System for Calibration of the Marshall Compaction Hammer.
System for Calibration of the Marshall Compaction
Hammer.
(6913 K)
Shenton, H. W., III; Cassidy, M. M.; Spellerberg, P. A.;
Savage, D. A.
NISTIR 5338; FHWA-RD-94-002; 149 p. January 1994.
Sponsor:
Federal Highway Administration, Washington, DC
Available from:
National Technical Information Service
Order number: PB94-145661
Keywords:
asphalt; bituminous; building technology; calibration;
compaction hammer; Marshall method; pavement design;
standards; tests
Abstract:
The Marshall method is used by many state and local
highway agencies for the design of hot-mix asphalt
pavement. Although the procedure is specified by several
industry standards, round-robin programs have confirmed
wide variability in Marshall test results. Much of the
scatter in the data is attributed to compaction hammer
variables, such as: variation in drop weight, drop
height, friction, hammer alignment, pedestal support and
foundation. With the objective of reducing the
variability of Marshall test results, a robust, easy to
use and relatively inexpensive test apparatus has been
developed for calibration of mechanical Marshall
compaction hammers. The system consists of a
spring-mass device with force transducer, power supply
and data acquisition system. The device replaces the
standard specimen mold during calibration. Force time
histories from multiple hammer blows are recorded and
analyzed to determine average peak force, energy and
cumulative impulse. The proposed calibration procedure
requires adjusting the number of blows to achieve a
"standard" cumulative impulse. A limited laboratory
evaluation program has been undertaken to demonstrate
the system. The variability of test results for
specimens prepared in calibrated machines was reduced by
as much as 60%, as measured by the reduction in standard
deviation and range of data for 15 specimens. A draft
calibration standard has been developed and formatted
according to AASHTO standards.
