What are the specifications of bituminous concrete

6. Building materials and mixtures of building materials

The chapter "Building materials and building material mixtures" can be found here as a clear PDF document!

Asphalt is a mixture of aggregates and bitumen as a binder, which, depending on its composition, contains a different proportion of voids. By varying its components according to type and quantity, the asphalt can be produced with very different properties and is therefore suitable for the respective applications
adapt to a large extent.

The quality requirements are to be coordinated with

  • the later stresses caused by traffic and weather with summer and winter temperatures. It must
  • the manufacturing process must be taken into account (e.g. asphalt mix production, temporary storage, transport, installation and compaction at high temperatures).

Aggregates

The choice of aggregates is based on the aspects of weather resistance, strength, affinity (adhesion) to the binding agent, resistance to polishing and color, but also local availability and transport costs.

As aggregates for the production of asphalt mix, natural solidification and sedimentation rocks as well as industrially produced aggregates (e.g. blast furnace slag, steel mill slag, metallurgical slag) and recycled building materials are suitable, provided they meet the respective requirements.

For use in road construction, the "Technical delivery conditions for aggregates in road construction”(TL Rock-StB) only according to the grain size:

  • Coarse aggregates (over 2 mm),
  • fine aggregates (2 to 0.063 mm) and
  • Filler (smaller than 0.063 mm).

Previously common terms such as “sand”, “chippings”, “noble chippings” or “crushed sand” are no longer used due to European requirements. The requirements associated with the earlier terms, e.g. on the fracture surface or origin, are now regulated by means of characteristic values ​​in the form of categories.

Aggregates for road construction must meet the requirements of TL Gestein-StB and be CE-marked. The CE marking is accompanied by an in-house production control, the correct and standard-compliant implementation of which is regularly monitored by an approved, neutral certification body.

The requirements and tests relate, among other things, to the

  • Grain size distribution, grain shape, the proportion of broken grain surfaces and the purity of the delivery grains,
  • Weather resistance (resistance to frost exposure and to frost and de-icing salt exposure) as well as resistance to heat exposure as a result of drying in the asphalt mixing plant,
  • Resistance to shattering and polishing (loss of fine roughness) of coarse aggregates.

The requirements are regulated in the TL Asphalt-StB and are defined with different values ​​depending on the type of asphalt mix and traffic load.

binder

Standard binders in asphalt road construction are road construction bitumen and polymer-modified bitumen in accordance with the TL Bitumen-StB. There the requirements for the individual types of binder are specified and the test methods for checking these requirements are named. In the case of road construction bitumen, the individual grades are named using the penetration limits or, in the case of polymer-modified bitumen, the penetration limits and the minimum value for the ring and ball softening point.

bitumen

  • is stored and processed in hot liquid at temperatures well below its flash point. Due to the transport temperature of over 100 ° C, but well below the flash point, bitumen in class 9 is the "Hazardous goods ordinance for road, rail and inland waterway transport“(GGVSEB) classified. According to DIN 4102-4, asphalt is assigned to building material class 1 (flame retardant),
  • is no hazardous substance in the sense of the Ordinance on Hazardous Substances,
  • is proven to be harmless to health. In the course of a so-called "Human study of bitumen“It was found that emissions from hot bitumen do not pose a health risk; there are no abnormal lung function findings,
  • is a non-water-polluting substance according to Appendix 1 of the "Administrative regulation for substances hazardous to water"(VwVwS).

Therefore, among other things, in the "Guidelines for structural measures on roads in water catchment areas“(RiStWag) pointed out in general that layers of asphalt are considered to be environmentally safe on the basis of existing studies, and that building materials that contain washable components may be used if they are bound with hot bitumen (see use for sealing drinking water reservoirs or for lining of drinking water pipes, etc.).

Due to its thermo-viscous behavior (change in viscosity with temperature), bitumen has a low viscosity at high temperatures and is therefore able to completely enclose the aggregates and make the asphalt mix workable and, above all, easily compactable. At normal temperatures it is tough and resilient. The relatively quick usability of the asphalt layers after their production is based on this - purely physical - behavior:

Apart from the cooling time, no further waiting time is required - a chemical process like the hardening of cement concrete does not take place.

The choice of the type of bitumen depends on the type of stress taking into account the workability and is regulated in ZTV Asphalt-StB 07, Table 2 - but see Table 13 "Recommended type and type of binder depending on the expected stress - recommendation of the DAV authors"On page 51. In the TL Asphalt-StB 07, additional binders are available for individual cases, e.g. for construction methods that are not regulated in the ZTV Asphalt-StB.

Common types of road bitumen:

70/100: (softer) for asphalt base courses, cycle paths and sidewalks or as an addition binder for asphalt base courses in load classes Bk0.3 to Bk1.0.
50/70: (harder) for asphalt base courses in the load classes Bk0.3 to Bk1.8 and as an addition binder for asphalt base courses in the load classes Bk1.8 to Bk100.
30/45: (hard) for asphalt surface courses made of mastic asphalt in the load classes Bk0.3 to Bk100, in combination with viscosity-changing additives or as a corresponding viscosity-changed binding agent.
20/30: (very hard) for asphalt surface courses made of mastic asphalt in the load classes Bk3.2 to Bk100, in combination with viscosity-changing additives or as a corresponding viscosity-changed binding agent.

