Abstract: The addition of suitable amount of coal gangue to cement mortar may increase cement mortar strength. When the content of coal gangue is 9%, the compressive strengths at 3 and 28 d increased 1.0 MPa and 2.0 MPa, respectively. The analysis by XRD, TGA-DTA and SEM showed that the addition of coal gangue prompted the hydration reaction at early stage of 7 days. The hydration products are AFt, C-S-H, AFm and Ca(OH)_2. These hydration products and crystal structures are different. After modification, hydration products increased and the hydration speed was quickened. As a result, the cement mortar strength increased.

Key words: coal gangue;cement mortar;performance analysis;microstructure