What aspect of soil does compaction NOT change?

Compaction primarily affects the physical properties of soil by reducing the volume of air between soil particles, leading to an increase in density and a decrease in moisture content. However, the specific gravity of the soil grains, which is defined as the ratio of the density of the soil material to the density of water, remains unchanged by compaction. This is because specific gravity is a property of the solid particles themselves, and compaction does not alter the fundamental characteristics of the soil grains.

Moisture level in the soil can be influenced by the compaction process, as increased density can lead to reduced pore space and potentially alter the water retention properties. Similarly, density directly reflects the effects of compaction, as it reflects the mass of soil particles per unit volume. The particle size distribution, which refers to the proportions of different sized soil particles present, also remains unchanged during compaction since the process does not alter the actual sizes of the particles. Thus, specific gravity stands out as the aspect of soil that compaction does not affect, confirming the accuracy of the selected answer.