Temperature transformation of blended magnesium potassium phosphate cement binders
Temperature transformation of blended magnesium potassium phosphate cement binders
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DOI：
10.1016/j.cemconres.2020.106332
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发表时间：
2021-03
影响因子：
11.4
通讯作者：
L. J. Gardner;S. Walling;C. Corkhill;S. A. Bernal;V. Lejeune;M. Stennett;J. Provis;N. Hyatt
中科院分区：
文献类型：
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作者：
L. J. Gardner;S. Walling;C. Corkhill;S. A. Bernal;V. Lejeune;M. Stennett;J. Provis;N. Hyatt
在这项研究中，一个多技术的方法被用来确定高温性能的磷酸钾镁水泥（MKPC）混合粉煤灰（FA）或地面粒化高炉矿渣（GBFS）相对于核废料固定应用。采用概念性火灾条件（高达1200 °C，30分钟）来模拟临时储存、运输或最终地质处置设施内可能发生的情况。暴露至400 °C后，主晶相鸟粪石-K（MgKPO 4·6 H2O）脱水为结晶不良的MgKPO 4（具有相应的体积和质量变化），MgKPO 4在800 °C下实现重结晶。XRD和SEM/EDX分析表明，在暴露于1000-1200 °C后，MgKPO 4和FA/GBFS组分之间发生反应，形成铝硅酸钾相，白榴石和六方钾霞石（KAlSi 2 O 6和KAlSiO 4），与降低的相对强度相当脱水鸟粪石-K相MgKPO 4的完全消除。这一点得到了固态NMR的进一步支持。（27 Al和29 Si MAS），其中在1200 °C下仅可观察到与原始FA/GBFS组分相关的残余特征。混合MKPC粘合剂的高温相变导致玻璃/陶瓷基质的发展，其中所有现有的孔隙通过烧结渗透并形成玻璃相，同时保持物理完整性（无开裂或剥落）。本研究表明，基于小规模样本，混合MKPC粘合剂应在与地质处置设施运行相关的防火性能参数下（至少高达1200 °C）表现令人满意。
In this study, a multi-technique approach was utilised to determine the high temperature performance of magnesium potassium phosphate cement (MKPC) blended with fly ash (FA) or ground granulated blast furnace slag (GBFS) with respect to nuclear waste immobilisation applications. Conceptual fire conditions were employed (up to 1200 °C, 30 min) to simulate scenarios that could occur during interim storage, transportation or within a final geological disposal facility. After exposure up to 400 °C, the main crystalline phase, struvite-K (MgKPO4·6H2O), was dehydrated to poorly crystalline MgKPO4(with corresponding volumetric and mass changes), with MgKPO4recrystallisation achieved by 800 °C. XRD and SEM/EDX analysis revealed reaction occurred between the MgKPO4and FA/GBFS components after exposure to 1000–1200 °C, with the formation of potassium aluminosilicate phases, leucite and kalsilite (KAlSi2O6and KAlSiO4), commensurate with a reduced relative intensity (or complete elimination) of the dehydrated struvite-K phase, MgKPO4.This was further supported by solid-state NMR (27Al and29Si MAS), where only residual features associated with the raw FA/GBFS components were observable at 1200 °C. The high temperature phase transformation of blended MKPC binders resulted in the development of a glass/ceramic matrix with all existing porosity infilledviasintering and the formation of a vitreous phase, whilst the physical integrity was retained (no cracking or spalling). This study demonstrates that, based on small-scaled specimens, blended MKPC binders should perform satisfactorily under fire performance parameters relevant to the operation of a geological disposal facility, up to at least 1200 °C.