Stone mastic asphalt concrete – a material for the construction of road surfaces

The construction of road surfaces has been transformed by the incredibly durable material known as stone mastic asphalt concrete (SMA). SMA is gaining popularity as a material for highways and roads with heavy traffic because of its exceptional resistance to deterioration and wear. Its distinct structure and composition provide a number of advantages over conventional asphalt mixtures.

Rich stone content is one of SMA’s primary characteristics, offering remarkable strength and stability. This makes it especially appropriate for heavily trafficked roads, like those that are used by buses and trucks. The asphalt binder fills in the spaces left by the interlocking stones to create a sturdy, long-lasting surface.

SMA is strong and has outstanding skid resistance, which increases driver safety. The stone matrix’s textured surface improves grip and lowers the chance of accidents, particularly in damp weather. This makes SMA a material of choice in locations where traffic safety is of utmost importance.

SMA’s durability is another benefit. Stone mastic asphalt concrete roads require less frequent maintenance, which ultimately saves time and money. Because of its durability, roads are smoother and more dependable because there are fewer potholes and cracks. SMA is a desirable alternative for public infrastructure projects because of its affordability.

SMA’s rising popularity can also be attributed to environmental factors. Because of its longer lifespan, repaving is less necessary, which lowers emissions from construction activities and the amount of natural resources used. Additionally, SMA can be made using recycled materials, which supports environmentally friendly building methods.

All things considered, stone mastic asphalt concrete is a practical and efficient option for contemporary road building. It’s a great material to use for long-lasting roads because of its strength, safety, durability, and environmental benefits. SMA will probably be essential in building infrastructure that can accommodate future demands as cities and towns grow.

Composition of mixtures

Although it may initially appear to belong to the category of traditional road surfaces based on oil-bitumen binders, stone mastic asphalt concrete GOST 31015-2002 is not.

Its structural characteristics and component composition set it apart from the competition.

The material’s stiff, crushed stone framework increases resistance to plastic deformations. Additionally, a substantial amount of bitumen binder, filling in all the empty space between the fillers, lowers the residual porosity of asphalt concrete (0–1%), resulting in a long-lasting coating resistant to harsh weather and transportation.

Properties

The following elements illustrate the makeup of crushed stone mastic asphalt concrete:

• crushed stone (70–80%);
• bitumen (5.50–7.50%);
• stabilizing additive;
• mineral powder.

The presented values indicate that stone mastic asphalt concrete differs from standard asphalt mixtures (GOST 9128-97) in that it contains a higher percentage of crushed stone and petroleum bitumen. Therefore, stabilizing fibrous additives are bound into the stone mastic asphalt concrete mixture to prevent delamination and maintain a homogeneous composition, especially during road works.

The composition of stone mastic asphalt concrete can be arranged in the following ways, depending on the percentage of filler used:

• Stone mastic asphalt concrete SMA 10 – the grain size of the crushed stone used should not be more than 10 mm.

• The second and most common brand is stone mastic asphalt concrete SMA 15 with a standardized filler grain size of 15 mm.

• Stone mastic asphalt concrete SMA 20 — maximum grain size 20 mm.

For use in building upper structural layers of road pavements 2-4 cm thick on city streets and highways of all technical categories in climate zones I–V, asphalt concrete crushed stone mixture of the aforementioned grades is advised.

Some advice: the adhesion coefficient and compressive strength of SMA mixtures used to build airfield pavements need to be raised by 25%.

When compared to traditional asphalt pavement, the use of stone mastic asphalt concrete on high-speed, high-traffic roads offers several benefits.

• high wear resistance, independent of climatic operating conditions;
• stable condition of the coating under various mechanical influences;
• the service life of road surfaces is 2-3 times longer than that of other similar coatings;
• increased coefficient of adhesion of car tires to the road surface;
• low noise level when driving vehicles.

Materials

The following specifications for the materials used are provided by the technology of stone mastic asphalt concrete:

1. Crushed stone:

• the grain composition must be from hard rocks according to GOST 8267–93;
• it is allowed to use crushed stone from metallurgical slags;
• the grade of the crushed stone used must be 1000–1200 and higher;
• the grains must have a cubic shape;
• the volume of needle-shaped and plate-shaped grains, by total weight, must not exceed 15%;
• frost resistance F50 and higher;
• the abrasion values ​​must correspond to the I-1 grade.

