In recent years stone mastic asphalt (SMA) mixtures are widely used in construction of roads that will have to endure large loads in the future. If we make a comparison of these mixtures with conventional asphalt concrete, it may be noted that SMA is more resistant to rutting and cracking processes and has high strength, durability and thinner coating. This is achieved due to a rigid frame structure in a coating layer. It allows transmitting load from the surface to adjacent layers through stone material particles being in direct contact with each other.
The composition of SMA includes large-sized gravel and stone chips (used to obtain mastic). Mastic is needed to fill the space between stones in macadam frame.
With all the advantages of SMA, there are still some tasks that require effective solutions. First of all it is about mastic runoff during transportation and laying of coating, which may lead to defects of a roadway. In order to prevent such outcome, it is necessary to add a stabilizing additive into SMA. By their structure such additives are special fibers that are distributed in a mixture and reinforce bitumen to prevent its runoff process.
In Russia “Hrizotop” is used as an additive for SMA. It was first used in 2002. First there were works on testing the additive and improvement of equipment for its production. Upon successful completion of these steps, “Hrizotop” received an approval to be produced on an industrial scale.
The benefits of this supplement are as follows:
- low expenditure (less than 0.3-0.35% by weight of the mineral mixture);
- ease of dosing and mixing;
- uniformity of structure
- absence of lumps;
- high strength and heat resistance of chrysotile fibers;
- simplicity of storage.