Transport- und Löseprozesse im Gesteinskorn beim Ablauf einer AKR sowie Grundlagenuntersuchungen an AKR-Gelen

在1498研究组内，子项目5将追求以下6个目标：1.阐明机械预损伤和循环加载在多大程度上可以将临界数量的氯化钠溶液驱动到混凝土中。2.集料颗粒中与加工有关的微裂纹的影响应针对另一种岩石类型进行验证。3.利用纳米CT系统，测定FIB循环气候储存试验方法中混凝土棱柱中形成的ASR-凝胶的体积。这里的主要目的是阐明是否存在一个临界量的凝胶，如果超过这个临界量，就会根据相应测量的膨胀和凝胶的组成而导致混凝土劣化。这些信息对于子项目3.4中的建模特别有用。合成ASR凝胶的膨胀压力将作为其组成、水含量和量的函数来测量。关于它的组成，除了钙的含量，这里特别感兴趣的是钠的含量，因为它受到外部供应的氯化钠的影响。此外，如果凝胶的膨胀能力保持在一定的水含量以下，以及需要多少量的凝胶才能产生有害的压力，这一点应该得到澄清。此外，还将通过测量岩石粉末在人工孔隙溶液中的膨胀压力来研究二氧化硅溶解在膨胀过程中的作用。对于热力学模型，还将确定合成ASR凝胶的溶解度积和反应热。所获得的数据对于在子项目3.5范围内模拟ASR破坏过程非常重要。作为温度和氯化钠浓度的函数，应确定二氧化硅的溶解速率。为此，将继续并延长在供资阶段1中已经开始的溶解实验，除其他延长外，还将使用另外两种集料(碎石、流纹岩)。通过运行扫描电子显微镜/EBSD分析，可以确定石英晶体的大小和变形的空间分辨率，石英将在溶解作用前后进行研究。了解溶蚀作用对石英微观结构的影响以及微观结构与溶解速率之间的关系是非常有意义的。6.利用图像分析软件，对混凝土薄片进行定性、定性、描述性评价。主要的重点是裂缝的检测，以更定量地表征裂缝的程度(裂缝的数量、宽度、长度和面积)，并通过得出适当的比值来比较ASR对不同混凝土造成的破坏程度。

Within the research group 1498, sub-project 5 shall pursue the following 6 objectives: 1. It is to clarify, to what extent a mechanical pre-damage and cyclic loading can drive a critical amount of NaCl solu-tion into concrete. 2. The influence of processing-related micro cracks in aggregate grains shall be verified for another rock type. 3. By means of a nanoCT-system, the volume of ASR-gel formed in concrete prisms during the FIB cyclic climate storage test method shall be determined. The main ob-jective here is to elucidate, if there is a critical amount of gel that, if exceeded, will cause concrete deterioration as a function of the correspondingly measured expansions and the composition of the gels. This information is of particular interest for the modelling in sub-project 3. 4. Swelling pressures of synthetic ASR-gels will be measured as a function of their composition, water content and amount. With respect to its composition, besides the Ca-content it is the Na-content that is of particular interest here, because it is affected by an external supply of NaCl. Furthermore it shall be clarified, if the swelling ability of a gel is preserved below a certain content of water and what amount of gel is necessary to produce a deleterious pressure. In addition, the role of SiO2 dissolution for the swelling process will be investigated by measuring swelling pressures of rock powders subjected to artificial pore solutions. For a thermodynamic modelling, also solubility products and enthalpies of reaction will be determined for synthetic ASR-gels. The obtained data are of great importance for modelling the ASR damaging process within the scope of sub-project 3. 5. As a function of temperature and NaCl concentration, SiO2 dissolution rates shall be determined. For that purpose, the dissolution experiments already started in funding period 1 will be continued and extended, for what two more aggregates (crushed gravel, rhyolite) will be used among other extensions. By running an SEM/EBSD-analysis, by what size and deformation of single quartz crystals can be determined spatially resolved, quartz will be investigated before and after the dissolution attack. It is of major interest to learn what influence the dissolution attack has on the quartz microstructure and what link between microstructure and dissolution rate exists respectively. 6. By means of an image analysis software, concrete thin sections shall be used for a more quantitative instead qualitative and describing appraisal. The main focus is the detection of cracks to characterize the degree of the cracking more quantitatively (number, width, lengths and area of the cracks) and by deriving an appropriate specific value to compare the degree of damage caused by ASR for different concretes.