雅思小作文练习（水泥和混凝土制作流程比较）

The first diagram shows the process of cement production, and the second digram illustrates how the concrete has been produced.

It is clear that there are five steps for the production of cement, from the original materials including limestone and clay into the end product: bags of cement. By contrast, to produce concrete, four different materials would be mixed together.

It can be seen that limestone and clay as the raw materials would be put into crusher then become powder at the first stage of cement production. The next step, powder would get totally mixed in the mixer. Then moving to the heating stage, powder would be heated in a rotating heater for a while. Then the grinder would be working on the heated powder, the result worked by grinder is the cement, but before it becomes the end of product, cement would be filled into bags. After the five steps, bags of cement are born.

Looking at the production of concrete. In a very big concrete mixer, four different raw materials would be put into it. They are cement, water, gravel(namely small stones) and sand, and percentages of them are 15%, 10%, 50%, and 25% in order. All of them would be completely blended together by the rotating mixer to produce concrete.