: Se deben alistar los materiales, consultar las especificaciones (forma, espesor, etc.) y nivelar el piso desde donde se van a tomar las medidas.Apuntalado: Se colocan los largueros paralelos en los muros, apoyados sobre puntales cada 60 cm. Se procede a nivelar los largueros y cuñar los puntales. Los puntales se deben arriostrar (sostener con diagonales) para evitar su caída por desplazamiento lateral.Formaleta: Se colocan las tablas apoyadas entre los largueros formando una superficie lo mas ajustada que se pueda para que no se escape el concreto por entre los espacios. La formaleta debe quedar nivelada.Armar el refuerzo: Se debe colocar el refuerzo calculado sobre la formaleta, apoyado de tal forma que al vaciar el concreto, el refuerzo quede totalmente rodeado por éste. El recubrimiento mínimo de concreto sobre el acero debe ser de 4 cm.Vaciado del concreto: Se debe hacer con cuidado para evitar que la formaleta se pueda caer. Recordando los cuidados y el procedimiento para hacer y vaciar concreto.
  • En este tipo de losa parte del concreto se reemplaza por otros materiales como cajones de madera, guadua y principalmente cuando se trata de viviendas de uno y dos pisos se reemplaza por ladrillos o bloques. De esta forma se disminuye el peso de la losa y se pueden cubrir mayores luces de manera mas económica.En este sistema, la losa tiene cuatro componentes: una torta inferior que se coloca sobre las tablas de la formaleta; los bloques o elementos aligerantes; la torta o plaqueta superior con refuerzo nominal y las viguetas en concreto reforzado.La torta inferior es un mortero con dosificación de 1:3 de 2 cm de espesor que permite cubrir el aligeramiento y el refuerzo principal de la losa o elementos aligerantes. Los bloques o elementos aligerantes se colocan de tal manera que formen las cavidades de las viguetas con separaciones entre si, entre 50 y 70 cm (promedio de 60 cm). La plaqueta superior es un concreto fundido monolítico con el sistema de piso , con 5.0 cm de espesor y debe tener un refuerzo de 1 varilla de ¼ de pulgada (numero 2) cada 30 cm en las dos direcciones.Las viguetas contienen el refuerzo principal. El ancho medio de viguetas es de 8 cm. Su altura se calcula según la luz (espacio a cubrir).El refuerzo superior e inferior se distribuye como se muestra.Todo el refuerzo a utilizar debe ser corrugado con fy = 420 Mpa = 4200 kg/cm² excepto las barras para los estribos No. 2 que tienen fy = 240 Mpa = 2400 kg/cm²
  • Según la magnitud de la carga por transmitir, la losa puede apoyar directamente sobre las columnas o a través de ábacos, capiteles o una combinación de ambos. En niEl punzonamiento es un esfuerzo producido por tracciones en una pieza debidas a los esfuerzos tangenciales originados por una carga localizada en una superficie pequeña de un elemento bidireccional de concreto, alrededor de su soporte. Este esfuerzo de punzonamiento produce un efecto puntual sobre su plano de apoyo. Debe tenerse en cuenta que este efecto puede aparecer en los forjados reticulares y en losas macizas. La rotura aparece de improviso, bruscamente y sin aviso produciendo consecuencias muchas veces fatales en los habitantes del lugar.La superficie crítica de punzonamiento es la superficie de rotura, que abarca el perímetro donde apoya la losa .ngún caso se admitirá que las columnas de orilla sobresalgan del borde de la losa.
  • Según la magnitud de la carga por transmitir, la losa puede apoyar directamente sobre las columnas o a través de ábacos, capiteles o una combinación de ambos. En niEl punzonamiento es un esfuerzo producido por tracciones en una pieza debidas a los esfuerzos tangenciales originados por una carga localizada en una superficie pequeña de un elemento bidireccional de concreto, alrededor de su soporte. Este esfuerzo de punzonamiento produce un efecto puntual sobre su plano de apoyo. Debe tenerse en cuenta que este efecto puede aparecer en los forjados reticulares y en losas macizas. La rotura aparece de improviso, bruscamente y sin aviso produciendo consecuencias muchas veces fatales en los habitantes del lugar.La superficie crítica de punzonamiento es la superficie de rotura, que abarca el perímetro donde apoya la losa .ngún caso se admitirá que las columnas de orilla sobresalgan del borde de la losa.
  • Precast concrete is a form of construction, where concrete is cast in a reusable mould or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. In contrast, standard concrete is poured into site specific forms and cured on site. Precast stone is distinguished from precast concrete by using a fine aggregate in the mixture so the final product approaches the appearance of naturally occurring rock or stone.By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. Many states across the United States require a precast plant to be certified (either by NPCA or PCI) for a precast producer to supply their product to a construction site sponsored by State and Federal DOTs.Ancient Roman builders made use of concrete and soon poured the material into molds to build their complex network of aqueducts, culverts and tunnels. Modern uses for precast technology include a variety of architectural and structural applications featuring parts of or an entire building system. Precast architectural panels are also used to clad all or part of a building facade free-standing walls used for landscaping, soundproofing and security walls. Stormwater drainage, water and sewage pipes and tunnels make use of precast concrete units. The advantages of using precast concrete is the increased quality of the material, when formed in controlled conditions, and the reduced cost of constructing large forms used with concrete poured on site.There are many different types of precast concrete forming systems for architectural applications, differing in size, function and cost.The New South Wales Government Railways made extensive use of precast concrete construction for its stations and similar buildings. Between 1917 and 1932, they erected 145 such buildings[1].
