Stone Mastic Mixture Production in Asphalt Plants

What is Stone Mastic asphalt?

Stone Mastic Asphalt manufacturing is like asphalt concrete. It may be necessary to use two pre-dosing silos, since a high proportion of coarse aggregate will be included in the composition. Due to the high proportion of coarse aggregates, the sieving process may not be healthy due to the possibility of shrinkage in the hot sieving upper sieves.

As with the asphalt plants we produce as Polygon Mach, the dosage and sieve capacity of the plant should be compatible with the intended production capacity. Since the low-grade fine-grained aggregate in Stone Mastic Asphalt does not form a thick layer around the coarse-grained aggregates in the dryer, the aggregates are directly exposed to fire and overheated.

During the production of Stone Mastic Asphalt, it is necessary to ensure that the aggregate temperature remains at the desired level. The point to be considered here is the temperature of the finished mixture and this temperature should not exceed 170 °C.
Stabilizing additives should be carefully added to the asphalt composition according to their characteristics. The ratio of the additive material and its homogeneous distribution in the composition greatly affect the quality of the mixture and thus the poured layer. The homogeneity and quality of supplementary materials upon delivery must also be maintained during storage and manufacture.

If additional materials are to be given to the mixture as bundles, the dimensions of the bundles must be suitable for the capacity of the mixer. Care should be taken that organic fibers do not absorb moisture during storage and manufacturing. Any clumping that may occur will affect the homogeneous distribution in the mixture.
The inclusion of additional materials in the mixture is usually carried out automatically and with appropriate equipment. Some equipment manufacturers offer different dosing systems for different additives. If the production to be made is low, additives can be added to the mixture manually from the cover.

Initially, the binder material adheres to the surfaces of coarse, coarse aggregates with a large surface area. Equal distribution of additional materials is of great importance for a homogeneous mixture. The data of the manufacturers regarding the additives to be added to the mixture must be taken into account. The most important issue to be considered in fibers is that their balanced distribution in the mixture takes place during the additional mixing time (at the time of adding the binder and after it).

Doing dry premixing longer than necessary can cause the fibers to become dusty (turn into elephants). Since the organic fibers in the form of pellets have different densities, the dry premix time may not be sufficient to dissolve the pellets. Dissolution and homogeneous distribution of organic fibers should be checked from time to time.
Determining the most appropriate mixing time required for the even distribution of lumps in the dry mix significantly eliminates the decrease in production efficiency in the premix and postmix times.

Storage and Transport

As with other asphalt types, stone mastic asphalts should not be kept in silos for a long time. Bitumen, which is the binding material in the material that has been waiting in the silo for a long time, can be exposed to negative changes.

Loading ramps of transport vehicles must be clean. To prevent the asphalt from sticking to the ramps, only solvents that do not damage the asphalt should be applied or a light layer of water should be used.
The use of diesel oil is prohibited as it will adversely affect the quality of the mixture and in terms of working safety. Transport vehicles should be covered with a windproof cover at all times, including in summer, to prevent cooling of the asphalt and hardening of the binder as a result of the material coming into contact with the oxygen in the air. In small-scale jobs or low-efficiency work, thermally insulated truck-mounted tanks or horizontal belt heating boiler trailers are very suitable.

It is absolutely wrong to produce the mixture at high temperature in order to prevent mixture cooling in long transport distances. If the material mixed with the binder separates and flows during transportation and laying, the binder material hardens. This causes problems in the compression process.

Manufacturing, transport and laying processes must be carried out in harmony with each other. With a good planning, we can shorten the waiting time of the transport vehicles and prevent the temperature losses of the mixed material directly related to this.

In addition, waiting times should not occur in asphalt paver work. Continuously progressive paver operation is a prerequisite for regular compaction and a healthy surface layer.

Rules to be Considered in Spreading and Compacting

Stone Mastic Asphalt should be laid without any problems using an asphalt paver.

*Mixing heat should be evenly distributed in the asphalt paver boiler. For B50/70, B70/100 or PmB 45 asphalt bitumens, the temperature should not be lower than 150 °C. In the meantime, cold material should not be left in the far corners of the asphalt paver boiler.

*The laying speed of the asphalt paver used should be adjusted so that it does not compress the material too much and that no impact vibrations occur.

*Pressing should be done immediately and with the roller very close to the asphalt paver. A minimum of two rollers is required for each paver strip laid.

*Cylinder press application should be done with tandem or 3-wheeled cylinders heavier than 9 tons.

*The vibratory press should be done at sufficient material temperature and after a static press.

*After the layer temperature drops below 100°C, vibratory compaction is not performed. Since the layer thickness is less than 2 cm and the lower layer causes hard layers, loosening (concrete, stone coatings, etc.) or breaking the aggregate, vibratory compaction is not performed.

*Rubber wheel rollers are not suitable for Stone Mastic Asphalt compaction.

*The handwork required to complete the Stone Mastic Asphalt must be done quickly and at the same speed as the asphalt paver. Roller compaction should be done immediately after paving.

*Pre-compression applied automatically by the asphalt paver should be taken into account for the paving thickness of the layer.

*The minimum values given can be evaluated as a result of experience and should be used in exceptional cases. Under normal circumstances, the layer thickness should nowhere fall below the lowest value. Particular attention should be paid to joints and joints.

Surface Operations

The amount of material to be spread is generally between 1 and 2 kg/m². It has become common to use 0.25 to 2 mm crushed sand, dusted and lightly coated with bitumen, with grain sizes of 1 to 3 mm. Crushed stone chips between 2 and 5 mm should not be used due to excessive decibel level.

The material to be spread is either immediately after the asphalt paver or between the first roller passes; It should be applied on a sufficiently warm and binding layer.

It is essential to use a spreader machine to obtain a smooth surface.
After laying, compacting and finishing, it must be opened to traffic after at least 24 hours to allow the coating layer to cool. Opening to traffic without waiting for this period will cause deformation of the coating layer and the formation of ruts.

After the material is taken out of the heater, it should be emptied and weighed by avoiding a jarring movement, by turning it upside down. This process should be completed within 10 seconds.
Make your work easier with Polygonmach stone mastic asphalt, quality and solid asphalt.

Stone Mastic Asphalt,Properties and Uses of Stone Mastic Guss Asphalt

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

Aggregate

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.

Binding Material

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 Supplements

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.