6.7 Compacted Density and Moisture Content
The relative density of a pavement material is expressed as the ratio of the in situ density to the maximum laboratory density obtained by standard laboratory procedures. This provides a practical method of controlling the void content of the material during construction.
When the content and size of the voids is small, a slight increase in moisture content can lead to significant loss of strength due to the development of positive pore-water pressures. High void contents resulting from inadequate compaction can cause loss of pavement shape and low resistance to wear. In general, a satisfactory void content is obtained when a pavement material is compacted to specified density.
The effect of moisture change is generally more significant to the performance of a granular material than is a variation in density. A material’s sensitivity to moisture changes should be judged from results of strength testing at different moisture contents as determined from laboratory RLT testing at varying saturation levels. Materials that suffer large variations in strength following small changes in moisture content are referred to as moisture-sensitive and should be avoided wherever possible.