  • In the United States, a concrete masonry unit (CMU) — also called concrete block, cement block or foundation block — is a large rectangular brick used in construction. Concrete blocks are made from castconcrete, i.e. Portland cement and aggregate, usually sand and fine gravel for high-density blocks. Lower density blocks may use industrial wastes as an aggregate. Those that use cinders (fly ash or bottom ash) are called cinder blocks in the US and breeze blocks (breeze is a synonym of ash)[1] in the UK. Clinker blocks use clinker as aggregate. In non-technical usage, the terms 'cinder block' and 'breeze block' are often generalized to cover all of these varieties. Lightweight blocks can also be produced using aerated concrete.Contents[hide]1 Sizes and structure2 Uses3 Gallery4 See also5 References6 External links[edit] Sizes and structureConcrete blocks may be produced with hollow centres to reduce weight or improve insulation. The use of blockwork allows structures to be built in the traditional masonry style with layers (or courses) of overlapping blocks. Blocks come in many sizes. In the US, the most common size is 8 in × 8 in × 16 in (20 cm × 20 cm × 41 cm); the actual size is usually about 3/8 in (1 cm) smaller to allow for mortar joints. In the UK, blocks are usually 44 cm × 21.5 cm × 10 cm excluding mortar joints (approximately 17.3 in × 8.5 in × 3.9 in).[edit] UsesConcrete block, when reinforced with concrete columns and tie beams, is a very common building material for the load-bearing walls of buildings, in what is termed "concrete block structure" (CBS) construction. American suburbanhouses typically employ a concrete foundation and slab with a concrete block wall on the perimeter. Large buildings typically use copious amounts of concrete block; for even larger buildings, concrete block supplements steelI-beams. Tilt-wall construction, however, is replacing CBS for some large structures. The holes inside concrete block allow rebar and concrete (creating reinforced concrete) to run vertically through the block to compensate for the lack of tensile strength. Because most people find the appearance of concrete block to be drab and unattractive, exposed surfaces are generally given a decorative finish of stucco, brick, paint or siding.This makes glazed masonry an ideal fit for areas in which special attention must be paid to moisture issues and sanitation codes. This includes car washes, pools, locker rooms, shower stalls and dining areas such as cafeterias and commercial kitchens.In the United States, concrete masonry standards are maintained by the National Concrete Masonry Association.Breeze blocks are no longer used in the UK[2] because of their low compressive strength.[citation needed] Despite this, the term is still widely used to refer to concrete blocks more generally.
  • Developed in Sweden in the late 1920s, autoclaved cellular concrete (ACC) is a lightweight precast concrete building material that is cured under elevated pressure inside special kilns called autoclaves. Though ACC has been used successfully throughout most of the world since the end of World War II, ACC made a mark in the United States only recently. ACC, sometimes known as autoclaved aerated concrete, is made with all fine materials-nothing coarser than finely ground sand. What makes ACC different from lightweight aggregate concrete is that ACC contains millions of microscopic cells that are generated during the manufacturing process. In addition, ACC is unlike many other concrete products because it may be drilled, sawed, chiseled, nailed, or screwed using conventional carpentry tools. Several FormulasAlthough several formulas are used for manufacturing ACC, the basic raw materials are portland cement, limestone, aluminum powder, water, and a large proportion of a silica-rich material-usually sand or fly ash. Once raw materials are mixed into a slurry and poured into greased molds, the aluminum powder reacts chemically to create millions of tiny hydrogen gas bubbles. These microscopic, unconnected cells cause the material to expand to nearly twice its original volume—similar to the rising of bread dough—imparting the lightweight cellular quality to ACC. After a setting time ranging from 30 minutes to 4 hours, the foam-like material is hard enough to be wire cut into the desired shapes and moved into an autoclave for curing. The autoclave uses high-pressure steam at temperatures of about 356° F (180°C) to accelerate the hydration of the concrete and spur a second chemical reaction that gives ACC its strength, rigidity, and dimensional stability. Autoclaving can produce in 8 to 14 hours concrete strengths equal to strengths obtained in a concrete moist-cured for 28 days at 70° F (21°C). The final products are usually shrink wrapped in plastic and transported directly to the construction site. ACC, which is about one-fourth of the weight of conventional concrete, is available in blocks, wall and roof panels, lintels, and floor slabs. Each of these products can be manufactured in a range of sizes depending on specific applications, allowing for maximum efficiency and flexibility in construction. ACC can be used for all types of structures ranging from single-family housing to large industrial complexes. ACC is an inert, nontoxic substance that has an energy-efficient and pollution-free manufacturing process. Perhaps the most significant environmental benefit of using ACC is that fly ash can be used as the silica-rich component. The electric utility industry generates more than 50 million tons of fly ash each year—only a fraction of which can be recycled. ACC is reasonably frost and sulfate resistant, allowing it to be used around the world in all climatic zones and for a wide range of applications. When it is used on the exterior, ACC is normally protected by stucco or other protective coatings. ACC also is an inorganic material, making it 100 percent termite and vermin proof and resistant to rotting and mold. Autoclaved Aerated concrete (AAC), or otherwise known as Autoclave Cellular Concrete (ACC), is a lightweight, precast building material. AAC provides structure, insulation, fire and mold resistance in a single material. AAC products include blocks, wall panels, floor and roof panels, and lintels.It has since been refined into a high thermally insulating concrete-based material used for construction both internally and externally. Besides insulating capability, one of AAC's advantages in construction is its quick and easy installation since the material can be routed, sanded and cut to size on site using