Holistic approach of pre-existing flaws on the decay of two limestones

Abstract

This study aims to understand the influence of the microfacies and the determination of pre-existing flaws on the weathering behavior of two types of limestones. Therefore, both Lede and Noyant limestones were independently weathered by strong acid tests and freeze-thaw cycles. In order to characterize the weathering patterns inside the stones, a combination of high resolution X-ray CT, SEM-EDS and thin section microscopy was used. The advantage of high resolution X-ray CT is its non-destructive character and the obtained 3D structural information. By using this technique, a time-lapse sequence of the weathering patterns was obtained for both gypsum crust formation as well as crack formation due to freezing and thawing. This way, a clear link could be made with the initial non-weathered state. Thin section microscopy and SEM-EDS provided additional chemical information. The focus of this study lies in the processes that occur in the bioclast fragments in the stone and the influence of the surrounding cement or matrix. The results show that weathering patterns vary for both limestones although the causes of weathering were similar. In case of the Noyant stone, the weathering by crystallizing gypsum was mainly restricted to the microporous matrix of the stone, while in case of the Lede stone, several foraminifera and shell fragments were preferentially recrystallized. In general, the underlying microstructure determines the weathering pattern of the stone.

Sourcing limestone masonry for restoration of historic buildings, a spectroscopic pilot study

“…The topic represents a scientific challenge partly because the geological source originally exploited will show variability in physical and chemical properties and, in settings where construction spans the millennia buildings may be comprised of a variety of rock types divorced in terms of geographical source location and geological origin. Superimposed on these considerations is the fact that weathering of masonry may take many forms, be distinct from weathering of natural outcrops and, involve a diverse range of highly site specific biogenic and/or abiogenic natural and anthropogenic processes [1,3,4]. Hence, replacement masonry needs not only be a good match in color and texture to the original, but also needs to be durable and weather in a fashion akin to the degraded masonry, therefore ideally sourced from the same geological strata [5].…”

Neutron radiography and X-ray computed tomography for quantifying weathering and water uptake processes inside porous limestone used as building material

“…The processes can somehow be compared with the crystallizations inside the highly-porous foraminifera of the Lede stone, acting as primary crystallization spots [19]. In the case of the Euville stone, a thick external gypsum crust was identified with a porous dissolution zone underneath.…”

“…and quantitative (calculation of partial porosity, estimation of dimensional changes, computation of interconnectivity, etc.) characterizations of the pore modification processes in a building stone in full 3D [19,20,22,23]. Our main objective is to employ HRXCT, SEM and neutrons to visualize, quantify and interpret alteration and weathering processes inside natural building stones.…”

Towards a more effective and reliable salt crystallization test for porous building materials: state of the art

“…Sometimes, cylinders are used; this shape has the advantage of reducing corner effects and stress concentrations [27,28]. Additionally, when using X-ray CT to monitor the weathering dynamically, cylinders allow the analysis of a larger volume at a specific resolution [23,29].…”