『Abstract
One of the properties that makes marble such an excellent construction
and ornamental material is its low porosity. It is very difficult
for water or decay agents to penetrate the internal structure
of materials with no or few pores, so enhancing the durability
of these materials. However, environmental temperature fluctuations
bring about significant physical changes in marbles that result
in an increase in porosity, due to the appearance of new microcracks
and the expansion of existing ones. These cracks offer new paths
into the marble which make it easier for solutions containing
pollutants to penetrate the material. Thermal expansion tests
were performed on three different types of marble known as White,
Tranco, and Yellow Macael (Almeria, Spain), after which an increase
in porosity (from 17 to 73% depending on marble type) was observed,
mainly due to crack formation. The structural changes occurring
during thermal expansion tests were more significant in the case
of White Macael samples, a fact that is not only related to its
mineralogical composition but also to the morphology of the grains,
grain boundaries and crystal size. Our research suggests that
thermally weathered White Macael marble could be more susceptible
to decay by other contaminant agents than Tranco or Yellow Macael.
The use of hot-stage environmental scanning electron microscopy
is proposed as a valid tool for observing, both in situ and at
high magnification, changes in the fracture system of building
stones induced by thermal stress.
Keywords: Marble; Microcracks; Thermal expansion anisotropy; Grain
boundaries』
Introduction
Materials and methods
Marbles
Methodology
Results
Characterzation of marbles
Thermal expansion tests
Hot-stage ESEM
Discussion and conclusions
Acknowledgments
References