Moisture Retention Characteristics of Base and Sub-base Materials

Soil water retention refers to the relationship between the amount of soil water and the energy with which it is held. This relationship is important for characterizing water movement through granular materials. In this project, we generated soil moisture retention data of 18 non-recycled and 7 recycled materials used in pavement construction. The results showed that water retention of non-recycled materials was nearly similar. The major differences among the curves were in the inflection points (air entry values) and in the water contents either near saturation or at 15,300 cm of suction. Using this database, we also developed Pedo-transfer functions that can predict (1) water retention or (2) the parameters of functions that describe water retention from easily measurable properties of the pavement materials. Water retention of concrete with and without shingles was only slightly different. This is partially because shingle chips imbedded in the concrete were large. Traditionally, the influence of matric suction has not been directly considered in pavement design. The water retention data in this report will be helpful in developing resistance factors for Minnesota Flexible Pavement Design Program either through physical modeling or through statistical relationships between design criteria and the water contents.