What is the primary feature of Type II (modified/moderate) Portland cement?

Type II Portland cement is characterized primarily by its ability to provide better resistance to alkali attack compared to other cement types. This enhanced resistance is particularly beneficial in environments where concrete structures may be exposed to high levels of alkali, which can lead to durability issues like alkali-silica reaction. This modification allows Type II cement to perform better in specific conditions, making it suitable for various applications, particularly where moderate sulfate resistance is required and where concrete may face exposure to salinity or similar conditions.

The other options, while related to different types of cements or applications, do not accurately describe Type II Portland cement. Type I cement would be more likely to produce high heat of hydration, and heavy or heavyweight concrete is beyond the scope of Type II, which is more focused on moderate performance and resistance features. Hence, the primary designation of Type II cement emphasizes its improved alkali resistance.