What describes Type II concrete?

Type II concrete is specifically formulated to provide moderate sulfate resistance. This characteristic is particularly important in environments where the concrete will be exposed to sulfate-rich soils or water that can cause deterioration over time. The moderate sulfate resistance feature of Type II concrete ensures that it can withstand the effects of sulfates without significant degradation, thus extending its longevity and structural integrity.

When comparing this with the other options, it's clear that they describe different types of concrete or characteristics that don’t align with the fundamental properties of Type II. High strength would correspond more closely with certain high-performance or special concrete mixes, while low permeability is a quality that might describe other specific formulations used for submerged or underwater applications. Fast-setting formulations do not relate to Type II concrete as it is more about its resistance to sulfate attack rather than the speed at which it sets. Thus, the emphasis on moderate sulfate resistance makes it the correct choice for describing Type II concrete.