Artificial turf is a kind of plastic carpet, in texture and appearance to a natural grass comes close. Preferably it is used on sports fields such. B. used for hockey and football , but in recent years also increasingly in the commercial ( trade fairs , events, exhibition rooms) and private sector (as a replacement for natural grass or, for example, on balconies and roof terraces ) as flooring. Its use has become controversial due to eroding microplastic particles.
Manufacture and use
The sport-functional and technical properties are not only determined by the synthetic turf surface, but by the entire surface system, including the elastic layer (EL) or elastic base layer (ET) . Due to the rapid further development of synthetic turf coverings and the large number of types of coverings, high demands are placed on project planning, expert selection of coverings and consistent construction supervision. Technical requirements and care instructions include DIN 18035-7 (sports fields, synthetic turf areas).
Artificial turf is mainly produced using the so-called tufting process. The yarns used are made of polypropylene , polyethylene or polyamide . The tufted backing (carrier fabric) is coated with latex and mostly additionally stabilized. Today, soccer fields are usually filled with sand and / or rubber granules .
Despite the mostly similar appearance, there is a multitude of different synthetic turf qualities, which have a different fiber structure (straight, curled), fiber density and pile height depending on the application (soccer, hockey, tennis, golf, multi-purpose or similar). For hockey use, synthetic turf surfaces without pole filling are usually used. Synthetic turf is usually laid in rolls with a width of 1–4 m.
The laying takes place on an elastic layer made of PUR- bound rubber granulate or foam sheets or plates. Another group of coverings is designed so that it is laid directly on the mineral or asphalt substrate without an elastic layer. The connection of the covering joints of the roll material or the lines to be inserted is made by seam bandages made of polyester or polyamide fleece and PUR coating compound or (only for unfilled coverings) by sewing with a PES thread secured by a PUR binder on the back of the covering.
The synthetic turf surface is usually water-permeable. On the one hand, this property improves the sporting and protective function, and on the other hand, the soil is not sealed, so that rainwater can be released to the lower layers. The water permeability is usually achieved by perforation with holes about 4 mm in diameter at a distance of 10-15 mm.
The base layer must ensure the stability of the pavement system (constant evenness even under load) and water drainage. The creation is carried out according to the known rules of sports field construction (for example DIN 18035-6 and -7). Mineral base layers must in particular be designed to be frost-resistant. As a rule, the top base layer should be bound ( e.g. drainage asphalt ).
The drainage only takes place in the case of moderately heavy rainfall, exclusively in the vertical direction (i.e. through the base course). When there is heavy rain, there is also superficial runoff to the edges of the square (with a pitch of 0.5–1%), where a sufficiently efficient water drainage must be ensured.
The direct laying of synthetic turf coverings on unbound (mineral) base courses is problematic. This is particularly true in Switzerland because stable grain mixtures are not always available due to a lack of broken rock material. Over time, non-step-resistant grain mixtures lead to unevenness that is reflected on the surface of the pavement. Stability is also important during the laying of the pavement when transport vehicles move the heavy rolls of turf and apply the pile layer filling so that the base layer remains level. The condition in the water-saturated state is decisive for the step resistance of unbound / mineral base courses (for example, no segregation of the fine parts of the base course material may occur when stepping on). Suitable materials consist in principle of broken rock of sufficient strength with a maximum grain of at least 24 mm and a low fine grain content.
Manufacturers of artificial turf for private gardens also recommend structural preparation of the subsoil: First, the upper topsoil is removed to a depth of 10–12 cm and replaced with a sand bed compacted with rammers or vibrating plates, or a sand-cement mixture. This is followed by a geo-fleece, which on the one hand serves to seal against unwanted plants and on the other hand to stabilize the subsurface. In addition, fall damping can be added for play facilities before the artificial turf is laid over it.
Artificial turf pitches without granulate filling (full synthetic turf) are played on when wet. The lawn is watered regularly - for example during half-time breaks. The wetness reduces the risk of abrasions in tackles or falls and reduces the abrasion of the fiber material.
Artificial turf pitches in football are usually filled with granules, which then accumulate in the environment in the form of microplastics . The most common form of backfilling is SBR recyclate, which is made from old car tires . In addition, there are now also granulates specially tailored to the needs of football, which contribute to a large extent to dampening the playing field and have a decisive influence on the jumping and rolling behavior of the ball. Regular refilling of the heavily used playing field areas (penalty area, center circle) contributes significantly to the lifespan and quality of the synthetic turf base layer.
The usual formula, which helps to make decisions about the sports field surface, states that artificial turf is best suited for 800 to 2500 hours of use per year and is therefore recommended.
The costs of building a new artificial turf field (standard dimensions 105 m × 68 m) are between 460,000 euros and 600,000 euros. Decisive factors in the cost calculation are the external factors, such as the nature of the subsoil or the accessibility of the construction site, as well as the product-specific factors, which can vary depending on quality, manufacturer and regional price differences.
