Table 4 Factors and levels of central-composite design (CCD).

From: Optimizing fluidity and tensile strength of magnetically driven epoxy-cement repair materials based on response surface

Variables

Real values of coded levels

1

0

− 1

ER content, A1 (%)

9

7

5

Water-cement ratio, A2

0.55

0.5

0.45

Fe3O4 content, A3 (%)

20

15

10

SAC content, A4 (%)

7.5

5

2.5

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