Many historical earthen buildings are damaged due to fire exposure in the past. It is important to understand the strength degradation of rammed earth after elevated temperature for guiding the strategy of building protection or rehabilitation. A total of 24 unconfined compression tests are conducted on lime-stabilized rammed earth specimens after elevated temperature up to 700°C. A quasi-linear reduction in strength and stiffness is found for rammed earth with the increase of temperature. At high temperature, the ductility of rammed earth is enhanced, e.g., strain at peak strength of 2.5% and 1.5% at 700°C and 20°C, respectively. Microstructural analyses demonstrate that with the increase of temperature, the specimen becomes more porous with reduced calcium carbonate precipitation, explaining the strength reduction. A new thermal damage model is proposed to describe the behavior of rammed earth after elevated temperature, in which the closure of pores is captured to show unrecoverable deformation, and the skeleton part is simulated using a thermal damage variable in a statistical manner to present the damage evolution (strain softening). By comparing with the measured stress-strain curves, one can confirm that the proposed method can provide effective prediction for the response of rammed earth after elevated temperature.

中文翻译：

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高温后石灰稳定夯土应变软化的统计损伤模型


许多历史悠久的土制建筑过去因火灾而受损。了解夯土在高温后的强度退化情况，对指导建筑物保护或修复策略具有重要意义。在高温至 700°C 后，对石灰稳定的夯土试样进行了总共 24 次无侧限压缩试验。 随着温度的升高，夯土的强度和刚度呈准线性降低。在高温下，夯土的延展性增强，例如，在 700°C 和 20°C 时，峰值强度的应变分别为 2.5% 和 1.5%。微观结构分析表明，随着温度的升高，样品的多孔性增加，碳酸钙沉淀减少，解释了强度降低的原因。提出了一种新的热损伤模型来描述高温后夯土的行为，其中捕获孔隙的闭合以显示不可恢复的变形，并使用热损伤变量以统计方式模拟骨架部分以呈现损伤演变（应变软化）。通过与实测应力-应变曲线的对比，可以确认所提方法可以为高温后夯土的响应提供有效的预测。