standard carbon steel band saws, hand saws and drills.Even though regular cement mortar can be used, 98% of the buildings erected with AAC materials uses thin bed mortar, which comes to deployment in a thickness of 1/8 inch. This varies on national building codes and creates solid and compact building members. AAC material can be coated with a stucco compound or plaster against the elements. Siding materials such as brick or vinyl siding can also be used to cover the outside of AAC materials.Produced for more than 70 years, AAC offers considerable advantages over other construction materials, one of the most important being its very low environmental impact.AAC’s high resource efficiency gives it low environmental impact in all phases of its life cycle, from processing of raw materials to the disposal of AAC waste.AAC’s light weight also saves energy in transportation. The fact that AAC is up to five times lighter than concrete leads to significant reductions in CO2 emissions during transport. To reduce the need for transportation, AAC manufacturers apply the principle of producing as near to their consumer market as possible.AAC’s excellent thermal efficiency makes a major contribution to environmental protection by sharply reducing the need for space heating and cooling in buildings.In addition, AAC’s easy workability allows accurate cutting that minimizes the generation of solid waste during use. Unlike other building materials AAC can eliminate the need to be used in combination with insulation products, which increase the environmental impact and cost of construction.Autoclaved aerated concrete AAC is a very strong but lightweight and easy-to-use construction material for outdoors and indoors alike. The production process involves curing aerated concrete in a pressurised steam chamber, known as an autoclave, to give AAC its strength.  Produced for more than 70 years, AAC offers considerable advantages over other construction materials: • Great energy efficiency - AAC has excellent thermal insulation properties, reducing the need for space heating or air conditioning  • Excellent fire resistance - AAC provides the ultimate security against fire, resisting even intense heat and easily fulfilling all fire safety standards  • Outstanding structural performance - AAC has an extremely high strength to weight ratio and is stable, making it the construction material of choice for all buildings including earthquake zones • High resource efficiency - AAC is much lighter than brick or concrete and does not usually need to be combined with insulation materials, so it is extremely cost-effective • Low environmental impact - AAC is a natural product made from lime, cement, fine sand, other siliceous materials, water and small amounts of aluminium powder. No raw materials are wasted in the production process, and AAC from demolition sites can be reused or recycled • Sound insulation - AAC has excellent sound insulation properties compared to other building materials with the same weight
  • Developed in Sweden in the late 1920s, autoclaved cellular concrete (ACC) is a lightweight precast concrete building material that is cured under elevated pressure inside special kilns called autoclaves. Though ACC has been used successfully throughout most of the world since the end of World War II, ACC made a mark in the United States only recently. ACC, sometimes known as autoclaved aerated concrete, is made with all fine materials-nothing coarser than finely ground sand. What makes ACC different from lightweight aggregate concrete is that ACC contains millions of microscopic cells that are generated during the manufacturing process. In addition, ACC is unlike many other concrete products because it may be drilled, sawed, chiseled, nailed, or screwed using conventional carpentry tools. Several FormulasAlthough several formulas are used for manufacturing ACC, the basic raw materials are portland cement, limestone, aluminum powder, water, and a large proportion of a silica-rich material-usually sand or fly ash. Once raw materials are mixed into a slurry and poured into greased molds, the aluminum powder reacts chemically to create millions of tiny hydrogen gas bubbles. These microscopic, unconnected cells cause the material to expand to nearly twice its original volume—similar to the rising of bread dough—imparting the lightweight cellular quality to ACC. After a setting time ranging from 30 minutes to 4 hours, the foam-like material is hard enough to be wire cut into the desired shapes and moved into an autoclave for curing. The autoclave uses high-pressure steam at temperatures of about 356° F (180°C) to accelerate the hydration of the concrete and spur a second chemical reaction that gives ACC its strength, rigidity, and dimensional stability. Autoclaving can produce in 8 to 14 hours concrete strengths equal to strengths obtained in a concrete moist-cured for 28 days at 70° F (21°C). The final products are usually shrink wrapped in plastic and transported directly to the construction site. ACC, which is about one-fourth of the weight of conventional concrete, is available in blocks, wall and roof panels, lintels, and floor slabs. Each of these products can be manufactured in a range of sizes depending on specific applications, allowing for maximum efficiency and flexibility in construction. ACC can be used for all types of structures ranging from single-family housing to large industrial complexes. ACC is an inert, nontoxic substance that has an energy-efficient and pollution-free manufacturing process. Perhaps the most significant environmental benefit of using ACC is that fly ash can be used as the silica-rich component. The electric utility industry generates more than 50 million tons of fly ash each year—only a fraction of which can be recycled. ACC is reasonably frost and sulfate resistant, allowing it to be used around the world in all climatic zones and for a wide range of applications. When it is used on the exterior, ACC is normally protected by stucco or other protective coatings. ACC also is an inorganic material, making it 100 percent termite and vermin proof and resistant to rotting and mold. Autoclaved Aerated concrete (AAC), or otherwise known as Autoclave Cellular Concrete (ACC), is a lightweight, precast building material. AAC provides structure, insulation, fire and mold resistance in a single material. AAC products include blocks, wall panels, floor and roof panels, and lintels.It has since been refined into a high thermally insulating concrete-based material used for construction both internally