Reflective Cracking Study: Initial Construction, Phase 1 HVS Testing, and Overlay Construction
This first-level report describes the design and construction of a Heavy Vehicle Simulator (HVS) test track that will be used to validate Caltrans overlay strategies for the rehabilitation of cracked asphalt concrete. The report also summarizes the first phase of HVS testing, carried out on six separate sections to crack the pavement, as well as design and construction of the overlays for the reflective cracking HVS experiments. The construction, preliminary field and laboratory data, and accelerated pavement tests reveal several issues regarding the performance of the asphalt concrete pavement cross section tested under the Heavy Vehicle Simulator. The test track was constructed in September 2001. HVS testing took place between December 21, 2001, and March 25, 2003. Each section was trafficked with a 60 kN (13,500 lb) load using a bi-directional loading pattern with wander. Pavement temperature at 50 mm depth was maintained at 20°C (68°F) using a temperature control chamber. Findings from the HVS testing include: • Analysis of deflection measurements revealed that the modulus of the asphalt concrete was significantly affected by the asphalt concrete temperature. • The performance of the HVS test sections appeared to be significantly influenced by the behavior of the aggregate base. Sections that were tested during the dry months lasted longer both in fatigue and surface rutting than the sections tested during the wet months. • Air-void contents and thicknesses were similar for the test sections; therefore, the effect of these variables could not be addressed. • Deflection results could not be satisfactorily used as an indicator of aggregate base performance. Aggregate base moduli were higher during the cold/wet months but decreased rapidly when tested under the HVS. The aggregate base moduli of the sections during the dry/warm months were lower than those during the cold/wet months, but the sections tested during the dry period had longer pavement lives. Deflections determined with the RSD during HVS testing and an FWD after testing were used to determine overlay thicknesses. A full-thickness design of 90 mm (3.5 in) was selected for the AR4000-D control section and one of the modified binder mixes (MB-G). The remaining sections were designed as half-thickness (45 mm) (1.7 in). The overlays were placed on June 14, 2003.