Q:

What is concrete made of?

A:

Quick Answer

Concrete is composed of aggregates, which can be any or a combination of sand, gravel or rocks that is held together by cement. The cement itself, when mixed with water, serves as a paste that holds all the components of the concrete together once the cement sets and hardens.

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Full Answer

One of the earliest evidence of manmade concrete were the floors of royal palace of Tiryns in Greece, which was constructed around 1400 to 1200 B.C. The ancient Romans were one of the most prolific users of concrete, using the material for their architectural and other construction works.

During a 700-year period between 300 B.C. to 476 A.D., the Romans used a concrete material called opus caementicium that was made from pumice as an aggregate with pozzolana and quicklime as cement. Modern-day analysis show that opus caementicium had similar compressive strength to modern Portland cement. However, since the Romans did not use any reinforcements, opus caementicium had significantly lower tensile strength compared to modern reinforced cement.

The proportions of the materials used for making modern-day concrete varies according to its application. For example, the proportions used on concrete for floors, driveways and sidewalks is ideally one part cement, two and half parts sand and three parts gravel. On the other hand, the recommended concrete mix proportions for high strength floors and columns is one part cement, one part sand and two parts gravel.

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Related Questions

  • Q:

    How does cement harden?

    A:

    Cement hardens through a process called hydration. This process begins when water is mixed in with cement and an aggregate such as gravel or crushed limestone is added to form concrete.

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  • Q:

    How is polished concrete made?

    A:

    Polished concrete is made by crushing the slab’s surface to reveal the aggregate or stones in the concrete or topping mixture. It is an attractive floor finish in which the exposed concrete is left as the last finish.

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  • Q:

    How is cement made?

    A:

    Modern cement is made by combining certain chemicals that include aluminum, calcium, silicon, iron and other ingredients in a controlled process. These chemicals are derived from limestone, clay, slate, iron ore, chalk with shale, slate and blast furnace slag. When exposed to high temperatures, these materials form a rock-like substance, which when grounded into powder form and becomes what is commonly referred to as cement.

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  • Q:

    How is prestressed concrete made?

    A:

    Prestressed concrete is made by embedding strands of high-strength steel into the concrete. Prestressed concrete plants have the equipment to carry out this hefty task.

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