This thesis presents, firstly, details of an experimental study of effects of desorption and adsorption on the tensile strength and creep of concrete and mortars. According to the results of previous research, time-dependent microcracking is the basic mechanism of tensile creep and the contribution of restricted adsorption and desorption are not identical for compressive and tensile creep. To supplement and to clarify the previous findings, the experimental programme consists of - (1)

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... n of variations in the tensJle strength of concrete on desorption and subsequent adsorption of water, methanol, benzene and kerosene. In order to draw comparisons, strength variations in compression and indirect tension for the same exposure conditions were also evaluated. (2) -Tensile creep studies of zero percent R.H. and on resaturation with water and methanol. (3) -Evaluation of the surface energy of desiccated concrete and mortars on water and methanol sorption using Bangham's equation and Griffith's criterion for brittle fracture. (4) -Determination of the effects of changes in ambience on the surface energy of concrete and mortar.