The carbonation of recycled aggregate was accelerated by sparging with supercritical carbon dioxide (scCO₂) to reduce the amount of time needed for carbonation, which is necessary for the pH neutralization of recycled aggregate. To accelerate the carbonation process, pressurized scCO₂ was sparged into two different types of recycled aggregates immersed in water for 1 h, followed by standstill for 2 h (in total, a 3 h treatment process). The reduction of the pH of the treated aggregates due to carbonation was investigated using batch extraction experiments. A continuous column extraction experiment for the scCO₂-sparged recycled aggregate was also performed to identify the effect of pH reduction under the condition of non-equilibrium reaction. From XRD, SEM/EDS, and TG/DTA analyses, much of the portlandite in the recycled aggregates was consumed. In its place, calcite was created as a secondary mineral during only 3 h of treatment (1 h scCO₂ sparging and 2 h stationing), indicating satisfactory carbonation of the aggregate. The results of the batch extraction experiments for both of the two recycled aggregate types also showed that the average pH of scCO₂-sparged aggregate decreased from 12.0 to <9.8 (the tolerance limit for recycling). The pH of the eluent from the column packed with the scCO₂-sparged aggregate also remained as <9.8, suggesting that a 1 h scCO₂ sparging process is sufficient to carbonate waste concrete aggregate and to create an alternative construction material resource.

中文翻译：

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使用加压超临界二氧化碳喷射工艺加速回收骨料的碳化

通过用超临界二氧化碳（scCO ₂）鼓泡来加速回收骨料的碳化，以减少碳化所需的时间，这对于中和回收骨料的pH值是必需的。为了加速碳酸化过程，将加压的scCO ₂喷入两种不同类型的循环聚集体中，将其浸入水中1小时，然后停顿2小时（总计3小时处理过程）。使用分批萃取实验研究了由于碳化导致的处理后的骨料的pH降低。scCO _2的连续柱萃取实验还进行了喷洒的回收骨料，以鉴定在非平衡反应条件下pH降低的影响。通过XRD，SEM / EDS和TG / DTA分析，回收了骨料中的许多波特兰石被消耗掉了。取而代之的是，方解石仅在处理3小时（scCO ₂喷射1小时和静置2小时）期间就被作为次要矿物生成，表明聚集体发生了令人满意的碳化。两种回收骨料的批提取实验结果还表明，scCO ₂喷射骨料的平均pH从12.0降至<9.8（回收极限）。装有scCO ₂喷射的聚集体的色谱柱的洗脱液的pH值仍保持在9.8以下，表明scCO 1 h₂喷射过程足以使废混凝土骨料碳酸盐化并创造替代建筑材料资源。