Soil Testing Atterberge Limit test This testing method is used as an integral part of several engineering classifications systems to characterize the fine‑grained fractions of soils and to specify the fine‑grained fraction of construction materials. The liquid limit, plastic limit and plasticity index of soils are also used extensively, either individually or together, with other soil properties to correlate with engineering behavior such as comprehensibility permeability, compatibility, shrink‑swell and shear strength