Porosity changes in a granite close to quarry faces: quantification and distribution by ¹⁴C-MMA and Hg porosimetries

¹ Laboratoire de Microanalyses Nucléaires, Université de Franche-Comté, France
² Département de Géosciences, Université de Franche-Comté, France
³ Department of Chemistry, Laboratory of Radiochemistry, University of Helsinki, Finland
⁴ Finnish Center for Radiation and Nuclear Safety, Helsinki, Finland

Corresponding author: claude.dubois@univ-fcomte.fr

Received: 19 February 1999
Revised: 7 July 1999
Accepted: 7 January 2000
Published online: 15 February 2000

Abstract

The microcrack distribution in a low porous granite exposed to weathering after quarrying was investigated in order to detect its microstructural evolution. Two blocks (A and B) were taken in the same granite body from two quarry faces respectively exposed during a few weeks and twenty years. Porosimetry by injection of carbon-14-methylmethacrylate (¹⁴C-MMA) was used for analysing the porous medium. Measurements of optical densities of autoradiographs provided data for the localization and the quantification of porosity. Results are compared with those obtained by mercury porosimetry. Average porosity of sample A was found to be 0.37 ± 0.03% whereas average porosity in sample B reaches 1.07 ± 0.45%. Most of the porosity increase may be explained by the opening of grain boundaries.