Hint: We must know that the portland cement is a common material and is the basic ingredient of concrete. Portland cement forms a paste with water that hardens on binding with sand and rock. Complete step by step answer: We can use portland cement popularly as a binding material in the form of a finely ground powder that is prepared by burning and grinding a mixture of limestone and clay or limestone and shell.
- When it is mixed with water, the Constituents of Portland cement reacts chemically with the water that leads to the process of hydration and decomposition or hydrolysis.
- These processes make the mixture harden and thus it develops strength.
- Portland cement is composed of following chemicals, namely, \ ( tricalcium aluminate), \ ( tricalcium silicate), \ ( Dicalcium silicate), \ (Sodium oxide), \ (Potassium oxide), \ (Calcium sulfate dihydrate ) and \ (Tetracalcium- aluminatferrite) The Portland cement is composed of 60% calcium oxide, 25% silica, 7% of alumina, 2 to 2.5% magnesia and 2 to 2.5% ferric oxide.
We know calcium silicates and calcium aluminates are forms of Calcium oxide. So, Portland cement does not contain calcium phosphate. $\therefore $The correct option is the option D. Additional information: We must know that Joseph Aspdin from England is the inventor of the basic process of Portland cement manufacturing.
- Portland cement has been named so for the resemblance of the cement when set to portland stone from the Isle of Portland.
- There are five types of Portland cement available in the world market depending upon their content, properties and usage.
- Percentage of above mentioned contents of Portland cement varies from type to type.
Note: Calcium phosphate has nutritive value; we can use it as an antacid and also as a dietary supplement in veterinary medicines. It is used in medicine as a calcium supplement dose.
Which one is not present in Portland cement?
Portland cement gets its strength from chemical reactions between the cement and water. The process is known as hydration. Hence option D is not present in portland cement. Was this answer helpful?
What is Portland cement made of?
This article is about the building product of cement. For the Australian heritage-listed production site, see Portland Cement Works Precinct, Bags of portland cement wrapped and stacked on a pallet. 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.
What is the CO 2 content of Portland cement?
Environmental effects – Portland cement manufacture can cause environmental impacts at all stages of the process. These include emissions of airborne pollution in the form of dust; gases; noise and vibration when operating machinery and during blasting in quarries; consumption of large quantities of fuel during manufacture; release of CO 2 from the raw materials during manufacture, and damage to countryside from quarrying.
- Equipment to reduce dust emissions during quarrying and manufacture of cement is widely used, and equipment to trap and separate exhaust gases are coming into increased use.
- Environmental protection also includes the re-integration of quarries into the countryside after they have been closed down by returning them to nature or re-cultivating them.
Portland cement is caustic, so it can cause chemical burns. The powder can cause irritation or, with severe exposure, lung cancer, and can contain a number of hazardous components, including crystalline silica and hexavalent chromium, Environmental concerns are the high energy consumption required to mine, manufacture, and transport the cement, and the related air pollution, including the release of the greenhouse gas carbon dioxide, dioxin, NO x, SO 2, and particulates,
- Production of portland cement contributes about 10% of world carbon dioxide emissions,
- The International Energy Agency has estimated that cement production will increase by between 12 and 23% by 2050 to meet the needs of the world’s growing population.
- There are several ongoing researches targeting a suitable replacement of portland cement by supplementary cementitious materials.
Epidemiologic Notes and Reports Sulfur Dioxide Exposure in Portland Cement Plants, from the Centers for Disease Control, states: Workers at portland cement facilities, particularly those burning fuel containing sulfur, should be aware of the acute and chronic effects of exposure to SO 2, and peak and full-shift concentrations of SO 2 should be periodically measured.
An independent research effort of AEA Technology to identify critical issues for the cement industry today concluded the most important environment, health and safety performance issues facing the cement industry are atmospheric releases (including greenhouse gas emissions, dioxin, NO x, SO 2, and particulates), accidents, and worker exposure to dust.
The CO 2 associated with portland cement manufacture comes mainly from four sources:
|CO 2 source||Amount|
|Decarbonation of limestone||Fairly constant: minimum around 0.47 kg (1.0 lb) CO 2 per kg of cement, maximum 0.54, typical value around 0.50 worldwide.|
|Kiln fuel combustion||Varies with plant efficiency: efficient precalciner plant 0.24 kg (0.53 lb) CO 2 per kg cement, low-efficiency wet process as high as 0.65, typical modern practices (e.g. UK) averaging around 0.30.|
|Produced by vehicles in cement plants and distribution||Almost insignificant at 0.002–0.005. So typical total CO 2 is around 0.80 kg (1.8 lb) CO 2 per kg finished cement.|
|Electrical power generation||Varies with local power source. Typical electrical energy consumption is on the order of 90–150 kWh per tonne cement, equivalent to 0.09–0.15 kg (0.20–0.33 lb) CO 2 per kg finished cement if the electricity is coal-generated.|
Overall, with nuclear or hydroelectric power, and efficient manufacturing, CO 2 generation can be reduced to 0.7 kg (1.5 lb) per kg cement, but can be twice as high. The thrust of innovation for the future is to reduce sources 1 and 2 by modification of the chemistry of cement, by the use of wastes, and by adopting more efficient processes.
What is the chemical reaction of Portland cement?
Composition – ASTM C150 defines portland cement as: hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) produced by pulverizing clinkers which consist essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulfate as an inter ground addition. The European Standard EN 197-1 uses the following definition: Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates, (3 CaO·SiO 2, and 2 CaO·SiO 2 ), the remainder consisting of aluminium- and iron-containing clinker phases and other compounds. The ratio of CaO to SiO 2 shall not be less than 2.0. The magnesium oxide content ( MgO ) shall not exceed 5.0% by mass. (The last two requirements were already set out in the German Standard, issued in 1909). Clinkers make up more than 90% of the cement, along with a limited amount of calcium sulfate (CaSO 4, which controls the set time), and up to 5% minor constituents (fillers) as allowed by various standards. Clinkers are nodules (diameters, 0.2–1.0 inch ) of a sintered material that is produced when a raw mixture of predetermined composition is heated to high temperature. The key chemical reaction distinguishing portland cement from other hydraulic limes occurs at these high temperatures (>1,300 °C (2,370 °F)) as belite (Ca 2 SiO 4 ) combines with calcium oxide (CaO) to form alite (Ca 3 SiO 5 ).