Concrete By Mr. Brower

Uses of Concrete Roads, bricks, canals, dams, caskets, tunnels, bank vaults, headstones, water tanks, steps, buildings, missile silos, walls, floors, sculptures, mantels, picnic tables List goes on and on ...

Is it cement or concrete? Cement is an ingredient in concrete Cement makes up about 25% of concrete

Purpose of Cement Cement is added to water to make a “cement paste” Adding water to cement starts a chemical reaction (hydration)that forms hard crystals called “hydrates.” Demo CuSo4.5h20

Hydration

Hydration

Purpose of Cement The cement paste is called a “binder” To make cement cheap to buy a “filler” is added to the cement paste “Aggregates” (sand and gravel) are used as filler. They make up 70% of concrete.

How is Cement Made? Limestone, clay and sand are dug out of the Earth Heated to 2732 degrees Other materials such as gypsum are then added End product is ground to fine grey powder called Portland cement.

“Admixtures” Admixtures that speed up the rate of hydration are called “accelerators.” Example: Sugar Admixtures that slow down hydration are called “retardants” Example: Calcium Carbonate

Concrete After a mixture of cement, sand, gravel and water undergoes hydration, concrete forms Before complete hydration, the concrete is held in place by “forms”

Concrete After the concrete hardens, the forms are removed

https://www.youtube.com/watch?v=a5Eioq_gfTY Portland Cement Video Review