Preparation and comprehensive performance optimization of green insulation building materials based on blast furnace slag

In this study, blast furnace slag (BFS) was employed to prepare insulation materials via alkali activation and foaming. The alkali activation mechanism and the effect of processing conditions on material properties were investigated using techniques such as FT-IR, XRD , SEM-EDS, TG-DSC, BET, and XPS. The results showed that: (1) The alkali activation process can be divided into four stages: dissolution, depolymerization , polymerization, and condensation. (2) The material exhibits a type IV adsorption-desorption isotherm, with mesopores uniformly distributed in the range of 50–500 μm; (3) Compared to unmodified and solely thermally treated samples, after modification with PP fibers (12 mm in length at 1.2 wt%) and calcination at 400 °C for 2 h, the compressive strength of the PP fiber-modified material reached 0.89 MPa-a 4.93-fold increase-while that of the biomass fiber-modified material reached 0.85 MPa, representing a 4.67-fold improvement; (4) Following waterproof treatment, the material exhibited an average contact angle of 125.15°, average volumetric water absorption of 8.2 %, and thermal conductivity of 0.042 W/(m·K), which is 27.59 % lower than that of the untreated material. The material meets the performance requirements in terms of thermal conductivity , compressive strength , density, high-temperature resistance, corrosion resistance , and freeze-thaw durability, demonstrating excellent environmental characteristics and offering a novel approach to sustainable development in the construction and steel industries as well as achieving the "Carbon Peaking and Carbon Neutrality " targets. • Blast furnace slag, a bulk solid waste, was used as raw material to prepare building thermal insulation materials. • The mechanisms of alkaline activation reaction and pore formation during the material preparation process were studied. • The strength, thermal stability, corrosion resistance , and freeze-thaw resistance of the prepared materials were optimized. • The properties of the prepared building thermal insulation materials meet the industry standards.