Asphalt refers to a natural or technically produced mixture of the binding agent bitumen and aggregates , which is used in road construction for pavement pavements , in building construction for floor coverings , in hydraulic engineering and less often in landfill construction for sealing . For technical and economic reasons, asphalt pavements are divided into various layers. A distinction is made here between asphalt base , asphalt binder and asphalt surface courses . Depending on the thickness and position, they contribute to the load-bearing capacity of the overall structure, provided that all layers are connected to form a compact structure . Asphalt is almost chemically inert (slow reaction behavior ) and has a thermoplastic behavior.
The word is derived from ancient Greek ἄσφαλτος ásphaltos "asphalt, resin", which in turn is a verbal noun of σφάλλεσθαι sphállesthai "to fall" negated by means of alpha privativum . This probably goes back to the fact that asphalt was originally used as a binding agent in the construction of walls and protected the walls from being knocked over (falling over). The Romans called the material pix tumens , "swelling or billowing pitch"; from this the term bitumen arose . Asphalt and bitumen were used for embalming of corpses used. An Arabic name for it is therefore “mum”, derived from the Persian-Arabic mûm or môm for wax, from which Mumia was Latinized .
Definition of terms
The building material asphalt is commonly mistakenly equated with tar . Unlike asphalt, whose binding agent bitumen is obtained from petroleum , the binding agent tar is created by pyrolysis of wood or coal . Tar is considered to be extremely hazardous to health and its use in road construction in the Federal Republic of Germany has been prohibited since 1984. This fact is laid down in Technical Rules for Hazardous Substances 551 . In the period before his ban tar was a commonly used building material in the construction industry , for. B. in the so-called dust removal .
Outwardly, the two substances differ slightly in terms of smell and appearance. Bitumen, for example, has a neutral odor and a black color, while tar, on the other hand, has a slightly sweet smell and a light brown color.
Material containing tar must also be disposed of separately when it is recycled . The Europe-wide waste catalog , implemented in Germany through the Waste Catalog Ordinance , classifies waste materials containing tar as hazardous waste. Removed asphalt, on the other hand, can be recycled without hesitation.
The strength of asphalt is determined by the temperature conditions. At low temperatures (winter) it is elastic , at high temperatures (summer) it is viscoelastic . This temperature behavior has a direct influence on the elasticity and shear modulus of the asphalt. The modulus of elasticity describes the stress in the asphalt that occurs as a result of load-related deformation . It fluctuates between 1000 N / mm² in summer and 9000 N / mm² in winter. The shear modulus reflects the stresses that are generated in the asphalt as a result of shear deformations.
The material properties of asphalt depend on the mixing ratio and the properties of the two components bitumen and aggregate . The mixing ratio is roughly 95% aggregate and 5% bitumen , but this ratio can be changed slightly up or down. The amount added (so-called binder content ) and the hardness (i.e. the type of binder ) of the bitumen change the material behavior significantly. The type of binder also determines the softening point , which can be proven with the ring and ball test; the hardness of the binder is determined with the needle penetration .
The aggregate takes on the supporting function in the asphalt and its grain size composition , the so-called grading curve , has to be adapted to the load. If certain grain sizes, i.e. grain proportions , are missing in the grading curve, such as in open-pore or stone mastic asphalt , then one speaks of a failure grain .
In order to achieve good load-bearing behavior, the grain composition must be set so that the rock mixture is as dense as possible . Together with proper compaction during paving, an asphalt with few voids is created (exception: open-pored asphalt). Furthermore, the aggregates must be frost-resistant and, in the case of an asphalt surface course, polish-resistant.
Asphalt is impermeable to water if the voids content is ≤ 2–3% by volume. Asphalt also shows no signs of erosion when flowed through ; the adhesion between mineral and bitumen and the cohesion of the bitumen prevent this.
The building material asphalt now carries the significant share of the construction materials for the road surface of roads. According to information from 2005, for example, 95% of all paved roads in the Federal Republic of Germany had an asphalt surface layer . A closer look reveals that around 75% of the municipal and city streets as well as the federal highways have an asphalt surface. The remaining 25% have a plaster or concrete ceiling . Asphalt is used almost exclusively on German federal highways.
In 2016, 41 million tons of asphalt mix were produced in Germany . Of this, 26.6% was reclaimed asphalt that was recycled. In Austria, the asphalt mix production amounts to 7 million tons annually.
Based on archaeological excavations, it can be established that natural asphalt was already used in early antiquity (around 1200 BC) to manufacture weapons and equipment as well as to color jewelry and sculptures . The material was often used in the Mesopotamia region in particular , as there were natural asphalt deposits here. The peoples living there, for example the Sumerians , made vessels and reed boats ( guffa ) , which were sealed with asphalt. They also used the material as a mortar for mud bricks . Such a reference can also be found in Gen 11.3 ELB at the Tower of Babel , which, according to strictly biblical chronology, dates from approx. 2300–2200 BC. Is classified.
Over the millennia, the fields of application expanded, so that around 2000 BC In addition to Mesopotamia, natural asphalt was also used as a sealing material for baths, boats, canals, toilets and embankments in India and Europe . In Mohenjo-Daro , one of the two main centers of the Indus culture in Pakistan, a 12-meter-by-7-meter pool was sealed with a thick layer of asphalt. Around 2100 BC In BC King Gudea of Lagasch, a city-state in southern Mesopotamia, had over a hundred tons of asphalt delivered by ship. So it seems that a buoyant trade in petroleum products is not a modern privilege . Around 2050 BC Chr. Was the Nanna- ziggurat of Ur , a three-stage tower with asphalt laid fire bricks and large, covered with asphalt terraces . In the 7th century BC Asphalt was already used in road construction in the Assyrian and Babylonian empires . There it was used as joint material or as a mortar bed for boulevards ( Aibur-Schabu ). Asphalt was also used to seal the Semiramis Hanging Gardens . At the end of the 1980s it was proven that the Egyptians had used petroleum asphalt from the area of the Dead Sea ("Judenpech") to embalm their pharaohs , which historians had ruled out until then. During the time of the Roman Empire , he served around 100 BC. As grout for Roman roads in Pompeii . Starting from Pliny the Elder , asphalt was named Bitumen Iudaicum "Judenpech". The Romans, as the great road builders of antiquity, hardly used bitumen, they mainly used wood tar pitch .
Middle Ages to 17th century
After the fall of the Roman Empire and the beginning of the Middle Ages , asphalt lost its importance, which only changed again in the 18th century. The extraction of bitumen from natural asphalt began in Arabia around the year 1000 . This was achieved by heating the natural asphalt and allowing the bitumen to sweat out.
Like petroleum, asphalt was also used in medieval and early modern medicine .
In addition to its use as a building material, asphalt was also used for medical purposes in the 15th century in the Inca Empire in South and Central America.
On his exploratory trips Sir Walter Raleigh discovered a natural asphalt lake on March 22, 1595 , which is located on the island of Trinidad ( La Brea Pitch Lake ). He used the opportunity and the properties of the asphalt to seal leaks , as otherwise his ship would no longer have been seaworthy . The asphalt protruding from the underground is still used in road construction today.
In 1712 the Greek doctor Eirini d'Eirinis discovered the gigantic asphalt deposit of La Presta in the Val de Travers in Switzerland . At first he was only interested in its medical application. Because of the technical advantages of this material, he finally wrote his “ Dissertation on asphalt or natural cement” in 1721 and founded modern asphalt technology with his research . From the more than 100 km long labyrinth of tunnels and tunnels of the asphalt mines in the Val de Travers asphalt was extracted and exported all over the world for around three centuries (from 1712 to 1986). After various owners, the mines came into the possession of the English company Neuchâtel Asphalt Company Ltd. in 1873 . and were bought up in 1960 by the largest European road construction company, the English company Tarmac . In France, further important deposits were discovered in 1756 near Lobsann in Alsace and in 1797 near Seyssel in Upper Savoy.
Mastic asphalt , a mixture of asphalt mastic (melted, pulverized asphalt stone) and asphalt tar (formerly known as goudron ), partially enriched with gravel or sand , was initially used to produce road surfaces . In 1835, the first sidewalks in Paris (on the Pont Royal and Pont du Caroussel ) were paved in this way. A few years later, the mastic asphalt was also used in road construction (in Lyon in 1838 and in Paris in 1840). However, the softening of the material in summer proved to be a problem.
Therefore, people soon switched to using rammed asphalt (crushed natural asphalt stone) instead (in Paris as early as 1854, in London , Vienna and Berlin only around 1870). This was applied to a concrete base and then compacted to a thickness of just a few centimeters by tamping . Due to the effects of traffic , the rammed asphalt was further compacted and polished at the same time . It turned out to be a disadvantage that the road surfaces were extremely smooth when it rained, and vehicles (especially those with rubber tires ) could easily slip , which led to numerous traffic accidents . In 1928 the Vossische Zeitung was still outraged that the Berlin civil engineering administration, despite the high risk of accidents, did not want to abandon the use of rammed asphalt , as had already happened in Paris and Vienna.
The common today rolled asphalt ceiling (a mixture of sands certain grain size and petroleum bitumen ) were in North America developed in the 1870s, spread to Europe, but only at the beginning of the 20th century ( Stuttgart 1911, Hamburg in 1912 and Dresden in 1913).
The building material asphalt gained increasing importance at the beginning of the 20th century, which was partly due to the steadily falling material price. The first asphalt mixing plants went into operation in the United States in 1907 . In 1914, the AVUS in Berlin was provided with an asphalt surface for the first time in order to achieve greater resistance.
In addition to being used in road construction, asphalt has also been used to seal dams since 1923 . In order to speed up the paving and improve the paving quality, the use of road pavers was first tested in California in 1924 . To determine the quality of the building material, several test methods were developed in the following years , which are still valid today. The ring-and-ball test was introduced in 1936 , the Fraass breaking point a year later and the Marshall test in 1939 .
From 1950 onwards, special additives made it possible to pave asphalt even when it was cold (so-called cold asphalt ). In order to determine the thickness of paved asphalt, a non-destructive test method using isotopes was developed and successfully tested in Austria in 1959 .
Out of a desire, surface water to start - and landing runways of airports as quickly as possible to deduce, was in 1963 in England , the incorporation of porous asphalt . Shortly afterwards, in 1968, stone mastic asphalt was paved for the first time . Asphalt recycling began to be used in the United States in the early 1970s . In order to obtain the most reliable sealing possible, asphalt has been used in landfill construction since 1979.
In addition to its suitability as a building material, asphalt is also used in art . This is how Asphalt Art was born in Austria in 1998 . Michael Scheirl has been using asphalt as the base material for his asphalt pictures ever since.
In civil engineering parlance, natural counterparts of artificially produced construction asphalt, i.e. H. natural bitumen with a relatively high proportion of rock fragments or grains (e.g. certain oil sands ), known as natural asphalt . This is not to be confused with the similar but not identical geoscientific asphalt term, which only refers to the organic matter without mineral components.
