Development and characterization of ternary blended cement incorporating slag and thermally activated waste eggshell: Hydration, microstructure, macro properties, and carbonation durability

초록

To reduce limestone resource consumption and recycle biomass waste simultaneously, this study utilized waste eggshell powder as a limestone substitute and systematically explored the regulatory mechanism of its thermal activation modification on the hydration, microstructure, mechanical properties, and durability of a ternary system containing slag and cement. The eggshell powder was thermally activated to varying degrees by adjusting the calcination treatment time (10/20/30 min). A cementitious system incorporating eggshell powder (ESP), thermally activated eggshell powder (CESP), and limestone was designed. Microstructural evolution was analyzed via characterization techniques such as isothermal calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, mercury intrusion porosimetry, and thermogravimetric analysis. Macroscopic properties were evaluated through compressive strength, ultrasonic pulse velocity, surface resistivity, and rapid carbonation experiments. The CO2 emissions of the production process were calculated, and the effect of the thermal activation time on sustainability was discussed. This study revealed that moderate calcination effectively removes organic matter from eggshell powder, seals its pores, and promotes calcium oxide formation. The experimental results revealed that the 28-day compressive strength of the mixture incorporating the CESP reached 47.42 MPa, representing a 32.3 % increase compared with that of the sample containing uncalcinated ESP, whereas the carbonation degree was reduced by up to 33.4 %. This study provides a novel approach for the resource utilization of eggshell waste and establishes a theoretical foundation and a technical pathway for developing high-performance biomass waste cementitious materials.

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