The statement 'The higher the Plasticity Index, the more clay is present in the soil' is:

The statement 'The higher the Plasticity Index, the more clay is present in the soil' is:

• A. False
• B. Not enough data
• C. True
• D. Cannot be determined

Answer: (C)

The key idea is that the Plasticity Index (PI) reflects how plastic the fine fraction of soil is, which is dominated by clay minerals. PI = LL − PL, so soils with more clay typically have higher liquid and plastic limits, and their difference grows. Therefore, as clay content increases in the soil’s fines, the PI tends to rise. While mineralogy can tweak exact values—some clays are more plastic than others—the general trend is that higher PI indicates more clay, making the statement true.

The key idea is that the Plasticity Index (PI) reflects how plastic the fine fraction of soil is, which is dominated by clay minerals. PI = LL − PL, so soils with more clay typically have higher liquid and plastic limits, and their difference grows. Therefore, as clay content increases in the soil’s fines, the PI tends to rise. While mineralogy can tweak exact values—some clays are more plastic than others—the general trend is that higher PI indicates more clay, making the statement true.