A gamma ray spectrometer using an Americium source has been built. The source and the detector are mounted on two separate towers and can move vertically. The studied sample is mounted on a platform that can move horizontally. The movements of the towers and the platform are controlled and synchronized by a computer which is also used to define the parameters of each test, to run the test, and to collect the data. This equipment has been used to analyze the capillary moisture transfer through two cement pastes.