This paper presents the elasto-viscoplastic stress-strain behavior of pure kaolin soil and its cementmixture under drained one-dimensional compression. A study was made of the effects of the degrees of wetting combined with ageing effects on the stress-strain-time behavior. Effects of the degree of saturation and its variations for a wide range (0.8% to 100%) on the stress-strain-time behaviour during creep and subsequent continuous monotonic loading in one-dimensional compression tests were evaluated. Also the effects of ageing that develop at different stress levels on the behavior of unsaturated specimens were evaluated. A new mathematic model developed in the framework of a non-linear three-component model is proposed on the basis of test results.