SMAPOL is a polyester stabilising agent that can be added to bituminous mixtures. It can be used to stabilise and reinforce SMA mixtures. It is an anti-sedimentation agent for SMA gap-graded mixtures, where it reduces asphalt skid.
SMA gap-graded mixtures contain a pre-formulated surplus of bitumen binder that has a tendency for flowing down the surface of the aggregate during storage, transportation or road application in high temperatures. Fibrous additives like SMAPOL are applied in order to prevent this and reduce asphalt skid. The manufacture of SMAPOL involves the use of high mechanical strength synthetic fibres that are also used for the production of car tyres. The fibres are recycled from car tyres in the process of their mechanical grinding and rubber separation. The average fibre composition is 75% polyester, 20% polyamide and 5% polypropylene.
A small content of tyre rubber has a positive effect on the mechanical and rolling parameters of asphalt surfaces, as the addition of rubber helps reduce braking distance and noise.
The synthetic fibres that SMAPOL stabilising additive is made of do not absorb humidity. They do preserve their mechanical properties when mixed into asphalt surfaces, and provide asphalt’s additional reinforcement.
SMAPOL is supplied in the form of pellet so that it can be automatically dosed when added to concrete mixtures in bulk bitumen manufacturing plants directly from big bags and silos. SMAPOL pellet is also convenient for pneumatic and mechanical dosages.
The recommended dosage of SMAPOL additive to keep bitumen binder’s skid below 0.3% according to the technical guidelines published by the General Board of National Roads and Motorways (GDDKiA) (WT-2 2014) is between 0.2% and 0.3% of the weight of mineral-asphalt mixture, i.e. between 2kg and 3kg of additive per 1 tonne of mineral-asphalt mixture.