Types of concrete

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Concrete is produced in various compositions, solutions, and performance characteristics to meet various needs.

Video Types of concrete

Mixed design

Modern concrete concrete design can be tricky. The selection of concrete mixes depends on the needs of the project both in terms of strength and appearance and in relation to local laws and building codes.

The design begins with determining the concrete requirements. This requirement takes into account the weather conditions that the concrete will be exposed in service, and the required design power. The compressive strength of the concrete is determined by taking a standard cylinders standard preserved sample.

Many factors need to be taken into account, ranging from the cost of various additives and aggregates, to the trade off between "slumps" for easy mixing and placement and highest performance.

The mixture is then designed using cement (Portland or other cement material), coarse and fine aggregates, water mixtures and chemicals. Mixing methods will also be determined, as well as usable conditions.

This allows concrete users to be confident that the structure will work properly.

Different types of concrete have been developed for specialist applications and are well known by these names.

Concrete mixes can also be designed using a software program. Such software gives users the opportunity to select their preferred mix design methods and input material data to get the right mix design.

Maps Types of concrete

Historical concrete composition

Concrete has been used since ancient times. Ordinary Roman concrete for example is made of volcanic ash (pozzolana), and hydrated lime. Roman concrete is superior to other concrete recipes (for example, which consist of only sand and lime) used by other cultures. In addition to volcanic ash to make ordinary Roman concrete, brick dust can also be used. In addition to the usual Roman concrete, the Romans also invented hydraulic concrete, made of volcanic ash and clay.

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Modern concrete

Plain concrete is a layman's term for the concrete produced by following mixing instructions that are generally published on semen packages, usually using sand or other common materials as aggregates, and often mixed in improvisation containers. The ingredients in a particular mixture depend on the nature of the application. Regular concrete can usually withstand pressure from about 10 MPa (1450 psi) to 40 MPa (5800 psi), with lighter tasks such as dazzling concrete having a much lower MPa rating than structural concrete. Many types of pre-mixed concrete are available which include cement powder mixed with aggregate, requiring only water.

Typically, concrete batches can be made using 1 part Portland cement, 2 parts of dry sand, 3 parts of dry stone, 1/2 parts water. The parts are heavy - not volume. For example, 1-cubic-foot (0,028 m ³ ) of concrete will be made using 22 lb (10.0 kg) of cement, 10 lb (4.5 kg) of water, 41 lb (19 kg ) dry sand, dry stone 70 lb (32 kg kg) (1/2 to 3/4 stone). This will create a 1-cubic-foot concrete (0.028 m ³ ) and will weigh around 143 pounds (65 kg). Sand should be mortar sand or bricks (washed and filtered if possible) and stones should be washed if possible. Organic materials (leaves, twigs, etc.) Must be removed from sand and rock to ensure the highest strength.

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High-strength concrete

High-strength concrete has a compressive strength greater than 40 MPa (5800 psi). In the UK, BS EN 206-1 defines high quality concrete as concrete with a compressive strength class higher than C50/60. High-strength concrete is made by lowering the water-cement ratio (W/C) to 0.35 or lower. Often silica fume is added to prevent the formation of free calcium hydroxide crystals in the cement matrix, which may reduce the strength of the cement aggregate bonds.

The low W/C ratio and the use of silica fume make concrete mixtures significantly less applicable, which is likely to be a problem in high quality concrete applications where tightly enclosed cages tend to be used. To compensate for the reduction in workability, superplasticizers are usually added to a high strength mix. Aggregates should be chosen carefully for high-strength mixtures, since weaker aggregates may not be strong enough to withstand the loads imposed on concrete and cause failure to start in aggregate rather than in the matrix or in the void, as is usually the case in general. concrete.

In some applications high quality concrete design criteria are elastic modulus rather than final compressive strength.

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Concrete plates

Concrete plates are architectural concrete that has a superior surface finish. Once the concrete floor has been laid, the floor (pigmented) hardener is impregnated on the surface and textured mold to replicate stones/bricks or even stamped wood to provide an attractive textured surface. After sufficient hardening, surfaces are cleaned and generally sealed to provide protection. The wear resistance of the stamped concrete is generally good and hence found in applications such as parking lots, sidewalks, walkways etc.

