Carbonation of alkali-activated Binders and Concretes - Mechanisms and Implications (CaaB)

碱激发粘结剂(AABS)和以其为基础的混凝土(AAB混凝土)是具有广泛应用前景的建筑材料。然而，为了能够安全地使用这些材料，必须回答几个关于它们的性能的公开问题；这对于关于它们的耐久性的问题尤其必要。耐久性的一个特别重要的方面是这些材料对来自周围空气的二氧化碳的反应，即它们的碳化作用，以及当碳化发生时它们提供的对嵌入钢筋的腐蚀的保护。文献中存在关于这些问题的相互矛盾的报告，影响这些进程的重要参数目前没有得到很好的理解。此外，目前尚不清楚现有的抗碳化测试方法在多大程度上适用于AAB混凝土。该项目通过研究这些混凝土的早期表面碳化及其后果、酚酞喷雾方法的适用性以及二氧化碳浓度、淋溶和相对湿度对AAB混凝土碳化的影响，有助于澄清这些问题。为此，钙含量有系统变化的AAB浆体和混凝土将暴露在特定的碳化条件下，然后使用建筑材料技术以及化学和矿物学分析技术的方法进行分析。特别是，空间分辨方法，如拉曼显微镜和微型XRF，将被用来解释和详细研究碳化前沿的推进。这些研究的主要目的是首次系统地发展AAB混凝土碳化的机理模型，同时考虑同时淋洗。基于这些模型，将对有意义的加速测试方法提出建议，以测试其抗碳化性能。此外，还将确定AAB混凝土的应用潜力和极限。

Alkali-activated binders (AABs) and concretes based on these (AAB concretes) are promising building materials for a wide range of applications. To enable a safe use of these materials, however, several open questions regarding their properties have to be answered; this is particularly required for questions regarding their durability. A particular important aspect of durability is the response of these materials to access of carbon dioxide from the surrounding air, i.e. their carbonation and the protection that they provide against corrosion to embedded steel reinforcement when carbonation occurs. Contradictory reports regarding these issues exist in the literature, and important parameters influencing these processes are currently not well understood. In addition, it is not clear to what extent currently existing carbonation resistance testing methods are applicable to AAB concretes. The project contributes to the clarification of these issues by studying the early surface carbonation of these concretes and its consequences, the applicability of the phenolphthalein spray method, and the influence of carbon dioxide concentration, leaching and relative humidity on the carbonation of AAB concretes. To this end, AAB pastes and concretes with systematically varied calcium contents will be exposed to defined carbonation conditions and subsequently analysed using methods from construction materials technology as well as chemical and mineralogical analytical techniques. In particular spatially resolved methods, such as Raman microscopy and micro XRF, will be employed to account for, and study in detail, the advancement of the carbonation front. The principal aim of these investigations is to develop systematically for the first time mechanistic models of the carbonation of AAB concretes, considering also simultaneous leaching. Based on these models, recommendations will be given regarding meaningful accelerated testing methods for their carbonation resistance. In addition, potentials and limits of the applicability of AAB concretes will be identified.