Engineering and sulfate resistance properties of slag-CFBC fly ash paste and mortar

• Slag (S) was mixed with CFBC fly ash (CA) to produce non-cement SCA binder.
• The hydration products of SCA are ettringite, C–S–H and C–A–S–H.
• SCA paste and mortar have high strength and low drying shinkage.
• SCA mortar has good resistance to sulfate attack.

This study explores a SCA cement produced by mixing slag (S) and circulating fluidized bed combustion (CFBC) fly ash (CA). The hydration products of SCA cement detected by X-ray Diffraction and Thermogravimetric Analysis were ettringite, calcium silicate hydrate and calcium aluminium silicate hydrate, all of which produced dense microstructure. The compressive strengths of SCA paste and mortar specimens reached 75 MPa at 28 days. The expansion of SCA paste and mortar compensated for drying shrinkage, thereby leading to low ultimate shrinkage. The SCA mortars had good resistance to sulfate attack with the strength loss about 15% or less.