**2. Materials and Methods**

The materials used in this research were:


The composition of studied materials is presented in Table 1.

**Figure 1.** XRD patterns of flue gas desulfurization (FGD) gypsum.


**Table 1.** Composition of studied materials.

*\** calculated with reference to I+G mixture; B and HEMC were added to I+G mixture.

The compositions were labelled as follow: I—gypsum binder; G—FGD gypsum (1 wt.%, 3 wt.%, 5 wt.% or 10 wt.%); B—sodium bicarbonate (0.5 wt.%, 1 wt.% or 2 wt.%); C—HEMC (0.3 wt.%).

For all compositions, the water to binder ratio was 0.6.

The following analysis were performed on binder pastes:

