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Effects of Test Conditions and Mixture Proportions on Behavior of High-Strength Concrete Exposed to High Temperature.


pdf icon Effects of Test Conditions and Mixture Proportions on Behavior of High-Strength Concrete Exposed to High Temperature. (1034 K)
Phan, L. T.; Carino, N. J.

ACI Materials Journal, Vol. 99, No. 1, 54-66, January/February 2002.

Keywords:

concretes; high temperature; high strength concrete; spalling; compressive strength; elasticity; silica fume

Abstract:

Mechanical properties of high-strength concrete exposed to elevated temperatures were measured by heating 100 mm x 200 mm cylinders at 5 degrees C/min up to temperatures of up to 600 degrees C/min. Heating was carried out with and without a sustained stress, and properties were measured at elevated temperatures as well as after cooling to room temperature. Four mixtures with water-cementitious material ratios (w/cm) ranging from 0.22 to 0.57, and room-temperature strengths ranging from 51 MPa to 98 MPa, were used. Two of the mixtures contained silica fume. Measured compressive strengths and elastic moduli were normalized with respect to room temperature values, and analysis of variance was used to determine whether the test method, the value of w/cm, or the presence of silica fume affected the results. The influence of these variables on the tendency for explosive spalling was also examined. Results indicate that losses in relative strength due to high-temperature exposure were affected by the test method and w/cm, but there were significant interactions among the main factors that resulted in complex behaviors. The presence of silica fume does not appear to have a significant effect. Measurements of temperature histories in the cylinders revealed complex behaviors that are believed to be linked to heat-induced transformations and transport of free and chemically combined water.