What is the classification for a sand-silt-clay mix that contains plastic fines?

The classification for a sand-silt-clay mix that contains plastic fines is identified as SM-SC, where 'SM' indicates sandy silt and 'SC' indicates sand with clay. This designation is based on the Unified Soil Classification System (USCS), which categorizes soils based on their grain size distribution and plasticity.

In this case, since the mix includes plastic fines, it suggests the presence of clay or silt that exhibits plasticity. The classification SM-SC reflects both the sandy component and the silty or clayey aspect of the material, showcasing the mixture's characteristics.

The presence of plastic fines is a key factor because it attributes specific engineering properties to the soil, such as its ability to retain moisture and its compaction behavior. This nuance is captured in the hybrid classification SM-SC, recognizing the significant role of both sand and plastic fines in the engineering context. Understanding these classifications is vital for assessing how the soil will behave under load and during construction activities.