Many techniques have been used in an attempt to prevent reflection cracking in asphalt overlays including stress relieving membranes, fabrics, bond breakers, and changes in mix design. Glass fiber reinforcements have been used in the plastics industry for increasing the fatigue life and fracture toughness of plastic products for many years. This paper describes the successful development of the use of glass fiber reinforcement in conjunction with an asphalt polymer to minimize reflection cracks in an asphalt overlay. The system is also used to reduce excavation of deteriorated cracks and joints before overlaying.
The glass fiber reinforcement is a high strength woven glass with a tensile strength of 1750 N/cm (1000 lb/in.) width. The asphalt polymer was specially designed for use with the glass fiber reinforcement and has excellent properties of adhesion, low-temperature flexibility, and high softening point.
The combined properties of the system are the key to performance. The asphalt polymer adheres to the old road, the glass fiber reinforcement, and the new overlay, protects the glass fiber reinforcement, acts as a stress relieving membrane, and transfers the stresses to the reinforcement. The glass fiber reinforcement distributes the stress over the width of the repair to a level below the fracture point of the overlay. Laboratory tests were used to determine the physical properties and characteristics of the system, but no laboratory tests were found to predict the field performance. Evaluation of the system was performed through field trials. Over a five-year period 150 field trials were installed in 21 states. These trials included transverse and longitudinal cracks in bituminous roads and transverse joints, longitudinal joints, and interslab cracks in portland cement concrete base roads. Approximately 30 480 m (100 000 ft) of the repairs were monitored for crack reflection. The asphalt polymer/glass fiber reinforcement system was 89% effective in reducing reflection cracks. The average age of the trials was 21 months with a range of 6 to 56 months. All trials were exposed to a minimum of one winter.
In recent trials this system has been used to reinforce badly distressed areas around joints or cracks in lieu of partial or full depth excavation. Cost savings greater than ten to one have been demonstrated for the asphalt polymer/glass fiber reinforcement system with equivalent or better performance than excavation.