1. Bitumens:

• for the production of SMA mixtures, it is recommended to use petroleum bitumen in accordance with GOST 22245-90 or PBB (polymer-bitumen binder);

• in case of using PBB, if the requirements for bitumen flow indicators are met, it is permissible not to introduce fibrous stabilizing additives into the material;
• all bitumens used must have sufficient adhesion to the surface of the crushed stone used, otherwise it is necessary to introduce a cationic adhesive additive.

1. For the production of SMA mixtures only sand from crushed solid rocks according to GOST 8736–93 grades 1000 and higher is used. The amount of clay particles in the material should not exceed 0.5%.
2. Mineral powder according to GOST 16557-78 is produced by crushing dolomite or calcareous rocks. It is permissible to use mineral powder produced from crushed volcanic rocks with a fraction of no more than 0.16 mm.

A stabilizing additive must be present in the structure of SMA due to the high volume of bitumen binder. This component is essential to preparing a mixture with those mechanical and physical properties, which sets this material apart from other conventional forms of asphalt concrete.

Stabilizing component of mixtures

In order to improve the quality of asphalt concrete, its preparation, transportation, and laying, stabilizing additives’ type and properties are crucial.

At the high temperatures needed for production and laying, fibrous structuring additives help keep mixtures homogeneous and hot bitumen on the crushed stone’s surface, preventing segregation and stratification of solutions.

The following were added to mixtures as stabilizers at different times:

• rubber crumb;
• asbestos fibers;
• polymer fibers;
• mineral components;
• thermoplastic polymers;
• various products based on silicic acid;
• acrylic threads;
• cellulose fibers.

Cellulose fibers in the form of fibers or specially formulated granules derived from them are the most widely used because of their low cost of production. This substance has the capacity to retain a significant amount of bitumen on the coating’s surface for an extended period of time while preventing delamination of the composition.

According to test results, cellulose fibers must have a uniform composition, be free of impurities, and contain at least 50% of threads with a length of 0.1 to 2.0 mm. This ensures a high degree of homogeneity in mixtures and the ideal thickness of the bitumen film on the surface.

The following table lists the essential performance characteristics of cellulose fiber that this kind of fiber needs to possess.

The German company JRS’s products are the most well-liked in Russia. Take the stabilizing additive "VIATOP 66" as an illustration.

This material is made of bitumen-coated granular cellulose that has been compacted into a three-dimensional structure. In comparison with other comparable materials, the performance characteristics of highways can be greatly increased, labor costs can be significantly decreased, and the service life of the road surface can be increased by five times by adding the presented additive to the asphalt concrete mixture.

The above-mentioned stabilizing additive’s qualities greatly minimize the need for a dosage schedule and shorten the time needed for the granules to mix in the mixer. Additionally, the bitumen impregnation prevents the cellulose fibers from burning when they come into contact with the heated aggregate.

In comparison to conventional asphalt, stone mastic asphalt concrete (SMA) offers superior longevity, skid resistance, and durability for use on road surfaces. SMA provides exceptional resistance to rutting and deformation by combining a rich blend of stone and mastic, which makes it a great option for high traffic areas and severe weather. This novel asphalt blend ensures smoother, more dependable travels for all road users by extending the life and safety of roads while also lowering maintenance expenses and interruptions.

For building road surfaces, stone mastic asphalt concrete has shown to be a reliable and long-lasting choice. Its special makeup, which includes a larger percentage of coarse aggregates, guarantees exceptional load-bearing capacity. This makes it perfect for roads and high-traffic areas where durability and stability are needed.

Regarding performance and safety, using stone mastic asphalt concrete has several benefits. Because of the material’s improved skid resistance, especially in damp conditions, there is a decreased chance of accidents. Its resistance to deformation under high loads also contributes to the long-term maintenance of a safer and smoother driving experience.

The durability of stone mastic asphalt concrete is another important advantage. The mix is made to endure a wide range of weather, from scorching heat to below-freezing temperatures, without suffering appreciable damage. In addition to its technical benefits, this results in fewer repairs and lower maintenance costs.

All things considered, stone mastic asphalt concrete is a dependable and effective option for contemporary road building. Many of the common issues that traditional asphalt surfaces encounter are addressed by its unique combination of strength, safety, and durability. This material presents a compelling solution that promises longevity and performance for anyone involved in road infrastructure projects.

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