General Contractor Practice Exam

All of the following soil provisions are considered expansive except for which of the following?

1. At least 10% of soil particles are less than 10 micrometers in size

2. High swell potential

3. Low plasticity

4. Presence of clay minerals

The correct answer is: At least 10% of soil particles are less than 10 micrometers in size

Expansive soils, commonly known as shrink-swell soils, are primarily characterized by their ability to change volume with changes in moisture content. The correct option indicates a soil property that does not contribute to expansiveness. The first choice mentions that at least 10% of soil particles are less than 10 micrometers in size. This describes a soil texture characteristic and does not inherently indicate expansiveness. While fine particles can be part of expansive soils, the mere presence of a percentage of small particles does not mean the soil will exhibit expansive behavior on its own. In contrast, the other options highlight features commonly associated with expansive soils. High swell potential indicates a greater likelihood of volume changes when wet or dry. Low plasticity implies that the soil does not have the ability to deform without breaking, which is often not a characteristic of expansive soils, as they tend to be more plastic due to their clay content. Lastly, the presence of clay minerals is a critical factor as expansive soils typically contain clay minerals such as montmorillonite, which are known for significant shrink-swell behavior. Therefore, the option indicating a specific soil particle size does not align with the properties that make soil expansive, marking it as the exception among the options provided.