Use of Foamed Tar for Construction of Flexible Pavement with Existing Unpaved Road Structure

Low-volume and unpaved roads constitute the majority of the road network throughout the developing and developed world. Upgrading these unpaved roads to conform to standards of low-volume flexible asphalt pavements is a costly exercise. In most instances, this involves constructing an entirely new pavement base. Recent technological advances in the field of deep in situ recycling have provided pavement engineers with an alternative to standard rehabilitation and reconstruction methods of flexible pavements. One such technique of stabilization is foamed tar treatment of inferior natural pavement materials through the application of deep in situ recycling to produce a stabilized base for lowvolume flexible pavements. Foamed tar technology and the concept of deep in situ recycling, and its advantages over current reconstruction methods, were reviewed. Health aspects relating to implementation of the stabilization process were addressed with respect to the use of gasifier tar in a controlled recycling environment. The engineering properties of foamed tar mixes were compared with existing stabilization techniques. A test section was constructed with particular attention to the flexibility of foamed tar for placement time, workability, and durability to environmental conditions. Performance testing results were analyzed. In conclusion, the benefits of foamed tar stabilization for developing an improved road network in a cost-effective manner were evaluated.