Sixth, the State of New York reported scaling when deicing chemicals are used. New
York reported problems with a bridge made with concrete containing 50 percent GGBF slag
and a sidewalk containing concrete mixes of 25-50 percent GGBF slag. Neither the GGBF
slag producers nor FHWA addressed this concern in their comments. However, the
Province of Ontario submitted a study that showed that the scaling resistance of concrete
surfaces exposed to freezing and thawing in the presence of deicing salt was influenced by
(1) the type and quantity of cementing material in the concrete mix, (2) the curing regime
used, and (3) the use of high alkali Portland cement. According to the Ontario study, the use
of 25 percent or less GGBF slag would result in reduced alkali-silica reactions without
increased salt scaling. The study also recommends a specific curing regime that prevents or
reduces the scaling problem.
Seventh, the State of North Carolina commented that GGBF slag is suspected with
other factors to have contributed to significant problems in a bridge deck. North Carolina
also commented that it permits use of GGBF slag in its specifications, however, although it
provided no other information about the performance of the product in other applications.
From additional comments submitted by the GGBF Slag producers and FHWA, it, is clear
that other states which use GGBF slag cements in bridge decks have not experienced
problems; that no commenter could state conclusively that GGBF slag was a factor in the
bridge deck problem; and that, even if GGBF slag was a factor, a combination of several
factors contributed to the problems with the bridge deck, potentially including the use of a
high level of retarder in the concrete mix.
Finally, the State of Idaho commented that it used slag in the past but does not
currently do so because the slag may contain low levels of radiation.' Potential users of
GGBF slag should note that the slag used in Idaho was from elemental phosphorous
production, not blast furnace slag. GGBF slag does not contain radioactive components.
After reviewing the performance comments, EPA agrees with FHWA that GGBF slag
is suitable for some, but not all, concrete applications and, therefore, it should not be blindly
substituted for Portland cement without regard for its effects on the characteristics of the
concrete mix. EPA' further agrees that education is necessary but notes that FHWA recently
awarded a contract for the development of guides for the use of various recovered materials
in highway construction applications. Blast furnace slag is one of the materials to be
addressed. These guides should increase the information available to agencies
cement and concrete containing GGBF slag.
Because the use of GGBF slag in cement and concrete can be beneficial both to users
of concrete and in reducing the quantities of this material requiring disposal, EPA concludes
that cement and concrete containing GGBF slag should be designated under RCRA section
6002. Under the exceptions in RCRA section 6002, in those instances where the use of
GGBF slag will not meet a procuring agency's reasonable performance requirements, the