Large deposits of natural asphalt can be found in Trinidad ( La Brea Pitch Lake is the origin of Trinidad natural asphalt ), in Venezuela ( Lago de Guanoco ), in the Swiss municipalities of Buttes and Travers and in Alsace . Pechelbronn in Alsace was the first place in Europe to extract oil from natural asphalt. The occurrence has been documented since 1498. The petroleum from the Pechelbronn layers was initially used medicinally for skin diseases . Commercial use began in 1735 and ended in 1970.
Natural asphalts also exist in California (for example in the La Brea Tar Pits ), Colorado , Argentina, Syria, Alberta (including the Athabasca oil sands ), on Cuba , on the Dead Sea . The mine in Selenica in Albania , which has been known since ancient times, is important for Europe . Also known is the natural asphalt called Gilsonite , which has been mined in the US state of Utah and in Kermanshah in Iran since the middle of the 19th century . With its help, the grip and durability of engineered asphalt can be improved.
A German natural asphalt deposit, for example, is located in Vorwohle in the Holzminden district in Lower Saxony . The only natural asphalt underground mine in Germany is currently located in Holzen, Lower Saxony . This asphalt is processed in Eschershausen . The other 15 mining areas were closed in the 1950s and 1960s for economic reasons. In Switzerland, natural asphalt from the canton of Neuchâtel was also used.
Most of the paved asphalt is produced in asphalt mixing plants. A system can either be stationary or mobile , depending on requirements . Their performance ranges from 130 tons to 350 tons of mix per hour. It is also possible to add asphalt to the manufacturing process and thus recycle it.
The mix is produced in an electronically controlled process in which the individual components of the asphalt mix are selectively put together and mixed. For this purpose, the aggregates are first added to the drying drum in a pre-dosed amount . Here the moisture contained in the rock is evaporated and the required temperature of the asphalt is generated. The fine dust fraction (also called filler ) that occurs in the mixing system , especially in the drying drum , is separated off with the aid of a dust extraction system and can be weighed and added again later. The pre-dosed aggregate leaves the drying drum and enters the mixing tower . There, the exact dosage of the warm aggregate takes place , usually after previous sieving into different grain sizes. Once the desired grain composition has been put together using the scales, the hot bitumen is injected into the mixing container and mixed with the aggregate for about 15 seconds. The fresh mix can then be brought to the loading area of a truck at temperatures that are usually between 160 ° C and 180 ° C via loading silos or directly .
Use of renewable raw materials
As RapsAsphalt an asphalt is referred to, a significant amount of rapeseed oil in bitumen content contains. Like normal asphalt, it is produced as a mixture of the binding agent bitumen and aggregates and can also be used in the same areas of application. It only differs from asphalt in the composition of the binder. Another development is the Vegecol product , in which, according to the manufacturer, the entire bitumen content has been replaced by products made from renewable raw materials .
Most often, asphalt is used to pave a floor surface . A distinction is made between rolled asphalt and mastic asphalt . Rolled asphalt only achieves the required degree of compaction through the use of road rollers , mastic asphalt, on the other hand, can be processed as a liquid and does not have to be compacted .
In addition to its use in road and path construction, asphalt offers other uses. It is suitable for traffic areas at airports, parking lots, on railways as a base layer underneath the railroad, but also as a sealing system in hydraulic engineering and landfill construction. In garden and landscape architecture , for example, colored asphalt is used to design paths, squares and leisure facilities .
Apart from the above-mentioned use cases, asphalt is also used as a surface for racing and test tracks . In this case, particularly high-quality and polishing-resistant minerals as well as a bitumen refined with plastic additives, similar to the polymer bitumen in road construction, are used. The multi-layered covering is heavily stressed by the regular braking and acceleration processes , and there are also high demands on the grip of the surface layer. In this context, the addition of tungsten in the mix represents a new development . The result, an extremely rough asphalt surface, is used in the run-off zones of the Circuit Paul Ricard to brake vehicles that have strayed off the track quickly and without significant damage.
In a special technique of etching , aquatint called asphalt dust is used. The world's first surviving photograph, the heliography by Joseph Nicéphore Nièpce , is based on the light sensitivity of certain asphalt layers.
Asphalt base course
Asphalt base layers (seldom also referred to as bituco gravel or bitumen gravel ) are installed as the first bound asphalt layer in the road surface and assume the load-bearing function of the paved asphalt package . They lie on a further, unbound base course (e.g. frost protection layer ) or a possibly hydraulically bound base course (e.g. base courses with hydraulic binders ) or, with appropriate construction methods, directly on the subgrade . The asphalt base course is usually covered with the road surface , consisting of a binder and surface course or just a surface course.
Asphalt base courses give the binder and / or surface course a uniform, stable base. During the period of use (up to 50 years if properly manufactured), they should carry the traffic loads in a firm bond with the binder and surface course and distribute them on the base in such a way that the entire pavement is not damaged. A minimum thickness of 8 cm is required to meet these requirements. When building over old (uneven) pavement pavements, leveling layers should not be less than 6 cm thick at individual points.
A distinction is made between different types of mix in the asphalt base course, with bitumen 50/70 or 70/100 according to DIN EN 12591 being used as the binding agent.
|Asphalt base course||AC 32 TS
AC 22 TS
|AC 32 TN
AC 22 TN
|AC 32 TL
AC 22 TL
|Minimum installation thickness in cm||8.0||8.0||8.0|
|Degree of compaction in%||≥ 98.0||≥ 98.0||≥ 98.0|
The asphalt foundation layer is a modification of the asphalt base course . This is a bituminous bonded base course, which is subject to low requirements and is used as a replacement for high-quality unbound base courses or soil consolidation . A large part of this base layer consists of reclaimed asphalt and can be built using hot or cold paving.
