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The main raw materials required for the manufacture of Portland cement are:
A) Limestone and clay
B) Limestone and gypsum
C) Limestone and calcium chloride
D) Limestone and silica

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Last updated date: 15th Jul 2024
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Answer
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Hint: We need to remember that the portland concrete was created from characteristic concretes made in Britain starting in the eighteenth century. Its name is gotten from its similitude to Portland stone, a kind of building stone quarried on the Isle of Portland in Dorset, England.

Complete answer:
The primary fixings utilized for assembling concrete are calcium oxide, silica and alumina.
Lime stone which is calcium carbonate when warmed gives calcium oxide and carbon dioxide. Sand is silicon dioxide or silica.
Sand stone is calcium silicate when warmed gives calcium oxide or lime and silica. Earth soils contain aluminum oxide or alumina.
Limestone commonly found in sullied structure here and there blended in with calcium silicate is the most reasonable crude material for concrete.
Subsequent to crushing and synthetic testing sand dirt and so on are added to get a reasonable level of fundamental fixings.
Little level of magnesium oxide and iron oxide is likewise required. Gypsum calcium sulfate is added to the concrete powder to change the setting time.
Limestone and clay are crude materials utilized in the production of Portland concrete.

Hence option A is correct.

Note:
Now we can discuss about the Portland concrete clinker is made by warming, in a concrete furnace, a combination of crude materials to a calcining temperature of over \[600^\circ C\] and afterward a combination temperature, which is around \[1450^\circ C\] for current concretes, to sinter the materials into clinker.
We need to remember that the materials in concrete clinker are alite, belite, tricalcium aluminate, and tetra-calcium alumino ferrite. The aluminum, iron, and magnesium oxides are available as a transition permitting the calcium silicates to shape at a lower temperature, and contribute little to the strength. For uncommon concrete, like low warmth and sulfate safe types, it is important to restrict the measure of tricalcium aluminate framed.