What is the difference between concrete and cement?

Cement and concrete are two terms people often get confused with and use out of places. People often say ‘cement sidewalk’ or ‘cement mixer’ but the proper terms are ‘concrete sidewalk’ and ‘concrete mixer’. While it may seem harmless using these words interchangeably, it is still technically incorrect. Even though both cement and concrete are construction materials, they are two distinct products.
The cement is actually one of the ingredients of the mixture we call concrete. It is primarily made up of lime and silica. Those two materials constitute for about 85% of cement. Other ingredients include calcium, iron, aluminum and a few others. These materials are mixed and heated in large kilns to very high temperature, ranging from 2,700°F to 3000°F, to form a product known as clinkers. Clinkers are small pellets which resemble marbles. These are later ground into a finely powdered form and gypsum is often added. The final product is what we call cement. When water is added to cement, a chemical process takes place, allowing it to harden. The cement acts as a binding product that helps to hold the ingredients of concrete together.
Cement is basically divided into two types; hydraulic and non-hydraulic. Hydraulic cement uses water to start a chemical reaction and hardens irrespective of the water content and becomes water resistant. This is suitable for wet conditions and underwater structures. Non-hydraulic cement, on the other hand, doesn’t harden when mixed with water which makes it unsuitable for most conditions.
The most prevalent type of cement is the Portland cement or Ordinary Portland Cement (OPC). Portland cement is a generic name for the hydraulic cement used in construction. It was developed by Britishman Joseph Aspdin in 18th century. Portland cement itself is classified into 8 types, according to specifications.
Concrete is actually a mixture of cement, water and other aggregates. The aggregates include crushed mostly chemically inert materials like stones, gravel and sand. The amount and type of aggregates vary according to application of concrete. They usually make up 60% to 80% of the mixture. Cement constitute for up to 15% of the total mass of concrete and the latter cannot be made without the former. The ratio of water to cement is very important, as it determines the strength of concrete. Too much water will weaken the mix.
Concrete is one of the most used construction materials, due to its strength, durability and resistance to fire and water. It gets stronger over time because of the continued hardening.

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