concrete

Cement, first millennium b.c. – The foundation of civilization. Literally.

Concrete

Reinforced concrete

Chemical reaction – water
Self-healing – bacteria poop calcium?
sensors

Ancient Romans – The Romans made concrete by mixing lime and volcanic rock. For underwater structures, lime and volcanic ash were mixed to form mortar, and this mortar and volcanic tuff were packed into wooden forms. The seawater instantly triggered a hot chemical reaction. The lime was hydrated – incorporating water molecules into its structure – and reacted with the ash to cement the whole mixture together.

Roman dam construction was characterized by “the Romans’ ability to plan and organize engineering construction on a grand scale”. Roman planners introduced the then novel concept of large reservoir dams which could secure a permanent water supply for urban settlements also over the dry season. Their pioneering use of water-proof hydraulic mortar and particularly Roman concrete allowed for much larger dam structures

Some examples of concrete innovation

• Smart Concrete – By adding carbon fiber to concrete mixture, a slab of concrete is able to conduct electricity. “Smart concrete” has many potential applications, including helping structural engineers to identify trouble spots in a concrete structure long before stress or cracking is visible to the human eye.

• Concrete Canvas Shelters (video 2:10) – Tents that turn into concrete in less than 24 hours. Concrete Canvas tents are “buildings in bag.” Watch as the quick construction of these shelters is demonstrated, highlighting their ability to provide refuge and a sterile medical environment in disaster areas.

Concrete that helps identify stress
As buildings and bridges made of concrete age and are exposed to weather and accidents, the concrete in them can crack. Often there is nothing to see, but the structure may be come weak and need to be repaired or replaced. It would be great if these structures could tell structural engineers that they had problems. Now, with this new concrete that conducts electricity, they can.

• Ask – What happens to concrete structures over time? How do engineers know when they become a safety risk? What happens if the concrete structure isn’t repaired or replaced?
• Imagine
• Plan, Create
• Improve

Engineering ideas

• concrete, conductivity, carbon fiber

Do it
Now it is your turn. Here are some challenges for you to work on…

• Make Concrete Nesting Tables with Legos (video 1:22) – Did you know you can use Lego Bricks to make concrete furniture? In this episode of HomeMade Modern Ben Uyeda shows how to make a set of modern concrete nesting tables using quikrete cement mix.

Learn more…

• Smart Concrete – able to conduct electricity can help structural engineers to identify trouble spots in a concrete structure long before stress or cracking is visible to the human eye.