Asphalt binder course
An asphalt binder course is installed between the underlying, coarse-grained asphalt base course and the overlying, fine-grained asphalt surface course , on roads subject to heavy traffic ( stress classes Bk100 to Bk3.2) . It transfers the forces caused by traffic (including especially the thrust forces ) to the lower layers of the road and prevents deformation. Originally the binder course was used to bind unbound base courses in order to obtain a level surface. The name of the binder course is derived from this usage.
On roads with less traffic ( construction classes IV to VI), asphalt binder 0/11 is used to level the profile . This facilitates the installation of a uniformly thick top layer with the required evenness.
There are three different types of asphalt binder . They consist of a graded aggregate - chippings , quality crushed sand , natural sand and rock dust - and road bitumen or polymer modified bitumen as binder. The RStO recommend a layer thickness of 4 to 8 cm, depending on the construction class.
|Asphalt binder||AC 22 BS||AC 16 BS||AC 16 BN|
|Installation thickness in cm||7.0 to 10.0||5.0 to 9.0||5.0 to 6.0|
|Degree of compaction in%||≥ 98.0||≥ 98.0||≥ 98.0|
Asphalt surface course
Asphalt surface courses (seldom also referred to as wearing courses) are the topmost, directly stressed layers of the asphalt pavement. They are subject to the direct effects of traffic, weather and de-icing agents .
The uniform thickness of 4 cm provided for surface layers is not appropriate for all types of mix: very coarse-grained mixes should be thicker, very fine-grained ones can be thinner (rule of thumb: minimum paving thickness = largest grain × 2.5). Since the asphalt surface layer is specifically intended to be worn out by daily traffic, it should be renewed at regular intervals as part of a so-called paving program in order to maintain the road.
Traffic areas are to be built in such a way that, taking economic efficiency into account , they meet the requirements not only during commissioning but also in the long term, are easy to maintain and generally require little maintenance effort. There are different types of mix for this. The difference lies in the composition of the aggregates and the binder content. The various asphalt surface courses are explained below.
Asphalt concrete (hot paving)
Asphalt concrete (outdated, depending on grain size and fine asphalt concrete or asphalt coarse concrete ) is used in road construction as a covering layer and is for road load classes to Bk0,3 (formerly construction classes II to VI) BK10 and means of all kinds as well as for other traffic surfaces according to RStO suitable. The of voids composite asphaltic concrete aggregate consists of a mixture (coarse and fine Gesteinungskörnung and filler) having graduated particle size distribution and road bitumen or polymer modified bitumen . The largest grain of the aggregate mixture can be up to 16 mm.
In order for the asphalt concrete surface course to have adequate roughness , it must be blunted . This is particularly necessary to increase the initial grip . To dull it, raw or binder-coated sanding material (broken aggregate of the delivery grain size 1/3 or 2/5) is sprinkled onto the still hot asphalt surface layer and pressed firmly in with rollers . Scatter material that has not been bound must then be removed.
The properties required for the construction of asphalt concrete in traffic areas according to the RStO are regulated in the ZTV / TL Asphalt-StB 07/13. ZTV LW apply to asphalt concrete in rural roads. After requirement distinguishes various types of asphalt concrete and is particle size distribution, the type and amount of the binder properties of the mix ( compression temperature , void content ) and properties of the layer ( layer thickness , installation weight , degree of compaction , void content ) to. The choice of mix type depends on the traffic load and the desired surface structure (fine to coarse).
|Asphalt concrete||AC 16 DS||AC 11 DS||AC 11 DN
AC 11 DL
|AC 8 DS
AC 8 DN
AC 8 DL
|AC 5 DL|
|Installation thickness in cm||5.0 to 6.0||4.0 to 5.0||3.5 to 4.5||3.0 to 4.0||2.0 to 3.0|
|Degree of compaction in%||≥ 98.0||≥ 98.0||≥ 98.0||≥ 98.0||≥ 97.0|
|Void content in% by volume||≤ 6.5||≤ 5.5||≤ 5.5||≤ 5.5||≤ 5.5|
Asphalt concrete (hot installation)
Warm asphalt concrete is an outdated type of mix and is no longer included in the current directive. It is suitable for surface layers of building classes IV to VI, i.e. traffic areas with low traffic loads . It should not be used on roadways. After paving and compaction, the asphalt concrete only achieves its final impermeability through subsequent compaction under traffic. In terms of content, the asphalt concrete in hot paving consists of a mineral mixture 0/5, 0/8 or 0/11 and a flux bitumen FB 500. To improve the surface grip, the top layer should be blunted with gravel after installation. The paving takes place at a mix temperature of around 60 ° C, while hot asphalt concrete is processed at 120 ° C.
In the regulations , the installation is of asphalt thermal installation for reasons of environmental protection is no longer provided, it is only occasionally the use of this material. The flux or cut bitumen used is no longer standardized in Germany and is often prohibited by law.
Stone mastic asphalt
The grit mastic asphalt ( English Stone Mastic Asphalt , SMA for short ) is a special type of asphalt for surface courses with a higher bitumen and gravel content. Either ordinary road construction bitumen or polymer-modified bitumen ( PmB for short ) can be added. The aim is to increase its durability, making it suitable for high traffic loads such as on motorways. In addition, stabilizing additives (e.g. cellulose or synthetic fibers ) have to be added. These additives have the task of holding the bitumen, so to speak, "overdosed" but required in this amount , to the minerals during manufacture , transport and installation and preventing it from running off. The surface structure is coarse-grained and similar to that of drain asphalt (open-pored asphalt, see below). SMA also has a noise reduction effect similar to that of porous asphalt, albeit to a lesser extent by around 2 dB (A) .
