Abstract: The hydrated products of slag and fly ash cementitious materials with difference specific area and water-binder ratio were studied by means of XRD and SEM.Its mechanical properties, microstructure and morphological characteristics were discussed.The results showed that the strength of the samples tended to increase with specific area increasing; And the strength of the samples tended to increase and then decrease with the water-binder ratio increasing.When the specific area of slag was 500 m²/kg, and the water-binder ratio was 0.44, the slag-fly ash cementitious material can reach better compressive strength and flexural strength.

Key words: Cementitious material, Slag, Fly ash, Water-binder ratio, Specific area