and externally. Besides insulating capability, one of AAC's advantages in construction is its quick and easy installation since the material can be routed, sanded and cut to size on site using standard carbon steel band saws, hand saws and drills.Even though regular cement mortar can be used, 98% of the buildings erected with AAC materials uses thin bed mortar, which comes to deployment in a thickness of 1/8 inch. This varies on national building codes and creates solid and compact building members. AAC material can be coated with a stucco compound or plaster against the elements. Siding materials such as brick or vinyl siding can also be used to cover the outside of AAC materials.Produced for more than 70 years, AAC offers considerable advantages over other construction materials, one of the most important being its very low environmental impact.AAC’s high resource efficiency gives it low environmental impact in all phases of its life cycle, from processing of raw materials to the disposal of AAC waste.AAC’s light weight also saves energy in transportation. The fact that AAC is up to five times lighter than concrete leads to significant reductions in CO2 emissions during transport. To reduce the need for transportation, AAC manufacturers apply the principle of producing as near to their consumer market as possible.AAC’s excellent thermal efficiency makes a major contribution to environmental protection by sharply reducing the need for space heating and cooling in buildings.In addition, AAC’s easy workability allows accurate cutting that minimizes the generation of solid waste during use. Unlike other building materials AAC can eliminate the need to be used in combination with insulation products, which increase the environmental impact and cost of construction.Autoclaved aerated concrete AAC is a very strong but lightweight and easy-to-use construction material for outdoors and indoors alike. The production process involves curing aerated concrete in a pressurised steam chamber, known as an autoclave, to give AAC its strength.  Produced for more than 70 years, AAC offers considerable advantages over other construction materials: • Great energy efficiency - AAC has excellent thermal insulation properties, reducing the need for space heating or air conditioning  • Excellent fire resistance - AAC provides the ultimate security against fire, resisting even intense heat and easily fulfilling all fire safety standards  • Outstanding structural performance - AAC has an extremely high strength to weight ratio and is stable, making it the construction material of choice for all buildings including earthquake zones • High resource efficiency - AAC is much lighter than brick or concrete and does not usually need to be combined with insulation materials, so it is extremely cost-effective • Low environmental impact - AAC is a natural product made from lime, cement, fine sand, other siliceous materials, water and small amounts of aluminium powder. No raw materials are wasted in the production process, and AAC from demolition sites can be reused or recycled • Sound insulation - AAC has excellent sound insulation properties compared to other building materials with the same weight
  • Concrete Contractor Home > Tilt-up Construction: History and Uses Tilt-up Construction: History and UsesIt all started with a flowerpot.In 1849, French gardener Joseph Monier wanted to make a more durable flowerpot, so he used iron mesh to reinforce garden pots and tubs. That was the beginning of reinforced concrete and the basis of tilt-up concrete (in some regions referred to as tiltwall or precast panel concrete), an idea that wouldn't be fully developed until more than 50 years later.In the early years of the 20th century, concrete was rapidly becoming the most popular building material. The world saw many firsts in those early decades: the first concrete streets, houses and high rises. Back then, concrete was solely produced off-site and walls were built vertically. But in the early 1900s, Robert Aiken was designing and building reinforced retaining walls at the Camp Logan Rifle Range in Illinois. Instead of using the usual method in making concrete walls, Aiken poured the walls in wall panels flat on the ground, like a sidewalk, and tilted the panels up onto a prepared foundation to form the walls. Steel rods were then used to anchor the walls to concrete footers. Thus, tilt-up concrete construction was born. Aiken, who became known as the father of tilt-up concrete, soon realized that this method would be advantageous in other structures and used it on a number of buildings throughout Illinois. The first complete tilt-up building was a concrete factory on Aiken's own farm near Zion City, Illinois. Aiken poured the walls flat on a bed of sand, around door and window fames, and then tipped them up onto their foundation. In 1906, Aiken used the tilt-up method to construct the Memorial Methodist Church in Zion, as well as a two-story ammunition and gun house at Camp Logan. From here, Aiken refined his methods to include a steel tipping table that was used in the construction of 15 buildings in five different states.  Thomas Edison and a model of his tilt-up concrete houses in Union New Jersey.  Thomas Edison, that intrepid inventor, saw the writing on the wall and realized that tilt-up construction was the way of the future. In 1908 he created an entire village of tilt-up concrete houses in Union, New Jersey that is still standing almost 100 years later. Although Aiken's steel tipping table made tilt-up construction easier, the new method of building with concrete didn't really start gaining popularity until the development of the mobile crane in the late 1940s. The mobile crane allowed large panels to be lifted into place with much greater ease than before. Ready-mix concrete also came about around this same time, allowing tilt-up construction to become even more efficient a method of building commercial structures. These innovations couldn't have come at a better time. After World War II, business was booming in the United States and there was a great need for commercial and industrial structures. Because tilt-up concrete allowed builders to offer high quality projects at an economical price and with a reduced construction schedule, it became very popular. The tilt-up structures built in that era are still wearing their age well. Even the first tilt-up buildings are still being used today, a testimony to their strength and durability. In 1994, tilt-up concrete got even further validation when an earthquake hit