Table 5.
Design and results of Response Rurface Analisis.
| Test number | Factor coding | Factor 1 | Factor 2 | Test result | |||
|---|---|---|---|---|---|---|---|
| X1 | X2 | Sand-binder ratio | Mass concentration (%) | 3 days compressive strength (MPa) | 7 days compressive strength (MPa) | 8 days compressive strength (MPa) | |
| 1 | 1 | 1 | 8 | 74 | 0.785 | 0.987 | 1.520 |
| 2 | 0 | − 1 | 6 | 70 | 0.784 | 1.336 | 1.970 |
| 3 | 0 | 0 | 6 | 72 | 0.884 | 1.701 | 2.110 |
| 4 | 0 | 1 | 6 | 74 | 1.306 | 2.297 | 2.812 |
| 5 | − 1 | 0 | 4 | 72 | 2.401 | 3.481 | 4.317 |
| 6 | 1 | − 1 | 8 | 70 | 0.492 | 0.625 | 0.765 |
| 7 | − 1 | − 1 | 4 | 70 | 1.709 | 2.881 | 3.467 |
| 8 | 1 | 0 | 8 | 72 | 0.555 | 0.891 | 0.938 |
| 9 | − 1 | 1 | 4 | 74 | 3.511 | 4.668 | 5.410 |