North Carolina Building Contractor License Practice Exam

Compacted fill material must be compacted to what percentage of proctor density?

1. 85 percent

2. 90 percent

3. 95 percent

4. 100 percent

The correct answer is: 90 percent

Compacted fill material must be compacted to 90 percent of Proctor density to ensure adequate soil stability and load-bearing capacity. This level of compaction is generally accepted as a standard in construction practices, particularly in North Carolina, to minimize settlement and enhance the performance of the fill material. Achieving 90 percent Proctor density means that the fill material is compacted sufficiently to reduce air voids and increase density, which consequently improves the engineering properties of the soil. This level of compaction helps in providing a stable foundation for structures, which is crucial in regions subject to varying weather conditions and soil behavior. Exceeding this compaction requirement, such as 95 or 100 percent, may lead to issues like increased construction costs, difficulty in achieving such high levels of compaction due to potential over-densification, and reduced flexibility of the soil, potentially causing cracking or subsidence under load. Hence, while higher compaction levels are sometimes desirable for specific engineering purposes, the standard requirement recognized in typical construction scenarios is 90 percent Proctor density.