Commercial, public, private area
In addition to its original use in sports, artificial turf has also established itself in numerous other areas as a floor covering and alternative to natural turf. Artificial turf is particularly popular at trade fairs and exhibitions, as it is more resilient than natural turf and can be dismantled without leaving any residue. Public institutions also use artificial turf for green areas and playgrounds - in this context, artificial turf is also used in schools, kindergartens and day-care centers. In the private sector, artificial turf is chosen as an alternative to turf, if either no prerequisites for natural turf can be created in the corresponding location (such as on roof terraces or balconies). In addition, artificial turf in private areas is also increasingly being laid for the green area in the garden / front yard, where it serves to avoid a messy appearance with little maintenance. There it is an alternative to sealing and gravel gardens , which comes closer to the appearance of naturally grown lawn.
The minimum level of maintenance for the artificial turf consists of brushing the field, which must be done every two weeks, regardless of the type; Details must be provided by the flooring manufacturer at the latest when the flooring is accepted in the form of instructions for use and care (mandatory according to DIN 18035-7). In addition to being towed to level the bedding material, the dirt must be removed before each use, especially before brushing on, as the whisk or peeling mats distribute the bedding material and work it into the fibers. If there is dirt, no matter in what form, on the surface, it will inevitably also be distributed and incorporated into the litter material. A thorough cleaning is required at least once a year, during which the backfill is filtered through a sieve to remove impurities. During this process, the fines are also extracted at the same time. This is the only way to ensure water permeability and elasticity in the long term. This annual measure is often carried out by specialist companies as part of a 4- or 5-year service contract. On this occasion, the experts also get an idea of the condition of the square, check the seams and lines and carry out appropriate repairs if necessary. After a service contract has expired, the association or municipality must devote itself to this task. Subsequent services would be much more expensive, which is why there are devices for weekly maintenance that can also carry out the annual deep and deep cleaning. These devices are far cheaper than the service over the entire service life of the covering. Assuming a maximum service life of the artificial turf of 15 years, 13 basic cleanings are necessary in any case. According to one of the largest flooring manufacturers, annual cleaning costs € 0.35 per m². Even if the basic maintenance of artificial turf is comparatively manageable, it should be ensured that the leaves are blown off regularly in autumn, for example.
An overview of the weekly maintenance (or after 30 hours of use at the latest) of an infilled artificial turf:
- Towing and leveling of the bedding material, which has to be moved from the overcrowded to the undercrowded areas
- Removal of all contamination prior to any use, especially prior to towing
- Immediate refilling of missing bedding material
- gentle loosening of compacted pavement areas
- The fibers are straightened up by being towed against the lying direction
The filling height of the artificial turf surface determines how often the towing and leveling is necessary. If the spaces are filled too low (there are no binding specifications, only suggestions from DIN 18035), the maintenance effort increases. Artificial turf coverings with a low level of filling (approx. 20 mm free-standing fibers) are more susceptible. Coverings that are not properly cared for can still be used for their intended lifespan (today an average of around 15 years is assumed), but the properties of the covering are then no longer in a reasonable relationship to the high acquisition costs of artificial turf. Caring for artificial turf is definitely easier and cheaper than correct caring for natural turf. Nevertheless, the maintenance staff of the artificial turf must be trained as well as the maintenance team of a golf or soccer field with natural green.
Irrigation can help optimize the playing characteristics of an artificial sports field. The higher the demands on it, the higher the maintenance effort. Assuming that a high-end product was actually laid for demanding applications, it also requires more attention than that of a medium quality.
The average life cycle of an artificial turf system is approx. 12 to 15 years. Afterwards, a new artificial turf usually has to be laid. The dismantling of an area of 6,500 m² (average of the size of a soccer field) costs around 20,000.00 euros. This already includes the proper disposal or recycling of all materials. The elastic base layer under the lawn can in most cases be used at least twice. Should the base course also have to be replaced, the additional costs of dismantling the base course will be around 35,000 euros. Dismantling is more complex if the artificial turf is to be replaced by vegetation, for example to restore green areas: Due to the structural changes and compaction of the subsoil, there is no longer any soil suitable for plant growth. It is then a matter of dismantling a paved area.
Problems and criticism
The rubber granulate used in artificial turf - mostly from used tires - is a main source of synthetic rubber - microplastics , directly after the material from tire wear on roads and contributes significantly to the pollution of soils and oceans : FIFA estimates that 1–4% of the plastic filling is lost and gets into the environment and has to be replaced every year. According to surveys by the Norwegian environmental authorities, around 3,000 tons of rubber granulate enter the fjords there every year . In Germany, the emission is estimated at around 8,000 to 11,000 tons per year. A ban on artificial turf pitches is being discussed at EU level . According to estimates, between 3,500 and 5,000 artificial turf pitches would be affected in Germany. According to a study by the Eidgenössische Materialprüfungs- und Forschungsanstalt , artificial turf pitches made up 3 percent of rubber emissions in Switzerland in 2018 , while tire wear accounted for 97 percent .
