Mineralogical and geochemical composition of a cementitious grout and its evolution during interaction with water

IF 6.6 2区 材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY
Sylvain Grangeon, Mathieu Debure, Valerie Montouillout, Erik Elkaim, Catherine Lerouge, Nicolas Maubec, Nicolas Michau, Xavier Bourbon, Christelle Martin, Benoit Cochepin, Nicolas Marty
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Abstract

In the present study, the chemical composition, mineralogy, and mechanisms of alteration of a cementitious grout based on a CEM III/C with addition of smectite, hydrotalcite, and silica fume, are studied using a combination of chemical and physical methods. This material was designed in the context of geological repository of radioactive wastes, with a twofold aim: first, to fill the technical voids left by drilling operations at the interface between the geological formation and the disposal galleries. Second, to neutralize a potential acidic transient due to pyrite oxidation, and to create an environment that favors low corrosion rates of carbon steels. The grout is mainly composed of calcium silicate hydrates having a Ca/Si ratio of ~0.8, incorporating Al in the bridging site of the Si chains (C-A-S-H), and accounting for 29–36 wt.% of the sample. It also contains silica fume (38–48 wt.%), smectite with interlayer Na (11–17 wt.%), hydrotalcite with interlayer CO32− (3–4 wt.%), and lower amounts of portlandite, calcite, and possibly gibbsite and gypsum. Upon alteration by water in a flow-through reactor, the main modifications affecting the sample are calcite and gypsum dissolution, hence releasing aqueous Ca2+ that is adsorbed in smectite interlayer by replacing Na+, and stoichiometric C-A-S-H dissolution. The evolution of solution chemistry and of the solid phase composition are reproduced successfully using a thermokinetic model.

Abstract Image

水泥基灌浆料的矿物学和地球化学组成及其与水作用过程中的演变
本研究采用化学和物理相结合的方法,研究了基于 CEM III/C 的水泥基灌浆料的化学成分、矿物学和变化机理,并添加了埃克石、水滑石和硅灰。这种材料是在放射性废物地质处置库的背景下设计的,有两个目的:第一,填补地质构造和处置廊道之间的界面上钻孔作业留下的技术空隙。其次,中和黄铁矿氧化可能产生的瞬时酸性,并创造有利于降低碳钢腐蚀率的环境。灌浆料主要由硅酸钙水合物组成,Ca/Si 比约为 0.8,在硅链(C-A-S-H)的桥接部位含有 Al,占样品的 29-36%。它还含有硅灰(38-48 重量%)、含层间 Na 的闪长岩(11-17 重量%)、含层间 CO32- 的水滑石(3-4 重量%),以及较少量的波长岩、方解石,可能还有辉绿岩和石膏。水在流动反应器中改变样品时,影响样品的主要变化是方解石和石膏的溶解,从而释放出水溶液中的 Ca2+,Ca2+通过取代 Na+吸附在辉绿岩夹层中,以及化学计量的 C-A-S-H 溶解。利用热动力学模型成功地再现了溶液化学和固相组成的演变过程。
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来源期刊
npj Materials Degradation
npj Materials Degradation MATERIALS SCIENCE, MULTIDISCIPLINARY-
CiteScore
7.80
自引率
7.80%
发文量
86
审稿时长
6 weeks
期刊介绍: npj Materials Degradation considers basic and applied research that explores all aspects of the degradation of metallic and non-metallic materials. The journal broadly defines ‘materials degradation’ as a reduction in the ability of a material to perform its task in-service as a result of environmental exposure. The journal covers a broad range of topics including but not limited to: -Degradation of metals, glasses, minerals, polymers, ceramics, cements and composites in natural and engineered environments, as a result of various stimuli -Computational and experimental studies of degradation mechanisms and kinetics -Characterization of degradation by traditional and emerging techniques -New approaches and technologies for enhancing resistance to degradation -Inspection and monitoring techniques for materials in-service, such as sensing technologies
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