Optimization of Spatially Resolved Laser Ablation ICP MS to Study Transport Phenomena Concerning Concrete Durability

混凝土结构部件的使用寿命取决于CO2、氯化物或酸等物质通过孔隙系统进入混凝土内部的运输以及在那里发生的化学和物理过程。与水接触的混凝土结构部件的孔隙系统中的运输过程也控制着与环境有关的物质（如重金属）的释放。在所有情况下，骨料颗粒和粘合剂基质之间的界面过渡区（ITZ）对运输和使用寿命有决定性影响。为了了解运输过程中的ITZ的效果，从而混凝土的耐久性，有必要知道ITZ中的相关物质的分布，硬化水泥浆基质和aggregate.Laser烧蚀耦合质谱LA-ICP-MS是一种分析方法，具有很大的潜力，在建筑材料的表面或深度的元素分布的空间分辨率。然而，到目前为止，该方法在混凝土中的应用一直受到定量分析准确性的限制。这是由于混凝土作为一种材料具有复杂的微观结构。该项目的第一个资助阶段专注于优化LA-ICP-MS在混凝土中的应用。由于混凝土成分复杂，包括不同硬度、多矿物集料和硬化水泥浆体，因此有必要开发新的评价策略，以获得对硬化水泥浆体与集料之间界面过渡区主要元素的定量评价。拟议继续进行的研究工作现在集中于调查过渡区及其对迁移现象的影响。为了实现这一点，通过压缩与骨料颗粒混合的研磨的硬化水泥浆以及将研磨的硬化水泥浆压到骨料切片上来生产片剂，即没有过渡区的理想化的“混凝土”。 带有过渡区的普通混凝土试件是通过将新鲜水泥浆浇注到骨料切片或立方体上，并将新鲜水泥浆与骨料颗粒混合而制成的。试样成分旨在涵盖硬化水泥浆基质的各种可能的元素成分，并提供有关所选矿物添加剂对过渡区影响的信息。水吸附试验被用来提供更多的信息，在运输过程中的过渡区的作用。混凝土的LA-ICP-MS的优化与改进的定量分析的元素分布在硬化粘结剂膏和ITZ将使显着更好的量化和理解的微观结构对混凝土强度的影响，有害物质的运输，从而混凝土的耐久性。

The service life of concrete structural components is determined by the transport of substances like CO2, chlorides or acids through the pore system into the concrete interior and there the chemical and physical processes which occur. Transport processes in the pore system of concrete structural components in contact with water also control the release of environmentally relevant substances such as heavy metals. In all cases, the interfacial transition zone (ITZ) between the aggregate particles and the binder matrix affects transport and therefore service life decisively. In order to understand the effect of the ITZ on transport processes and thus the durability of concrete, it is necessary to know the distribution of the relevant substances in the ITZ, the hardened cement paste matrix and the aggregate.Laser ablation coupled with mass spectroscopy LA-ICP-MS is an analytical method with great potential for the spatial resolution of distributions of elements over the surface or in the depth of building materials. However, up to now the application of this method to concrete has been restricted by the accuracy of the quantitative analysis. This is due to the complex microstructure of concrete as a material.The first funding phase of the project focused on the optimization of LA-ICP-MS for application to concrete. Owing to the complexity of concrete composition with constituents of different hardness, polymineral aggregates and hardened cement paste, it was necessary to develop new evaluation strategies in order to obtain a quantitative assessment of the main elements, especially in the interfacial transition zone between the hardened cement paste and aggregate.Following the successful optimization of the method, the proposed continuation of the research work now focuses on the investigation of the transition zone and its effect on transport phenomena. To realise this, tablets are produced by compressing ground hardened cement paste mixed with aggregate particles as well as pressing ground hardened cement paste onto aggregate slices, i.e. idealized "concretes" without transition zones. Normal “concrete” specimens with transition zones are produced by pouring fresh cement paste onto aggregate slices or cubes as well as mixing the fresh paste with aggregate particles. The specimen compositions aim to cover a wide range of possible elemental compositions of the hardened cement paste matrix and provide information on the effect of selected mineral additions on the transition zone. Water adsorption tests are used to provide more information on the role of the transition zone in transport processes. The optimization of LA-ICP-MS for concrete with an improved quantitative analysis of element distributions in the hardened binder paste and the ITZ will enable significantly better quantification and understanding of the effect of microstructure on concrete strength, the transport of damaging substances and herewith the durability of concrete.