ABSTRACT
Gas adsorption has been one of the most popular techniques used for the study of pore structure in materials that contain micropores and mesopores. When a dean solid surface is exposed to a gas, the gas molecules impinge upon the solid and may reside on its surface for a finite time; this phenomenon is called adsorption. Adsorption processes may be classified as physical or chemical, depending on the nature of the interaction forces involved between the gas and the solid. For pore structure characterization in cement-based materials, physical adsorption is used and will be considered throughout this chapter. Physical adsorption is a reversible process because it is the result of a relatively weak interaction between the solid surface and the gas molecules. Therefore, almost all the gas adsorbed on the solid surface can be removed by evacuation at the same temperature at which it was adsorbed, a process that is called desorption.
