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 do you know how much cement you need?

    A:

    The ratio of cement by volume for standard concrete is one part Portland cement, three parts aggregate and three parts sand. General purpose mortar requires one part Portland cement, one part hydrated lime and three parts sand.

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  • Q:

    What are the mix ratios for cement and sand?

    A:

    The basic mix ratio for concrete is one part water, two parts cement and three parts sand. An alternative ratio is one part cement, two parts sand and three parts gravel with enough water added until the mixtures reaches the consistency of thick mud. Lime is also a common additive to the mix.

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  • Q:

    What are concrete mixing ratios?

    A:

    Concrete mixing ratios are the formula for calculating the correct amount of each ingredient used, including water, cement, sand and aggregate, to produce concrete with the properties desired. A basic concrete ratio is one part cement, two parts sand, and three parts gravel, slowly mixing in water until workable.

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  • Q:

    What is the melting point of concrete?

    A:

    Concrete does not actually have a melting point, but it decomposes into various components due to the makeup of concrete, which is mostly sand and gravel with Portland cement added. A temperature of thousands of degrees Fahrenheit is needed to decompose concrete.

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