Civil Engineering Reference
In-Depth Information
10
High-volume ground granulated blast
furnace slag (GGBFS) concrete
İ. B. Topçu, Eskişehir osmangazi university, Turkey
DOI
: 10.1533/9780857098993.2.218
Abstract
:
Ground granulated blast furnace slag (GGBFS) is a by-product
of the iron-making process and because of its high calcium silicate content
it has excellent cementious content and has been used in the construction
industry for years as a replacement for ordinary portland cement (opC).
GGBFS is also routinely used to limit the temperature rise in large
concrete pours and is therefore a desirable material to use in mass concrete
placements where control of temperatures is an issue. The more gradual
hydration of GGBS cement generates both lower peak and less total overall
heat than opC. GGBFS was approved for use at a 70% replacement even
though it is only allowed to use a maximum 25% instead of cement. It has a
higher proportion of the strength-enhancing calcium silicate hydrates (CSH)
than concrete made with only opC, and a reduced content of free lime,
which does not contribute to concrete strength.
Key words
: ground granulated blast furnace slag, high replacement level,
workability, strength, durability.
10.1 Introduction
Ground granulated blast furnace slag (GGBFS) has been used in the
construction industry for years as a replacement for ordinary portland
cement (opC). Ground granulated blast furnace slag also has a lower heat
of hydration and, hence, generates less heat during concrete production and
curing. GGBFS is a desirable material to use in mass concrete placements
where control of temperatures is an issue. GGBFS can be used instead of
cement with the ratios from 10% to 90%. However, because of its low
heat generating characteristics, GGBFS was approved for use at a 70%
replacement even though it is only allowed to use maximum 25% instead
of cement (Richardson, 2006).
The general GGBFS literature indicates that the replacement of opC by
GGBFS typically results in lower early strengths (7 to 28 days), greater
long-term strengths, lower chloride ion permeability, less creep, greater
sulphate attack resistance, greater alkali silica reactivity (ASR) durability,
enhanced workability, less bleeding, lower heat of hydration, and increased
steel corrosion resistance. Results for drying shrinkage and freeze-thaw
durability are somewhat mixed, although in general, the use of slag appears
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