春骥 TOEFL Listening · Roman Concrete

Questions

Question 1 Main Idea

What is the talk mainly about?

A The construction techniques used to build Roman harbors and seawalls B Why Roman concrete remains durable and how it differs from modern concrete C The environmental damage caused by deteriorating modern concrete structures D A comparison between volcanic ash and other types of construction aggregate

Question 2 Detail

According to the professor, what happens when seawater penetrates Roman concrete?

A It causes the lime content to evaporate and create air pockets B It dissolves the volcanic ash and weakens the overall structure C Seawater initiates chemical processes forming minerals that strengthen it D It has no significant effect because the concrete is already fully hardened

Question 3 Inference

What can be inferred about modern reinforced concrete from the professor's discussion?

A It was originally developed by Roman engineers and later forgotten B Steel reinforcements inside it rust and expand in marine environments C It is generally less expensive to produce than ancient Roman concrete D It cannot be used for any structure that will contact salt water

Question 4 Vocabulary

The professor describes Roman concrete as having 'extraordinary longevity.' What does 'longevity' mean in this context?

A The ability to last for a very long time without breaking down B The capacity to support extremely heavy loads without collapsing C The flexibility to bend slightly under pressure without cracking D The resistance to catching fire under high temperatures

打开听力文本

Why do some Roman harbors and seawalls still stand after two thousand years, while modern concrete structures begin to crack within decades? The answer lies in the concrete itself. Roman builders used a mixture that included volcanic ash, known as pozzolana, along with lime and seawater. What's fascinating is that this wasn't just ordinary concrete. When seawater penetrates Roman concrete, it triggers a chemical reaction that produces new mineral compounds. These compounds actually fill in tiny cracks and make the material stronger over time. Modern Portland cement, by contrast, starts deteriorating almost as soon as it contacts salt water. The steel reinforcements inside modern concrete rust and expand, causing the structure to fracture from within. Now, one thing to know is that Roman concrete didn't use steel reinforcement at all. It relied entirely on the chemical properties of its ingredients. Researchers have recently analyzed samples from ancient Roman harbors and confirmed that these new minerals—called aluminum tobermorite—are what give the material its extraordinary longevity. So what does this mean for us today? It suggests that looking backward at ancient technology might help us design more sustainable building materials for the future.