氧化钙砂的致密性对其碳酸化效果及抗水化性能的影响

Effect of Compactness of CaO Clinker on Its Carbonation and Hydration Resistance

在二氧化碳气氛下对氧化钙砂进行碳酸化处理时,无论是低密度还是高密度钙砂,碳酸化速率都由扩散过程控制·对低密度钙砂,碳酸化反应在表面和内部同时发生,每个CaO晶粒都被生成的碳酸钙包围,并在生成的碳酸钙中有显微裂纹产生;但对高密度钙砂,碳酸化反应只在表面发生,并在钙砂表面形成一层与钙砂基体结合良好的致密碳酸钙保护层·水化试验结果表明:碳酸化处理能够有效地改善钙砂的抗水化性能,但由于经碳酸化处理的低密度钙砂因显微裂纹的原因,在水化过程中容易开裂崩坏,因此碳酸化处理只适合于改善没有明显显气孔率的高密度钙砂的抗水化性能·

CaO clinkers of different compactnesses were carbonated at 700℃ in CO_2 atmosphere with the carbonation rate controlled by diffusion process, regardless of the difference between compactnesses. For the clinker of low compactness, the carbonation reaction occurred simultaneously both on surface and inside pores, and each CaO grain was surrounded by CaCO_3 thus formed, in which microfissures were found. But for the high-compactness samples, carbonation reaction only occurred on surface, with a compact CaCO_3 layer thus formed which was combined well with the substrate material. Hydration test result showed that the clinkers after carbonation can effectively improve the hydration resistance of the CaO clinkers of either low or high compactness. However, the carbonated low-compactness clinker is prone to breakage during hydration process. It is therefore concluded that only the compact CaO clinker with low apparent porosity is suitable to carbonation for improving its hydration resistance.