L1：
讲座
1. What is the lecture mainly about?
The origins of cement making
The different chemical properties of Roman, Egyptian, and Portland cement
Efforts to develop an environmentally friendly building material
The discovery of a cost-effective building material
2. According to the professor, what happens during the process of preparing Portland cement that contributes to air pollution?（多选题）
Limestone reacts with magnesium oxide to form greenhouse gases.
Large amounts of fossil fuels are burned to melt rock.
Heated limestone emits carbon dioxide.
Large amounts of dust and powder are discharged into the air.
3. What property of magnesium oxide led the researchers to think that it could replace lime stone in cement making?
Magnesium oxide melts at a lower temperature than limestone.
Magnesium oxide can be carved into large blocks easily.
Magnesium oxide absorbs carbon dioxide when heated.
Magnesium oxide is harder than limestone.
4. What does the professor imply about the researchers who are trying to improve the process of making cement?
They have ignored the technological advances made by ancient cultures.
They have not focused enough on the practical uses of concrete.
They need a more complete understanding of the chemical properties of concrete.
They are not concerned about the environmental impact of making cement.
5. The professor discusses research based on an analysis of pyramids in Egypt.
What does the professor imply about the concrete made as a result of this research?
It requires large amounts of magnesium oxide.
It is too costly to produce in large quantities.
Its production is less harmful to the environment than that of Portland cement.
Its success is due to improved methods of heating limestone.
6. What does the professor imply when he says this:
It is not likely that the pyramids were built with cement.
Modern building materials rarely hold up as well as ancient ones.
Researchers may have overlooked the environmental benefits of a new technology.
There might be a material that is more durable than Portland cement.