This type of asphalt was developed in Germany in the 1960s, when asphalt mastic surfaces were sprinkled with chippings to increase the stability and then rolled in. This also significantly reduced the abrasion caused by the spikes that were still approved at the time .
|Stone mastic asphalt||SMA 11 S.||SMA 8 S.||SMA 8 N||SMA 5 N|
|Installation thickness in cm||3.5 to 4.0||3.0 to 4.0||2.0 to 3.5||2.0 to 3.0|
|Degree of compaction in%||≥ 98.0||≥ 98.0||≥ 98.0||≥ 98.0|
|Void content in% by volume||≤ 5.0||≤ 5.0||≤ 5.0||≤ 5.0|
For stone mastic asphalt in traffic areas of the load classes Bk100 to Bk3.2 with special loads, particularly polishing-resistant coarse aggregates ( PSV min 53) must be used, since the chippings are more stressed by polishing . This is due to the significantly lower proportion of sand compared to asphalt concrete and the smaller contact area between the tire and the road.
Stone mastic tolerate in terms of compressibility and deformation resistance larger variations in coating thickness - for example, uneven ground - as asphalt concrete, because it is relatively insensitive to densification and deformation is.
The areas of application for stone mastic asphalt include:
- Highly used streets
- Traffic areas that can only be withdrawn from traffic for a short time
- In the context of repairs on an uneven surface with corresponding fluctuations in the installation thickness
- Residential and access roads in the municipal area
Mastic asphalt is an asphalt that is characterized by its high proportion of bitumen and rock grains smaller than 0.063 millimeters (the so-called filler). It consists of coarse and fine aggregates, rock flour and bitumen. The grain size distribution and binder content are set so that the cavities in the aggregate mixture are completely filled with bitumen and there is also a slight bitumen excess . As a result, unlike other types of asphalt, it can be processed as a liquid , i.e. i.e. it does not have to be condensed .
Mastic asphalt is mainly used in the construction of high-traffic roads (motorways) and often on bridges . The particular advantage of using it on bridges is that the bridges do not have to be passable with an asphalt paver or road rollers at the time of installation . The bridge - including the asphalt road on it - can therefore be completed before the road adjoining the bridge is completed.
The transport to the construction site takes place with special mastic asphalt pots , the installation is done with special paving planks or by hand. In order to achieve sufficient grip , fine-grain chippings must be sprinkled on and rolled in when paving. Light-colored grit improves visibility at night and also reduces the heating of the surface in strong sunlight , which has a positive effect on deformation stability.
|Mastic asphalt||MA 11 S
MA 11 N
|MA 8 S
MA 8 N
|MA 5 S
MA 5 N
|Installation thickness in cm||3.5 to 4.0||2.5 to 3.5||2.0 to 3.0|
Mastic asphalt does not have a self-supporting grain structure . Most of the load is transferred via the mortar, which has to be considerably stiffer (harder bitumen, more filler) than, for example, asphalt concrete. The stiff mortar requires significantly higher production and installation temperatures . By varying the composition, the processability and deformation resistance can be controlled over a wide range, while the grip depends on the integrated grit.
Asphalt mastic is a mixture of bitumen and rocks with a grain size of less than 2 mm. In hydraulic engineering , it is used to fill the joints of stone fillings. It is mainly used to seal structures, although its use fell sharply in the 1990s. Standardization is no longer included in the current directive. Asphalt mastic with a lower bitumen content (approx. 12-14%) is occasionally used in road construction as a repair material to improve surfaces .
Asphalt base course
The base course mix is a type of asphalt that combines the functions of the asphalt surface and the asphalt base course. It is mainly used in agricultural road construction as well as on cycle paths and sidewalks , where, due to the relatively low volume of traffic, a fastening with a good cost / benefit ratio is required. Only broken aggregates can be used. If heavy soiling is to be expected after installation, such as B. on agricultural roads , the hot surface should be sprinkled with raw or binder-coated sand to improve the roughness.
|Asphalt base course||AC 16 TD|
|Installation thickness in cm||5.0 to 10.0|
|Degree of compaction in%||≥ 97.0|
|Void content in% by volume||≤ 6.5|
Open-pored asphalt (short OPA or English Porous Asphalt, PA ) is also referred to as drain asphalt (sometimes also drainage asphalt ), whispering asphalt or whispering or noise- optimized asphalt . Open-pored asphalt is a special type of asphalt concrete that was developed in the 1980s.
|Open-pored asphalt||PA 11||PA 8|
including sealing in cm
|5.0 to 6.0||4.5 to 6.0|
|Degree of compaction in%||≥ 97.0||≥ 97.0|
|Void content in% by volume||22.0 to 28.0||22.0 to 28.0|
The composition is characterized by its high proportion of coarse aggregates , which results in a high content of contiguous voids . Rainwater can be drained down through these cavities. A bitumen seal prevents the water from running off into the subsoil or into the road surface . This consists of polymer-modified or rubber-modified bitumen , and is used to trafficability broadcast with chippings 8/11 or 5/8. This layer is called Stress Absorbing Membrane Interlayer ( SAMI for short ) in English-speaking countries . As an alternative to SAMI, a thin layer of mastic asphalt is also installed as a seal. The advantage of the mastic asphalt sealing is that, compared to SAMI, no binding agent can penetrate the open-pored grain structure and thus reduce the acoustic effect. The surface water is drained laterally through the incline (at least 2.5%) - a combination of longitudinal and transverse slope - of the road. In order to be able to safely drain off the accumulating water, either special drainage channels are installed at the edge of the road , or the paved road edge , such as a paved gutter , must be lower by the thickness of the surface layer so that the water can flow away unhindered. All in all, only a very thin film of water forms on the road surface as a result of all these measures . This has a significant positive impact on road safety : On the one hand reduces the spray mist , resulting in much better visibility, and on the other is hydroplaning -Danger significantly reduced.
