Effects of Calcium Carbide Slag Incorporation on the Multiscale Performance of Sulfoaluminate Cement Mortars

TL;DR

Adding calcium carbide slag to sulfoaluminate cement improves strength and durability by altering the material's microstructure and reducing ion permeability.

Contribution

The study identifies 9% calcium carbide slag as the optimal dosage for enhancing SAC mortar performance through microstructural and electrochemical improvements.

Findings

9% CCS increased compressive strength by 6.53% and reduced drying shrinkage by 22.47% at 28 days.

CCS reduced chloride ion permeability, with electrical flux and diffusion coefficient decreasing by 39.98% and 28.89%, respectively.

CCS promotes denser hydration products and limits moisture migration, improving the internal pore structure.

Abstract

This study investigated the effects of calcium carbide slag (CCS) (0–12 wt%) incorporation on the workability, electrochemical properties, durability, and microstructure evolution of sulfoaluminate cement (SAC) mortar. Results showed that increasing CCS content reduced mortar fluidity and shortened setting time, indicating that CCS accelerates early hydration. A 9% CCS content was determined to be the optimal dosage; at 28 days, compared to the control group, this dosage group exhibited a 6.53% increase in compressive strength, a 22.47% decrease in drying shrinkage, and a 0.279% decrease in mass loss. These performance improvements stemmed from CCS’s ability to inhibit pore connectivity and limit moisture migration. Electrochemical analysis further revealed that the 9% CCS dosage group had the highest charge transfer resistance and resistivity (30.00% higher than the control group), reflecting a denser matrix and greater ion transport resistance. Consequently, chloride ion permeability was significantly reduced, with electrical flux and diffusion coefficient decreasing by 39.98% and 28.89%, respectively. Microstructural observations confirmed that CCS promotes the formation and densification of hydration products, effectively improving the internal pore structure. While 9% CCS can serve as an effective functional supplementary material, its long-term durability and sustainability still face practical application challenges. Future research should focus on establishing predictive models for chloride ion permeation lifetime and conducting quantitative sustainability assessments of CCS-SAC composites, particularly evaluating material cost, energy consumption, and carbon dioxide emissions.

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