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RAPID, CATASTROPHIC DECAY OF BUILDING LIMESTONES: IMPLICATIONS FOR MASONRY SELECTION AND LIFETIME BEHAVIOUR

建筑石灰石的快速、灾难性腐烂：对砌体选择和使用寿命行为的影响

基本信息

批准号：
EP/D009162/1
负责人：
Kenneth Grattan
金额：
$ 26.58万
依托单位：
City, University of London
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%2FD009162%2F1
关键词：
RAPID CATASTROPHIC DECAY BUILDING LIMESTONES

项目摘要

Stone is widely recognised as a sustainable construction material and as a store of much of the world's tangible cultural heritage. With this recognition has come an understanding that stone has a finite life that can be drastically curtailed when it is placed in the often-aggressive urban environments. In particular, many common building limestones experience seemingly unpredictable, episodic and sometimes catastrophic breakdown as stone strength is exceeded by gradual decay, the slow accumulation of internal stresses and/or subjection to extreme external stresses such as a severe frost. Episodes of rapid decay may be interspersed with periods of relative stability marked by, for example, the formation of pollution-derived calcium sulphate crusts. To control potential catastrophic decay it is therefore necessary to understand why rapid retreat is triggered, what allows it to continue, how it can be halted and how the causes can be avoided in the first place. This is particularly true where inappropriate conservation could accelerate decay, and where choices have to be made between possible replacement stone and stone selection in relation to new structures. To achieve this understanding four questions need to be asked.1. What processes are responsible for rapid retreat?2. What physical, chemical and mineralogical characteristics determine stone susceptibility to rapid retreat and how do these properties change during decay?3. How do microclimatic conditions at and beneath the stone surface change as stone retreats and how do these influence decay mechanisms?4. What permits continued weathering despite rapid loss, of weathered material in which, for example, damaging salts are concentrated?This interdisciplinary project will examine these questions through field studies of stone structures in Oxford and nearby areas built of oolitic limestone (e.g. Bath and Cotswold limestones) that is prone to rapid retreat. Linked to this will be the development of fibre optic sensors that will allow moisture and salt movement within individual blocks to be monitored in relation to environmental conditions, including temperature, relative humidity and surface wetting. These data, and the same sensor technology will be combined with analyses of weathered stone to design laboratory experiments using different varieties of Bath Stone to simulate breakdown patterns and the dynamics of salt and moisture movement as blocks retreat and are progressively sheltered. Results from field studies and controlled laboratory experiments will be combined to explain (model) the factors that determine overall susceptibility to either rapid retreat or stability and the operation of the processes responsible for decay. In particular, results will be used to determine what triggers positive and negative feedbacks that respectively accelerate and decelerate change within the stone decay system. This understanding will be used, in discussion with end-users, to develop protocols for limestone conservation and the selection of new and replacement stone matched to specific environmental conditions.

石头被广泛认为是一种可持续的建筑材料，也是世界上许多物质文化遗产的储存库。有了这种认识，人们就认识到石头的寿命是有限的，当它被放置在经常具有攻击性的城市环境中时，它的寿命可能会大大缩短。特别是，许多常见的建筑石灰石会经历看似不可预测的、偶发性的、有时是灾难性的破坏，因为石头的强度因逐渐腐烂、内应力的缓慢积累和/或遭受极端的外部应力（例如严重的霜冻）而超过。快速腐烂的时期可能会穿插着相对稳定的时期，例如，以污染引起的硫酸钙结壳的形成为标志。因此，为了控制潜在的灾难性衰退，有必要首先了解为什么会引发快速撤退、是什么让它持续下去、如何阻止它以及如何从一开始就避免其产生的原因。当不适当的保护可能加速腐烂，以及必须在可能的替代石材和与新结构相关的石材选择之间做出选择时，尤其如此。为了实现这一理解，需要提出四个问题：1．哪些过程负责快速撤退？2．哪些物理、化学和矿物学特性决定了石材对快速退缩的敏感性以及这些特性在腐烂过程中如何变化？3。当石材退缩时，石材表面及其下方的微气候条件如何变化？这些如何影响腐烂机制？4。尽管风化材料迅速流失，但是什么允许持续风化，例如，有害盐集中在其中？这个跨学科项目将通过对牛津和附近由易于快速退缩的鲕粒石灰岩（例如巴斯和科茨沃尔德石灰岩）建造的地区的石头结构进行实地研究来研究这些问题。与此相关的是光纤传感器的开发，该传感器将允许监测各个块内的水分和盐分与环境条件（包括温度、相对湿度和表面润湿）的关系。这些数据和相同的传感器技术将与风化石材的分析相结合，设计实验室实验，使用不同品种的浴石来模拟分解模式以及随着块体退缩和逐渐受到保护的盐和湿气运动的动态。现场研究和受控实验室实验的结果将结合起来，解释（模型）决定快速消退或稳定的整体敏感性的因素以及导致衰变的过程的运行。特别是，结果将用于确定触发正反馈和负反馈的因素，这些反馈分别加速和减缓石材腐烂系统内的变化。在与最终用户的讨论中，这种理解将用于制定石灰石保护协议以及选择与特定环境条件相匹配的新石和替代石。