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From the time humans came out of their caves, they were
looking to build shelter for their families to guard against wind,
weather, cold and threatening predators. Once they started to work
the land and settled down, they began to build more permanent
dwellings. For centuries building techniques were honed and better
houses were erected. The most enduring construction was made of
stone. Pyramids are a good example of this lasting construction.
Man went on to build with concrete-type
substances as early as 3000BC when the Egyptians mixed mud with
straw to bind dried bricks. This opened a whole new range of
possibilities. The Greeks used lime mortars in 800BC. Between 300BC
and 476AD the Romans started to build with pozzolana cement. The
Coliseum and the Pantheon in Romeas well as the Pont du Gard
aqueduct in France are examples of this building technique's
permanence. Vitruvius, a famous 1st century Roman architect, wrote
of a mixture including 2 parts pozzolana (powdered volcanic rock)
and 1 part lime. Ancient builders added blood, milk, and animal fat
to the concrete.
The 18th and 19th centuries were prolific times for
improving concrete. Most important was the
invention of a cement in 1824 by Joseph Aspdin. He called it
portland cement after the town of Portland, England. In 1867
concrete was reinforced with iron bars (rebar) for the first
time.
The 20th century again spawned many types of concrete improvements. In the 1970's fibers were
introduced to concrete. The 1980's added the superplasticicers.
Research concludes that concrete can last 50000
years and withstand 50000 psi of compressive force given the right
mix and circumstances.
Concrete is a green
building product. |
