Which of the following is not true about the Portland cement?
Ο Α. CaO is the major raw material in the manufacture of Portland cement.
O B. The presence of 5% CaSO4.2H2O in Portland cement helps to delay the setting time of cement.
O C. The presence of excess unreacted CaO in the final cement product will add an improved quality to cement.
O D. Cement hardens with the addition of water.
The statement that is not true about Portland cement is that the presence of excess unreacted CaO in the final cement product will add an improved quality to cement.
Explanation:
Portland Cement:
Portland cement is a commonly used type of cement in construction. It is made by heating limestone (CaCO3) with other materials, such as clay, to produce clinker. The clinker is then ground into a fine powder, which is the Portland cement.
Analysis of Statements:
A. CaO is the major raw material in the manufacture of Portland cement.
This statement is true. Calcium oxide (CaO) is one of the main components of the raw materials used in the production of Portland cement.
B. The presence of 5% CaSO4.2H2O in Portland cement helps to delay the setting time of cement.
This statement is true. The presence of calcium sulfate dihydrate (CaSO4.2H2O), also known as gypsum, in Portland cement helps to control the setting time of the cement. It acts as a retarder, slowing down the hydration process and allowing more time for the cement to be properly mixed and placed.
C. The presence of excess unreacted CaO in the final cement product will add an improved quality to cement.
This statement is not true. Excess unreacted calcium oxide (CaO) in the final cement product can lead to a decrease in the quality of the cement. It can cause issues such as expansion, cracking, and reduced strength.
D. Cement hardens with the addition of water.
This statement is true. When water is added to Portland cement, it undergoes a chemical reaction called hydration, which leads to the hardening and setting of the cement.
Based on the analysis, the statement that is not true about Portland cement is: The presence of excess unreacted CaO in the final cement product will add an improved quality to cement.