Architectural concrete

Gray day, gray walls, gray surroundings, everything connected with the word gray - usually a word associations produces concrete. Attempting to stories about the fact that concrete is a wonderful material for the artist or architect with a vision and idea to reliably bring us to the great estates or "pear" pouring additional cubic meters of concrete in another twin of bridge or viaduct ...

However, this is only an illusion. Recently, more and more and more boldly enters the public space architectural concrete. There is currently no uniform definition, there is no reliable calculation rules to be met mean that what we meet it is the architectural concrete.

One of the many characteristics of states that define this as concrete, which besides that meet certain obvious features besides construction, are designed to shape the architectural value of buildings and their surroundings.

Another similar claims that it is a concrete, which the architect in the design process can give a certain color, texture and shape designed to perform important functions in the proposed facility.

Yet another treats it with a structural concretes, facade, facade - adding, besides the aforementioned characteristics, can be used to construct both the monolithic elements and the individual - prefabricated.

All as a basic feature of such concrete mention the fact that such an element, a building or a huge building in addition to the function of purely technical is something that affects the environment through how to perform and how you present, and as viewers look at these structures in the same way, how we evaluate the architecture - that is, not in terms of the material that has been given element made, but from the point of view of aesthetics and how it affects our senses.

Key features mentioned in these definitions suggest examples of how this might look like concrete:

• small repetitive elements whose dimensions do not exceed several tens of centimeters
  
• some whole - eg. features kitchen, a room or bathroom - even as large as several meters
  
• statues and monuments, architectural creations designed to change the environment to make their very existence exerting some influence on us
  
• powerful, massive objects whose appearance has a significant impact on how we perceive them, how hard blends (or the contrary) in the environment
  
• everything else that can fit between them
  

The second part of the definition described (and others that can be found in books or learned from the presentation of this dealing) concerns the possibility of forming a mold that for us already in a particular environment and the site affected. This means that the architect must be able to:

• give any color, including the possibility of etching or staining of certain layers in the depth of the surface sections
  
• give any shape - which in turn forces the use of such material and such chemicals (additives) to as much as possible to change the properties of the mix itself
  
• transmit any invoices - which in turn means that not only the same color, same shape - but also to a piece of concrete imitated any thing, and even that was her exact representation
  

There are only so gently circled boundary conditions (or otherwise - one that at the moment can be considered as the boundary), make this type of concrete, the vast majority of rules that are typical for him - in many cases is not applicable. Same form and manner design, basically an individual for each client, make the price however is one of the limitations, it is not the most important. It is usually a function of what we want to achieve. At its height it is necessary to use:

• high-quality cement
  
• high-quality chemical (or other modifiers of concrete features)
  
• high quality mineral additives (those which aim to influence certain characteristics of the mixture - eg. the rate of increase in strength)
  
• high-quality pigments - that stained weaker or stronger mix
  
• others (eg. armaments), contributing to the strength of concrete
  

Cement - currently known and used in high strength concrete which corresponding to class B 200, and more. In principle, every few years are discovered and new technologies. Currently, the most popular are among others:

• high-grade concrete (high strength concretes HPC) - strength class B 60 - B 120
  
• very high strength concretes (VHPC) - Strength class B 120 - B 180
  
• ultra high strength concrete (UHPC, Ultra High Performance Concrete) - Class B180 or higher
  
• self compacting concrete - a concrete mixture able to tightly fill the formwork (formwork) under its own weight without the use of vibrators
  
• fibroconcrete - concrete containing the micro-dispersed in the form of steel fibers, polymers fibers, glass fibers
  

To obtain such high strength - the need for cement, which by itself, without modification allows to obtain the highest quality concrete. The stronger, the better. This means that by doing architectural concrete are starting from a much higher ceiling than if cement was used, eg. 32.5 or 42.5. We should remember that the same class of cement really only says it, what is the minimum strength according to the standard, rather than what is the real strength of the cement. Other provides opportunities for cement, which has been standardized strength after 28 days is 72 MPa, and the other of which is a strength of 57 MPa, although both are designated as grade cement 52.5 ...

