4.4.2. Prediction of Compressive Strength of Concrete with GGBFS

The maturity model applied in this study is the equivalent age model, as shown in Equation (5), and the equivalent age was derived using calculated *Ea*. The compressive strength prediction, according to the equivalent age by GGBFS replacement ratio, is shown in Figure 9. From this figure, it is found that the compressive strength at an early age is delayed as GGBFS replacement ratio increased. The compressive strength development prediction curve approximately overestimates the compressive strength, but similarly simulates the delayed expression of initial compressive strength, due to the increase of GGBFS replacement ratio. Figure 10 compares the predicted compressive strength with the measured compressive strength. The compressive strength is predicted similarly in all compressive strength regions. Thus, very high correlation (R<sup>2</sup> = 0.91) is obtained. This proves that the compressive strength of concrete can be predicted in all strength at various curing temperatures and GGBFS replacement ratio.

**Figure 9.** Prediction of compressive strength in concrete using GGBFS based on equivalent age.

**Figure 10.** Comparison between predicted compressive strength and Measurement compressive strength.
