PORTLAND CEMENT CONCRETE - Materials for Civil and Construction Engineers - page 240

strength. Historical records are used to plot a strength-versus-water-cemen-
titious materials ratio curve, such as that seen in Figure 7.2. If historical data
are not available, three trial batches are made at different water-cementi-
tious materials ratios to establish a curve similar to Figure 7.2. Table 7.1 can
be used for estimating the water-cementitious materials ratios for the trial
mixes when no other data are available. The required average compressive
strength is used with the strength versus water-cementitious materials rela-
tionship to determine the water-cementitious materials ratio required for
the strength requirements of the project.

50

7

6

40

5

Non-air-entrained

30

4

3

Air-entrained

20

2

FIGURE 7.2 Example
trial mixture or field data
strength curves.

10

0.3 0.4 0.5 0.6 0.7 0.8

Water-cementitious materials ratio

T ABLE 7.1 Typical Relationship between Water-Cementitious
Materials Ratio and Compressive Strength of Concrete*

Water-Cementitious Materials Ratio by

Weight

Compressive Strength Non-Air-Entrained Air-Entrained

at 28 days, MPa (psi)** Concrete Concrete

48 (7000) 0.33 —

41 (6000) 0.41 0.32

35 (5000) 0.48 0.40

28 (4000) 0.57 0.48

21 (3000) 0.68 0.59

14 (2000) 0.82 0.74

*American Concrete Institute (ACI 211.1 and ACI 211.3)
**Strength is based on cylinders moist-cured 28 days in accordance with
ASTM C31 (AASHTO T23). Relationship assumes nominal maximum size
of aggregate about 19 to 25 mm (

3
4

to 1 in.).