Question map
Not attempted Correct Incorrect ★ Bookmarked
Loading…
Q20 (CDS-II/2015) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Applied everyday chemistry Answer Verified

Which of the following statements with regard to Portland cement are correct? 1. Silica imparts strength to cement. 2. Alumina makes the cement quick setting. 3. Excess of lime increases the strength of cement. 4. Calcium sulphate decreases the initial setting time of cement. Select the correct answer using the code given below.

Result
Your answer: —  Â·  Correct: D
Explanation

Portland cement's properties are determined by its chemical composition. Silica (SiO2) is a primary ingredient that reacts with lime to form dicalcium and tricalcium silicates, which are responsible for imparting strength and durability to the cement [1]. Alumina (Al2O3) acts as a flux and imparts quick-setting properties by facilitating the formation of tricalcium aluminate. While lime (CaO) is essential for strength, an excess of lime is detrimental as it causes the cement to expand, crack, and become unsound rather than increasing its strength [1]. Calcium sulphate, typically added in the form of gypsum, acts as a retarder; it increases the initial setting time to prevent 'flash set,' allowing for better workability. Therefore, only statements 1 and 2 are correct.

Sources

  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 13: Types of Rocks & Rock Cycle > 13.5. Some Rock-Forming Minerals > p. 175
How others answered
Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.
Community Performance
Out of everyone who attempted this question.
26%
got it right
✓ Thank you! We'll review this.

SIMILAR QUESTIONS

NDA-I · 2012 · Q42 Relevance score: 2.62

Which one among the following is the correct order of amount of lime (CaO), silica (Si02), alumina (AI203) and ferric oxide (Fe2O3) in Portland cement?

IAS · 2025 · Q31 Relevance score: 2.47

Consider the following statements : Statement I : Studies indicate that carbon dioxide emissions from cement industry account for more than 5% of global carbon emissions. Statement II : Silica-bearing clay is mixed with limestone while manufacturing cement. Statement III : Limestone is converted into lime during clinker production for cement manufacturing. Which one of the following is correct in respect of the above statements?

IAS · 2003 · Q145 Relevance score: 1.89

Which one of the following statements is not correct?

CDS-I · 2023 · Q52 Relevance score: 1.43

Which of the following statements with regard to the reaction given below are correct? CaO(s) + H2O(l) → Ca(OH)2 (aq) + Heat 1. Quicklime is used for white-washing of walls. 2. The solution of slaked lime is used for whitewashing of walls. 3. CaO reacts slowly with CO2 in air to form a thin layer of CaCO3 on walls. 4. Calcium hydroxide called 'slaked lime' is an inorganic compound. Select the correct answer using the code given below.