Lean Clay

08/20/26

“How can we describe clays that are less sensitive to moisture?”

Fat clays are famous for their volumetric sensitivity to moisture. At the other end of the spectrum are Lean Clays. Lean clays have a higher composition of silt and sand particles and therefore have lower Atterberg limits compared to fat clays. Consequently, lean clays are less volumetrically sensitive to moisture. To determine if a clay sample is fat or lean, fat clays have liquid limits greater than 50, and lean clays have a plasticity index greater than 7 or plot above the “A” line.