Of course, the only modification can not only cement. These types of concrete are different and much composition from what we know and what we can sometimes see. The most fundamental changes are among others:

• increase in the amount of cement, up to more than 700 kg / m3 of concrete, and in percentage terms - nearly 50% of all minerals (usually m3 of concrete uses 300-400 kg ordinary cement)
  
• decrease in water consumption (ratio w / c), even 0.2 (usual rate is at a level of approx. 0.4 - slightly more than 0.6)
  
• the use of high-performance superplasticizers
  
• the use of reinforcement
  
• using special fillers, usually silica fume and / or silica aggregate replacement. Because of the strength of a concrete which must move on the used mineral requires greater strength than that which is obtained concrete. The mere addition of silica fume can increase the strength of concrete in "norm" 28 days of well over 50% after 90 days - more than 60%, and that for an ordinary type of cement type 32.5
  

The increase in strength of concrete "by itself" after about 20 years, depending on the environment in which it is located can reach up to two and a half times ...

Of course, the very process of production of such concrete, the care must be subject to special supervision in order to have achieved the desired parameters and did not occur at the same time undesirable phenomena such as eg. excessive contractions or too high temperature hydration.

In the production process it is necessary, as was already indicated several times, the use of high-performance chemical additives, which are intended to among others:

• at the very beginning of a reduction in the required amount of water to be used to mix concrete in general he began to set. These are the most superplasticizers
  
• - increase strength and resistance to weather conditions, which can be obtained using a specific type of cement, for example by reducing the water absorption
  
• for purely aesthetic values, which are to make the concrete will actually architectural. This may be an illusion of color blur, partially plasticity outer layer allowing for imprinting a pattern or a decoration such as the ability or "etching" a portion of the outer level of the element
  

They take on the consistency of both the liquid (more often) as a powder, in both embodiments, however, the quantity must be measured very accurately, because in most of the cases, such substances are in tenths of a percent weight of the total or binder material (cement).

Strength requirements posed by architectural concrete means that it is not usually possible to use ready-made cement embodying accessories (indicated generally as CEM II or below), since the composition of mineral additives must be constant, independent of the batch of cement, and so strong chemistry can make that is, what will be achieved in the production process will not be suitable for anything. For this reason, the specific composition of the concrete mix is achieved simply by adding "pure" ingredients together according to a formula - means separately portland cement type CEM I (eg. white) separately dust silica and / or quartz, separately other fillers and only the individual chemical additives, as well as those for the reinforcement of concrete.

This is the simple reason, which have already been mentioned. Any kind of "supplement" contained in the finished cement - from dust to limestone is marked in the standard certain boundary conditions which must be met in order to be able to be used as a substitute for clinker. It would seem that the precise composition of the dust of "not less than 1% and not more than 3%," "1%", "shallowness to ..." allows the recognition of such dust behind homogeneous. Unfortunately - slight differences in "batch", which in the combustion process are obtained, cause obviously delicate, and sometimes more than subtle changes in the composition, which however is within certain standards, it is with such of advanced chemistry and with so high demands on the chemical composition of ready cements additives do not fulfill their role. It is necessary simply to buy the manufacturer of a particular type of filler of a particular thickness. Only this will ensure full repeatability mixture.

An essential attribute of architectural concrete is the color. In the concrete, it is obtained by using various kinds of pigments, cement, or those that can mix with cement. It is understood that without detriment to their strength can add no more than 5% relative to the amount of cement used in mortar or concrete

Basically, they are produced based on various iron oxides, and the amount and type of oxide (usually expressed as a percentage) are on the color with which we are dealing. There are a few exceptions. Belong to them:

• whites - or titanium oxides
  
• greens - or chromium oxides
  
• blues - or cobalt oxides
  

Using this type of pigment should be aware of a few basic principles. These are:

• color, which can be obtained by using pigments, cement does not depend proportionally on the amount of dye used. The initial change in the color are significant to gradually decrease. In extreme cases be significant (two- or three-fold) increase may, in fact, almost did not result in the resulting color intensity
  
• color can be strong and intense, but they are basically pastel colors. It is from the color, which is a mix of concrete. Typically, the ingredients are delicate shades of white or beige, which means that any color palette begins on or colorless / transparent, but a white or it shade
  
