建筑设计英文文献及翻译 第2页
蒙脱土的主要成分是FEBEX膨润土,包含两级储层非均质性。首先，一点点的钾是结构性的固定这层附属部件（如高层电荷）（夸德罗斯和利纳雷斯，1995年）。实际上化学反应并不显著，因为K+与复杂的交换不相关。其次,不同的阳离子交换 (主要是钙、镁、钠在合适的比例)通过交换反应将改变他们的在地球化学环境下的分布，因此也是碱性羽局部控制间隙水组成。
蒙脱土在热力学数据库中建立的化学组成（钙、铯、钾、镁或是钠）是相对简单的，并不是与任何真正的成分都相匹配。卡玛等人(2000)实验得到了离子活动的产品(IAP)和蒙皂石在80℃的溶蚀速率方程和pH值为8.8的FEBEX改性产品。IAP的平均值为5.0×10-53，而且蒙脱石的解散方程已给出：
考虑到平衡，能够logK-Temperature函数上的一点的值（logK1 = -52.3时，温度为80℃)。
水的基础物质Al3+,H+,和SiO2(液体)不得不被替换,而且蒙脱土的结构基础转变为））O10(OH)2，这样与数据库保持一致。没有铁物种都考虑在水相,因此所有包含在蒙脱土中的Fe3+转化为Al3+，以文持水相的平衡，这样使Al(OH)4的化学计量系数变为1.605。
利用数据库和范特霍夫方程就可以得到铝离子和氢氧根离子，和logK在80℃时的转换反应：
FEBEX-膨润土分解所得的新的logK为：
最后，这个化学公式稍有改变，由拉米雷斯等人所确定的（2002年），而且该公式被桑切斯等人使用在膨润土的一个0.5毫米的小块上，这与实验研究的成分组成相符合。在0-300℃的范围内，即runchFlow模型的规定，logK-Temperature函数是在类比蒙脱土-钙的函数归纳总结得来的。25℃时，logK=6.26，根据分解方程：
5、结论
该研究表明，膨润土屏障在碱性条件下的稳定性和化学性能的缓冲能力，将会在深的贮藏处发生。蒙脱土的分解率预计在长时间内（105年）会降低，当不考虑对流运输时，初始膨润土在接口附近的一小部分正在分解。次生矿物方沸石、水镁石、镁皂石和C-S-H阶段，这是一个紧密的阶段，是在实验室里观察模仿膨润土变更区域的沉淀。沸石类，C-S-H阶段，具有不同的钙/硅的比值，而且镁和硅酸盐在试验中被检测到，而且他们已被预测在对流的条件下在360天的运作过程中沉淀在模型中，在长时间内（105年）仅考虑扩散过程。
这个系统的复杂性已经被CrunchFlow数值模型捕捉。动力学的矿物溶解/沉淀应进一步约束,大量的矿物质,包括其依赖于超级碱性条件。应用地球化学模式的实施等主题所需要的基本性质和化学的耦合关系,还有特定粘土的过程，例如，阴离子的排除。但是,有一个基本知识的缺乏，即孔隙尺度的操作流程，和这些细节怎样去完善。
长期模型的预测必须在基本假设的基础上进行评估。这样做的目的不是对混凝土膨润土界面反应性预测的有信心，而是为了约束与贮藏室位置有关的反应过程，并指出一些模型的局限性（地球化学代码和热力学/动力学数据库的性能）。良好运作的详细定量模型试验，将会发展地球化学编码和提高改善热力学和动力学数据库。
Eur.J.Mineral.2009,21,177–191 Published online November 2008
Modelling concrete interaction with a bentonite barrier
RAUL FERNANDEZ1,*,JAIME CUEVAS2 and URS K.MADER1
1Institut fu¨r Geologie,Universita¨t Bern,Baltzerstrasse 1–3,CH-3012 Bern,Switzerland
*Corresponding author,e-mail:raul.fernandez@geo.unibe.ch
2Departamento Quimica Agricola,Geologiay Geoquimica,Facultad de Ciencias,Universidad Autonoma de Madrid,
Campus Cantoblanco,28049 Madrid,Spain
Abstract:The concrete–bentonite interface has been studied under the geochemical conditions expected in a repository for high-level radioactive waste.The alkaline conditions emanating from concrete will modify the mineralogy,pH and cation exchange properties of bentonite.The reactive transport geochemical model CrunchFlow was used to simulate column experiments with cement mortar in contact with compacted bentonite carried out at laboratory scale for a period of one year at 25 C and 120 C.The thermodynamic data and compositional properties of the minerals involved have been selected and adapted where necessary.An important improvement,compared with previous work,is the inclusion of an extended formula for montmorillonite in the database that fits the experimentally determined composition of FEBEX bentonite,and this allowed to tie the exchangeable cations specifically to this mineral phase.Kinetic rate laws have been selected and evaluated at both temperatures to predict the system behaviour at long timescales(105years).
Results predict the precipitation of hydroxides,zeolites,secondary clay minerals and cement hydration phases in bentonite with different distributions as a function of time and temperature.The predicted alteration produced at long timescales is not very significant under the boundary conditions of the modelling.The expected extension of significant mineralogical changes in the bentonite barrier is in the order of a few centimetres from the concrete interface,leaving the bulk of the bentonite unchanged in its barrier function.
Key-word :bentonite,alkaline plume,reactive tansporte modelling,CrunchFlow,
montmorillonite,concrete
1.Introduction毕业论文
http://www.751com.cnMany countries consider deep geological disposal for high-level radioactive waste,whereby a multiple-barrier system has to ensure waste isolation for 105–106 years.Several designs include substantial amounts of concrete(for support and as a buffer)and a engineered barrier system(EBS,e.g.,made from compacted bentonite)hosted in either claystone or crystalline basement rock .Hyper alkaline pore waters emanating from the outer concrete shell will interact both inward with the bentonite barrier surrounding the metal canisters,but also outward with the host rock environment.
The peak of the thermal pulse emitted from the waste canister is reduced by interim surface storage(50–100years).Most current repository designs limit the expected maximum temperature at the canister–bentonite interface to 100 C(Villar et al.,2006).The thermal pulse decays after a few 100 years,long before radionuclides are expected to be released as a 无耻悲鄙下流的网.学,网总是抄辣|文,论-文.网 Typical dimensions are 0.90 m for canister diameter,and 0.75 m for the radial
thickness of the bentonite overpack(ENRESA,1997).
Concrete pore waters originating from a Portland cement have high alkalinity(hyper
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