Portland cement is a type of hydraulic cement, which means it sets and hardens by chemical reaction with water. The powdered hydraulic cement reacts with water to form a paste, which then sets and hardens.
Portland cement has been used as an ingredient in concrete since the early nineteenth century. It did not become popular for construction until the development of reinforced concrete structures in the 1920s.
Portland cement is made from limestone, clay and other minerals found in areas where volcanoes have erupted. It is typically heated at extremely high temperatures before it is ground into a fine powder.
The limestone acts as an agent to decrease the melting point of silica, which makes aggregates such as sand and gravel easier to work with. In fact, there are more than 90 different types of Portland cement available.
Concrete requires three basic ingredients: water, aggregate (rock, sand or gravel) and Portland cement. Cement acts as the binding agent in concrete; it is what “glues” or hardens the mixture once it has been combined with water. Without Portland cement, you would not have concrete floors, sidewalks or bridges!
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the mid 19th century, and usually originates from limestone. It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum. Several types of Portland cement are available. The most common, called ordinary Portland cement (OPC), is grey, but white Portland cement is also available. Its name is derived from its similarity to Portland stone which was quarried on the Isle of Portland in Dorset, England.
Portland cement manufacturing plants are part of hydraulic cement manufacturing, which also includes natural, masonry, and pozzolanic cement. The six-digit Source Classification Code (SCC) for portland cement plants with wet process kilns is 3-05-006, and the six-digit SCC for plants with dry process kilns is 3-05-007.
Portland cement accounts for 95% of all cement produced. Most Portland cement is made in a rotary kiln. Basically
Portland cement is a type of hydraulic cement made by heating a limestone and clay mixture in a kiln and pulverizing the materials. It is a fine, powdery substance that becomes hard when mixed with water. It is used to make mortar and concrete, two of the most popular construction materials in the world. It is also one of the most common substances found in landfills.
Before it was developed, builders would use natural cements made from burning limestone and clay mixtures into clinker at high temperatures. The finished product was then ground up and mixed with water to form a paste-like material that would become hard over time. The process for making Portland cement has since been refined to limit emissions of carbon dioxide into the atmosphere.
Portland cement accounts for about 95 percent of all the cement produced in this country today; it is used everywhere from sidewalks to bridges, homes to skyscrapers, as well as roads and dams.
Portland cement is a type of cement, not a brand name. Many cement manufacturers make Portland cement.
For more information about cement and concrete technology, visit the Portland Cement Association Web site at:
www.cement.org
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the mid 19th century and usually originates from limestone. It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum. Several types of Portland cement are available. The most common, called ordinary Portland cement (OPC), is grey, but white Portland cement is also available. Its name is derived from its similarity to Portland stone which was quarried on the Isle of Portland in Dorset, England.
Portland cement manufactures typically include 95% clinker (which is mechanically ground into fine powder), with 5% gypsum added to control setting time. The quality of cement is primarily determined by the chemistry (calcium and silica ratio) of raw materials used during production process. In addition to controlling the chemistry of raw materials manufacturers need to control the temperature at which they are heated during grinding (at least 2500 degrees Fahrenheit).
Portland cement manufacturing plants are part of hydraulic cement manufacturing, which
Portland cement is the basic ingredient of concrete. Concrete is formed when portland cement creates a paste with water that binds with sand and rock to harden. Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients. Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore.
These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement. Bricklayer Joseph Aspdin of Leeds, England first made portland cement early in the 19th century by burning powdered limestone and clay in his kitchen stove. With this crude method, he laid the foundation for an industry that annually processes literally mountains of limestone, clay, cement rock, and other materials into a powder so fine it will pass through a sieve capable of holding water.
Although the dry process is the most modern and popular way to manufacture cement, some kilns in the United States use a wet process. The two processes are essentially alike except in the wet process, the raw materials are ground with water before being fed into the kiln.
The product
Portland Cement is a hydraulic cement, hence it derives its strength from chemical reactions between the cement and water. The process is known as hydration. Cement consists of the following major compounds (see composition of cement):
Tricalcium silicate, C3S – Dicalcium silicate, C2S – Tricalcium aluminate, C3A – Tetracalcium aluminoferrite, C4AF
The underlying chemical reaction that forms the basis of hydration is:
C3S + 2H -> 3CSH2 + CH
The formation of CSH gel is an important part of the hydration process as this gel becomes the major contributor to the strength of concrete. The by-product CH is responsible for increasing the porosity and decreasing the strength of concrete. Thus, we can conclude that cement having more tricalcium silicate will have higher compressive strength than a similar cement having more dicalcium silicate.