What is true about the "modified proctor" compared to the "standard proctor"?

The modified proctor test is designed to assess the compaction characteristics of materials with a focus on achieving higher density for specific applications, such as those used in heavy traffic areas. The key distinction between the modified proctor test and the standard proctor test lies in the amount of compactive energy applied.

In the modified proctor test, a greater compactive energy is utilized, which is delivered through a heavier hammer and more drops per layer compared to the standard proctor test. This increased energy level results in a denser sample. Therefore, it is crucial to recognize that option stating that the modified proctor requires more compactive energy is indeed accurate.

The other choices relate to different aspects of the test; for instance, using the same compactive energy or less energy does not reflect the purpose and execution of the modified proctor method. Additionally, the particle size focus does not differentiate between the protocols of the modified and standard tests but rather has to do with the gradation of the material being compacted. Understanding these distinctions helps clarify why the modified proctor is particularly useful for applications requiring greater material density and strength.