What is Cement?

Many people mistakenly believe that cement and concrete are the same thing. In fact, cement is a basic ingredient in concrete, but cement and concrete are not the same thing. So if cement and concrete are different, what exactly are they? Concrete is actually a combination of cement and aggregate rock materials. To learn more about concrete check out this article.

Cement is most commonly used as a binding agent. It is a substance that hardens and can be used to hold, or cement, materials together. There are two main types of cement: Hydraulic and Portland. Hydraulic cement is the type most commonly used in commercial, residential and industrial cement and concrete work. Hydraulic cement hardens even when under water. It forms a very strong and durable building material. Buildings and structures constructed with hydraulic cement are able to withstand a lot of wear and tear and hold up well in the face of a variety of environmental situations, such as rain, snow and flood.

The most common type of hydraulic cement is known as Portland cement. This type of cement is considered a general use cement. There are variations of this type of cement that have been designed for specific applications such as industrial structures in which high heat resistance is required, or for applications in which high strength early on is needed. For nearly all general construction and residential cement and concrete projects, ordinary Portland cement is likely to be used. In contrast to Portland cement and other varieties of hydraulic cement, non-hydraulic cement must be kept dry and not exposed to water in order to retain its strength. While non-hydraulic cement was the original form of cement, it’s lengthy drying and setting time make it less desirable for use today than hydraulic cement, such as Portland cement. It should be noted that Portland cement is a type of cement and is not a cement brand. There are a number of cement manufacturing companies who make Portland cement as well as other types of cement. Another type of cement, called slag cement, is commonly used with cement in the United States. This type of cement is created from a byproduct of manufacturing iron in a blast furnace. Slag cement can replace some of the Portland cement in creating a concrete blend.

What Exactly is Portland Cement Made of?
According to the Portland Cement Association,  “Portland cement, the basic ingredient of concrete, is a closely controlled chemical combination of calcium, silicon, aluminum, iron and small amounts of other ingredients to which gypsum is added in the final grinding process to regulate the setting time of the concrete.” Limestone, shells, chalk, clay, slate, silica and iron ore are commonly used ingredients in the manufacturing of Portland cement. Lime and silica account for about 85% of the materials combination. Portland cement comes in grey and white and is the most commonly used cement in the production of concrete.

Where Does Cement Get its strength?
When cement, such as Portland cement or other hydraulic cements, are mixed with water, they undergo a series of complex chemical reactions which contribute to the strength and stability of the cement. As the components crystallize on a molecular level they interlock and form strong bonds. Initial setting begins right away, but depending on the specific blend of cement the final setting and hardening of the cement can take more than twenty four hours from the time the cement is mixed to fully harden and solidify.

Safety Issues When Working With Cement
In general structures made of cement and concrete (created from cement) are very strong and safe. Care must be taken by cement workers to avoid breathing in the particulates from unmixed bags of cement. In addition wet cement can be very irritating to the skin and should be washed off immediately to avoid burns.