Artificial turf heats up much more in the sun than natural turf, and also more so than smooth surfaces such as stone and asphalt. The reason is, on the one hand, the relatively dark color and, on the other hand, the fibrous surface in which insulating air cushions form. Cooling due to evaporating moisture, as with natural grass, is completely eliminated. In a series of measurements at Brigham Young University in the US state of Utah, average values of 47.4 ° C (117.38 ° F ) were achieved over the whole day on the artificial turf of a soccer field , compared to 43.1 ° C (109.62 °) F) on asphalt and 25.7 ° C (78.19 ° F) on natural grass. The measurements showed temperatures of 93.3 ° C (200 ° F) as peak values.
On sports facilities, this can lead to burns when touching the artificial turf, to a strong sensation of heat, also through shoe soles, and to shoes being damaged by melting. In isolated cases, life-threatening dehydration problems and heat stroke, which were accelerated by the hot surface, have also been reported.
In hot weather, artificial turf can soften or melt, which leads to irreversible destruction. The mostly contained plastic polyethylene partially softens at temperatures around 80 ° C and melts just under 100 ° C. This can occur particularly in the area of light reflections from windows, which add to the directly radiated solar energy. The effect is particularly strong with thermal insulation glazing, where thin metal coatings on the glass also reflect the sun's infrared radiation. In Germany, football pitches became unusable several times in the middle of summer because the granules used for the filling softened and clumped into a tar-like mass on the shoes. In some cases, expensive repairs and replacement of the filling granulate were necessary.
The problem of heat is countered on sports fields by irrigation, which at least partially uses up water savings compared to natural grass. Glass reflections can be countered by window films. Such films can, however, the view and u. U. affect the thermal insulation properties.
On private land, building regulations limit the proportion of space that can be built on, including through the number of floor areas . According to a ruling by the Hanover Administrative Court on November 26, 2019, areas are also considered ancillary structures within the meaning of Section 19 Paragraphs 2 and 4 of the Building Usage Ordinance if they cover the soil and have a significant impact on soil flora and fauna. This also applies to designs that can be infiltrated, in the given case a wooden deck terrace and gravel gardens. There is no provision for the sealing to be only partially offset, as is the case with rainwater charges. The professional installation of artificial turf, even in simple versions for private gardens, involves a considerable structural change in the subsoil .
Use in different sports
Hockey is almost exclusively played on artificial turf that has been watered and no longer on natural turf. This makes the game much faster and more accurate, and the differences to indoor hockey are smaller. The development from turf to artificial turf began in the 1970s and by the 1990s top hockey was being played almost everywhere on artificial turf. The Olympic hockey tournament was first played on artificial turf in Montreal in 1976 . The usual color was also green for the artificial surface, but blue artificial turf was used for the first time at the 2012 Olympic Games in London .
The transition from natural turf to artificial turf has influenced the game of hockey so much that some experts speak of a "revolution". The fact is that the change not only affected the shoes, but also balls and rackets and tactically led to different game systems.
The top football associations UEFA and FIFA have now also approved artificial turf pitches for competition, provided the artificial turf systems meet the quality criteria of these associations. Since 2006, FIFA has certified 3,437 places in 149 countries.
At the international level, FIFA allows artificial turf to be used in all matches except those in the men's World Cup. Condition: The product must be certified. There are two options here, “FIFA Recommended 1 Star” or “FIFA Recommended 2 Star”. The “2 Star” variant is generally approved by UEFA, including in the Champions League. In German professional football, there is an agreement between the DFB and DFL that only natural grass is permitted from the 1st Bundesliga to the regional league. In German amateur football from the regional league down to the regional league, surface types B, D, E and G are permitted according to DIN 18035-7, and surface type A is also permitted in lower game classes.
In the new Salzburg stadium opened in 2003 (EM stadium Wals-Siezenheim , later renamed the Red Bull Arena ), the playing field was covered with artificial turf, which was replaced with natural turf in summer 2010. In 2002 , an artificial turf pitch was installed in the Luzhniki Olympic Stadium in Moscow , where Spartak Moscow played its home games until 2013. This flooring was used there for the first time in the Champions League in the 2006/2007 season . In spring 2006 the new Wankdorf stadium in Bern was also equipped with artificial turf. In France, two were in summer 2010 Erstligastadien the artificial turf from a German manufacturer (Polytan): the Stade du Moustoir in Lorient and Stade Marcel Picot in Nancy . Various certified artificial turf pitches also exist in the Scandinavian countries. Another provider was selected for the stadium of the Dutch first division club Heracles Almelo .
Golf, swing golf
Natural putting greens require a lot of maintenance (daily mowing, fertilizing and watering). Artificial turf offers the opportunity to greatly reduce maintenance costs. Another area of application in golf and swingolf are the driving range and teeing areas, which are subject to heavy wear and tear.
There are two types of artificial turf putting greens:
- Nylon putting greens are ideal for putting , chipping and pitching. Nylon surfaces are very dense, resistant and practically maintenance-free. They hardly fade and are suitable for all weather conditions.
- Putting greens made of polypropylene are filled with quartz sand and are particularly recommended if the green is to be played from a greater distance (from approx. 40 m). These greens also accept backspin . The sand filling distributes the impact energy of the ball. Filling with quartz sand does not bleach the fibers. These putting greens require regular maintenance, as fly seeds or moss can occasionally become lodged in the sand fill.
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