Final answer:
The most common Portland cement used for general construction purposes that is economical and has a long setting time is Type I Portland cement. It is used widely due to its versatility and cost-effectiveness in a variety of construction applications.
Step-by-step explanation:
The type of Portland cement that is most frequently used for general construction purposes and recognized for being economical and having a long setting time is called Type I Portland cement. This variety of cement is ideal for construction projects that don't require specialized properties, such as high early strength or resistance to sulfates. Type I Portland cement is the standard, go-to cement for many construction tasks because it is suitable for a vast array of applications and its cost-effectiveness.
Cement serves as a vital binder in construction, binding sand and gravel (aggregate) together to create concrete. This concrete, which can be made with lightweight aggregates like shale, clay, or slate, offers advantages like reduced load and improved thermal protection. Moreover, its use in Roman times showcased its durability, especially when volcanic Italian sand, known as pozzolana, was introduced to create a strong and durable mortar with the ability to set underwater.