Свойства и использование каменно-мастичного асфальта04.03.2022 10:05
It is a superstructure material with high slip resistance, made on a bituminous surface on roads with heavy traffic flow, with coarse stone content and voids filled with dense viscous mastic asphalt. The unrivaled longevity of stone mastic asphalts has been proven by 30 years of experience. This long life span is closely related to the fact that the crushed aggregate and bitumen ratio is much higher when compared to other asphalt types.
More than 7% bitumen was used in the component of the first Stone Mastic Asphalt that was laid. Asbestos fiber or rubber powder was used as additive material. The unique properties of these stabilizer additives used in the mixture played an important role in the durability and longevity of stone mastic asphalt with high bitumen ratio.
In today's mixtures, products other than the stabilizing additives used in those early days are also used (for example: organic and mineral fibers, thermoplastic materials or silicic acid).
It was designed in the 1960s as an asphalt wear layer resistant to extreme surface deformation of studded automobile tires. Asphalt mastic is laid on the asphalt, then high quality crushed aggregate of 5/8 or 8/11 mm is laid on it and compacted with a roller.
Main characteristics of Stone Mastic Asphalt Hot Mixture:
• High rate of crushed stone
• High rate coarse aggregate
• High rate bitumen
• Stabilizing additives
The aggregate, which consists of a high proportion of coarse-grained material, forms a main skeleton structure consisting of large spaces. These large gaps are filled with bitumen.
The task of stabilizing additives used in Stone Mastic Asphalt is to prevent the binding bitumen material from flowing from the aggregate. This yielding process occurs during production, transportation, laying and compaction. The thickness of the bitumen layer, which is filled on and between the aggregate, increases thanks to the additives, and at the same time, the fatigue and aging resistance of the asphalt increases.
Properties of Stone Mastic Asphalt
Stone Mastic Asphalt layers and friction surface are durable and long-lasting and have proven this feature on roads with heavy traffic and in harsh climatic conditions. Stone Mastic Asphalt can be used as a wear layer on all roads. This practice has become standard for high-traffic highways, intercity highways or urban roads.
Stone Mastic Asphalt has the following features in the right design, production and laying thanks to the highly crushed aggregate and mastic-characterized binders in the content of Stone Mastic Asphalt:
• Resistant to deterioration and deformations
• Resistant to friction and wear
• Climatic conditions and extreme pressure, friction, etc. It eliminates fractures caused by mechanical effects.
• Provides a rough and non-slippery surface.
• It has a long usage time.
Mixture composition of Stone Mastic Asphalt
The resistance of the Stone Mastic Asphalt surface against slipperiness, which is obtained thanks to the high ratio of coarse and low ratio of fine aggregates, is provided by the coarse aggregates, which are almost completely broken.
The grain shapes of the aggregates used are very important for the void ratios in Stone Mastic Asphalts. Flat and flat aggregates can adversely affect this void ratio, the filling ratio of the voids, and thus the asphalt compaction application.
Generally, 50/70 bitumen is used as a binder for Stone Mastic Asphalts.
70/100 or 160/220 bitumen can also be used in Fine Stone Mastic Asphalt compositions. On highways or bridges with heavy traffic flow, polymer modified bitumen may be more efficient.
Stabilizing additional materials are required due to the high bitumen ratio used in Stone Mastic Asphalts and the low surface area of the aggregates that adversely affect adhesion when compared to other mixed materials.
These additional materials; It prevents the bitumen from separating by flowing between the aggregates during manufacturing, transportation and application. The use of cellulose fibers as a stabilizing additive material has been proven over a long period of time.
Powder and granular materials or liquid materials can be used, provided that the stabilizing effect is clearly demonstrated. Natural or artificial silicic acids, rubber powders or polymers can also be used.