Carbonation-Cured Cementitious Materials Incorporating Waste Rubber/Slag with Balanced Mechanical Strength and Microwave Absorption Performance

Electromagnetic wave absorption ability and mechanical strength are critical performance metrics for cement-based microwave-absorbing materials. Enhancing electromagnetic wave absorption efficiency typically involves the incorporation of functional phases and optimization of pore structures. However, these modifications often introduce challenges, such as interfacial incompatibility between the functional phase and cement matrix, and reduced material density, which can compromise mechanical integrity. This study presents a structurally engineered, high-performance cement-based microwave-absorbing material fabricated from solid waste materials. By leveraging the poor interfacial compatibility between rubber powder and cement paste, the material achieves increased porosity, thereby improving impedance matching. Additionally, the presence of abundant dielectric and magnetic components in slag significantly enhances electromagnetic wave dissipation. Through the synergistic tuning of impedance matching and dissipation capacity, the cement-based microwave-absorbing material demonstrates a substantial improvement in electromagnetic wave absorption, with the absolute value of its reflection loss increasing by 2.8 times after CO2 curing. Furthermore, the application of CO2 curing technology facilitates the transformation of alkaline compounds such as Ca(OH)2 into CaCO3, resulting in notable gains in mechanical performance—compressive strength and flexural strength are elevated by 38% and 23%, respectively. This work not only achieves a balanced optimization of electromagnetic wave absorption and mechanical robustness in cement-based materials but also offers a sustainable pathway for the high-value utilization of industrial solid waste.