Assessment Techniques for Studying the Effects of Fire on Stone Materials: A Literature Review

ABSTRACT

Fire is one of the most severe threats to stone applied in civil engineering and architecture. In most cases, its effects are irreversible and have long-lasting repercussions. In addition to aesthetic alterations, fire can also induce important mineral-chemical, physical, and mechanical changes in stone. Research concerning the effects of fire on stone materials in recent decades has been providing valuable knowledge to inform present and future conservation and restoration actions. In this literature review, the properties and techniques used for studying the effects of fire on stone materials are appraised, summarized, and compiled. A comprehensive and practical overview of those effects is also given. Open porosity and P-wave ultrasonic velocity are the physical and mechanical properties that have been studied most. Other frequently researched areas include chemical-mineralogical changes, color, density, water absorption, uniaxial compressive strength, and modulus of elasticity are also very frequently investigated.     

金沙土遗址盐害分布与演化特征

金沙土遗址表面存在泛盐、粉化、空鼓等盐害。对这些盐害的分布特征与演化过程的研究是科学保护金沙土遗址的第一步，也是进一步探讨盐害致病机理的前提条件。本工作收集整理了2010～2020年金沙土遗址病害调查资料，通过现场调查和图像处理技术对盐害的类型、分布特征与演化过程进行定性和定量分析；采用X射线衍射、离子色谱和扫描电镜等测定了不同高度土样的成分、盐分含量以及微观结构。结果显示金沙土遗址主要的盐害类型为表面泛盐、粉化、空鼓、片状剥蚀和掏蚀；主要分布区域是西北向走廊和古河道附近，机挖坑侧壁最为严重；在探方侧壁上盐害由上到下依次由表面泛盐过渡到单独粉化，再到空鼓和片状剥蚀，最底层为掏蚀。金沙土遗址盐害的发育过程可以概括为四个阶段，每个阶段主要发育的盐害类型不同，依次为表面泛盐、粉化、片状剥蚀和掏蚀。越到后期，各类盐害分布范围越大，发展速度越快，对土遗址破坏性越大。离子浓度沿高度的分布与毛细上升作用有关，也与病害的劣化程度和发育进程有关。硫酸钙类是导致土遗址泛盐、粉化和脱落的主要盐分之一。