When acid phosphogypsum (APG) is recycled as aggregate of cemented backfill in mines, pretreatment is usually needed to reduce its adverse impact on the backfill. In this study, a new approach of using a neutral salt (CaCO) to pretreat APG has been proposed to enhance the strength development of the cemented PG backfill. The role of CaCO in cemented PG backfill acting as a reactant is explored. In the pretreatment stage, CaCO reacted with the residual acid in PG, and the generated calcium ions could solidify the impurities, such as soluble phosphate and fluoride, with solidification rates reaching 90% and 99%, respectively. This neutral modifier buffered pH values of PG aggregate from 1.8 to about 5.0, and excess dosage of CaCO did not adjust the pH value of aggregate to an excessively high level. Hence, there was no interference with the hydration reaction of the binder (cement). Using PG pretreated with CaCO as aggregate for cemented backfill effectively accelerated the setting process of backfill and increased the unconfined compressive strength (UCS) of the backfill matrix from 0.14 MPa to 2.27 MPa at 28-day age. The present results suggest that CaCO pretreatment is an effective way to improve the accessibility of PG as aggregate, thus significantly increasing the utilization rate of PG and enhancing the backfill performance.

中文翻译：

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用CaCO3预处理磷石膏以改善回填性能


当酸性磷石膏（APG）作为矿山胶结充填骨料回收时，通常需要进行预处理，以减少其对充填体的不利影响。在这项研究中，提出了一种使用中性盐（CaCO）预处理 APG 的新方法，以增强胶结 PG 回填体的强度发展。探讨了 CaCO 在胶结 PG 回填中作为反应物的作用。在预处理阶段，CaCO3与PG中残留的酸反应，生成的钙离子可以固化可溶性磷酸盐和氟化物等杂质，固化率分别达到90%和99%。这种中性改性剂将PG骨料的pH值从1.8缓冲到5.0左右，并且过量的CaCO3剂量并没有将骨料的pH值调节到过高的水平。因此，不会干扰粘合剂（水泥）的水合反应。使用CaCO预处理的PG作为胶结充填骨料，有效加速了充填体的凝结过程，并将充填体基质的无侧限抗压强度（UCS）在28日龄期从0.14 MPa提高到2.27 MPa。目前的研究结果表明，CaCO 预处理是提高 PG 作为骨料的可及性的有效方法，从而显着提高 PG 的利用率并提高充填性能。