Mechanical Properties of High Performance Concrete After Exposure to Elevated Temperatures.
Mechanical Properties of High Performance Concrete After
Exposure to Elevated Temperatures.
Lawson, J. R.; Phan, L. T.; Davis, F. L.
NISTIR 6475; 39 p. March 2000.
Available from: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
1-800-553-6847 or 703-605-6000;
Order number: PB2000-104063
concretes; mechanical properties; exposure; temperature;
building construction; explosions; high performance
concrete; spalling; structures; environments
This research effort aims to characterize the residual
mechanical properties of high performance concrete (HPC)
after being exposed to elevated temperatures. Residual
mechanical properties of four different types of
concrete were measured after being heated to 450 deg C.
The average compressive strength for these four types of
concrete, before being exposed to elevated temperatures,
ranged from an average of 40 MPa (6000 psi) to 100 MPa
(15000 psi). Three of the concrete types are high
performance concrete (HPC), and one represents
conventional normal strength concrete (NSC). The
following physical properties were measured for each
concrete specimen prior to thermal exposure: physical
dimensions, mass, and longitudinal resonant frequency
(which allowed for the calculation of Young's Modulus).
Before the elevated temperature exposure tests were
conducted, a baseline data set was generated for each of
the four specimen types after exposure to a nominal room
temperature of 25 deg C. Elevated temperature exposures
were accomplished by placing the specimens into an
electric furnace and heating them at a rate of 5 dec
G/min until they reached steady-state condition at one
of four selected temperatures. The selected temperatures
were 100 deg C, 200 deg C, 300 deg C, and 450 deg C. The
controlled furnace temperature rise time plus the steady
state heating period produced a total heating period of
six hours. Following this six hour thermal exposure and
after the concrete specimens cooled in the furnace to
room temperature, the specimens were weighed, and the
resonant frequency was measured again. The compressive
strength and dynamic Young's modulus of each specimen
was measured. Results from this study may be useful for
accessing post-tire properties of HPC. Explosive
spalling during heating was experienced with two HPC
types that contained silica fume. This spalling occurred
during the release of crystalline, chemically bound,
water at temperatures ranging from about 240 deg C to
280 deg C. Explosive spalling was not experienced with
either of the concrete mixtures that did not use silica