Optimization Design and Performance Characterization of Low-Carbon Cement-Based Fire-Resistive Coatings for Steel Structures

With the increasing global concern for environmental protection, the demand for low-carbon fire-resistive coatings is also growing. However, the traditional cement-based fire-resistive coatings generally contain a large amount of cement and exhibit shortcomings including high self-weight, low compressive strength, poor toughness, and poor heat resistance, which compromises their ability to delay the temperature rise and prevent structural failure effectively. Based on the Box-Benhken design, this study optimized the reasonable dosage of multiple low-carbon fire-resistive fillers, to improve the utilization ratio of solid waste and realize the favorable fire-resistance and high toughness. Additionally, thermodynamic simulations and microscopic analyses were conducted to understand both the thermal insulation and heat resistance mechanisms. The results showed that the dry density, thermal conductivity, and equilibrium temperature of designed low-carbon cement-based fire-resistive coating is 28.9%, 18.2%, and 8.05% lower than that of commercial fire-resistive coating (type CDGT-1), respectively. In addition, the compressive strength is 103.24% higher than the CDGT-1 coating and the residual compressive strength after 1,000°C is even 10 times higher. The solid-state processes that produced thermally stable anorthite and albite were the cause of the enhanced high-temperature resistance. Furthermore, the inclusion of titanium slag, fly ash cenosphere, and glass bubble increased the proportion of small pores, reduced the average pore size, and consequently raised the tortuosity and resistance of the heat transfer path. In terms of toughness, adding fly ash and polypropylene (PP) fibers facilitated the formation of a network structure and multiple ways for energy dissipation. The toughness index I5 and I10 of the prepared coating approximately meets the standards for elastoplastic materials, while the commercial coating is brittle. The resulting coating provides a low-cost and environmental protection design method for fire-resistive coatings for steel structures.