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High-performance concrete

High-performance concrete (HPC) is a relatively new term for concrete that complies with a set of standards above the most common applications, but not limited to strength. While all high strength concrete is also high performing, not all high performance high strength concrete. Some examples of standards currently used in connection with HPC are:

High-performance concrete

High-performance concrete is a new type of concrete being developed by agencies concerned with infrastructure protection. UHPC is characterized by being a steel fiber reinforced cement composite with a compressive strength of more than 150 MPa, up to and possibly exceeding 250 MPa. UHPC is also characterized by its constituent compositions: usually fine sand, silica fume, small steel fibers, and a special mix of high-power Portland cement. Note that there is no large aggregate. The current types in production (Ductal, Taktl, etc.) differ from normal concrete in compression by hardening their strain, followed by sudden brittle failure. Ongoing research into UHPC failures through tensile and sliding failures is being undertaken by various government and university institutions around the world.

Micro-reinforced ultra-high performance concrete

Ultra-performance ultrahigh concrete is the next generation UHPC. In addition to the high compressive strength, abrasion resistance and resistance of UHPC, micro reinforced UHPC is characterized by extreme toughness, energy absorption and chemical, water and temperature resistance. Continuous, multi-layered, three-dimensional micro-steel hijab exceeds UHPC in durability, tenacity and strength. The disconnected and dispersed fiber performance at UHPC is relatively unexpected. Micro-reinforced UHPC is used in explosion-proof, ballistic and earthquake-resistant construction, structural overlay and architecture, and complex facades.

Ducon is an early micro-reinforced UHPC developer, which has been used in the construction of the new World Trade Center in New York.

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Self-consolidating concrete

Concrete defects in Japan are found mainly due to the high water-cement ratio to improve workability. Bad compaction occurs largely due to the need for rapid construction in the 1960s and 1970s. Hajime Okamura imagines the need for highly applicable concrete and does not depend on mechanical strength for compaction. During the 1980s, Okamura and Ph.D. Kazamasa Ozawa students at the University of Tokyo develop a self-compacting concrete (SCC) that is cohesive, but can flow and take formwork without the use of mechanical compaction. SCC is known as self-consolidated concrete in the United States.

SCC is characterized by the following:

• extreme fluidity measured by flow , usually between 650-750 mm in the flow table, rather than a slump (height)
• no vibrator needed to condense concrete
• easier placement
• no bleeding, or aggregate segregation
• increase in liquid head pressure, which can damage safety and workmanship

SCC can save up to 50% in labor costs as it pours 80% faster and reduces damage to the formwork.

In 2005, concrete concentrates alone accounted for 10-15% of concrete sales in several European countries. In the precast concrete industry in the US, SCC represents more than 75% of concrete production. 38 US transportation departments accept the use of SCC for road and bridge projects.

This emerging technology is made possible by the use of polycarboxylate plasticizers instead of the old naphthalene polymers, and the viscosity modifiers to overcome aggregate segregation.

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Concrete vacuum

Concrete vacuum, made by using steam to generate a vacuum inside a concrete mixing truck to release air bubbles inside the concrete, is being investigated. The idea is that the vapor replaces the air normally above the concrete. When steam condenses into water it will create a low pressure above the concrete that will draw air from the concrete. This will make the concrete stronger because there is less air in the mix. The drawback is that mixing should be done in an airtight container.

The final strength of the concrete increased by about 25%. The vacuum concrete tightens so fast that the formwork can be moved within 30 minutes of casting even on columns as high as 20 feet. This is a considerable economic value, especially in precast factories because the forms can be reused at frequent intervals. The strength of vacuum concrete bonds is about 20% higher. The surface of the vacuum concrete is completely free of pitting and the top 1/16 inch is very resistant to abrasion. This characteristic is very important in the construction of concrete structures that must come in contact with water that flows at high speed. The bonds are good for old concrete and can, therefore, be used to coat sheet paths and other repair work.

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Shotcrete

Shotcrete (also known by the trade name Gunite ) uses compressed air to fire concrete onto (or to) a frame or structure. The biggest advantage of this process is that shotcrete can be applied above or on a vertical surface without formwork. These are often used for the repair or placement of concrete on bridges, dams, swimming pools, and in other applications where expensive formation or material handling and installation is difficult. Shotcrete is often used against ground or vertical rocks, as it eliminates the need for formwork. Sometimes used for rock support, especially in tunneling. Shotcrete is also used for applications where seepage is a problem to limit the amount of water entering the construction site due to high water tables or other underground sources. This type of concrete is often used as a quick fix for weathering for loose soil types in construction zones.

There are two methods of application for shotcrete.

• dry mixture - a mixture of dry cement and aggregate is charged into the machine and delivered with compressed air through the hose. Water required for hydration is added to the nozzle.
• wet mixture - a mixture prepared with all the water needed for hydration. The mixture is pumped through the hose. In the nozzle pressure air is added for spraying.

