MONITORING OF THERMAL CONDITIONS IN BUILDING STONE WITH PARTICULAR REFERENCE TO FREEZE-THAW EVENTS
MONITORING OF THERMAL CONDITIONS IN BUILDING STONE WITH PARTICULAR REFERENCE TO FREEZE-THAW EVENTS
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监测建筑石材的热状况，特别是冻融事件
DOI：
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发表时间：
2006
期刊：
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通讯作者：
K. Hall
中科院分区：
文献类型：
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作者：
K. Hall
尽管试图考虑冻融的影响，但对相关热状况的监测必须有效地与环境无关。这一点很重要，有几个原因。首先，尽管正在对冻融进行评估，但数据的性质也必须能够确定其他进程的空间和时间作用。其次，由于数据是“整体的”而不是(假设的)“特定的”，所以数据不会预先决定结果。第三，自相矛盾的是，由于能够用于评估多个过程，这些数据的性质有助于更详细地了解冻融活动本身。在考虑冻融时，重要的是要认识到，这个过程不是一个奇点，而是包括一系列机制，每一种机制都由热和湿度条件与任何给定建筑材料的性质之间的相互作用决定。在缺乏(所需)水分数据的情况下，热数据需要足以验证或使特定机制无效，并提供间接替代信息，表明是否确实发生了某种形式的冻融风化作用。在这方面，重要的不仅是冻融幅度和持续时间，而且还有相应的温度变化率(�˚T/�˚t)。此外，记录的速度必须足够快，以监测(如果它们发生)“放热”--水变成冰时重新释放的潜热；这是水存在并确实结冰的替代鉴定(“零幕”的发现也可以作为材料内是否存在冻结的水的替代)。在现实中，监测�˚T/�˚t率和放热的热数据采集要求实际上是相同的，即至少每隔一分钟进行一次高频热监测。过去，每隔一分钟进行一次热监控可能会产生后勤问题，但具有多通道、长寿命电池功率和大存储容量的现代数据记录仪可以轻松处理此类要求。所得到的数据是暂时性的，允许评估热应力，特别是与�˚T/�˚t事件i2°C·min-1相关的热应力。同样，这些数据能够解析与相转移时的潜热释放相关的短时间间隔热传递。值得注意的是，这样的数据不仅识别了外周血肿的发生
Although attempting to consider the impact of freeze-thaw, the monitoring of associated thermal conditions must, effectively, be context free. This is im- portant for several reasons. First, although freeze-thaw is being evaluated, data must be of a nature that also allows determination of the spatial and temporal role of other processes. Second, by being 'holistic' rather than (assumed) 'spe- cific' in character the data do not pre-determine the outcomes. Third, by being able to be used for evaluation of multiple processes the data are, paradoxically, of a nature that facilitates a more detailed understanding of freeze-thaw activity itself. In considering freeze-thaw it is important to recognize that the process is not a singularity but rather comprises a range of mechanisms, each determined by an interaction between thermal and moisture conditions with the properties of any given building material. In the absence of (the required) moisture data, the thermal data need to be adequate to validate, or invalidate, specific me- chanisms, as well as to offer indirect proxy information indicating whether or not some form of freeze-thaw weathering indeed took place. Significant in this regard are not just freeze-thaw amplitudes and durations but also the associ- ated rate of change of temperature (�˚ T/�˚ t). In addition, the record rate must be fast enough to monitor (should they occur) 'exotherms' - the latent heat re- leased as water turns to ice; this being a proxy identification that water was present and did indeed freeze (the finding of 'zero curtains' can also be used as a proxy for the existence of water that froze within the material). In reality, the thermal data acquisition requirements for monitoring of both �˚ T/�˚ t rates and exotherms are effectively the same; namely high-frequency thermal moni- toring at an interval of at least one-minute. Thermal monitoring at one-minute intervals may have produced logistical problems in the past but modern data loggers with multiple channels, long-life battery power and large storage capac- ities can handle such requirements with ease. The resulting data are of a tem- poral nature that allows for the evaluation of thermal stresses, especially those associated with �˚ T/�˚ t events i2 °C. min -1 . Equally, such data are able to resolve the short-interval heat transfer associated with latent heat release at phase transfer. Significantly, such data not only identify the occurrence of exo-