Effect of phosphate-to-magnesium ratio on the performance of magnesium potassium phosphate cement-based steel fireproof coatings

The existing fireproof coating on thick steel structures has many drawbacks, including its lack of environmental protection, susceptibility to detachment, prolonged drying duration, and intricate building procedures. In this study, magnesium potassium phosphate cement (MKPC) was selected for the development of inorganic fireproofing coatings, considering that it has better adhesion, fast hardening speed, and heat resistance compared to other cement-based materials. P/M (the mass ratio of dipotassium hydrogen phosphate to magnesium oxide) is the most important factor affecting the performance of MKPC, which indicates the ratio of the acid and base components of the system. When P/M changed, so did the content of hydration products (MKP). The experimental results demonstrate a direct correlation between the quantity of MKP and the performance of the coating. Consequently, the bonding and fire resistance mechanisms of MKPC coatings were investigated by studying the effect patterns of different P/M on the properties (bond strength, fire resistance limit, dry density, compressive strength) of MKPC fireproofing coatings in combination with microscopic tests such as SEM, TG-DSC, and MIP.