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

The microcrack distribution in a low porous granite exposed to weathering a fter quarrying was investigated in order to detect its microstructural evol ution. Two blocks (A and B) were taken in the same granite body from two qu arry faces respectively exposed during a few weeks and twenty years. Porosi metry by injection of carbon-14-methylmethacrylate (C-14-MMA) was used for analysing the porous medium. measurements of optical densities of autoradio graphs provided data for the localization and the quantification of porosit y. Results are compared with those obtained by mercury porosimetry. Average porosity of sample A was found to be 0.37 +/- 0.03% whereas average porosi ty in sample B reaches 1.07 +/- 0.45%. Most of the porosity increase may he explained by the opening of grain boundaries.