Civil Engineering Reference
In-Depth Information
the amount of the cement, the rate of the slag, the fineness of the binding
components and their chemical composition (Bilim, 2006). The hydration
speed of the slag and the temperature change is lower than those of the opC.
Therefore, because the partial replacement of the slag with opC creates
cement with lower hydration speed, the increase in the temperature of the
concrete produced by such cement remains lower (Soroka, 1993). Alshamsi
(1997) examined the effects of GGBFS and micro-silica on the hydration
temperature of the concrete. In the conclusion of this study, he declared
that the amount of the cement is significantly effective on the increase of
hydration temperature and GGBFS reduces the temperature increase in
cement paste more than micro-silica does. Additionally, it is reported that
those materials substituted by cement certainly affect the time for reaching
the peak temperature, and while GGBFS delays the time for reaching peak
temperature, micro-silica accelerates it. Slag concrete both decreases the
maximum temperature of the concrete and prolongs the time to reach this
maximum temperature by reducing the hydration heat (Bilim, 2006).
Bleeding
Wainwright and Ait-Aider (1995) pointed out that the bleeding of fresh
concrete is controlled by the fine materials in the mixture with respect to the
amount and reactivity of the cement. While the replacement of GGBFS with
opC brings about a decrease in the speed of hydration, it causes an increase
both in amount and speed of bleeding. The main reason for this increase is
the delay in the hydration mechanism caused by the slag poured to cement
paste; the decrease in the development speed of hydration products is a
result of this. olorunsogo (1998) examined the bleeding characteristics of
the mortar produced by cement with slag and the distribution of the granule
size of GGBFS. According to him, independently from the distribution of
granule size and the w/b rate, for the mixture of both w/b rates of 0.35 and
0.45, the higher the slag rate, the higher the rate and capacity of bleeding.
Whatever the rate of slag replacement and distribution of granule size were,
for all mixtures, the increase in the w/b rate from 0.35 to 0.45 caused an
increase at a percentage respectively of 86%, 83% and 71% in the bleeding,
rate of mortar with 0%, 30% and 70% slag. This increase in bleeding, together
with the increased rate of w/b, being a result of the larger average distance
between the granules, is caused by weak cohesive attractive forces which
occur because of the granule contact (Bilim, 2006).
10.3.3 Hardened concrete properties
unit weight, compressive strength and strength development, tensile strength,
splitting-tensile strength, modulus of elasticity, creep, shrinkage, permeability