For both additive methods such as accelerators and fiber reinforcement can be used.

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Limecrete

Limecrete or lime concrete is a concrete in which cement is replaced with lime. One formula that was successfully developed in the mid-1800s by Dr. John E. Park. We know that chalk has been used since Roman times either as mass concrete foundations or as lightweight concrete using a variety of aggregates combined with various pozzolans (fuels) that help achieve increased strength and set speed. This means chalk can be used in a wider variety of applications than ever before such as floors, safes or vaults. Over the last decade, there's a renewed interest in using chalk for this app again. This is because of the environmental benefits and potential health benefits, when used with other lime products.

Environmental Benefits

• Lime is burnt at lower temperatures than semen and so does 20% direct energy savings (though kiln etc. increases so that numbers change). A standard lime mortar has about 60-70% of the energy contained in cement mortar. It is also considered to be more environmentally friendly because of its ability, through carbonation, to reclaim its own weight in Carbon Dioxide (compensate for being released during combustion).
• Lime mortar allows other building components such as stones, wood and bricks to be reused and recycled because they can be easily cleaned from mortar/lime.
• Lime allows other natural and sustainable products such as wood (including woodfibre, wooden wool boards), hemp, straw etc. to use because of its ability to control moisture (if cement is used, this building will become compost!).

Health Benefits

• Plaster of chalk is hygroscopic (literally "looking for water") that draws moisture from the internal to the external environment, this helps to regulate the moisture creates a more comfortable environment and helps to control condensation and growth molds that have been proven has a connection with allergies and asthmas.
• Lime plaster and limewash are non-toxic, therefore they do not contribute to indoor air pollution unlike some modern paint.

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Transparent concrete

translucent concrete , used in penetrating paving, containing holes or voids, to allow air or water to move through concrete

This allows the water to flow naturally through it, and both can remove the normal surface water drainage infrastructure, and allow groundwater charging when conventional concrete does not.

It is formed by leaving part or all of the fine aggregate (fine). The remaining large aggregates are then bound by a small amount of Portland cement. When arranged, usually between 15% and 25% of the volume of concrete is a cavity, allowing water to flow about 5 gal/ftÃ,Â/min (70 L/mÃ,²/min) through concrete.

Installation

The translucent concrete is fitted with poured into shape, then dismantled, to equalize (not smooth) the surface, then packed or compacted in place. Due to its low water content and air permeability, within 5-15 minutes of tamping, the concrete must be covered with 6-mil poly plastic, or will dry out prematurely and not well hydrated and heal.

Characteristics

The translucent concrete can significantly reduce noise, by allowing air to be squeezed between the vehicle tires and the escape route. This product can not be used on the US state highway today due to the high psi ratings required by most states. The translucent concrete has been tested up to 4500 psi so far.

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Cellular concrete

Aerated concrete produced by the addition of air barrier agents to concrete (or light aggregates such as expanded clay aggregates or cork granules and vermiculite) is sometimes called mobile concrete , light aerated concrete, density concrete variable, Concrete Foam and lightweight or ultra-light concrete , should not be confused with autoclaved aerated concrete, which is produced offsite using completely different methods.

In 1977 working on A Pattern Language: City, Building and Construction , architect Christopher Alexander wrote in 209 patterns on Good Materials :

Ordinary concrete is too dense. It's hard and hard to work. After that, one can not cut it, or nail in it. And it's sic the surface is ugly, cold, and hard in feeling unless it is covered by an expensive layer that is inseparable from the structure.

And even concretely, in some form, is an interesting material. The liquid is strong, strong, and relatively cheap. It is available in almost every part of the world. A University of California engineering professor, P. Kumar Mehta, has just discovered how to turn rice husks left behind into Portland cement.

Is there a way to combine all these fine qualities of concrete and also has a light, easy to work, with a nice finish? There is. It is possible to use a variety of ultra-light concrete that has a density and compressive strength that is very similar to wood. They are easy to work with, can be nailed with regular nails, cut with saws, drilled with woodwork tools, easily repairable.

We believe that ultra-light concrete is one of the most fundamental bulk materials in the future.

The variable density is usually described in kg per m³³³, where the usual concrete is 2400 kg/mÃ,³. Density variables can be as low as 300 kg/mÃ,³, though at this density will have no structural integrity at all and will serve as filler or isolation use only. The variable density reduces the power to improve thermal and acoustic insulation by replacing heavy solid concrete with air or light materials such as clay, cork granules and vermiculite. There are many competing products that use foaming agents that resemble shaving cream to mix air bubbles with concrete. All achieved the same result: to move the concrete with air.

