It is well-known that the quality of asphaltic road oil plays a big role in the long life of a road covering. Asphaltic road oil should assure good wettability, adhesion to mineral materials, necessary heat stability and be aging resistant.

That's why a special attention is now paid to the possibility of modification of asphaltic road oils with various additives allowing to improve and regulate the abovementioned qualities.

Sulfur is one of such modifiers. Tests performed in Canada, the USA, Europe and Russia show that sulfur makes coverings more resistant to weather impacts, more durable and wearproof in comparison to the same coverings without addition of sulfur. The experience of the Russian Road Research Institute specialists did not become widely spread because there was no effective and safe technology for addition of sulfur to asphalt concrete. However, following the result of works of the Russian Road Research Institute, the Instruction on the use of sulfur additives in hot asphalt concrete mixtures was issued in 1986. At the same time GOST 9128-84 was changed as related to the use of sulfur in road coverings made of asphalt concrete.

At present there is a technology of production of sulfur asphalt binder (SAB), which contains up to 40% (by mass) of road asphalt oil is replaced by the cheap gas sulfur.

Figure. Example of sulfur asphalt concrete

The basis of the technology is formed by the principle of production of an activated sulfur/asphaltic road oil colloid solution that is stable during storage, melting and transfer and is used in the same manner as standard asphaltic road oil.

Figure 1. Colloid solution - SAB 30/70

Magnification in 160 times

This is achieved by processing of the mixture in apparatuses with electromagnetic fields.

A small volume of sulfur (5-7%, sometimes 10% by mass) comes into chemical interaction with asphaltic road oil. Namely this volume of sulfur is the most effective modifier of the organic binder.

The rest of sulfur with the greatly developed active specific area is in the colloidal state. It plays the role of a plasticizer and participates in formation of the structure of sulfur asphalt concrete produced on the basis of such binder.

The use of the activated colloidal mixture allows to produce more resistant, wearproof and heat stable road coverings, which is confirmed by laboratory tests (see the Application) and tests on the actual units of (see Figure 2).

Figure 2. A year after laying

LHC - standard asphalt concrete

RHC - sulfur asphalt concrete