United States Department of Transportation
i
Evaluation of Concrete Bridge Decks Comprising Twisted Steel Micro Rebar
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2020-11-01
[PDF-8.85 MB]
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Edition:Final, June 2016 to September 2020
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Abstract:The objective of this research was to investigate the effects of twisted steel micro rebar (TSMR) fibers on 1) the mechanical properties of concrete used in bridge deck construction and 2) the early cracking behavior of concrete bridge decks. This research involved the evaluation of four newly constructed bridge decks through a series of laboratory and field tests. Two decks were constructed without TSMR, and two were constructed with an addition of 40 lb of TSMR per cubic yard of concrete. Regarding laboratory testing, the conventional and TSMR specimens exhibited similar shrinkage and electrical impedance test results. During compressive strength, flexural strength, and splitting tensile strength testing, all specimens containing conventional concrete exhibited a brittle failure, while specimens containing TSMR exhibited an extremely ductile failure. No notable difference in behavior between conventional and TSMR specimens was apparent before initial cracking. Regarding field testing, sensors installed in the bridge decks indicated that the addition of TSMR does not affect internal concrete temperature, moisture content, or electrical conductivity and that the stiffness of the TSMR concrete was very similar to that of conventional concrete. Distress surveys showed that the conventional decks exhibited notably more cracking than the TSMR decks. The TSMR fibers exhibited the ability to limit both crack density and crack width. Chloride concentrations for samples collected over cracked concrete increased more rapidly than those for samples collected over non-cracked concrete. Although TSMR fibers themselves do not directly affect the rate at which chloride ions penetrated cracked or non-cracked concrete, the fibers do prevent cracking, which, in turn, limits the penetration of chloride ions into the decks.
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