• there is an infinite number of shades of cement pigments. Typically, manufacturers have several versions of each color, such as bile (including orange), red (including cherry or clay), brown, black or green. Blue pigment "likes to be" sensitive to UV radiation, so not every manufacturer has it in its offer. Different colors often obtained by mixing two or three colors together, it must be remembered that it is not always mixing different, it would seem obvious shades, we get the desired color
  
• you can keep repeatability, but keep in mind that to measure individual doses - scoops pigment very carefully, sometimes even to the tenth of a gram. Do not measure the amount of volume (e.g.,. 20 cm3). This is a very simple reason - the weight of each pigment varies considerably. Extreme examples are yellows (and in particular those orange) and black or green. The former are sold in large 20- or 15- (orange) kg bags, the latter are small "prescribed" 25 kg
  

Architectural concrete in many cases requires the strengthening reinforcement, if only for the reason that many elements have to carry heavy loads despite the small thickness and relatively large surface area. It is not always the same strength cement compressive make the concrete will not crack and can withstand what he should.

That's what reinforcement is used, is conditioned m.in .:

• what features it has to fulfill the item, monument, building, etc
  
• what is its thickness
  
• what is its surface
  
• under what conditions will be used
  

Traditionally, the reinforcement is intended either to the grid or single bars of the appropriate size (thickness), normally finned, arranged in a suitable location. In this case it is not so simple. Such narrow and conventional understanding of the term in too many cases causes a bright or white concrete "come out" characteristic rust infiltrates having its cause in the fact that the reinforcement are small bonfires rust, and the concrete is not always so tight, to stop them.

For this reason it is so popular. fiber reinforcement or having the appearance of the grid, but the word grid is made from materials other than steel derivatives - eg. plastics, often with a much better performance than traditional reinforcement, but also a much higher price, it happens that by orders of magnitude

The first is usually different size and thickness of the strips or threads made of almost all kinds of synthetic materials added in an amount specified by the manufacturer of concrete. Due to its shape and the amount of work as a traditional reinforcement they will not have the characteristic and often undesirable defects.

The second type is simply a grid, reminiscent of the traditional, but also created artificial materials - plays the same role as the first one

That's what reinforcement is or must be used, this decision forced by a designer, what would be the architectural concrete created.

Recently increasingly fashionable are individual projects of houses, buildings created not for the purpose of mass directory in which each developed project is shown surrounded by perfectly equal to the plot, which does not have any inclination or equal to the ruler, but for a specific location where it will be built, environment in which it is located and the function they have to fulfill. The surface of such a house or building is also the function and just as important as everything else. One of the basic material that is used is concrete, with a very simple indeed because - as with all glass and wood gives the enormity of possibilities in shaping the texture, color and the appearance.

Concrete understood not as a gray mass, and the concrete in the meaning and function of architectural concrete, the white or another color harmonizes with the environment, and the contrast with the color of glass and wood additionally helps to meet the assumptions of architects and originators.

White cement and its quality helps make the building itself does not look heavy bunker, allowing for the construction of lighter construction, thinner walls, giving a really big opportunities in shaping the external appearance of the building at the time tapping the walls and the structure itself

An alternative is to use a suitable type of concrete slabs which adhered to the walls make it necessary for watching it from outside the building people give the desired appearance, also in terms of color and texture. Of course, an important material that allows full use of concrete is white cement

Crossing the designers and contractors barriers that seem impenetrable, is in many cases the norm. Enormous strength, limits achieved by using materials of the highest quality, enormous amounts of added chemicals modifying the properties of materials and products make that in many cases the reality goes hand in hand with science, or is it the living tissue of the experimental. Many designers believe that the extremely high strength on the one hand can cause extreme to another location. So far not encountered yet spectacular disasters resulting from the underestimation or undervalued parameters of concrete. At the moment asked questions moving in two directions: how long and for what boundaries you will be able to increase the desired concrete performance by designing ever more sophisticated buildings, requiring higher and higher extreme values that must be satisfied that the buildings of the card design is a reality of our cities and streets.