Preparation and fireproof performance of alkali activated cement based fire resistive coatings with different alkali activators for steel structures

This study aims to develop fire resistive coatings based on alkali-activated slag cement (AASC) and comprehensively investigate the effects of various alkali activators on the passive fireproof performance of steel structures. The bulk density, mechanical strength, fireproof performance, cracking resistance, mineral phase assemblage, microstructure, and pore structure of AASC with various activators were systemically carried out. The results reveal that the bulk density, bonding strength, and fireproof performance of AASC fire-resistive coatings follow the specifications of Chinese standards. The AASC fire-resistive coatings demonstrate exceptional fireproof performance, and the maximum temperatures are about 50 % lower than the 538 °C specified by Chinese national standards for steel structure coatings. Among the four activators studied, a composite activator of CaO and Na 2 CO 3 could balance the physical performance needed by a fire resistive coating. With comprehensive consideration of splitting tensile strength, the quantity of C(N)-A-S-H gel, nominal crystalline to gel ratio, and capillary pore volume, AASC coating with a composite activator of CaO and Na 2 CO 3 demonstrates improved cracking resistance and excellent bond strength, via increasing nominal crystalline to gel ratio and the amount of C(N)-A-S-H gel. Results pointed out that the optimized activator is able to outperform alternative commercial cement-based binders for fire resistance, thus representing a promising technology. • The effects of alkali activators on AASC fire resistive coatings were studied. • Bulk density, mechanical strength, fireproof performance, and cracking resistance of AASC coatings were evaluated. • CaO and Na 2 CO 3 composite activator enhanced performance and cracking resistance of AASC coatings.