- 23 - 24 April 2018 Empa, Dübendorf, Switzerland
We all know the words, but what are they and how are they made and why are they used in structures as diverse as single family homes, bridges, dams and even the Sagrada Familia.
The words cement and concrete are not interchangeable, but they are intrinsically connected. Cement is a key ingredient of concrete. It is the binding agent that holds everything together.
Early forms of cement were first used thousands of years ago. No one knows for sure who first came up with the idea to use a cement substance to bind materials together to make concrete, bricks, and other building materials. The process can be traced back to Ancient Macedonia, but was more widely popularized during the Roman Empire. Early forms of cement used things like lime and pozzolana, a type of volcanic ash. The Romans were able to produce massive structures like the Pantheon and the Roman aqueducts using this formula.
The most common cement used in the making of modern concrete is Portland cement. Joseph Aspdin, a British stonemason patented the process in 1824. He heated a mixture of finely ground limestone and clay and then ground the mixture into a powder that hardened with the addition of water.
Concrete is a mixture of cement, water and aggregates. Aggregates make up approximately 70-80% of the mixture and cement and water make up the rest. Aggregates are usually inert coarse materials like gravel, crushed stone, sand or recycled concrete. The type of aggregate selected depends on the local availability and the application of the concrete.