Northridge, California. Even when roof connectors failed, tilt-up walls remained standing. Tilt-up concrete has proven to be impervious to wind, hail, mice and insects as well as being resistant to earthquake damage. Since the 1940s, tilt-up construction has undergone many more innovations and refinements, and has developed into a process that is used by many top concrete contractors and general contractors in the commercial construction industry. One such innovation occurred in the 1980s when curved tilt-up walls were introduced. This more complex method creates walls that resemble skateboarding ramps, such as those first seen on the ADC Telecommunications building in Juarez, Mexico. Because tilt-up concrete combines higher quality with higher resale values, faster delivery and lower maintenance, more than 15% of all industrial buildings are tilt-up. Tilt-up buildings range in size from 5,000 to over 1.7 million square feet. Individual panels can reach over 90 feet high and weigh 150 tons. Tilt-up construction is growing at an annual rate of about 20% and is used on about 650 million square feet of construction every year. In some parts in the country, such as Texas, tilt-up construction is responsible for almost 75% of new commercial construction, and the method is growing in popularity in Mexico, Canada and Australia as well. No matter what purpose it's used for, tilt-up concrete makes for construction projects that are extremely cost effective and efficient. Designing and building with tilt-up concrete is efficient because the wall panels can be formed and poured even while the rest of the building is being designed or even built. This overlapping of disciplines makes for speedier project completion. Tilt-up construction enables contractors and developers to control costs better too, because it utilizes ready-mix concrete which is made from native materials available near the job site. And no, tilt-up buildings do not look like concrete cracker boxes. Tilt-up walls can be finished in a wide variety of ways, including textured paint, reveals, a variety of wall claddings and other techniques that add to the building's visual appeal. While tilt-up concrete is most commonly used to construct one-story buildings, it is not unusual for this technique to be used for structures as tall as four stories. The tilt-up construction method has even been used for buildings as tall as ten stories. And this method is not restricted to just commercial buildings either. Tilt-up concrete houses are becoming more readily available around the country. One of the most stunning examples is located in Edmond, Oklahoma. This 4,000 square foot handicap-accessible residence includes family and living rooms with fireplaces, a formal dining room, a mother-in-law suite, a master suite with a cathedral ceiling and a master bath with a koi pond just outside. Tilt-up concrete has come a long way since Joseph Monier's flowerpot
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  • PROCESO PLACA FÁCILapoyar el perfil entrepiso colmena cada 89 cm sobre el muro o viga de soporte ( min. 1.5 cm / máx. 2.5 cm)instalar los bloquelones Santafé sobre los perfiles. se recomienda caminar sobre planchones.disponer la malla electro soldada, armar el hierro de refuerzo de vigas y dinteles y localizar los testeros para las vigas de borde.finalmente fundir la torta de concreto (min. 4 cm) y las vigas de borde al mismo tiempo.TENGA EN CUENTADistancia máxima entre apoyos con perfil colmena : 4.20 mCuando la distancia entre apoyos es mayor 2.50 m se requiere utilizar apuntalamiento temporal (cerchas y parales) durante la etapa constructivaLocalice las instalaciones eléctricas e hidráulicas por debajo de la malla electro soldadaEl perfil se puede perforar al tercio de la luz con orificio máx. De 3/4” para uso de instalaciones.Aplicar pintura anticorrosiva en el perfil colmena.Todo sobre placa fácil

4.2 concreto 2 Presentation Transcript

  • 1. SISTEMAS DE CONSTRUCCIÓN Y DE ESTIMACIÓN PROFESOR: Dr. Carolina Stevenson Arquitecta Universidad Nacional Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 2. PROBLEMA B RECOMENDACIONES 1. Edificaciones a nivel con alturas hasta de cinco o seis pisos contarán con una cimentación conformada por pilotes preexcavados y fundidos en situ, que trabajaran por fricción en los suelos granulares y cohesivos del perfil…Lógicamente para edificios a nivel de cinco o seis pisos de altura, una cimentación con pilotes resulta en costos elevados. 2. Los pilotes tendrían profundidades comprendidas entre 15 y 20 m y sería necesario utilizar elementos construidos por el sistema Kelly y no mediante hélice continua, ya que éstos últimos seguramente no lograrían atravesar los estratos granulares más superficiales. 3. Si se diseñan edificios a nivel de cinco o seis pisos con sótano y se retiran los rellenos descritos, se alcanzarían los niveles de arcillas y arcillas arenosas de color café y se podría diseñar un sistema de fundación conformado por una placa, bien sea de tipo macizo con vigas descolgadas o aligerada que reparta uniformemente las cargas al suelo de apoyo. Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 3. 4. Al igual que para edificios de cinco o seis pisos a nivel, edificios de mayor altura, siete, ocho, diez, quince y veinte pisos requerirán también una fundación mediante pilotes, que de acuerdo con el peso de las torres correspondiente a su altura aumentarán en profundidad. A manera de ejemplo, para edificios con alturas de diez pisos seguramente los pilotes tendrían profundidades cercanas a 25 ó 30 m, mientras que para edificios con alturas de quince y veinte pisos, los pilotes alcanzarían profundidades cercanas a 45 ó 50 m. 5. En el caso de que se diseñe un sótano y alturas de edificios hasta de diez pisos, se considera que es viable una solución de fundación combinada placapilotes, donde a la placa se le puede asignar un porcentaje de la carga variable entre el 30% y el 50% y a los pilotes la carga restante. Este sistema es válido con un buen porcentaje de cargas asignado a la placa, siempre y cuando se logre una coincidencia entre el centro de aplicación de la resultante de las cargas y el centro de gravedad de la losa de fundación. Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 4. Movimiento de tierras y cimentación 1. Las excavaciones a profundidades no mayores a 3.0 ó 3.5 m que corresponden a un nivel de sótano, pueden ser efectuadas en forma convencional mediante bermas y taludes y efectuando posteriormente su retiro, donde éstos invadan el área del sótano mediante trincheras o ventanas alternas. 