Garcia-Lodeiro Ines, Chhaiba Salma, Husillos-Rodriguez Nuria, Palomo Ángel, Kinoshita Hajime
Eduardo Torroja Institute for Construction Science (IETcc-CSIC), 28033 Madrid, Spain.
Department of Material Science and Engineering, University of Sheffield, Sheffield S10 2TN, UK.
Materials (Basel). 2025 Mar 7;18(6):1198. doi: 10.3390/ma18061198.
Magnesium phosphate cements (MPCs) are a class of inorganic cements that have gained significant attention in recent years due to their exceptional properties and diverse applications in the construction and engineering sectors, particularly in the confinement of radioactive waste. These cements set and harden through an acid-base reaction between a magnesium source (usually dead-burnt magnesia) and a phosphate source (e.g., KHPO). The dead-burnt MgO (DBM) used is typically obtained by calcining pure MgCO at temperatures between 1600 and 2000 °C. The present work explores the possibility of using low-grade magnesia (≈58% MgO), a secondary waste product generated during the calcination of magnesite for sintered MgO production. Low-grade magnesia is a by-product from the calcination process of natural magnesite. In this manner, the cost of the products could be substantially diminished, and the cementitious system obtained would be a competitive alternative while enhancing sustainability criteria and recyclability. This paper also evaluates the effect of the M/P ratio and curing conditions (especially relative humidity) on the mechanical, microstructural, and mineralogical development of these cements over a period of up to one year. Results indicate that low-grade MgO is suitable for the preparation of magnesium potassium phosphate cements (MKPCs). The presence of minor phases in the low-grade MgO does not affect the precipitation of K-struvite (KMgPO·6HO). Moreover, the development of these cements is highly dependent on both the M/P molar ratio and the RH. Systems prepared with an M/P ratio of 3 demonstrated good compressive strengths, low total porosity, and stable mineralogy, which are essential parameters for any cementitious matrix that aims to be considered as a potential confiner of radioactive waste.
磷酸镁水泥（MPC）是一类无机水泥，近年来因其优异的性能以及在建筑和工程领域的多样应用，尤其是在放射性废物封存方面的应用，而备受关注。这些水泥通过镁源（通常是死烧氧化镁）和磷酸盐源（如KHPO）之间的酸碱反应进行凝结和硬化。所使用的死烧氧化镁（DBM）通常是通过在1600至2000°C的温度下煅烧纯MgCO获得的。本研究探讨了使用低品位氧化镁（≈58% MgO）的可能性，低品位氧化镁是菱镁矿煅烧生产烧结氧化镁过程中产生的二次废品。低品位氧化镁是天然菱镁矿煅烧过程的副产品。通过这种方式，产品成本可以大幅降低，所获得的胶凝体系将成为一种具有竞争力的替代品，同时提高可持续性标准和可回收性。本文还评估了M/P比和养护条件（特别是相对湿度）对这些水泥在长达一年时间内的力学、微观结构和矿物学发展的影响。结果表明，低品位MgO适用于制备磷酸镁钾水泥（MKPC）。低品位MgO中次要相的存在并不影响鸟粪石（KMgPO·6HO）的沉淀。此外，这些水泥的发展高度依赖于M/P摩尔比和相对湿度。M/P比为3制备的体系表现出良好的抗压强度、低总孔隙率和稳定的矿物学，这些对于任何旨在被视为放射性废物潜在封存材料的胶凝基体来说都是至关重要的参数。
