Influence of mineral admixtures on carbonation curing of cement paste.

• Carbonation curing compensates strength decreasing effect of mineral admixture. • Chloride ion permeability resistance was improved by carbonation curing. • Fly ash exhibits the best promoting effect on carbonation curing and GGBS ranks second. • The formation of CaCO 3 mainly fills the pores with diameters of 0.1 ∼ 1 μm. This paper aims to investigate the influences of limestone powder, fly ash and ground granulated blast-furnace slag (GGBS) on carbonation curing of cement pastes. These three mineral admixtures were incorporated at percentage of 20% by weight to replace cement and compressive strength and chloride ion permeability test were performed to evaluate the carbonation curing effects. On the other hand, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry-differential thermal analysis (TG-DTA), mercury intrusion porosimeter (MIP) and scanning electron microscope (SEM) measurements were performed on typical samples. Experimental results show that the addition of mineral admixture decreased the compressive strength of uncarbonated specimens but strengthened the improvement effect of carbonation curing on compressive strength. This better improvement effect can partly compensate the decreasing strength induced by the incorporation of mineral admixtures. Among those mineral admixtures, fly ash exhibited the best improvement effect and GGBS ranked second. The chloride ion permeability of cement mortars were decreased by the addition of mineral admixtures but improved by the carbonation curing. The formation of CaCO 3 upon carbonation curing refined the pore structure and presented a higher effectiveness for filling pores with diameters of 0.1 ∼ 1 μm. Therefore, carbonation curing provides a good method for both efficiently recycling industrial wastes as mineral admixtures and capturing more greenhouse gas. [ABSTRACT FROM AUTHOR]