Influence of mono-carbonate hydrates on mechanical properties of CAC bonded castables fired at 800?C

The increase of intermediate-temperature strength of CAC bonded castables is significant for the spalling resistance. In this work, micro-sized calcium carbonate (MCC) powders were introduced into calcium aluminate cement (CAC)-bonded castables to form a novel calcium aluminate mono-carbonate hydrate C4ACH11 (3CaO.Al2O3.CaCO3.11H2O) rather than common hydrates C3AH6 (3CaO.Al2O3.6H2O) and C2AHx (2CaO.Al2O3.xH2O). The phase and microstructure evolution of C4ACH11 and the effect of C4ACH11 formation on the mechanical properties of corundum-based castables after heating at 800 degrees C has been studied. The phase composition and microstructure evolution of castables were characterized via utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG) as well as differential scanning calorim-etry (DSC). The results indicated that the introducing of MCC could dramatically improve the intermediate-temperature strength of the low and ultra-low CAC bonded castables owing to the preserved cross-linked lamellar microstructure after the dehydration and decomposition of the lamellar C4ACH11 precursors fired at 800 degrees C.