You should spend about 20 minutes on this task. To produce cement, the raw materials, limestone and clay are crushed into powder and then mixed before being heated in a rotating equipment with a heater at the bottom. The heated mixture is ground into even smaller particles ready to be bagged. In order to make concrete which is the major material for building purposes, a mixture consisting of cement, water, sand and gravel, a kind of small stones, is needed. Gravel and sand are the two major materials, representing 50% and 25% of the raw substances, while the ratios of cement and water are relatively low (15% and 10% respectively). These materials are mixed and rotated in a concrete mixer until the concrete is produced.
The diagrams below show the stages and equipment used in the cement-making process, and how cement is used to produce concrete for building purposes.
Summarise the information by selecting and reporting the main features, and make comparisons where relevant.
You should write at least 150 words.
