Probing salt crystallization damage mechanisms in porous limestone with neutron radiography and X-ray tomography

This article presents a comprehensive study on saline transport, pore filling due to salt crystallization and resulting salt damage in Savonnières limestone. The results were achieved by combining neutron radiography - for transport imaging - and X-ray micro-tomography - for pore structure and fracture visualization -- applied to samples subjected to repeated wetting-drying cycles. We studied capillary uptake and drying of water, 1.4m sodium sulfate and of 5.8m sodium chloride solution. The liquid penetration coefficients for the salt solutions result to be markedly lower than the one of water. Halite salt profiles were determined based on neutron radiographs of the dried samples. Porosity analysis of X-ray tomographic datasets allowed quantifying thenardite salt profiles and porosity decrease due to salt crystallization. The damaging character of both salts was assessed from these datasets too. By using high resolution synchrotron X-ray micro-tomography, the pore filling by the saline solutions and by the precipitated salt crystals was revealed in the multimodal pore structure of Savonnières limestone.