Physical weathering of marbles caused by anisotropic thermal expansion

Abstract

Marbles as building stones as well as in their natural environments show complex weathering phenomena. The most important damage scenario is based on the highly anisotropic thermal expansion coefficient a of calcite, i.e. extreme expansion parallel and contraction normal to the crystallographic c-axis. Therefore, the rock fabric and especially the latticepreferred orientation (texture) of calcite and/or dolomite as the predominant mineral phases in marbles have a significant influence on the mechanical weathering. The textures of marbles from five different locations vary from a more or less perfect prolate to moderate oblate shape of the [006] pole figure tensor. Accordingly, the texture-derived bulk thermal dilatation anisotropy covers a broad range from -0.048 to 0.680. The modelled thermal dilatations correlate with those obtained from experimental measurements. The difference in magnitude is basically explained by the microcrack fabrics which was not considered in the computations. All samples show a deterioration due to thermal treatment regardless of the strength of texture. The directional dependence of (a) the total magnitude of the thermal dilatation coefficient and (b) of the residual strain is highest in marbles with a strong texture, whereas the Carrara marble with a weak texture exhibits a uniform crack formation. The progressive loss of cohesion along grain boundaries due to dilatancy may serve as an example for the initial stage of physical weathering.

Marble bowing: comparative studies of three different public building facades

“…Therefore, the grain size cannot be the most important factor for marble degradation (see discussion in Zeisig et al 2002) as was suggested by Tschegg et al (1999). The grain shape anisotropy significantly triggers the thermal degradation, as shown for several samples by Siegesmund et al (2000) or Ruedrich et al (2001). Thus, grain boundary cracking is the most prominent factor for marble degradation; a substantial part of the observed directional dependence of residual strain must be attributed to shape fabrics.…”

“…Thermally treated marbles which do not return to initial length changes after heating or cooling can show an inelastic residual strain even as a result of very small temperature changes (Battaglia et al 1993). In a more systematic study, Siegesmund et al (1999Siegesmund et al ( , 2000, Zeisig et al (2002) or Ruedrich (2003) showed, that, depending on the length change behaviour under thermal treatment four distinct groups of marbles can be distinguished. Bortz et al (1988) and Thomasen and Ewart (1984) concluded that a variation in moisture contents may be responsible for the deformation.…”

“…Recently, physical weathering is considered to be the initial stage of deterioration of marbles (e.g. Siegesmund et al 2000Siegesmund et al , 2007.…”

“…For the quantification of the lattice preferred orientation (texture) of calcite crystals neutron diffraction was applied. The measurements were carried out at the time-of-flight texture diffractometer at the pulsed reactor IBR-2 of the Frank Laboratory for Neutron Physics of the Joint Institute of Nuclear Research at Dubna, Russia (Siegesmund et al 2000). The investigated sample of Peccia marble represents a c-axis fibre type with a weak tendency to form an intermediate fibre-type (cf.…”

Calcium phosphate coatings for marble conservation: Influence of ethanol and isopropanol addition to the precipitation medium on the coating microstructure and performance

“…Carrara marble was selected for the tests, because this lithotype was widely used in historic architecture and sculpture all over Europe, so that it is often adopted in research studies on marble deterioration and conservation [1,[24][25][26][27]. A slab with 50×50×1 cm 3 size was purchased from BasketweaveMosaics.com (USA) and sawn into cubic and prismatic specimens.…”