Concrete vs. Cement: What’s the Difference?

Cement is a powder that, when mixed with water, can bind other materials together, often as an ingredient in concrete. There are two categories of cement: hydraulic cement (which is set by using water) and non-hydraulic cement (which dries and hardens by reacting with carbon dioxide). Today, the most common type of cement is Portland cement—a type of hydraulic cement made with limestone, clay, shale, marl, chalk, bauxite, iron ore, and sand.

In cement production, the raw stone materials are fired in a rotary kiln at high temperatures in a process called sintering. This causes the raw materials to undergo a chemical reaction. The materials are then ground to create cement powder. The cement manufacturing process is a significant source of carbon dioxide emissions because the cement kiln is usually fired using fossil fuels, natural gas, or waste materials like plastic or used tires.

Concrete is a robust hard building material. The Roman Empire built the earliest concrete structures with a concrete mix of quicklime, pozzolana, and pumice. In modern times, the basic ingredients of concrete are cement, aggregates, and admixtures.

Cement makes up 10 to 15 percent of concrete and is the glue that binds it together. Aggregates are granular stone materials, such as sand or gravel, that can be classified as being fine aggregates or coarse aggregates, depending on the particle size. Admixtures are natural or manufactured chemicals added to the concrete mixture to enhance the concrete in specific ways; for example, calcium chloride speeds up cement hydration (shortening the setting time for concrete), and fly ash, which is a byproduct of coal-fired power plants, is added to increase durability.

Hardened concrete has high compressive strength, and it is not subject to rot or corrosion. Concrete does have low tensile strength, though, meaning when stretched, the concrete will break. Steel beams, which have higher tensile strength, can be embedded inside concrete to create reinforced concrete.

Concrete requires cement as an ingredient. While cement is wholly made out of crushed stones, concrete contains cement plus water, larger rocks, and chemical additives. Cement can be used in combination with other materials as a cement paste; standard cement uses include mortar to bind stones and bricks in masonry construction projects and grout to fill in cracks. Additionally, coloring can be added to a liquid cement mix to create building exteriors or floors. Concrete is used for building foundations, dams, bridges, roads, sidewalks, houses, and skyscrapers.

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