Effects of Elevated Temperature Exposure on Heating Characteristics, Spalling, and Residual Properties of High Performance Concrete.
Effects of Elevated Temperature Exposure on Heating
Characteristics, Spalling, and Residual Properties of
High Performance Concrete.
Phan, L. T.; Lawson, J. R.; Davis, F. L.
Materials and Structures, Vol. 34, 83-91, March 2001.
heating; spalling; concretes; compressive strength;
elevated temperature; high performance concrete;
explosive spalling; modulus of elasticity; residual
mechanical properties; steady-state test methods
Results of part of an ongoing research program, being
conducted at the National Institute of Standards and
Technology (NIST) to study effects of elevated
temperature exposure on performance of high performance
concrete (HPC), are presented. One of the objectives of
NIST's research program is to develop a fundamental
understanding of the heating characteristics and
spalling mechanism in HPC, and to quantify the potential
for spalling and the changes in HPC's material
properties as a result of high temperature exposure.
This paper describes results of NIST's experimental
program that focuses on effects of elevated temperature
exposure on residual mechanical properties of HPC.
Residual mechanical properties were measured by heating
the 102 mm x 204 mm cylinders to steady state thermal
conditions at a target temperature, and loading them to
failure after the specimens had cooled to room
temperature. The test specimens were made of four HPC
mixtures with water-to-cementitious material ratio
(w/cm) ranging from 0.22 to 0.57, and room-temperature
compressive strength at testing range from 51 MPa to 93
MPa. Two of the four HPC mixtures contained silica fume.
The specimens were heated to a maximum core temperature
of 450 C, at a heating rate of 5 C/min. Experimental
results indicate that HPCs with higher original strength
(lower w/cm) and with silica fume retain more residual
strength after elevated temperature exposure than those
with lower original strength (higher w/cm) and without
silica fume. The differences in modulus of elasticity
are less significant. However, the potential for
explosive spalling increased in HPC specimens with lower
w/cm and silica fume. An examination of the specimens'
heating characteristics indicate that the HPC mixtures
which experienced explosive spalling had a more
restrictive process of capillary pore and chemically
bound water loss than those which did not experience