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.

This report summarizes the activities and data collected during the construction of a pavement section used for investigating the performance of asphalt concrete pavements under accelerated pavement testing. This report also presents the preliminary results of six accelerated pavement tests conducted on the test section.

The pavement section was constructed in September 2001 at the Pavement Research Center, located at the University of California Richmond Field Station. The construction was performed by a highway contractor with the purpose of simulating highway paving operations. Under these conditions, the results from the tests can be translated into predicting the behavior of actual in-service pavements.

The pavement was composed of 90 mm of asphalt concrete, and 410 mm of recycled aggregate base on top of a prepared 200 mm subgrade. The layer thicknesses were designed according to Caltrans design procedures and checked using mechanistic methods to ensure limited rutting in the subgrade.

Preparation and construction of the subgrade, aggregate base, and asphalt concrete were completed according to Caltrans practice. Compaction of the asphalt concrete was controlled based on the maximum theoretical density of the mix.

Average in-situ relative densities for the subgrade and aggregate base were above 95 percent. Average air-void contents in the asphalt concrete layer were between 7 and 10 percent. Average thickness was 79 mm. Asphalt extractions from two samples indicated binder content by weight of aggregate of between 4.3 and 5.7 percent. The target binder content was 5.0 percent.

Deflection testing conducted during the construction of the pavement section showed the effect of the asphalt concrete layer on the behavior of the aggregate base and subgrade layers. The asphalt concrete provided an increase in confining pressure, which created an increase in the modulus of the aggregate base, as well as an additional cover that reduced the stresses on the subgrade and created an increase in the modulus of the subgrade. The intensive FWD testing conducted on the pavement section also helped identify portions of the section susceptible to premature failure. These areas were subsequently rejected as locations for HVS test sections.

In general, FWD testing indicated that areas of soft subgrade translated into areas of soft or low aggregate base modulus. The FWD testing also revealed the effect of asphalt concrete modulus on the behavior of the aggregate base. The data indicated that aggregate base modulus increased with asphalt concrete modulus.

FWD testing also revealed the effect of temperature on the modulus of the asphalt concrete, which is typical of asphalt concrete layer and important for the interpretation of the performance of asphalt concrete mixes.

The Heavy Vehicle Simulator (HVS) was used to test the asphalt concrete under conditions of accelerated loading. HVS test sites were selected within the constructed test section to evaluate their performance. The results were compared in terms of fatigue cracking, rutting, and surface deflections. Results indicate that the sections tested during the dry/warm season lasted longer than those tested during the wet/cold season.

The performance of the sections seems to have been controlled by the behavior of the aggregate base. Elevated moisture contents in the aggregate base were recorded during the wet/cold months with corresponding FWD results which indicated high aggregate base modulus values for the same period. The results suggest that the modulus of the aggregate base is not a good indicator of performance.

The results of the HVS test sections are being used to analyze the performance of asphalt concrete pavements and to develop performance models for pavement life prediction as defined in Research Goals 4.1, 4.5, and 4.7 in the PPRC Strategic Plan for 2003/2004.

This report is the first in a series of four reports that describe the results of accelerated pavement tests on full-scale pavements with “wet” base conditions at the Pavement Research Center, located at the University of California Berkeley Richmond Field Station (RFS). The report contains a summary of the results and associated analysis of a pavement section comprised of three lifts of asphalt concrete, an asphalt treated permeable base (ATPB) layer, and untreated aggregate base layers on top of a prepared subgrade and designated as Section 543. The pavement section is a termed a “drained’ pavement due to the inclusion of an ATPB layer between the asphalt concrete layers and the untreated aggregate base. Tests on this test section have been performed as part of the Goal 5 Accelerated Test Program for the evaluation of drained and undrained pavements under conditions of water infiltration.