The high proportion of cavities also absorbs the sound of driving noises and partially prevents them from occurring at all (through air evacuation), which is why it is also called whispered asphalt . This effect is particularly noticeable on roads where the tire-road noise is the main source of noise , such as B. on motorways . There are noise reductions of about 5 to 10 dB (A) achieved, which to the human auditory sensation about a reduction in a thirds to halving corresponds. However, the noise-reducing effect wears off after about six to eight years, as road dirt and tire abrasion clog the pores . Since it has not yet been possible to clean the pores, other approaches in the form of dirt- keeping or repellent layers are being tested.
The use of two - layer, open - pored asphalt ( ZWOPA or 2OPA for short ) was tested in Germany, for example, on the A 9 near Garching and the A 30 in the Osnabrück area . This building material consists of two layers of open-pored asphalt, the lower one with the grain size 0/16 and the upper layer with the grain size 0/8. In the area of testing on the A 9 near Garching, the ZWOPA had to be replaced early. Due to the short useful life, this was replaced by an OPA.
So far, hardly any problems have arisen in practice in other European countries. The resistance to rutting is very good, but at very low temperatures there is increased wear due to the use of snow chains . The snow chains can damage parts of the asphalt layer. What is a positive effect in normal humid weather, namely the faster drainage of the water, leads to increased salt consumption in winter , in alpine regions by an average of 40% more salt consumption.
Local damage is currently being repaired by replacing the top layer. The possibilities for large and small-scale renovation of damaged OPA coverings are still in the trial stage in Germany. All newly built Italian motorways have been provided with porous asphalt since 2003. Denmark , Switzerland and other European countries, especially the Netherlands , have been using porous asphalt on a large scale for years. In Austria , this construction method was used in the ASFINAG motorway and expressway network due to the short lifespan of e.g. Some of them abandoned less than 5 years shortly after the turn of the millennium. The originally existing OPA sections have now been completely replaced by other noise-reducing construction methods (e.g. noise-reducing stone mastic asphalt of the type SMA S3 defined in Austria or noise-reducing exposed aggregate concrete ceilings).
In the media it was often reported that porous asphalt, especially the so-called whisper asphalt , has a lower grip and thus poses a problem for road safety. If the OPA is intact, these claims are false. Mixtures with smaller aggregates tend to have better grip, but sufficient grip can also be achieved with coarser aggregates. However, since the single grain of coarser mix types is exposed to increased polishing stress and thus wear, the grip of OPA decreases faster than with conventional asphalt. In order to slow down this wear, higher demands must be placed on the quality of the mix, but the durability of conventional asphalt of good quality cannot be reached. Aged and worn OPA can therefore have too little grip for road safety. In this context, for example, after a number of accidents on the A 8 near Karlsbad, the nature and quality of the pavement was checked by the Baden-Württemberg Ministry for the Environment, Nature Conservation and Transport in 2004, as it was assumed that the noticeably rapid decrease in grip due to faulty or poor quality mix could have been caused.
Due to the higher demands placed on the new generation of OPA, the production costs are around three times as high as with conventional asphalt, while at the same time being less durable. For this reason, widespread use is not yet planned.
Porous mastic asphalt
Porous Mastic Asphalt ( PMA or PMA 5 for short ) is a further developed mastic asphalt with an open-pored surface structure and noise-reducing properties, which can be used on motorways and expressways as well as in load classes Bk32 to Bk0.3. The asphalt is self-compacting and does not require any compaction energy , neither by the paving machine nor by rolling (only smoothing). Subsequent scattering with a coarse aggregate is also unnecessary. The asphalt, which was first used in North Rhine-Westphalia in 2008 , is in the development phase and is therefore still a special construction method in German road construction. Further test routes followed u. a. 2011 north of Potsdam on the B 5 , in October 2011 in Erfurt (Moritzwallstraße) in town, in 2012 on several roads in Bavaria , and in 2013 in Hesse on the BAB 5 between the Ober-Mörlen and Friedberg junctions .
Compared to conventional asphalt, the fine-grained, binder-rich mortar settles down in the cavities of the gravel structure of the coarse aggregates during the paving process. Within the PMA layer there is a distribution of the voids in such a way that the area near the surface has a voids content of up to 20% by volume and the lower area has a voids content approaching zero. The surface is determined by a coarse aggregate and thus causes a noise reduction of approx. 4 dB (A) . Despite the OPA-like properties, an adjustment of the drainage or regular cleaning is not necessary.
Low temperature asphalt
Above all to save energy in the production of asphalt mixes and thus to reduce carbon dioxide (CO 2 ) emissions, but also under the aspect of health and safety at work , low-temperature asphalts ( NTA for short ) have been tested for some time . The normal asphalt formulation are additives in the form of waxes or zeolites added ( additives to mix), which allow the asphalt at lower temperatures and installed without causing its processing characteristics and its performance characteristics are affected. The NTA were developed in Germany and meanwhile also successfully used in the USA , France and numerous other countries. A production temperature reduced by 10 ° C saves up to 10% energy. In addition, as the temperature rises, more vapors and aerosols escape from the bitumen exponentially . A health hazard from these vapors and aerosols has not yet been proven, but they can represent an odor nuisance. The use of NTA significantly improves working conditions on construction sites . Since May 2006 the "Leaflet for Lowering the Temperature of Asphalt" (M TA) of the Research Association for Roads and Transport (FGSV) has regulated the use and execution of temperature- reduced asphalt.