Applications of foamed concrete include:

• Roof Insulation
• Blocks and Panels for Walls
• Leveling Flooring
• Void Fill
• Sub-Base and Road maintenance
• Bridge buffer and repairs
• Soil Stabilization

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Combined-composite cement

Cork waste granules were obtained during the production of a corkscrew from Cork's treated oak bark. This grain has a density of about 300 kg/mÃ,³, lower than the lightest aggregate used to make lightweight concrete. The cork granules do not significantly affect the hydration of cement, but cork dust is possible. The composite cork composite has several advantages over standard concrete, such as lower thermal conductivity, lower density and good energy absorption characteristics. This composite can be made with a density of 400 to 1500 kg/m³³, a compressive strength of from 1 to 26 MPa, and a bending strength of from 0.5 to 4.0 MPa.

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Roller-solid concrete

Roller-compacted concrete, sometimes called rollcrete , is a rigid concrete with low cement content placed using techniques borrowed from soil removal and paving work. The concrete is placed on the surface to be closed, and solidified in place using heavy heavy rollers which are usually used in soil work. The concrete mixture reaches high density and the drug over time into a strong monolithic block. Roller-compacted concrete is usually used for concrete pavement, but has also been used to build concrete dams, because the low cement content causes less heat to be generated during the drying process than is usual for conventionally-placed reinforced concrete.

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Glass concrete

The use of recycled glass as an aggregate in concrete has become popular in modern times, with large-scale research conducted at Columbia University in New York. This greatly increases the aesthetic appeal of the concrete. The latest research findings show that concrete made with recycled glass aggregates has shown better long-term strength and better thermal insulation due to its better heat properties than glass aggregates.

Asphalt concrete

Actually, asphalt is a concrete form too, with asphalt material replacing cement as a binder.

Fast power concrete

This type of concrete is able to develop high resistance within hours of production. This feature has advantages such as deleting initial work and for moving forward in the development process very quickly, an improved road surface that fully operates in just a few hours. The maximum strength and durability may vary from standard concrete, depending on the detail of the composition.

Rubber concrete

While "rubber concrete asphalt" is common, Portland rubber cement concrete ("PCC rubber") is still undergoing experimental testing, in 2009.

Polymer concrete

Polymer concrete is a concrete that uses polymers to bind aggregates. Polymer concrete can gain a lot of strength in a short time. For example, polymer blends can reach 5000 psi in just four hours. Polymer concrete is generally more expensive than conventional concrete.

Geopolymer concrete

The geopolymer cement is an alternative to ordinary Portland cement and is used to produce Geopolymer concrete by adding regular aggregates to the geopolymer cement slurry. It is made of aluminosilic inorganic (Al-Si) inorganic polymer compounds which can utilize 100% recycled industrial waste (eg fly ash, copper slag) as manufacturing inputs that produce up to 80% lower carbon dioxide emissions. Greater chemical and thermal resistance, and better mechanical properties, are said to be achievable for geopolymer concrete under atmospheric and extreme conditions.

Similar concrete was not only used in Ancient Rome (see Roman cement), but also in the former Soviet Union in the 1950s and 1960s. Buildings in Ukraine are still standing after 45 years.

Refractory cement

High temperature applications, such as masonry ovens and the like, generally require the use of refractory cement; Concrete based on Portland cement can be damaged or destroyed by high temperatures, but fireproof concrete is better able to withstand such conditions. The materials may include calcium aluminate cement, fire clay, ganister and high mineral in aluminum.

Innovative mixture

Ongoing research into alternative mixtures and constituents has identified a potent mixture of promising properties and very different characteristics.

One university has identified a mixture with a much smaller crack propagation that does not suffer from ordinary cracking and loses subsequent forces at high tensile stress levels. The researchers have been able to take the mixture beyond 3 percent of the tension, passing a more typical 0.1% point where failure occurs.

Other institutions have identified magnesium silicate (talc) as an alternative material to replace Portland cement in the mix. It avoids the usual high-temperature production processes of highly energy and intensive greenhouse gases and completely absorbs carbon dioxide while healing.

Gypsum concrete

Gypsum concrete is a building material used as floor coating used in wood framework and concrete construction for flame assessment, noise reduction, radiant heating, and floor flattening. It is a mixture of gypsum, Portland cement, and sand.

See also

• cemented composites are engineered
• Ferrocement
• Ready-made concrete
• Reinforced Concrete

References

Source of the article : Wikipedia