2. Para excavaciones a profundidades superiores a 3.5 m, se requiere la construcción de muros de contención tipo pantalla, cuyo espesor y longitud varía en función de la profundidad de excavación. A manera de ejemplo, si las excavaciones de los dos sótanos no sobrepasan una altura de 6 m, se pueden utilizar muros pantalla de 0.3 m de espesor. 3. Las excavaciones están gobernadas por el soporte horizontal de los muros pantalla y la magnitud del rebote elástico generado por el proceso de descargue. Para controlar la magnitud del rebote elástico el terreno normalmente este tipo de excavaciones se realizan por áreas pequeñas. CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 5. Movimiento de tierras y cimentación 4. Para excavaciones únicamente de un sótano se pueden diseñar placas de contrapiso convencionales y bajo las losas filtros en forma de espina de pescado vista en planta, que llevarán las aguas a pozos eyectores. Para excavaciones mayores a 3 m donde se diseñen placas de subpresión, sobre las losas se harán pisos falsos para que el agua que la logre atravesar se conduzca a los pozos eyectores y de allí a filtros o pozos de recarga construidos en la periferia o dependiendo de las dimensiones y profundidades de los sótanos también al sistema de alcantarillado. 5. Por delante de los muros pantalla para excavación de más de dos sótanos, se debe preveer el diseño de muros de limpieza y cañuelas, que podrían requerir fuera del espesor del muro pantalla un espesor adicional cercano a 15 ó 20 cm. Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 6. Concreto
  • 7. CONTENIDO Concreto in situ Estructura esqueletal Muros de concreto in situ / Formaletas Sistema Contech Sistema Outinord Entrepisos Concreto Prefabricado Muros con elementos cerámicos de concre Entrepisos Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 8. Concreto Armado El concreto reforzado es utilizado cuando el elemento a construir debe soportar al mismo tiempo esfuerzos de tension, compresion y/o combinaciones (eg. momentos flectores, corte) … CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 9. Concreto Armado Compresión Compresión Eje Neutral Tensión Barras ancladas en los extremos Tensión Canstilla de refuerzo Viga de concreto reforzado soportando la losa Losa y viga integradas por el refuerzo Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 10. Concreto Armado: PRETENSADO Deformación común Tension El refuerzo es tensado Compresion Aplicación de cargas de compresión Deformación durante la vida útil Los elementos de concreto pretensado son sometidos intencionadamente a esfuerzos de tensión compresión previos a su puesta en servicio con el objetivo de aumentar su resistencia. CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 11. Concreto Armado: POSTENSADO El postensionamiento es un método para la aplicación de compresión tras el vertido y posterior proceso de secado in situ del concreto. El refuerzo se posiciona en tubos protectores para que trabaje independientemente del concreto. CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 12. Concreto Armado Pros •El coeficiente térmico del concreto es similar al del acero eliminando posibles estrés interior. •El acero corrugado ayuda a mejorar la cohesión entre los dos materiales. •El concreto ayuda a proteger al acero contra la corrosión y el fuego. Cons •Corrosión y congelamiento pueden fácilmente dañar el concreto mal diseñado. •Cuando el acero se corroe expande y tiende a romper el concreto. Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 13. Concreto Reforzado: CON FIBRAS Concreto puede ser reforzado con elementos fibrosos (fibra de vidrio, paja, esterilla) para incrementar su integridad estructural. CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 14. Concreto Reforzado: CON FIBRAS Pros • Mejora cohesión y maleabilidad a larga distancia. • Mejora la resistencia a el congelamiento y fallo explosivo en caso de deshidratación. • Mejora elasticidad y resistencia la impacto. Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 15. Concreto: IN SITU Vs PREFABRICADO Concreto In Situ •Fácil de logra continuidad entre elementos. •Facilidad de crear uniones rígidas. •El control de calidad es laborioso. Concreto Prefabricado •Se puede garantizar la calidad. •Facilita la construcción en lotes estrechos. •Puede ser erguido rápido y en mal clima . •Las uniones son mas problemáticas. •Debe ser trasportado al sitio. •Las formas orgánicas son mas complejas de lograr. Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 16. Concreto In Situ Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 17. Concreto In Situ El concreto in situ es un material liquido que se vierte directamente en obra usando formaletas para darle forma mientras endurece y alcanza la resistencia necesaria... CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 18. Concreto In Situ: DISEÑO DE MEZCLAS -Se diseñan para obtener resistencias para distintas prácticas. -Se utilizan pruebas para determinar el peso o volumen de: -Cemento -Arena limpia -Agregados PRUEBA POR ESCURRIMIENTO O “SLUMP” Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 19. Concreto In Situ: DISEÑO DE MEZCLAS RELACIÓN AGUA – CEMENTO Esta relación debe controlarse frecuentemente con el fin de obtener uniformidad en la resistencia de la mezclas teniendo en cuenta que la humedad puede variar condiciones ambientales o contextuales. Sistemas de Construcción y Estimación – Prof: PREPARACIÓN DE UNA MUESTRA DE CONCRETO PARA PROBAR SU RESISTENCIA MALEABILIDAD DE LA MEZCLA CONCRETO ARMADO
  • 20. Concreto In Situ: ENSAYOS CANTIDAD DE PRUEBAS -Pruebas correspondientes a cada tipo de concreto -Una pareja de cilindros una vez por día -Una vez cada 40 m³ de estructura de concreto -Una vez cada 200 m² de placa o losa. -Tomar una muestra por cada 25 bachadas de cada clase de concreto -Si el volumen de concreto es tal que la frecuencia de ensayos es menor a 5 ensayos de un mismo concreto, se deben tomar 5 muestras seleccionadas al azar. -Si la cantidadConstrucción y Estimación – Prof: Sistemas de de concreto es La resistencia para estructuras de concreto esta entre los 2.5005.000psi (170-350k/cm2). CONCRETO ARMADO
  • 21. Concreto In Situ: PREPARACION MEZCLA A MANO: -Sobre una superficie uniforme -El cemento y la arena deben mezclarse hasta que haya un color uniforme -A la mezcla se agrega agua de amasado del centro hacia los bordes hasta obtener una masa -Se agrega gravilla dándole botes continuos hasta obtener una mezcla homogénea MEZCLA MECÁNICA: -El equipo debe garantizar un control de cantidades de materiales ya sea por peso o volumen -El agua debe ser añadida antes y durante la preparación -La consistencia del concreto –debe Sistemas de Construcción y Estimación Prof: CONCRETO ARMADO
