Abstract Refractory producers face many challenges in terms of producing MgO-containing castables due to the high likelihood of magnesia to hydrate in contact with water, resulting in Mg(OH)2 generation. The expansive feature of this transformation affects the performance of such refractories, as (i) if this hydrated phase is not accommodated in the formed microstructure, ceramic linings with cracks and low green mechanical strength will be obtained; and (ii) if crack-free pieces are prepared, they should present low porosity and reduced permeability, which require special attention when heating these materials. In both cases, spalling/explosion may be favored during the drying step of MgO-containing compositions. Hence, this work investigated the ability of various additives in the optimization of the drying behavior of Al2O3–MgO castables. Vibratable compositions were tested after incorporating polymeric fibers (PF), an organic salt (OAS), SiO2-based additive (SM) or permeability enhancing active compound (MP) into the dry-mixtures. Various experimental measurements were performed to infer the role of the drying agents to prevent the samples' explosion and whether they would also influence other properties of the castables. As observed, OAS and MP helped to inhibit the MgO-bonded samples' explosion even under severe heating conditions (2–20 °C/min) and increased their green mechanical strength and slag infiltration resistance when compared to the additive-free composition. On the other hand, the addition of polymeric fibers (PF) or silica-based compound (SM) to the formulations was not able to prevent the castables' explosion when using a high heating rate and other side effects (samples’ cracking during drying at 110 °C, high linear expansion and increased slag penetration during corrosion tests) could also be observed when testing these materials. Thus, the selection of suitable drying agents is a key issue, as they may allow the development of MgO-bonded castables with enhanced properties and lower spalling risk during their first thermal treatment.

中文翻译：

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高铝氧化镁结合耐火浇注料的快速干燥

摘要 耐火材料生产商在生产含 MgO 的浇注料方面面临许多挑战，因为氧化镁在与水接触时很可能发生水化，从而产生 Mg(OH)2。这种转变的膨胀特性会影响这种耐火材料的性能，因为（i）如果这种水合相没有容纳在形成的微观结构中，将获得具有裂纹和低生坯机械强度的陶瓷衬里；(ii) 如果制备无裂纹件，它们应具有低孔隙率和低渗透性，这在加热这些材料时需要特别注意。在这两种情况下，在含MgO组合物的干燥步骤期间可能有利于剥落/爆炸。因此，这项工作研究了各种添加剂在优化 Al2O3-MgO 浇注料干燥行为方面的能力。在将聚合物纤维 (PF)、有机盐 (OAS)、SiO2 基添加剂 (SM) 或渗透性增强活性化合物 (MP) 加入干混合物后，对可振动组合物进行了测试。进行了各种实验测量以推断干燥剂在防止样品爆炸方面的作用以及它们是否也会影响浇注料的其他性能。正如所观察到的，与不含添加剂的组合物相比，OAS 和 MP 有助于抑制 MgO 键合样品的爆炸，即使在严酷的加热条件下（2-20 °C/min）也能提高其生坯机械强度和抗渣渗透性。另一方面，在配方中添加聚合物纤维 (PF) 或二氧化硅基化合物 (SM) 并不能防止浇注料的 在测试这些材料时，还可以观察到使用高加热速率时的爆炸和其他副作用（样品在 110 °C 下干燥时开裂、高线性膨胀和腐蚀测试期间熔渣渗透增加）。因此，选择合适的干燥剂是一个关键问题，因为它们可以开发出在首次热处理期间具有增强性能和较低剥落风险的 MgO 粘结浇注料。