Processed cement was discovered by Joseph Aspdin in 1824 and was called Portland cement because it resembled a grey stone mined from the island of Portland off the coast of England. People often confuse cement with concrete. Concrete is a mixture of cement, aggregates and water that hardens to form a building material used for everything from sidewalks to skyscrapers. Behind water, concrete is the most consumed substance on earth, with almost one ton of it being used for each human every year.
Cement is to concrete what flour is to fruit cake.
While different types of cement vary in their ingredients, four common elements are found in all types of cement. The most common material used for cement is limestone because it is rich in calcium. It is blasted from its rockbed and then crushed to form pieces that are 2 inches in size or less. The feed is then homogenized through a separator that strains particles that are too coarse for the kiln. Fine material passes through the separator while coarse material is returned to the mill for further grinding.