Repair asphalt (cold asphalt)
Especially for smaller repairs, such as in potholes , winter damage and the closing of supply risers and - cut , cold asphalt is commonly used. The production of ramps is also possible. This is asphalt mix that can be processed when cold . A lot of heating energy can be saved in the manufacturing process itself . Cold asphalt mixes are usually mixed at 80 ° C to 100 ° C. Long-term cold mixes were chippings and a penetration bitumen produced. There is an increasing number of high-quality cold mixes in Germany that use polymer-modified bitumen or standard road construction bitumen with the addition of additives . These modern processes enable the shelf life to be increased to up to two years. It is now possible to guarantee permanent repairs with some cold mixes. Recognized certification bodies also confirm that selected cold asphalts can be installed in frosty conditions (−10 ° C). This shows the great advantages of the cold mix as a repair product in contrast to hot mixes (e.g. mastic asphalt). These can no longer be used at temperatures below freezing point . Through cracks in the surface layers, water penetrates into the superstructure of the roads and traffic routes. In the winter months , the frost-thaw cycle causes enormous surface damage (potholes). The permanent repair of such damaged areas is guaranteed by the weather resistance of the new cold asphalt . It is important to ensure that cold mixes, in particular, seal and compact the seams , as the renewed penetration of water should be prevented here.
Liquid impermeable asphalt
It may be necessary to design asphalt pavements in such a way that water-polluting substances (such as fuels or other hazardous substances) cannot penetrate the subsoil. This type of asphalt paving can be installed in bottling plants or petrol stations , for example . In this case, special requirements are placed on the binders, aggregates and the formation of joints. The term impermeable to liquids can only be used if the leaked substances have penetrated no more than two thirds of the thickness of the asphalt layer from the time they were detected until the time they were removed.
Design with asphalt
Design with colors
Through the use of colored aggregates , color pigments and / or colorable binders as well as the use of asphalt paint or an asphalt face , the asphalt surface can be adapted to the respective requirements of the colored design. Further options for creating optical effects are applying or removing processes.
Colored asphalt can be produced as asphalt concrete , stone mastic asphalt and mastic asphalt, preferably in grain sizes 0–5 mm, 0–8 mm and 0–11 mm. When using colorless binding agents, it is essential to check their suitability for the intended traffic loads and the softening point before installation. Colorless binders are not always suitable here, as black asphalt surface layers in the sun can reach temperatures of up to 80 degrees Celsius. Special highly stable color asphalts are used to load class BK100 (RStO 2012). Since the grain distribution is of decisive importance for the transmission of traffic loads, the rolled asphalts are visually very coarse-grained and often unattractive for traffic loads from Bk1.8. Colored mastic asphalt, also mixed as 0-11 S asphalt, has a more closed surface because the cavities are filled. The texture of the asphalt surface layer can be varied via the size of the aggregate. In the case of new types of thin-layer paint asphalt, the load is transferred via the binder. Highly stable mixtures allow a maximum grain size of 5 mm. This makes the texture more pleasing.
Thin-layer colored asphalt
Thin-layer colored asphalt is colored asphalt that is mixed with a new binder on the construction site. This rolled asphalt is installed in grain sizes up to 5 mm with a thickness of 1 cm to 2 cm. In contrast to normal rolled asphalts or colored asphalts, it is not the mineral but mainly the binding agent that serves to transfer the load . Thin-layer colored asphalt is significantly harder in comparison , but at the same time more flexible . There are no expansion joints here . The softening point is over 150 ° C and it has no ruts. In the track formation test based on the "TP Asphalt", part 22 (ruts test), the results (absolute ruts depth RD air 0.3 mm – 2.1 mm) are like the requirements of Rhineland-Palatinate for a highly stable stone mastic with the resistance to deformation of a maximum of 3.5 mm. Thin-layer colored asphalt is therefore also suitable for extreme loads. Even more stable mixtures (up to Bk100 according to RStO 2012) are available for bus transport.
Colored asphalt for high traffic loads up to Bk100 (bus traffic)
Colored asphalt for high traffic loads is a colored asphalt that was developed for extreme inner-city loads from bus traffic, especially at braking and acceleration points (bus stops and bus stations). The binder is milky and can be made in many colors by choosing the additives . Luminous colors are achieved by adding pigments . Since conventional (“black”) asphalts have a maximum softening point of approx. 80 degrees Celsius and normal colored asphalts have an even lower softening point, this temperature is already reached by solar radiation on hot days. Heating the radiation of heat from the engine waiting buses , the area in addition and slows down an incoming bus at this point, then the known damage. Colored asphalt for high traffic loads counteracts this effect with its softening point> 150 degrees Celsius and protects the binder layer below . As the temperature decreases by approx. 7 degrees Celsius per cm, a highly stable asphalt binder is in the safe area. Colored asphalt for high traffic loads is installed a maximum of 2 cm and can also be designed with the asphalt embossing technique. Its surface has a pleasing texture, as the binder is mainly responsible for the load transfer and is mixed with a maximum grain of 5 mm. The material is mixed on site.
