Five test methods for porosity of completely decomposed granite in Hong Kong

Abstract

This paper presents the results of a laboratory examination of the porosity values of Hong Kong completely decomposed granites. Five methods are used to measure the porosity values. They are the conventional physical test, helium instrument, mercury injection, thin section measurement and scanning electronic microscopy (SEM). The porosity from the physical test is an absolute porosity with the largest values (average = 44.88%). The porosity from the thin section represents voids or cracks between mineral grains on a plane section and has the smallest values (average = 7.7%). The porosity from the helium instrument is an opening porosity. The porosity from the SEM also represents the voids on a SEM image. The porosity from mercury injection is an effective porosity. The porosity values from the SEM are closely between the opening and effective porosity values. They have the average values between 30% and 35%. In other words, the SEM method can be used to effectively estimate the opening or effective porosity in meso and/or micro scales. © 2004 Elsevier Ltd.