Performance Evaluation of an Eco-Binder Made with Slag and CFBC Fly Ash

Abstract

Performance of the engineering properties of paste manufactured with an eco-binder was evaluated. The eco-binder without cement, SCA, was made with slag (S) and fly ash (CA) that had been created by circulating fluidized bed combustion (CFBC). Experimental results show that the pure slag paste hardly sets and the pure CA paste gives very little strength. But when slag and CA are mixed together, the SCA paste not only has proper setting times but also has sufficient strength. The compressive and tensile strength of SCA paste can reach 80 MPa and 4.6 MPa, respectively, at 28 days and higher at longer ages. In addition, the early expansion of the SCA paste compensates for its later shrinkage so that the ultimate drying shrinkage of SCA paste is lower than that of ordinary portland cement paste. The hydration products of the SCA paste detected by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray (EDX) are ettringite, calcium silicate hydrate (C-S-H), and calcium silicate alumina hydrate (C-S-A-H). All of them are bonded together and generate self-cementitious properties in SCA paste.