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(a)
(b)
(c)
(d)
FIGURE 6.8
Slumps of concretes with the same water-cement ratio: (a) no
water reducer, (b) conventional water reducer, (c) mid-range water reducer, (d) high-
range water reducer (Superplasticizer).
the cement surfaces. As a result, the clusters of cement grains are broken
apart. Mutual repulsion of like charges pushes the cement grains apart,
achieving a better distribution of particles [see Figure 6.9(c)], more uniform
hydration, and a less-viscous paste.
Water reducing admixtures can be used indirectly to gain strength.
Since the water-reducing admixture increases workability, we can take ad-
vantage of this phenomenon to decrease the mixing water, which in turn
reduces the water-cementitious materials ratio and increases strength.
Hewlett (1978) demonstrated that water reducers can actually be used to
accomplish three different objectives, as shown in Table 6.8.
1. Adding a water reducer without altering the other quantities in the mix
increases the slump, which is a measure of concrete consistency and an
indicator of workability, as will be discussed in Chapter 7.
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