Cementitious materials - Concrete Mix Design, Quality Control and Specification - page 23

GGBS Concrete

5

4

3

% GGBS
70

2

50

30

1

0

0

0 2 4 6

Temperature Rise °C per 100 kg Cement

8 10 12 14

Figure 2.3 Maximum temperature rise for different cement systems and pour thick-
nesses. (After Bamforth, P. B., Proc. Inst. Civ. Engrs. , 2, 69, 777-800, 1980.)

Nineteen-year field exposure trials showed excellent chloride penetration
resistance of concretes containing GGBS. A ternary blend with GGBS and
silica fume was tested and showed further reductions in chloride penetration.

2.4.6 Autogenous shrinkage
Aldred and Lim (2004) showed that low water to cementitious ratio
concrete (w/cm = 0.3) containing replacement with GGBS exhibited rapid
autogenous shrinkage, significantly greater than for the reference Portland
cement concrete (Figure 2.4). The rapid autogenous shrinkage of GGBS
concrete can be largely offset by ponding with water during the early curing
period, which prevents a meniscus from forming.

2.5 SILICA FUME

Silica fume is a powerful tool at the disposal of the concrete technologist.
As with other such tools, the material has to be understood and correctly
used if full benefit is to be obtained and deleterious side effects avoided. In
the authors' opinion, it should be used in proportions of no more than 10%
of the cement content of a mix. Some specifications call for as much as 15%
or more to be used which is very difficult to use, expensive, and special care
is required. Because of its high surface area, silica fume should only be used
together with a superplasticiser.