Portland cement, the main subject of this site, is the most common type of cement – ‘basic cement’, if you like. In particular OPC (Ordinary Portland Cement) is the normal, grey, cement with which most people are familiar.
The origins of Portland cement
Portland cement was invented and patented in 1824 by Joseph Aspdin from Leeds, England. Aspdin produced cement by heating powdered limestone mixed with clay in a furnace at high temperature. The furnace product called ‘clinker’ was then ground with a small amount of gypsum into a powder to make ‘Ordinary Portland Cement’, the most commonly used type of cement (often referred to as OPC). Aspdin’s cement was not particularly strong but it was cheap and set quickly (a useful property at a time when the canals and railways were being built) and it became popular.
Portland cement, the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-speciality grout, was developed in England in the mid 19th century, and usually originates from limestone. James Frost produced what he called “British cement” in a similar manner around the same time, but did not obtain a patent until 1822. In 1824, Joseph Aspdin patented a similar material which he called Portland cement because of its similarity in colour to Portland limestone. It was Aspdin who first used the name “Portland” to describe his product in 1824. This cement has been known by this name throughout the world ever since.
Portland cement is caustic, so it can cause chemical burns. The powder can cause irritation or, with severe exposure, more serious effects.
The burn severity depends on the concentration: the higher the concentration of cement in soil, the more severe it is for bare skin to be exposed for long periods. Effects on skin range from redness to third-degree burns.
Once wet with water (it reacts exothermically) it can cause severe skin burns if not promptly washed off with water.[32] With dry cement on one’s
Portland cement is an ingredient in the most commonly used type of concrete, which is called Portland cement concrete or PCC. Concrete is a mixture of water, sand, coarse rock and Portland cement. The cement typically makes up from 10 to 15 percent of the total mixture by weight. When mixed with water, the cement reacts chemically and becomes like glue that holds the aggregates together to make concrete.
The first portland cement was made in 1824 by a British builder named Joseph Aspdin who lived in Leeds, England. He baked powdered limestone and clay in his kitchen stove, crushed it into powder and sold it as a “cement” for use in construction.
Aspdin’s cement was not particularly strong, but it was cheap and did set hard quickly. Aspdin originally called his invention “portland stone,” but then discovered that some people were confusing it with natural portland stone (a high quality building stone native to England). Aspdin decided to call his product “Portland Cement.”
Today there are many different types of portland cements manufactured to meet particular needs of construction projects on land and at sea.
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.
Portland cement manufacturing begins with mining and then grinding raw materials that include limestone and clay, to a fine powder, called raw meal, which is then heated in a rotating cement kiln. This process produces clinker (rounded nodules between 1mm and 25mm across), which is then ground with a small amount of gypsum into a powder to make ordinary Portland cement. The next step in the process is called finish milling, or grinding. The clinker is ground with about 5% gypsum to make cement. The material can be ground to the required
Portland cement is made from a mixture of calcium carbonate (generally in the form of limestone), silica, iron oxide and alumina. A high temperature kiln, often fuelled by coal, heats the raw materials to a partial melt at 1450°C, transforming them chemically and physically into a substance known as clinker. The clinker is then ground down with a small quantity of gypsum into a powder to make ‘Ordinary Portland Cement’, the most commonly used type of cement (often referred to as OPC).
Portland cement was developed from natural cements made in Britain beginning in the middle of the 18th century. Its name is derived from its similarity to Portland stone, a type of building stone quarried on the Isle of Portland in Dorset, England.
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.
Portland cement is manufactured by crushing, milling and proportioning the following materials:
– Lime or calcium oxide, CaO: from limestone, chalk, shells, shale or calcareous rock
– Silica, SiO2: from sand, old bottles, clay or argillaceous rock
– Alumina, Al2O3: from bauxite, recycled aluminum, clay
– Iron oxide, Fe2O3: from clay, fly ash, gilsonite or iron ore
The raw materials are proportioned to meet a desired chemical composition and fed to a rotating ball mill with water. The materials are ground to a fine powder in this process and can be blended to produce different types of cement. It is burned at 2200 degrees Fahrenheit (1200 degrees Celsius) in a rotating kiln to form clinker. Cooling the clinker (a few hundred degrees Fahrenheit) and then mixing with gypsum controls the setting time of Portland cement when water is added.
The name Portland cement is used today to describe a variety of building materials prized for their strength and durability. The name comes from its similarity in color to Portland stone, a limestone from the Isle of Portland in the English Channel. But how did it come to be?
In 1824 Joseph Aspdin, an English stonemason, first made Portland cement by burning finely ground chalk and clay until the carbon dioxide was removed. Aspdin called the product “Portland cement” because of the concrete’s resemblance to Portland stone.
Aspdin’s son William developed a better method for making what he called “hydraulic cement.” This was much harder than Aspdin’s product, and more resistant to water. His method of manufacture is still used today.
Today, we know that hydraulic cements are those that set and harden by chemical interaction with water. These include Portland cements as well as other types of hydraulic cements such as calcium aluminate cements, calcium sulfate cements (gypsum), lime-based cements (lime putty) or mixtures of them (blended cements).