Cementitious properties and microstructure of an innovative slag eco-binder

Circulating fluidized bed combustion fly ash was used to activate the hydration of ground granulated blast furnace slag to produce non-cement SCA eco-binder without Portland cement (OPC). The engineering properties of SCA paste and mortar with air or water curing were evaluated. The microstructure and hydration products of the SCA binder were investigated by scanning electron microscope, and X-ray diffraction. The hydration products of SCA were ettringite (AFt), calcium silicate hydrate (C–S–H) and calcium aluminate silicate hydrate (C–A–S–H) so that the SCA paste had proper setting times, dense microstructure and high strength. The compressive strengths of SCA pastes and mortars reached up to 70 MPa at 28 days and even higher at longer ages. The early expansion of SCA paste and mortar due to the AFt formation compensated for their drying shrinkage to lead to a very low ultimate shrinkage. The SCA binder is a promising alternative to OPC.