  • 22. Concreto In Situ: VACIADO -El concreto no debe ser vaciado a más de 45 minutos después de su preparación -No puede ser transbordado ni verterse en caída libre -Previo a verterse, se deben revisar los encofrados de las armaduras y la superficie sobre la cual se vaciaría el concreto -El concreto debe colocarse en capas horizontales, en forma continua -Se debe vibrar adecuadamente -Se puede compactar con rodillo -Durante el fraguado se pueden producir fisuras, para evitarlas se recubre la superficie con paños Sistemas lona. húmedos de de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 23. Concreto In Situ: FORMALETA El concreto es un material esencialmente moldeable, requiere ser vaciado dentro de un molde. La función de la formaleta es crear una forma en negativo para rellenar y desmoldar en positivo. Debe tener las siguientes propiedades: 1.Reproducir la forma diseñada con exactitud. 2 Prestar la rigidez necesaria para el trajín durante el vaciado. CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 24. Concreto In Situ: FORMALETA 3 Tener el ajuste perfecto para que sea hermética y no permita la salida del concreto/pasta . 4.Facilitar la colocación del armado y su recubrimiento manteniendo su posición durante el vertido y vibrado del concreto. 5. Garantizar un buen curado del concreto, evitar la pérdida de agua durante el proceso de fraguado, así como protegerlo de las temperaturas externas. SISTEMAS Sistemas de Construcción y Estimación – Prof: ESQUELETALES
  • 25. Concreto In Situ: FORMALETA MATERIAL -Madera ordinaria (material más utilizado) -Madera cepillada (concreto a la vista) -Pino (Cualquier Madera que no contenga Taninos) -Guadua -Lámina de hierro o acero -Tableros Aglomerados PREPARACIÓN, COLOCACIÓN Y DESCIMBRADO -Prefabricación (Formaleta metálica) -Adicionar a las caras ACPM, ACEITE o GRASA/PARAFINA -Las tablas se clavan a los refuerzos mediante taches de hierro, pasadores o tornillo de tuerca y arandela -Colocación centrada: Utilizar puntales, parales, riostras Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 26. FORMALETAS FORMALETAS TRADICIONALES se que humedecer antes de Formaleta de tienenconcreto para evitar que madera verter el tomen agua del concreto y, por lo tanto, absorban cemento. FORMALETAS INDUSTRIALIZADAS Modulares Trepadoras Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 27. FORMALETAS: MADERA Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 28. FORMALETAS FORMALETAS TRADICIONALES Soluciones hibridas Formaleta de madera son todavía ampliamente utilizadas. FORMALETAS INDUSTRIALIZADAS Modulares Trepadoras Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 29. FORMALETAS FORMALETAS TRADICIONALES Formaleta de madera FORMALETAS se pueden repetir elementos Al modular y ahorrar tiempo en INDUSTRIALIZADAS el montaje y en el desmontaje. Modulares Trepadoras Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 30. FORMALETAS: MODULARES Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 31. FORMALETAS FORMALETAS TRADICIONALES Formaleta de madera FORMALETAS INDUSTRIALIZADAS Encofrado trepante es aquel Modularesque se desliza verticalmente y por tanto pierde su apoyo en el suelo. Trepadoras Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 32. FORMALETAS FORMALETAS TRADICIONALES Formaleta de madera FORMALETAS INDUSTRIALIZADAS Se crea una plataforma en cada altura Modularesdonde se puedan realizar los trabajos de encofrado, aplomado y desencofrado, y a su vez debe de servir como soporte estructural para transmitir al muro ejecutado la solicitaciones requeridas. Trepadoras Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 33. FORMALETAS FORMALETAS TRADICIONALES Formaleta de madera FORMALETAS INDUSTRIALIZADAS Estas consolas tienen adaptadas Modularesplataformas inferiores para la recuperación de conos y encajes. Trepadoras Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 34. FORMALETAS: TREPADORA Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 35. FORMALETAS: TREPADORA Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 36. FORMALETAS FORMALETAS TRADICIONALES Formaleta de madera FORMALETAS INDUSTRIALIZADAS Modulares Trepadoras Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 37. Concreto In Situ: VIBRADO La vibración del concreto consiste en una serie de sacudidas con una frecuencia elevada de 12.500 a 16.000 rpm. El objetivo de la vibración es eliminar los huecos y sacar el aire, asegurando mejor compactación y contacto entre varillas y concreto. CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 38. Concreto In Situ: CURADO El curado consiste en garantizar que el concreto tenga la cantidad de agua suficiente para que la acción química continúe hasta que se encuentre completamente endurecido. CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 39. Concreto In Situ: CURADO MÉTODOS DE CURADO A. Curado por medio de agua y cubiertas protectoras húmedas B. Aplicación de compuestos selladores a las superficies C. Curado por vapor A . B . Sistemas de Construcción y Estimación – Prof: C . CONCRETO ARMADO
  • 40. Proceso constructivo: sistema esqueletal COLUMNA Paso 0: Lectura e interpretación de planos, cimbrada de la columna Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 41. Proceso constructivo: sistema esqueletal COLUMNA Paso 1: Armado de refuerzos Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 42. Proceso constructivo: sistema esqueletal COLUMNA Paso 2: Ubicación de formaletas laterales Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 43. Proceso constructivo: sistema esqueletal COLUMNA Paso 3: Vertido del concreto Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 44. Proceso constructivo: sistema esqueletal COLUMNA Paso 4: Retiro de formaletas y curado Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 45. MUROS DE CONCRETO FUNDIDO IN SITU http://www.youtube.com/watch?v=-Uh67yT4VIY&feature=related Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 46. MUROS DE CONCRETO SISTEMA CONTECH Sistema de construcción industrializado que utiliza módulos de aluminio fundido de diferentes dimensiones, que ensamblados conforman la formaleta para los muros de la edificación. Con el sistema se pueden realizar los trabajos de colocación del refuerzo, instalaciones, formaleta y fundida del concreto en un solo día, dejando un tiempo adecuado SISTEMAS Sistemas de Construcción y fragüe y para que el concreto Estimación – Prof: se pueda repetir el mismo proceso ESQUELETALES
