Term: Portland cement
History and Development of Portland Cement
– Portland cement developed from natural cements made in Britain in the 18th century
– Named after Portland stone, a building stone quarried in Dorset, England
– John Smeaton experimented with different limestones and additives for construction
– Roman cement was popular but replaced by portland cement in the 1850s
– James Frost and Edgar Dobbs made advancements in cement production
Composition and Manufacturing of Portland Cement
– Portland cement is a hydraulic cement that hardens and forms a water-resistant product
– Consists of hydraulic calcium silicates, calcium sulfate, and other compounds
– Clinkers make up over 90% of the cement, along with minor constituents
– High temperatures cause chemical reactions to form key components of portland cement
– Calcium oxide and belite combine to form alite
– Portland cement clinker is made by heating a mixture of raw materials in a cement kiln
– Fusion temperature of about 1,450°C is required to sinter the materials into clinker
– Alite, belite, tricalcium aluminate, and tetracalcium alumino ferrite are the main components of clinker
– Aluminium, iron, and magnesium oxides act as a flux and contribute little to strength
– Limestone and clay are the primary raw materials used in clinker-making
Types and Uses of Portland Cement
– Ordinary portland cement (OPC) is the most common type of portland cement
– White portland cement is also available
– OPC is grey and named after its resemblance to portland stone
– Different types of portland cement have specific characteristics and uses
– Various standards regulate the composition and properties of portland cement
– Portland cement is a basic ingredient in concrete, mortar, stucco, and grout
– It is widely used in construction due to its low cost and availability
– Concrete, made with portland cement, is a composite material consisting of aggregate, cement, and water
– It provides strength, durability, and versatility to various construction projects
– Portland cement is essential for the development of modern infrastructure.
Cement Grinding, Setting, and Hardening
– A 10 MW cement mill produces cement at 270 tonnes per hour
– Calcium sulfate (usually gypsum or anhydrite) is added to the clinker to achieve desired setting qualities
– The grinding process in a cement mill produces a powder with a broad particle size range
– The specific surface area is used to measure the fineness of the cement
– Cement is stored in silos for one to 20 weeks of production
– Cement sets through a complex series of chemical reactions
– The interlocking of crystals gives cement its strength
– Carbon dioxide is absorbed to convert portlandite into calcium carbonate
– Warm water immersion speeds up the setting process
– Gypsum is added to prevent quick setting
Environmental Impact and Innovation in Cement Manufacturing
– Wet cement is caustic and can cause skin burns
– Cement dust can cause severe eye or respiratory irritation
– Chromium(VI) levels are regulated in some countries
– Cement production has environmental impacts like dust emissions and CO2 release
– Research is ongoing for suitable replacements for Portland cement
– Decarbonation of limestone and kiln fuel combustion are major sources of CO2 emissions in cement manufacturing
– Cement kilns can be used for waste disposal or processing
– Concrete emits less CO2 compared to other modern building systems
– Innovation focuses on reducing CO2 emissions and adopting more efficient processes
– Worker exposure to dust and particulates is a concern in cement manufacturing
– Cement kilns efficiently destroy hazardous organic compounds in waste streams
– The use of supplementary cementitious materials can contribute to a more sustainable cement industry.
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 early 19th century by Joseph Aspdin, and is usually made 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 resemblance to portland stone which was quarried on the Isle of Portland in Dorset, England. It was named by Joseph Aspdin who obtained a patent for it in 1824. His son William Aspdin is regarded as the inventor of "modern" portland cement due to his developments in the 1840s. The term portland in this context refers to a material or process, not a proper noun like a place or a person, and should not be capitalized.
The low cost and widespread availability of the limestone, shales, and other naturally occurring materials used in portland cement make it a relatively cheap building material. Its most common use is in the production of concrete, a composite material consisting of aggregate (gravel and sand), cement, and water.