Experience in Rehabilitation of Low-volume Roads Using Soft Asphalt and Otta Seal Technologies

摘要

In Lithuania more than third (33.9%) of state roads are gravel roads. Maintenance of these roads needs large budget and operation of them results in social discomfort. The best method to improve driving conditions and avoid social discomfort for the inhabitants living close to gravel roads is to reduce dustiness using suppressants or even construct asphalt pavement. But, dust suppressants are not enough efficient due to wet and rainy climate in Lithuania. Also, the performance of conventional asphalt pavement used for low-volume roads was unsatisfactory, due to thin frost resistance layer or weak subgrade. And those additional works significantly increase road construction costs up to 25%.As alternative solution the use of soft asphalt and Otta Seal technologies were proposed. Therefore, in 2012 the trial sections were constructed in order to clarify the effectiveness and functionality of soft asphalt and Otta Seal technologies under current traffic and climate conditions. Measurements of roughness and condition of soft asphalt pavement and Otta Seal were carried out in spring, summer (only condition of soft asphalt pavement) and autumn every year. The average roughness of all the trial sections with soft asphalt pavement or most of the trial sections with double Otta Seal complies with the requirements (≤ 3.5 m/km) to the roads of regional significance. Besides, the roughness of the trial sections with soft asphalt is similar to that of the sections with asphalt base course-pavement. Trial road sections with soft asphalt pavement are in good condition after 30–32 months of operation, and longitudinal cracks were observed as the main defect, which tends to heal in summer period. The Otta Seal also represented the ability to self-heal under high pavement temperature. However, the condition of trial sections with Otta Seal were not as good as soft asphalt pavement. The formation of the most defects were identified as causes of inappropriate amount of binder, insufficient maintenance in summer period and unqualified procedure of applying Otta Seal. Based on the results of this research the conclusions and recommendations were made for further application of soft asphalt and Otta Seal in Lithuania.