FAIR-FACED CONCRETE TERMS
Fair-faced Concrete Jargon
the most important words to look up
Fair-faced concrete is the term used to describe concrete surfaces that assume a design function and whose appearance is subject to special requirements. The quality of the fair-faced concrete surface is determined by the formwork shell (excluding post-processed surfaces).
The requirements are defined by standards and guidelines.
FAIR-FACED CONCRETE CLASS AND REQUIREMENT CLASS
These terms are used to describe the technical and design requirements and are defined in the guideline for exposed concrete and shuttered concrete surfaces. They contain predefined and summarized definitions of requirements / requirement classes for planning, tendering and execution.
The fair-faced concrete classes in connection with the non-class-forming requirements are intended to support and facilitate communication between clients, architects, planners and the construction department, as well as to enable fair-faced concrete quality that is suitable for tendering and verifiable.
THE FAIR-FACED CONCRETE TEAM
The fair-faced concrete team represents a coordinated network of all participants in order to achieve the defined requirements in mutual agreement. An architectural concrete coordinator can be used to serve as an interface between the client, the planner, the local building supervision and all the companies carrying out the work.
STRUCTURAL CONCRETE / TEXTURED CONCRETE / PHOTOGRAVURE CONCRETE
Since concrete can also be called cast stone, it is obvious that its shape should be given plasticity by the formwork skin. Textures, patterns and structures are usually reproduced on the concrete without undercuts, by inserting matrices or by using special formwork skins.
The photo engraving technique works with a similar principle as photo concrete (produced by special screen printing foils), in that linear or punctual depressions create a shadow play that corresponds to the original image (as a grayscale image).
Through-coloring can be achieved by adding fine pigments in the desired shades. Further influences on the coloring are the water-cement ratio, the formwork skin surface, the type of cement and the general aggregate.
Glazes and paints also allow the coloring of concrete, although these are only applied to the surface and also change or conceal the concrete's own surface structure.
A screen printing process is used to produce photo concrete. Contact retarders are used to create different wash-out depths and roughness. These screen printing foils reproduce photos as a fine dot grid in gray tones. The roughened surface structure is exposed by subsequent washing-off/out of the unhardened top layer. The viewing position and the incidence of light are largely responsible for the appearance of the image, since the depth of the relief creates a shadow.
Due to different protection requirements for the finished concrete surfaces, there is a wide range of curing methods such as coatings, sealers, hydrophobic coatings and anti-graffiti protection.
The possibilities of aftertreatment by painting and thin coatings range from increasing the diffusion resistance and impregnation against liquids, to protection against chemical and mechanical attack, to crack bridging.
In general terms, formwork is a formative boundary in which the concrete is placed and hardens. The type of formwork or the formwork system is selected according to the requirements of the component to be produced.
In general, formwork consists of several components and is separated at least in formwork skin and support structure (commonly called formwork).
Additionally, stiffening constructions, connectors, spacers, etc. may be necessary.
Formworks are differentiated in their materiality (steel, aluminium, wood...) and their type / system.
The formwork skin is the surface of the formwork that comes into contact with the concrete and contributes significantly to the surface design.
By definition, a draining effect of the formwork skin allows surfaces free of pores and voids to be achieved.
FRAME IMPRESSION AND SHUTTERING SKIN JOINT
The frame imprint is the image of the formwork elements and their joints in the concrete surface. This can be prevented/reduced e.g. by the use of matrices. The joint pattern of adaptive fair-faced concrete matrices, which in this case can be described as the formwork skin, does not have to correspond to the element joints.
Porosity is defined as the maximum percentage of pores per surface. The test is carried out using test surfaces with a size of 50 x 50 cm. The percentage of pores is compared with "approximate" specifications, whereby a slight excess is possible.
Small openings of 1-15mm are designated as pores.
SINGLE CURVED SURFACE
These are uniaxially curved surfaces. The simplest example of this in architecture is the arch. Simply curved surfaces are called unwindable, which means that they can be produced by deforming flat surfaces.
DOUBLE CURVED SURFACE
Double-curved surfaces can usually no longer be unwound and can be curved in different directions, both positively and negatively. The most obvious example in architecture would be the vault.
Shells are usually thin, high-performance load-bearing structures which, due to their special shape, can transfer loads vertically and over the surface. The ratio of the shell thickness to the span width is very small and thus shows a high material efficiency. The planning, calculation and execution of such structures requires high competence and care in all areas.
The use of high-performance concrete allows extremely slim design of load-bearing components, especially in combination with textile reinforcement (carbon reinforcement).
UHPC has a dense structure and low porosity due to its fine particle composition. This results in a dense and resistant surface with less susceptibility to cracking and reduced penetration of liquids.
SCC SELF-COMPACTING CONCRETE
Self-compacting concretes are usually high-strength due to their fine-particle composition and have a high flowability. This property allows the fresh concrete to spread and compress itself, allowing air voids to escape. They are used in fine-particle or complicated structural elements where conventional compacting (vibration) is not possible or where special exposed concrete requirements are given.
In-situ concrete is the concrete that hardens at its destination. The origin of the concrete itself is not significant, as it is usually supplied as ready-mixed concrete.
Prefabricated concrete parts are components and elements that are produced under conditioned conditions in a factory. These are then transported, moved and assembled/casting/stored. Prefabricated parts are mainly used in system buildings, components with a high number of pieces or complex components whose production on site is difficult or impossible.
REINFORCEMENT / ARMOURING
Concrete can hardly absorb tensile forces and is therefore reinforced by steel or plastics (CFRP, GFRP). This reinforcement can be in the form of fibers, rods, mats or spatial baskets. Furthermore, a slack or pre-stressed installation is possible.
PURAcrete is the flat formwork matrix for the production of exposed concrete surfaces with special requirements.
In addition, basic formwork with this draining formlining is upgraded for the favourable use as fair-faced concrete formwork.
The structural matrix can be used as an adaptive formlining in both in-situ concrete construction and precast concrete construction.
Through product adaptations, different applications and requirements can be fulfilled, such as the production of non-porous surfaces (according to standard), formwork matrices for multiple use and the production of photo concrete or relief patterns, ornamental concrete surfaces and structural concrete.
PURAarc is a specially developed production technique for the manufacture of the formwork bodies of single-curved and double-curved exposed concrete components.