Polymer modified bitumen (PmB) are factory-made mixtures of bitumen and polymers, in which the polymers change the elastoviscous behavior of the bitumen and thus make the binder more suitable for special loads. The TL Bitumen-StB differentiates between elastomer-modified bitumen and plastomer-modified bitumen. The use of elastomer-modified bitumen (modification type “A” according to Table 2 of TL Bitumen-StB 07) has become established in Germany. The plastomer-modified bitumen (modification type "C" according to Table 3 of TL Bitumen-StB 07) is only used sporadically. Therefore, in the following only applications with elastomer-modified bitumen will be discussed.

Advantages of the PmB:

  • higher cohesion and better adhesion to aggregates,
  • larger plasticity range (temperature range between breaking point and softening point),
  • large elastic recovery after relief,
  • higher fatigue resistance.

 

Areas of application of PmB:

  • particularly heavily used traffic areas,
  • for aggregates with unfavorable adhesive properties,
  • Open-pored asphalt layers,
  • on bridge structures, especially steel bridges.

 

Common types of polymer modified bitumen:

45 / 80-50 A: (relatively soft) for thin asphalt surface courses in hot construction in the load classes Bk3.2 to Bk100.
25 / 55-55 A: (hard) for asphalt surface courses in the load classes Bk3.2 to Bk100, asphalt binder courses in the load classes Bk3.2 to Bk32.
10 / 40-65 A: (very hard) for very highly deformation-resistant pavements with heavy traffic in the load class Bk100, sometimes also in combination with viscosity-changing additives.
40 / 100-65 A: (highly elastomer-modified) for open-pored asphalt surface courses to reduce noise in the load classes Bk3.2 to Bk100.

With regard to occupational safety, reuse and the environment, PmB like road construction bitumen are to be assessed.

Colorable binders (often also called "colorless" binders) are synthetic binders based on mineral oil that appear transparent in thin layers. They can be colored with pigments, but can also be used without pigments in order to let the stone colors emerge. Their properties largely correspond to those of road construction bitumen. In this way, special design or traffic-directing effects can be achieved, especially in urban areas (see Section 11 in the structural engineering section).

Viscosity modified binders are factory-made mixtures of bitumen and viscosity-changing additives; In addition to lowering the temperature, they also offer a number of other advantages (see page 3/4 in the DAV guidelines “Temperature-reduced asphalt“).

Reuse of asphalt

The highest quality recycling, i.e. the reuse of reclaimed asphalt in the production of asphalt mix (in the hot mix process) is legally required and makes sense economically, ecologically and structurally. It has therefore been state of the art in Germany for years and is anchored in the technical regulations for asphalt. Now it is a matter of consistently implementing the highest quality reuse in the sense of maximum added value in practice to further specifically promote and demand in order to conserve valuable resources on the one hand and to exploit the economic advantages on the other.

Comprehensive information on the subject of reusing asphalt granulate, pictures, graphics and practical information can be found in the DAV guide “Reusing asphalt”.

The Recycling and Waste Management Act (KrW- / AbfG) stipulates in § 22 that a manufacturer must design his products in such a way “that the generation of waste is reduced during their manufacture and use and the environmentally compatible recycling and disposal of those that arise after their use Waste is assured. ”The producer is responsible for his product during the entire life cycle. Section 37 of the KrW- / AbfG obliges all federal authorities as well as all legal entities under public law subject to federal supervision "to examine whether or not in the design of work processes, the procurement or use of material and consumer goods, in building projects and other contracts and to what extent products can be used that are characterized by durability, ease of repair, reusability or recyclability, lead to less or less polluting waste than other products, or are made from waste for recycling. "The waste laws of all federal states contain identical (provisions or) requirements with the obligation of the state authorities to proceed accordingly. In concrete terms, this means that legally an asphalt made using reclaimed asphalt must be preferred to a product made exclusively from new raw materials. This is also not a problem technically. As a rule, asphalt can be completely reused in the production of asphalt mixes. In the technical regulations for the construction of traffic area pavements made of asphalt, this is implemented in the TL Asphalt-StB in conjunction with the TL AG-StB and the ZTV Asphalt-StB. These are supplemented by the "Leaflet for the reuse of asphalt" (M WA), which contains a lot of help and information for daily work.

Construction materials with typical tar / pitch components are to be sent to special recycling processes.

Material for reuse in asphalt mixes must be of recycling class A according to the "Guidelines for the environmentally friendly recycling of construction materials with typical tar / pitch components as well as for the recycling of asphalt in road construction "(RuVA-StB) correspond.

 

TL asphalt starboard

The TL Asphalt-StB contain requirements for asphalt mix that is used for the construction of traffic area pavements and also describe the possible uses of asphalt granulate for all types of asphalt mix - also for asphalt mix with polymer-modified bitumen as a binding agent - with the exception of the production of open-pored asphalt (PA ). Of course, all requirements for the asphalt mix also apply without restriction when using asphalt granulate. For the asphalt granulate, the requirements of the "Technical delivery conditions for asphalt granulate ”(TL AG-StB).