Fibers, Percolation, and Spalling of High-Performance Concrete.
Fibers, Percolation, and Spalling of High-Performance
Concrete.
(1192 K)
Bentz, D. P.
ACI Materials Journal, Vol. 97, No. 3, 351-359,
May/June 2000.
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Keywords:
concretes; fibers; spalling; high performance concrete;
water cement ratio
Abstract:
While the strength and durability of high-performance
concretes (HPCs) are often greatly superior to
conventional concretes under ambient conditions, their
failure is sometimes rapid and dramatic during exposure
to a fire, characterized by the explosive spalling of
layers from the exposed concrete surface. This failure
mode is rarely encountered in conventional concretes of
higher w/c ratios. In these concretes, it is suggested
that the interfacial transition zones (ITZs) surrounding
each aggregate particle provide a convenient escape
route for the vapor built up during the thermal
exposure. In HPC, these ITZ regions are thinner and not
percolated, but can be repercolated by the addition of
just a few (0.2 to 0.5% by volume) fibers. Here,
simulations are conducted to determine the relative
eflciency of different length fibers in creating a
percolated network, and to investigate the effects of
aggregate volume fraction and gradation on ITZ
percolation.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899