An innovative application that is rapidly becoming widespread is the so-called “foamed bitumen”. The potential of expanded bitumen was already known fifty years ago, but this material has been exploited only recently and this technology has been awarded by SITEB for its usefulness in many applications. By adding foamed bitumen and cement to a graded mixture of crushed and inert materials it is possible to build high quality bearing layers with bitumen/hydraulic binder. When cold water (15-25°C) gets in touch with bitumen (160-200°C), there is an immediate expansion of the mixture due to the rapid vaporisation of water.

The bitumen increases its volumes 15 times and reduces its viscosity top e perfectly combined with other materials during mixing with the necessary moisture to obtain the required characteristics.

This technique allows preparing homogeneous mixtures.
For example, in a prescription with 3% of foamed bitumen + 3% of cement, thanks to the expansion of bitumen, the 3% in liquid weight, corresponding to 6% in volume (ratio of absolute density 1:2), considering an expansion of 15 times, becomes approximately 90% in volume of the material to recycle. In this case, 10 parts of the material to bind are mixed with 9 parts of foamed bitumen, instead of 100 parts of material with 6 parts of liquid bitumen.
The expanded bitumen can be used to stabilize substrate layers and for cold recycling.

Anyway, foamed bitumen is not suitable for absorbing tangential and traction stress (only minimal) and therefore it is not suitable for superficial layers of pavements (binder and mat) while is particularly suitable for replacing bitumen basis and combined cement basis (with a better mechanical performance).

The laying technique is dual:
· On-site foamed bitumen with recycler
· Foamed bitumen with semi-mobile equipments in the storage area (KMA 200)

With the mobile recyclers the existing road surface is milled and crushed. At the same time, water, cement and foamed bitumen are added by tank mixing. Then the material is profiled using a grader and compacted with machines of adequate weight.
With the semi-mobile equipment placed in a specific area, it is possible to prepare a mixture with grading curve of crushed, foamed bitumen, correction, and cement, to load it on a truck, to lay it as a regular hot conglomerate with a vibratory finishing machine and to compact the surface with a pneumatic tyred roller.