Abstract Cement paste leaching and concomitant decalcification is a common cause of concrete structure deterioration. Such alterations entail microstructural changes that condition concrete durability. This study analysed those changes in cement pastes exposed to accelerated decalcification, layer-by-layer, from the surface in contact with the leaching agent, 6 M NH4NO3, to the unaltered area. The microstructural changes were analysed with BSEM, MIP and BET whilst the mineralogical and nanostructural alterations in each layer were assessed with XRD, FTIR, 29Si and 27Al MAS NMR and BSD. Decalcification affected not only portlandite and CSH gel, but also the anhydrous clinker and ettringite, inducing major micro- and nano-structural changes, particularly in the two layers closest to the leaching agent. CSH gel decalcification was more intense in the outer layers where long chain gels co-existed with silicon rich gels. BDS, in turn, revealed differences between the amount of bound water in the surface interfacing with the leaching agent and in the leaching front. More specifically, larger numbers of water molecules were tightly bound to silanol groups in the outer, whereas hydroxyl group distribution was more orderly in the inner layers.

中文翻译：

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加速脱钙过程后波特兰水泥浆的矿物学和微观结构变化

摘要 水泥浆浸出和伴随的脱钙是混凝土结构劣化的常见原因。这种改变需要微观结构的变化，从而影响混凝土的耐久性。本研究逐层分析了暴露于加速脱钙的水泥浆的那些变化，从与浸出剂 6 M NH4NO3 接触的表面到未改变的区域。使用 BSEM、MIP 和 BET 分析微观结构变化，同时使用 XRD、FTIR、29Si 和 27Al MAS NMR 和 BSD 评估每层的矿物学和纳米结构变化。脱钙不仅影响硅酸盐和 CSH 凝胶，而且影响无水熟料和钙矾石，引起显微和纳米结构变化，特别是在最靠近浸出剂的两层中。CSH 凝胶脱钙在长链凝胶与富硅凝胶共存的外层中更为强烈。反过来，BDS 揭示了与浸出剂接触的表面和浸出前沿的结合水量之间的差异。更具体地说，更多的水分子与外层的硅烷醇基团紧密结合，而内层的羟基分布更有序。