Development and Performance of Interlayer Stress-Absorbing Composite in Asphalt Concrete Overlays

An interlayer stress-absorbing composite (ISAC) was developed and evaluated for the purpose of effectively alleviating or mitigating the problem of reflection cracking in an asphalt concrete (AC) overlay. ISAC materials and performance properties were carefully selected through comprehensive theoretical studies and laboratory evaluation programs. The ISAC system consists of a low-stiffness geotextile as the bottom layer, a viscoelastic membrane layer as the core, and a very high stiffness geotextile for the upper layer. In order to evaluate the effectiveness of the ISAC layer to control reflective cracking, a laboratory pavement section with an AC overlay placed on a jointed portland cement concrete slab was constructed and tested in an environmental chamber. A mechanical device was used to simulate thermal strain in the slab, and the joint was opened and closed at an extremely slow rate. The testing was conducted at −1.1°C, and strain in the overlay was monitored using a sensitive linear variable differential transducer device. The force required to pull and push the slab was monitored using a load cell placed between the slab and a hydraulic ram. Performance of ISAC was evaluated by comparing the cycles to failure of an ISAC-treated overlay with the performance of a control section without ISAC and of test sections containing two commercially available products. The base isolation properties of the ISAC system were demonstrated in the laboratory evaluation studies, which indicated that the ISAC system vastly outperformed the control section and the sections with the two commercial products tested. Several years of field performance testing have show that the ISAC system is highly effective for mitigating reflective cracking in AC overlays used on both airport and highway pavement systems.