Substance-preserving restoration of hydrophobic, weathered natural stones with the use of a non-destructive, depth-graded characterization of the pore structure

利用孔隙结构的非破坏性、深度分级表征，对疏水性、风化的天然石材进行物质保留修复

• 批准号: 496342862
• 负责人: Professorin Dr.-Ing. Jeanette Orlowsky
• 金额: --
• 依托单位: Lehrstuhl Werkstoffe des Bauwesens
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/496342862?language=en
• 关键词: Substance; preserving; restoration; hydrophobic; weathered

In a previous DFG project, the performance of organosilicon compounds was comprehensively investigated on up to 30 years natural weathered hydrophobic sandstones. Besides capillary water uptake, the focus was on the extent and increase of surface stone damage due to long-term weathering, which was recorded with depth-dependent NMR measurements in 200 µm steps.The investigation consisted of 5 sandstone types with different mineralogical composition, treated with 11 hydrophobic agents, exposed at 7 locations and measured after 2, 17 and 24/30 years of weathering. From more than 7600 laboratory measurements it can be concluded that the hydrophobic effect of the agents within the stone does not decrease over 30 years. For all analysed stone types, the hydrophobing treatment cannot stop weathering processes near the surface. Accordingly, the damaged depth determined after 2 years increases many times over in the course of a weathering of 30 years. This near-surface damage, which means the penetration of water near the surface, causes spalling, surface roughening, sanding, gypsum efflorescence, crusts and scaling, soiling and biogenic growth. Some agents, especially those applied on Baumberger, Schleeriether and Eichenbühler sandstones, show, even in unweathered condition, an insufficient water-repellent effect. In this case the damaged depths are more pronounced. In the follow-up project, the valuable source material (450 naturally weathered prisms) will be further investigated. In addition to the previously analysed front surfaces of the prisms, the roof surfaces, which are generally more severely weathered, will be examined in order to supplement and expand on existing knowledge. The follow-up project focuses on the cleaning of the weathered natural stones and a subsequent post-hydrophobing of the samples. During the cleaning process 4 different methods are used and their effect on the stone properties is investigated. The change of the pore structure due to cleaning will be characterized by means of single-sided NMR and evaluation routines to be developed. The post-hydrophobic treatment is carried out with comparable agents as well as with a water-based system and a system, including a biocide. The agents used are clearly described and reproducible by their CAS numbers. Finally, the samples are exposed to natural outdoor weathering again. This project enables the experimental development of suitable, substance-preserving procedures for the restoration of long-term weathered natural stone facades/objects under defined boundary conditions without destroying actual building fabric. In addition, a non-destructive measuring method will be available at the end of the project, which will enable the quantification with high resolution of depth-dependent changes in the sandstone pore structure.

在之前的DFG项目中，对有机硅化合物在长达30年的天然风化疏水砂岩上的性能进行了全面研究。除了毛细吸水，重点是长期风化导致的表面岩石损坏的程度和增加，这是通过深度相关的NMR测量以200 µm的步长记录的。调查包括5种不同矿物成分的砂岩类型，用11种疏水剂处理，在7个地点暴露，并在风化2年、17年和24/30年后进行测量。从7600多个实验室测量结果可以得出结论，结石内的疏水作用在30年内不会减少。对于所有分析的石材类型，疏水处理不能阻止表面附近的风化过程。因此，2年后确定的损坏深度在30年的风化过程中增加了许多倍。这种近地表损害是指水渗入近地表，造成剥落、表面粗糙、起砂、石膏风化、结壳和结垢、污染和生物生长。某些试剂，尤其是用于Baumberger、Schleeriether和Eichenbühler砂岩的试剂，即使在未风化的条件下，也显示出不足的防水效果。在这种情况下，受损深度更明显。在后续项目中，将进一步调查有价值的源材料（450个自然风化棱柱体）。除了前面分析的棱柱体的前表面，屋顶表面，这通常是更严重的风化，将被检查，以补充和扩大现有的知识。后续项目的重点是对风化的天然石材进行清洗，并对样品进行后续疏水处理。在清洗过程中，使用了4种不同的方法，并研究了它们对石材性能的影响。将通过单侧NMR和待开发的评价程序来表征清洁引起的孔结构变化。后疏水处理用类似的试剂以及水基系统和包括杀生物剂的系统进行。所用试剂通过其CAS编号进行了明确描述和重现。最后，将样品再次暴露于自然户外风化。该项目能够实验性地开发适当的、物质保存的程序，用于在规定的边界条件下恢复长期风化的天然石材立面/物体，而不破坏实际的建筑结构。此外，在项目结束时将提供一种非破坏性测量方法，这将能够以高分辨率量化砂岩孔隙结构随深度的变化。