  • 47. MUROS DE CONCRETO SISTEMA CONTECH Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 48. MUROS DE CONCRETO SISTEMA CONTECH http://www.youtube.com/watch?v=k990Z5E2OQQ&feature=fvsr Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 49. MUROS DE CONCRETO SISTEMA OUTINORD Procedimiento de industrialización en obra gruesa, que permite construir rápidamente basándose en el principio de rotación diaria de la formaleta, permitiendo una velocidad de construcción con baja ocupación de personal. Permite fundir in – situ y en una SISTEMAS Sistemas de Construcción y Estimación – Prof: misma operación muros longitudinales y transversales con sus ESQUELETALES
  • 50. MUROS DE CONCRETO SISTEMA OUTINORD Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 51. MUROS DE CONCRETO SISTEMA OUTINORD Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 52. MUROS DE CONCRETO SISTEMA OUTINORD http://www.youtube.com/watch?v=0Mvcsd7DsL4&feature=related Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 53. ENTREPISOS POR COMPOSICION Maciza Aligerada consta de una sección de concreto reforzado en dos direcciones diseñada dependiendo de los apoyas y la distribución de as cargas. POR DISEÑO Planas Compuestas Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 54. SUPERESTRUCTURA -CONCRETO - PLACAS Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 55. ENTREPISOS POR COMPOSICION Maciza Aligerada parte del concreto se remplaza por otros materiales (cajones de madera/ guadua, ladrillos o bloques). De esta forma se disminuye el peso de la losa. POR DISEÑO Planas Compuestas Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 56. SUPERESTRUCTURA -CONCRETO - PLACAS Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 57. SUPERESTRUCTURA -CONCRETO - PLACAS Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 58. ENTREPISOS POR COMPOSICION Maciza Aligerada POR DISEÑO Planas transmiten las cargas directamente a las columnas, sin la ayuda de vigas. Pueden apoyarse directamente sobre las columnas o Compuestas a través de ábacos, capiteles o una combinación de ambos. Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 59. ENTREPISOS POR COMPOSICION Maciza Aligerada POR DISEÑO Planas transmiten las cargas a través de vigas y viguetas principalmente. Compuestas Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 60. SUPERESTRUCTURA -CONCRETO - PLACAS Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 61. Concreto P refabricado Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 62. Concreto P refabricado Elementos prefabricados ayudan a mejorar calidad y duración del proceso constructivo en concreto. CONCRETO … Sistemas de Construcción y Estimación – Prof: ARMADO
  • 63. Concreto P refabricado Los bloques de concreto (especialmente huecos) ayudan a reducir el peso total de la construcción y a mejorar el aislamiento térmico y acústico. Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 64. Concreto P refabricado PLACAS ALVEOLARES Permite múltiples aplicaciones en función de su forma de colocación: puede ser horizontal como entrepiso, inclinada como SISTEMAS cubiertaSistemas de Construcción y Estimación – Prof: o rampa, o vertical como cerramiento o muro. ESQUELETALES
  • 65. C oncreto Celular de Autoclave El ACC(Autoclaved Cellular Concrete) es un tipo de concreto prefabricado curado bajo alta presión dentro de hornos especiales (autoclaves)… CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 66. C oncreto Celular de Autoclave Pros • Mejora las propiedades de aislamiento térmico • Mejora la resistencia al fuego. • Mejora la relación peso/resistencia. • Mas liviano que ladrillo o típico bloque de concreto . • Mejora las propiedades acústicas. Sistemas de Construcción y Estimación – Prof: CONCRETO ARMADO
  • 67. Concreto P refabricado: TILT-UP Sistemas como el tilt-up ofrecen rapidez y eficacia en la construcción, durabilidad garantizada y control en los acabados. CONCRETO Sistemas de Construcción y Estimación – Prof: ARMADO
  • 68. CELDA REFORZADA – BLOQUE DE CONCRETO- La mampostería modular se basa en el fundamento de que el ancho del bloque debe ser múltiplo de su longitud. Ello permite construir distribuciones arquitectónicas basadas a su vez en medidas resultantes de múltiplos de la longitud del bloque. SISTEMAS Sistemas de Construcción y Estimación – Prof: ESQUELETALES
  • 69. CELDA REFORZADA – BLOQUE DE CONCRETO La mampostería modular se basa en el fundamento de que el ancho del bloque debe ser múltiplo de su longitud. Ello permite construir distribuciones arquitectónicas basadas a su vez en SISTEMAS medidas resultantesy Estimación – Prof: de múltiplos de la longitud del bloque. Sistemas de Construcción ESQUELETALES
  • 70. CELDA REFORZADA – BLOQUE DE CONCRETO- El mortero de pega debe ser lo suficientemente plástico (tamaño máximo del agregado de 12 mm dia.) y los bloques deben ser colocados con la suficiente presión para que el mortero sea expulsado de la junta y los elementos queden bien conectados. El mortero de relleno de SISTEMAS Sistemas de Construcción y Estimación – Prof: ESQUELETALES
  • 71. CELDA REFORZADA – BLOQUE DE CONCRETO- Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 72. CELDA REFORZADA – BLOQUE DE CONCRETO- Los bloques de concreto deben permanecer secos antes y durante la colocación, para evitar que al perder humedad en la pared se contraigan y causen grietas. Así SISTEMAS serán capaces de absorber el Sistemas de Construcción y Estimación – Prof: ESQUELETALES
  • 73. CELDA REFORZADA – BLOQUE DE CONCRETO1 . 4 . 2 . 5A. 3 . 5B . http://www.youtube.com/watch?v=H2CaWrtsXOc&feature=related Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 74. ENTREPISOS – PLACA FÁCIL CON BLOQUELÓN Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 75. ENTREPISOS- BLOQUE CERAMICO Y VIGUETAS SEMIPRE Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 76. ENTREPISOS- BLOQUE CERAMICO Y VIGUETAS SEMIPRE Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 77. ENTREPISOS- BLOQUE CERAMICO Y VIGUETAS SEMIPRE Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 78. ENTREPISOS- BLOQUE CERAMICO Y VIGUETAS SEMIPRE Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 79. ENTREPISOS – SISTEMA PREPLACA Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 80. ENTREPISOS – SISTEMA PREPLACA Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 81. ENTREPISOS – SISTEMA PREPLACA Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES
  • 82. ENTREPISOS – SISTEMA PREPLACA http://www.youtube.com/watch?v=rzLpB_2P8nU&feature=player_embedd ed#! Sistemas de Construcción y Estimación – Prof: SISTEMAS ESQUELETALES