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(14, 40, 70, 100, and 130 °F) and six frequencies of loading evaluation of the First Article upgrades and the production
(0.1, 0.5, 1.0, 5.0, 10, and 25 Hz). It is desirable that equipment units.
for performing such testing be available to highway agencies
at a reasonable cost, and that the test procedure be appropri-
1.2.2 Simple Performance Test Specimen
ate for agency laboratories. A recently completed FHWA
Fabrication System
pooled fund study identified several issues associated with the
test protocol, and concluded that the overall time required to A major criticism of the NCHRP Project 9-19 performance
perform the testing must be shortened if highway agencies are tests is the size of the specimen used in the testing. To ensure
going to use it for routine testing (3). The most efficient that fundamental properties are measured, a 3.94 in. diame-
approach to reducing the time requirements for dynamic ter by 5.91 in. tall test specimen must be used. These test spec-
modulus master curve testing is to minimize the number of imen dimensions were determined through an extensive
temperatures used in the testing. The current low temperature specimen size and geometry study conducted during NCHRP
testing requirement of 14 °F significantly increases the cost of Project 9-19 (4). Test specimens are obtained by first manu-
the environmental system and increases the loading capacity facturing gyratory specimens that are 5.91 in. diameter by 6.5
and cost of the testing equipment. If testing at this tempera- to 6.9 in. tall. The test specimen is then obtained by cutting a
ture can be eliminated, the cost of the equipment, the com- 3.94 in. diameter core from the middle of the gyratory sam-
plexity of the procedure, and the overall time required to ple, and sawing the ends to produce a test specimen 5.91 in.
develop a master curve can be significantly reduced. In Phase tall with smooth, parallel ends. Many engineers and techni-
IV of NCHRP Project 9-29, an abbreviated testing protocol for cians consider this multi-step test specimen fabrication
developing dynamic modulus master curves was developed process a significant obstacle to implementation of the SPT in
based on analysis of numerous dynamic modulus master routine practice.
curves produced using AASHTO TP62. Details of this analy- In Phase I of NCHRP Project 9-29, workshops were held
sis are presented in Chapter 2 and a recommended standard with potential users and manufacturers of the SPT. Both users
practice for developing dynamic modulus master curves for and manufacturers agreed that a low-cost, automated system
routine mixture evaluation and flexible pavement design is for test specimen fabrication would enhance the SPT. An
presented in Appendix A. equipment specification for such a system was developed in
The abbreviated testing protocol includes testing at three Phase I of the project. The primary purpose of the specification
temperatures between 39.2 and 115 °F using four frequen- for the Simple Performance Test Specimen Fabrication System
cies of loading between 0.01 and 10 Hz. The low tempera- was to encourage equipment manufacturers to develop equip-
ture required some modification of the SPT developed in ment for test specimen fabrication that speeds the process of
Phases I and II of NCHRP Project 9-29. To minimize costs, preparing the required test specimen. The specification pro-
the SPT was originally designed for testing only at room vided tolerances for critical specimen dimensions and required
temperature and above. The modifications required for that the test specimen be fabricated from an existing gyratory
master curve testing were: (1) improved cooling capacity, sample in 15 minutes or less. In Phase II of the project, Shed-
(2) additional load capacity, and (3) software required mod- works' Inc. was awarded a contract for final design and fabri-
ification to include 0.01 Hz load control. Cost estimates cation of an innovative device where the gyratory specimen is
from potential vendors indicated that the additional cool- gripped by a chuck similar to that used in a lathe. Automated
ing and loading capacity would only add approximately diamond-tipped cutoff blades saw the gyratory specimen to
5 percent to the cost of the SPT. length, and an automated diamond-core barrel then cores the
In the second task to continue the development of the SPT, test specimen from the gyratory specimen.
the equipment specification was revised to produce a device Shedworks encountered many problems during final design
capable of performing dynamic modulus master curves using and fabrication of the equipment in Phase II; therefore, deliv-
the abbreviated protocol. This equipment also maintains the ery of the first-article device was extended to Phase IV of
capability to perform the flow number and flow time testing. the project. Chapter 4 presents the results of a series of specifi-
The revised equipment specification is presented in Appen- cation compliance tests that were performed on the Shedworks
dix B. The revised equipment specification was used to device. Appendix C presents the equipment specification for
upgrade the First Article devices that were purchased and the Simple Performance Test Specimen Fabrication System. A
evaluated in Phase II of the project and to procure and eval- Recommended Standard Practice for preparing SPT specimens
uate additional production units. New equipment was is included in Appendix A. This practice is a generic procedure
procured from Industrial Process Controls, Ltd. and Medical for SPT specimen fabrication that does not require use of
Device Testing Services, Inc. Chapter 3 includes details of the the Simple Performance Test Specimen Fabrication System.
