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CHAPTER 1
Introduction and Research Approach
1.1 Problem and Purpose with each test. In Phase II, two First Article devices were pro-
cured and evaluated. This evaluation concluded that the SPT
NCHRP Project 9-19: Superpave Support and Performance is a reasonably priced, user-friendly device for measuring
Models Management recommended three candidate simple stiffness and permanent deformation properties of asphalt
performance tests to compliment the Superpave volumetric concrete. Additional work, however, was needed to further
mixture design method. These are: flow time, flow number, refine the SPT for use in routine practice. This additional work
and dynamic modulus. The recommended tests are con- was undertaken in Phases IV and V of NCHRP Project 9-29.
ducted in uniaxial or triaxial compression on cylindrical spec- These phases of the project included four major activities di-
imens that are sawed and cored from over-height gyratory rected at implementation of the SPT in routine practice:
compacted samples. Data from all three candidates were
shown to correlate well with observed rutting in field pave- 1. Enhancement of the SPT to perform dynamic modulus
ments, and the dynamic modulus appears to have potential master curve testing required for pavement structural
as a simple performance test for fatigue cracking (1). The design and analysis.
dynamic modulus is also the primary material input for flexi- 2. Procurement and evaluation of SPTs with dynamic mod-
ble pavement structural design in the Mechanistic-Empirical ulus master curve testing capability.
Pavement Design Guide (MEPDG) completed in NCHRP 3. Development of equipment for rapid preparation of test
Project 1-37A (2). The use of this test for both mixture evalu- specimens for the SPT.
ation and structural design offers a potential link between 4. Ruggedness testing for dynamic modulus and flow num-
mixture design and structural analysis that has been an ber tests conducted in the SPT.
underlying goal of a substantial amount of past flexible pave-
ment research. The ruggedness experiments were performed and docu-
The objective of NCHRP Project 9-29 is to stimulate the mented in Phase V of the project. This report documents the
development of commercial testing equipment capable of work completed in Phase IV of the project.
performing the NCHRP Project 9-19 performance tests. It is
envisioned that this equipment will be used for two purposes:
1.2 Scope and Research Approach
1. As a simple performance test to compliment Superpave
1.2.1 Simple Performance Test System
volumetric mixture design, and
2. For the asphalt concrete material characterization required Phase IV included two major tasks aimed at continued de-
by the MEPDG and other similar flexible pavement struc- velopment of the SPT. The first of these was the development
tural design methods. of an abbreviated testing protocol for developing dynamic
modulus master curves for use in routine mixture evaluation
In Phase I of NCHRP Project 9-29, a detailed purchase and flexible pavement design. AASHTO TP62, Determining
specification for the Simple Performance Test System (SPT) Dynamic Modulus of Hot-Mix Asphalt Concrete Mixtures, is the
was developed. The SPT is capable of performing the three recommended standard describing the testing and analysis
NCHRP Project 9-19 performance tests, and standardizes the required to develop dynamic modulus master curves for the
instrumentation, data acquisition, and data analysis associated MEPDG. This standard requires testing at five temperatures
