Improving effect of carbonization hardening on the performance of lightweight calcium carbide slag cement based materials under the coupled effect of sulfate attack and dry-wet cycle

To promote the sustainable use of calcium carbide slag (CS) and rice husks while improving CO₂ sequestration, lightweight materials were previously developed by incorporating foam and raw rice husks into a carbonization-hardening calcium carbide slag cement-based matrix, and their basic properties were characterized. However, the performance evolution of carbonate-curing lightweight materials under combined sulfate attack and dry-wet cycles remains unexplored despite their crucial role in predicting service life. Therefore, this study investigates the influence of carbonization hardening on the performance development of lightweight calcium carbide slag cement-based materials under combined erosion of sulfate and dry-wet cycles. Key parameters such as compressive strength, mass variation and relative dynamic elastic modulus are systematically evaluated. Microstructural degradation mechanisms are elucidated by XRD, TG-DTA, MIP and SEM analyses. The results show that carbonization hardening not only increases the initial compressive strength before erosion but also mitigates performance degradation during exposure. Compared to standard-curing samples, carbonate-curing samples exhibit significantly lower compressive strength reduction rates (28.57–40.35% vs. 31.59–47.83%), lower mass loss (1.49–9.22% vs. 2.60–10.89%), and higher retained relative dynamic elastic modulus (75.21–63.56% vs. 73.47–62.33%). then coupled erosion. Microstructural analysis shows that sulfate attack induces expansive gypsum and AFt formation, promoting the development of microcracks and performance degradation. In contrast, carbonization hardening refines the pore structure via CaCO₃ deposition, reducing porosity and improving sample resistance to sulfate dry-wet synergies. These results provide crucial insights into the durability improvement of sustainable lightweight materials in aggressive environments and support their practical engineering applications.