A preliminary study on waste marble powder-based alkali-activated binders

Marble, as a widely used building decoration material, produces a significant amount of waste marble powder (WMP) during processing. To investigate the potential of WMP as a precursor in the preparation of alkaliactivated binders, this paper uses WMP as the only precursor and conducts a series of macroscopic mechanical and microscopic characterization tests. The variables included the alkali activator modulus (Ms), Na2O dosage, and curing conditions. The results showed that increasing the Na2O dosage shortened the setting time of the binders, reduced the fluidity, and improved the strength. With the increase in the modulus of the alkali activator, the binder setting time was prolonged, the fluidity first increased and then decreased, and the strength decreased. Increasing the precuring temperature and prolonging the high-temperature curing time was beneficial to developing early strength. Sealed curing was more favorable for stable strength development than standard curing. Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) characterization tests revealed that the dissolution of WMP occurred in the alkali activator, and the hydration products contained carbonate, C-S-H, N-CS-H, and other substances. The results of the gray correlation analysis showed that the Na2O dosage had a greater influence on the binder fluidity than the alkali activator modulus, while the setting time was the opposite. The effects of the four studied factors on the long-term flexural and compressive strengths of the specimens were in the consistent order of Na2O dosage > alkali activator modulus > precuring temperature > high-temperature curing time.

Automated summary

This study investigates the potential of waste marble powder (WMP) as a precursor in the preparation of alkali-activated binders through various mechanical and microscopic characterization tests. The results show that increasing the Na2O dosage shortens setting time, decreases fluidity, and improves strength. Increasing the alkali activator modulus prolongs setting time, increases fluidity initially and then decreases, and reduces strength. Increasing the precuring temperature and prolonging high-temperature curing time enhance early strength development. Sealed curing ensures more stable strength development than standard curing. Characterization tests reveal that WMP dissolves in the alkali activator and forms hydration products containing carbonate, C-S-H, N-CS-H, and other substances. Gray correlation analysis shows that Na2O dosage has a greater impact on fluidity, while the alkali activator modulus has a greater impact on setting time. The effects of the four factors on long-term flexural and compressive strengths follow the order of Na2O dosage > alkali activator modulus > precuring temperature > high-temperature curing time.