Brazilian iron ore fines were reduced in a laboratory fluidized bed with different Ca-based additives at 800 degrees C using 0.5 L/min H-2-0.5 L/min N-2. The fluidization results show that pure CaO and Ca(NO3)(2)center dot 4H(2)O only slightly prolong the fluidization time, with defluidization occurring eventually. However, mixtures of Ca(NO3)(2)center dot 4H(2)O and Fe(NO3)(3)center dot 9H(2)O could effectively inhibit defluidization. Reduction results of CaO/Fe2O3 suggest that Ca-based additives mainly inhibit defluidization through the physical spacer effect Microstructure observations indicate that 2CaO center dot Fe2O3 could suppress the growth of sharp-pointed whisker, and the introduction of Fe2O3 allows the Ca species to adhere tightly to the surface of the sticky iron, thereby decreasing its adhesiveness. Moreover, Fe2O3 is demonstrated to be a general binder capable of enhancing the ability of ineffective additives to prevent defluidization. (C) 2017 Elsevier B.V. All rights reserved.