We investigated the effect of soil water conditions and soil compaction on the age-hardening process of loamy sand and silty loamy sand in relation to the tensile strength. Soil samples from Germany (loamy sand) and Poland (silty loamy sand) were moulded at water contents 10 %, 15 %, 20 % and compacted up to 1.35, 1.45, 1.55g/cm3. The samples were stored at constant water content. At intervals after moulding, the tensile strengths of the moist samples were measured with the indirect tension (Brazilian) test. The maximum aging time was 10 days. With increasing time the soils became stronger at the same water content. The higher the initial water content the less pronounced was the strength increase with time. Furthermore, increase in bulk density resulted in higher values of tensile strength. Two different mechanisms of age-hardening could be identified.