High-entropy materials (HEMs) are a novel class of materials characterized by the incorporation of at least five principal elements, resulting in four core effects: high-entropy, severe-lattice-distortion, sluggish-diffusion, and cocktail effects. Inspired by these principles, this study proposes the concept of a high-entropy solid waste-based binder (HESWB), synthesized from blast furnace slag (BFS), fly ash (FA), carbide slag (CS), red mud (RM), and desulfurization gypsum (DG). The roles of individual components in influencing strength development, hydration behavior, and pore structure were systematically analyzed. Compared to ordinary Portland cement (PC), HESWB-based concrete exhibited a 24% and 14% reduction in static elastic modulus for natural coarse aggregate and ceramsites, respectively, a more than 82% reduction in autogenous shrinkage, and almost no chloride penetration after 28 d. These improvements are attributed to the synergistic effects among the diverse components, which refine the pore structure and alter the hydration kinetics. This study not only introduces a sustainable approach for utilizing industrial solid wastes but also demonstrates the potential of HESWBs to enhance concrete durability and performance, offering promising implications for future cementitious systems.

Natural Hydraulic Lime (NHL) has exceptional application in restoring ancient buildings compared to Portland cement and conventional air-hardening lime, but the characteristic of slow early performance development limits its fields of application. This paper studied the physical and mechanical properties, hydration exothermic properties, phase composition and transformation, and microstructure evolution of slag powder/metakaolin composite NHL during the early hardening process. The influence of slag powder/metakaolin on the hardening process and performance development of NHL are systematically evaluated. Results show that slag powder can improve the fluidity of NHL-based mortar; slag powder/metakaolin generates calcium aluminate hydrate (C₃AH₆), calcium carboaluminate hydrate (C₄AĈH₁₁) and calcium silicate hydrate (C—S—H) through pozzolanic reaction to promote the setting and hardening of NHL-based materials and significantly improve their compressive and flexural strength. This study provides reference for promoting the application of pozzolanic material composite NHL in the restoration of ancient buildings.

The Great Wall is one of the greatest construction projects in the history of human civilization, and the traditional lime mortar is an important guarantee standing for centuries without falling. Exploring the phase and composition ratio of ancient mortar used in the Great Wall through modern scientific and technological means and analyzing its performance evolution process, we could effectively understand the characterizations of traditional technology. The use of the past for the present is of great significance in guiding and promoting the conservation and restoration of endangered ancient buildings. Therefore, four representative locations were selected in the Dazhuangke of the Great Wall. The physical properties, phase composition and ratios of the ancient mortar samples were systematically analyzed by X-ray fluorescence spectroscopy, X-ray diffractometry, thermogravimetric-differential thermal analysis, Fourier transform infrared spectroscopy, iodine-starch test, mercury-pressure test and scanning electron microscopy, respectively. The comparison with the modern repair mortar reveals the evolution pattern of the performance of ancient mortar. The results show that the ancient mortar is a pure air-hardened lime mortar. The type of lime is a magnesian lime. No water-hardening components occur in the mortar, and no aggregate components or organic additives appear. The long-term carbonation process can inhibit the crystallinity of calcite crystalline calcium carbonate, refine the granularity of calcium carbonate, and effectively improve the denseness of the mortar hardening body. This could be one of major reasons for the superior performance of ancient mortar.