Colored asphalt attachment
In this process, a binder tailored to the asphalt is applied to the asphalt and sprinkled with colored grit . This can come about with or without a pattern. The result after curing is a decorative colored surface that is traffic- resistant up to loads corresponding to load class Bk1.8 (RStO 2012).
Asphalt paints are applied in a wet film thickness of 0.3 mm to 0.6 mm in two to four layers on cleaned, oil- and grease-free asphalt and have excellent adhesion and elasticity . Compared to marking paint, the drying process takes significantly longer, but less than an hour in normal weather. In order to obtain sufficient coverage and durability, wet film thicknesses of 0.6 mm are preferred. In contrast to asphalt paints, marking paints often do not have the desired balance for surface application, as during production more emphasis was placed on fast drying time and abrasion resistance than on elasticity, which can lead to cracking and flaking when applied over a large area. The variety of colors is almost limitless and multi-colored surfaces can also be created with gradients .
Design with joints
Since ancient times , the arrangement of joints has given the user information and the surfaces an overall picture. Joints were indispensable for reasons of the weight of stones and slabs or for structural reasons (manufacture, breaking strength , expansion joint ). In contrast to stones and concrete, asphalt can be built without joints , especially if the construction joints (e.g. with the CAR method ) in the asphalt are temperature-controlled welded. Joints are the weak points in paving . Water can penetrate through them, the stones or slabs can shift and vacuum sweepers remove the necessary joint fillings . Joints in the asphalt embossing process are not weak points, as they are dummy joints that do not allow any water to penetrate. The asphalt embossing process not only combines the creative diversity of the joints with the construction material asphalt, but it is also possible for the first time to leave large areas smooth and then to emboss dummy joints according to the designer’s taste.
Asphalt embossing process
In addition, the surface can be structured using various patented processes . Steel templates or plastic templates are embossed with a vibrating plate in the asphalt that is still warm or warmed up by computer . With this process, not only can every natural paving stone or slab pattern be imitated without the weak point of an open joint, it can also be used to create completely new patterns, since the resulting dummy joints are used exclusively for design and not for construction ( expansion joint ; weight-related joint ).
The temperature-controlled heating plays an important role here. It is important that the asphalt is not only heated on the surface , but that the heat penetrates deep into the asphalt. Only in this way ensures that when memorizing the grain is not damaged a plastic mask. If the heat is too great, the bitumen would burn. Only high-quality heating devices can meet this middle ground between deep heating without burning the surface . After heating, a plastic template with wide webs is stamped into the asphalt using a vibrating plate. A thermoplastic inlay with the same dimensions is inserted into the resulting joints . In a second heating cycle , this thermoplastic is welded to the asphalt . It is important that with this method the thermoplastic material is approximately 1 mm deeper than the asphalt surface. So the main burden of traffic lies on the asphalt, not on the thermoplastic. This type of design therefore withstands high traffic loads up to construction class II.
Recycling of reclaimed asphalt
Due to the fact that asphalt is a thermoplastic building material , some of it can be reused several times. For this purpose, the asphalt is to be removed, for example by milling ( milled asphalt ) or breaking up ( demolished asphalt ) and - if necessary after preparation by breaking - it must be added to the manufacturing process again. The prerequisite for this is that the reclaimed asphalt is free of foreign matter and harmful substances (e.g. tar). The legal basis for the reuse of asphalt in Germany is the Recycling Management Act . In Switzerland and Austria, the corresponding "Leaflets on handling reclaimed asphalt" apply.
In addition to being reused in the mixing plant (so-called Recycle in Plant ), the asphalt surface can also be renewed on the spot (Recycle in Place) . With this method, various hot recycling processes are used in which the asphalt layer is heated and then loosened . In the next step, additives can be added and the mix can be re- installed and compacted .
Norms and standards
- DIN EN 55469 Bitumen and coal tar pitch - Terms for bitumen and preparations made from bitumen
- DIN EN 12597 Bitumen and bituminous binders - Terminology
- DIN EN 12697 test method for hot asphalt
- DIN EN 13108-1 Asphalt mix - Mix requirements - Part 1: Asphalt concrete
- DIN EN 13108-5 Asphalt mix - Mix requirements - Part 5: Stone mastic asphalt
- DIN EN 13108-6 Asphalt mix - Mix requirements - Part 6: Mastic asphalt
- DIN EN 13108-7 Asphalt mix - Mix requirements - Part 7: Porous asphalt
- DIN EN 13108-20 and -21 (quality standards for asphalt)
- DIN EN 13043 (aggregate standards)
- Germany ( FGSV publishing house)
- Additional technical contract conditions and guidelines for base courses in road construction (ZTV T-StB), withdrawn since 2009
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- Additional technical contract conditions and guidelines for paving rural roads (ZTV LW)
- Technical delivery conditions for aggregates in road construction (TL Gestein – StB)
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- Guidelines for the standardization of the superstructure of traffic areas (RStO 12)
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- Leaflet for the reuse of asphalt (M WA)
- Leaflet Thin layers in hot installation on sealing (M DSH-V), withdrawn with the introduction of ZTV BEA-StB 09
- Leaflet for the construction of compact asphalt pavements (M KA)
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- Leaflet for the conception and initial testing of asphalt mix for the construction of paved traffic areas (M KEP)
- ÖNORM B 3580 to B 3586 asphalt mix - mix requirements
- ÖNORM EN 1097 test method for mechanical and physical properties of aggregates
- SN 670401 to SN 670443 test method for hot asphalt
- SN 670434-8a-NA Asphalt mix - Mix requirements - Part 8: Reclaimed asphalt
- SN 640431 Different types of asphalt
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