Final answer:
Natural cement rock produces hydraulic cement when heated and pulverized. Quicklime, formed from calcite in limestone, is combined with clay minerals to create cement. This hydraulic cement is essential for construction.
Step-by-step explanation:
The naturally occurring clayey limestone that produces a hydraulic cement when calcined and finely pulverized is often referred to as natural cement rock or natural cement stone. This material contains components of both clay and limestone, and its unique composition allows it to chemically react with water to harden, unlike non-hydraulic lime produced from pure limestone.
When limestone rich in calcite (CaCO3) is heated in a lime kiln, it decomposes to form calcium oxide (CaO), also known as quicklime. Quicklime is then mixed with clay minerals and other materials, and this mixture is calcined again to form cement clinker, which is then ground to create the final product - hydraulic cement. This process and the resulting product are integral components of the construction industry.