Book 3, Question 54
Why Is Concrete So Strong?
Concrete is a mix of cement, sand, gravel, and water. It hardens into a kind of artificial rock, and it loves being squeezed! Let's see how it gets so tough.
From the book
Page from A Million Whys Book 3
More fun facts
- Concrete is made of sand, water and cement.
- Well-made concrete is waterproof, stormproof, fireproof, strong and cheap.
- Bad concrete, with too much sand and too little cement, can be very dangerous in an earthquake.
- Concrete is weak when it is pulled, but steel is strong under that kind of pulling force, called tension.
- Roman sea walls and piers built about 2,000 years ago still stand strong in Italian waters.
- Over time, new minerals grow inside Roman sea concrete and make it even stronger.
Sources: BBC, BBC, Smithsonian Magazine
Questions kids ask
How has Roman concrete lasted so long?
As water seeps through it, new minerals grow inside and fill the gaps, which makes the concrete even stronger over time.