Salt damage in brick and stone: Direct observation of a salt crystallization sequence.

砖石中的盐害：直接观察盐结晶序列。

• 批准号: EP/D075459/1
• 负责人: Christopher Hall
• 金额: $ 6.76万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FD075459%2F1
• 关键词: Salt; damage; brick; stone; Direct

Look closely at an old brick or stone building and you will often notice that its surface is crumbling away. This is a particular problem in buildings that are close to the sea or exposed to a polluted atmosphere. As a result much of the detail and the finish of the stonework, particularly in carvings and statues, is lost over time. A common cause is that the water that is drawn into the stone from the ground or from rain contains dissolved ions. These form salt crystals inside the pores of the stone when the water evaporates. As the crystals grow, they press against the pore walls, causing cracks to spread through the stone. The level of damage caused is closely connected to the type of salt that forms.Sodium sulphate is a salt that is often observed in this kind of damage. It is a complex salt, as it can form crystals with different shapes and properties. To date, scientists have tried to understand how sodium sulphate damages stone by considering the behaviour and properties of the two most common crystals it can form, namely anhydrous thenardite and the hydrate mirabilite. However, Pel and co-workers in the Netherlands, measuring the solubility of sodium sulphate crystals formed when sodium sulphate solution evaporates inside a porous material, have found indirect evidence that a third kind of sulphate crystal is formed, called sodium sulphate heptahydrate. This is a most important but unexpected result, as it means that in order to understand crystallization damage caused by this salt, it may be necessary to consider the properties of the heptahydrate crystal, in addition to those of thenardite and mirabilite. Because this result from the Netherlands is so important, we need to be sure that it is correct: that is, we need direct evidence of the presence of this crystal to provide independent verification of their observations. We plan to use high energy synchrotron X-rays to look inside blocks of brick and stone soaked in sodium sulphate solution as they cool slowly order to see what kinds of crystals form. Each crystal has a unique X-ray fingerprint. Using special synchrotron X-ray techniques that we have developed we expect to observe the entire crystallization sequence.

仔细观察一座古老的砖石建筑，你会经常注意到它的表面正在剥落。在靠近大海或暴露在污染大气中的建筑物中，这是一个特别的问题。结果，随着时间的推移，石制品的大部分细节和完成程度，特别是雕刻和雕像，都消失了。一个常见的原因是，从地面或雨水吸入石头的水含有溶解的离子。当水分蒸发时，这些物质会在石头的毛孔内形成盐晶体。随着晶体的生长，它们会挤压孔壁，导致裂缝在石头中蔓延。造成的损害程度与形成的盐的类型密切相关。硫酸钠是这种损害中经常观察到的一种盐。它是一种复杂的盐，因为它可以形成不同形状和性质的晶体。到目前为止，科学家们一直试图通过考虑硫酸盐可能形成的两种最常见的晶体--无水芒硝酸盐和水合物芒硝酸盐--的行为和性质来了解硫酸钠是如何损害石头的。然而，荷兰的Pel和他的同事测量了硫酸钠溶液在多孔材料内蒸发时形成的硫酸钠晶体的溶解度，发现了间接证据，证明形成了第三种硫酸盐晶体，称为七水硫酸钠。这是一个最重要但意想不到的结果，因为这意味着为了了解这种盐造成的结晶损害，除了亚硝酸盐和芒硝酸盐之外，可能还需要考虑七水晶体的性质。因为荷兰的这个结果是如此重要，我们需要确保它是正确的：也就是说，我们需要这个晶体存在的直接证据来为他们的观察提供独立的验证。我们计划使用高能同步加速器X射线观察浸泡在硫酸钠溶液中的砖块和石块的内部，当它们慢慢冷却时，看看形成了什么类型的晶体。每个晶体都有一个独特的X射线指纹。利用我们开发的特殊同步辐射X射线技术，我们有望观察整个结晶过程。