Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry
Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry
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DOI：
10.1016/j.cemconres.2009.05.016
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发表时间：
2009-09-01
影响因子：
11.4
通讯作者：
Pera, Jean
中科院分区：
文献类型：
--
作者：
Coumes, Celine Cau Dit;Courtois, Simone;Pera, Jean
为了在水泥中固化一种化学成分复杂的低放射性废物，将两种工艺流程--超滤产生的料浆和盐度为600GXL(-1)的蒸发器浓缩物混合在一起，进行了研究。由于废物中含有的硼酸盐和磷酸盐导致水泥的凝结时间很长，因此不可能与波特兰水泥(OPC)直接粘结。根据一种经典的方法，这一困难可以通过对废物进行预处理来解决，以减少不利的水泥-废物相互作用。确定了一个两阶段工艺，包括在60℃下通过向废水中添加钙和氢氧化钡来沉淀磷酸盐和硫酸盐，并用OPC和铝酸钙水泥(CAC)的混合物包裹以将硼酸盐转化为四硼铝酸钙。用30%的废料装载量得到的材料符合规格。然而，前处理步骤使该过程复杂且成本高昂。然后开发了一种新的替代方法：在室温下用OPC和硫铝酸钙水泥(C(S)BARA)的混合物直接包覆废物。抑制凝结作用的原因可能是在水化过程中，巴拉水泥表面的C(S)生成了大量的钙矾石和一水合硫铝酸钙，它们的结构中包含了硼酸盐。因此，废物负荷量可以增加到56%，同时保持实验室规模的可接受性能。(C)2009爱思唯尔有限公司。保留所有权利。
Investigations were carried out in order to solidify in cement a low-level radioactive waste of complex chemistry obtained by mixing two process streams, a slurry produced by ultra-filtration and an evaporator concentrate with a salinity of 600 gxL(-1). Direct cementation with Portland cement (OPC) was not possible due to a very long setting time of cement resulting from borates and phosphates contained in the waste. According to a classical approach, this difficulty could be solved by pre-treating the waste to reduce adverse cement-waste interactions. A two-stage process was defined, including precipitation of phosphates and sulfates at 60 degrees C by adding calcium and barium hydroxide to the waste stream, and encapsulation with a blend of OPC and calcium aluminate cement (CAC) to convert borates into calcium quadriboroaluminate. The material obtained with a 30% waste loading complied with specifications. However, the pre-treatment step made the process complex and costly. A new alternative was then developed: the direct encapsulation of the waste with a blend of OPC and calcium sulfoaluminate cement (C (S) over barA) at room temperature. Setting inhibition was suppressed, which probably resulted from the fact that, when hydrating, C (S) over barA cement formed significant amounts of ettringite and calcium monosulfoaluminate hydrate which incorporated borates into their structure. As a consequence, the waste loading could be increased to 56% while keeping acceptable properties at the laboratory scale. (C) 2009 Elsevier Ltd. All rights reserved.