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A water-based fire resistive nano-coating was prepared via adding CaAlCO 3 -layered double hydroxides (CaAlCO 3 -LDHs) as an inorganic filler to intumescent fire retardant coating. The influence of CaAlCO 3 -LDHs on the coatings properties was investigated by thermogravimetry (TG), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), cone calorimeter (CONE) and fire performance test. The results showed that CaAlCO 3 -LDHs could improve the quality of the residual char layer, increase the degree of the cross-linking and the carbon accumulation, and enhance the oxidation resistance of the char layer. The addition of 5 mass% CaAlCO 3 -LDHs to the coating could reduce the fire hazards of the coating itself, lower the rate of flame propagation and thermal degradation, and improve the char structure and fire resistance of the coating, which was attributed to the synergistic effect of CaAlCO 3 -LDHs and the intumescent fire retardant (APP/PER/MEL). [ABSTRACT FROM AUTHOR]

• Addition of MgAlCO 3 -LDHs and CaAlCO 3 -LDHs improved thermal insulation of IFR coating. • Metal ions from LDHs were chelated with carbon materials to form 3D reticular char. • LDHs can delay oxidation and improve degradation performance of char layers. MgAlCO 3 -layered double hydroxides (LDHs) and CaAlCO 3 -LDHs were respectively added as a synergistic agent to intumescent fire retardant (IFR) coatings. The 2.4 wt% of MgAlCO 3 -LDHs and the 6.7 wt% of CaAlCO 3 -LDHs were found to possess the best thermal insulation according to the fire performance tests. Further characterization by a cone calorimeter shows that the MgAlCO 3 -LDHs are superior to decreasing the specific extinction area of IFR coating, and the CaAlCO 3 -LDHs are advantageous in some other properties such as heat release rate, effective heat combustion and total heat release. Moreover, the X-ray diffraction (XRD) results infer that the flame retardant of char layer is primarily dependent on the amorphous structure formed after exposure to fire, the X-ray photoelectron spectroscopy (XPS) measurements of O 1s , C 1s , P 2p and N 1s reveal that the LDHs fillers suppress the oxidation of the IFR coating, and the Fourier transform infrared spectroscopy (FTIR) tests demonstrate that the LDHs protect the bridge frame structures. It is concluded that the LDHs can prevent the degradation and improve the thermal insulation of IFR coatings. [ABSTRACT FROM AUTHOR]